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Digital Voice Over HF

Brian Levy (W2BRI) on October 29, 2003
View comments about this article!

In these digital times, where amateurs can bounce weak signals thousands of miles and establish reliable communication with ease, the efforts to improve our digital communication arsenal are gaining great momentum. With each new digital mode applied to moon bounce, meteor scatter and DX, the old assumptions and records fall away bringing new expectations and desires. At the forefront of this new, inventive effort is the drive to deliver a digital voice product for amateur radio that will bring with it advantages over current modes and techniques.

It isn't enough to take current phone communications like two meter FM and turn them digital, rather, it is the passion of modern day inventors to give current amateurs a mode that's superior to what we have, better audio quality, higher signal to noise, and simultaneous data with voice. With this in mind, the people from AOR have released the ARD9800 Fast Radio Modem, a digital voice modem for the amateur operator and ham market.

The ARD9800 is a small modem device 3x1x6 inches able to connect to almost any amateur operator's rig. This device is unique - it can deliver near FM-like sound quality on HF and still maintain strict FCC bandwidth limitations.

The real trick to decent quality digital audio is the compression engine used to fit the necessary data stream within regulated bandwidths. You see, in the past, decent audio quality required so much data, the 3.0 khz HF phone requirement was just too narrow. However with the advent of faster chips, and better compression schemas, the dream of better HF audio communication is finally here. AOR is the first commercial player out of the gate with a product that starts to bring us obvious benefits over current HF SSB communications.

Just as SSB came into its own back in the 1950's and replaced the AM mode for the most part, so too digital voice will shape the future of the HF bands. As my wife wandered by my shack one evening and heard my friend Juan coming out of my HF rig, I remarked that we were using forty meters. Her face changed into surprise, and she said, "That's HF?" Yes, I replied, and explained that we were using digital voice over radio. "I thought you were on FM or something like that," she said. To say the least, she's not a fan of HF noise and was completely impressed by the audio quality and lack of hiss, hash and crackle. Imagine working your schedule on HF, but no longer contending with the natural noise that comes with HF usage. Digital voice technology brings the dream of high quality audio framed against a noiseless background closer to practical reality.

Connecting the ARD9800 to your radio is a fairly easy process if you have the necessary cables. A special microphone cable connects your radio to the modem via your rig's microphone port, and your radio's headphone jack gets plugged into the modem's audio in connector. I highly recommend buying these cables from AOR for your specific radio (the modem works on all modern HF rigs according to AOR), because figuring out the pin assignments on the microphone cable can get frustrating and the manual is not as clear as I would like it to be. My understanding is they are constantly upgrading and working on the manual. As of the time of this writing I was supplied with a second manual with more improvements included. I myself got a hold of the AOR made cables, and it made things much more pleasant.

Once the connection between the modem and the radio are complete, all one needs to do, is get on frequency with another modem owner and try your hand at digital communication. The modems can be used on any HF band except 60 meters, and will work in any mode: AM, FM, and SSB. When a user presses the PTT on the their modem's microphone, a short ring is heard. This ring is a digital header being sent by your modem to alert other modem users on frequency that digital communication is about to be sent. Once the short header ring sounds, those listening with their digital modems will hear their speaker go quiet, the familiar HF din will cease, and clear audio will start to be heard. It's almost magical to see these modems work the first time and see the amazing transformation that takes place when digital communication takes over.

However, this new product is not without its faults, and readers should not believe at this early stage of development digital voice is a perfected mode of operation without its own shortcomings. It too has its own quirks and operational issues that must be explained. For instance, the modems sometime do not recognize the initial data header and will not decode the digital voice stream. As a result the receiving station can end up listening to data noise instead of digital voice. Also, it is sometimes hard to get the audio levels just right to make communication possible. There are instances where the modems work only one way, from station A to station B, but not in the reverse. Station A never receives the digital audio, only digital noise. In the many experiments made with this product, it was never fully clear why the modems did not always work perfectly, although, it was probably do to operator error on one side of the transmission.

Also, AOR has instructed owners to make sure certain conditions are met when using the modem. For instance, a switching power supply cannot be used with the product or on the radio utilized with the modem. It seems that these power supplies introduce unwanted distortions in the transmissions that impede successful contact. I cannot explain this completely, however I have had to switch to a different power source to make the modem work right. So a linear power supply or battery must be used instead. In addition, all receive and transmit DSP must be turned off in order for the modems to work properly. Users also must make sure all narrow filters are turned off so the full data stream can get through the IF or audio bandwidth of the radio on transmit and receive.

Despite all these issues, potential buyers should realize that this product represents the cutting edge of amateur radio technology and that all their work and experimentation is truly groundbreaking and unique. Buyers will be working with an entirely new mode of communication for HF, and will discover the characteristics and limits of the technology. It is a truly fantastic opportunity to be at the forefront of a new amateur mode, helping shape and drive the way this new technology is applied and used.

These modems are also capable of other functionality, like slow-scan TV with an optional memory module, and as a data modem, but for the purpose of this article, the topic of digital voice communication was the most compelling feature and therefore the complete focus. Those amateurs stuck in the old ways beware, for a new mode is upon our service that will alter the radioscape of our hobby. As more amateurs experiment with digital voice, the nature of our bands will change bringing the new sounds of data intermixed with the cadence of SSB communications. As digital techniques improve, and new modes are introduced, ham radio will further evolve into an exciting and rich future. For those that think everything has been done before them, pick up this device and see that we are simply scratching the surface of what is to come.

For more information on the AOR modem check out:

By Brian Levy, W2BRI

Member Comments:
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Digital Voice Over HF  
by K2VJK on October 29, 2003 Mail this to a friend!
This sounds like an interesting new mode of communications. Since we are in the digital age, this might be very useful (especially if BPL gets around). Would like to hear from anyone who has, or is using this equipment. 73s
RE: Digital Voice Over HF  
by AE4X on October 29, 2003 Mail this to a friend!
Interesting. Seems to be in the infancy stage so I don't think I'll buy this new technology yet. Time will tell where this goes. The beauty of ham radio, though, is there is always experimentation and new ideas.
This will be something to monitor and, like the other comment, perhaps this is useful mode for BPL (which I doubt will ever come to fruition).
RE: Digital Voice Over HF  
by N6AJR on October 29, 2003 Mail this to a friend!
seems like some one figured out how to use MP3 compression codecs on the hf band..neet
RE: Digital Voice Over HF  
by KZ9G on October 29, 2003 Mail this to a friend!
As compression techniques progress, codecs will allow "FM quality" voice transmissions in SSB bandwidths. In the future, digital transmission of voice and data will become commonplace over narrowband radio systems. Voice quality should be quite good, and negate most noises. IMHO, whether it rivals narrowband, high signal-to-noise ratio, analog voice transmission will yet to be determined.

The new APCO Project 25 digital voice and data standard for public safety systems has had "voice quality" comparison tests performed against the current analog standard. The new P25 standard performed quite admirably when similar signal levels where compared. In fact, the P25 standard probably edged out the analog reception throughout these somewhat subjective voice quality tests.

Digital is coming...even to ham radio!
RE: Digital Voice Over HF  
by LNXAUTHOR on October 29, 2003 Mail this to a friend!
- great! so this means that instead of:

"CQ Contest! CQ Contest! CQ Contest!"

with my non-digital rig all i'll hear is noise?

- seems the same?


Digital Voice Over HF  
by G5FSD on October 29, 2003 Mail this to a friend!
I'm not sure I like this. If it gets through when normal SSB is unreadable, then it would be good. If it's about the same, then it's just another layer of cruft, an obstacle between the airwaves and the operator, removing the 'feel' of radio. I WANT to hear the sound of HF, the noise, the fading, the encroachment of QRM.. it's all part of the magic. I don't want FM quality on HF, you might as well use Echolink!

This is just another thing that (as noted) can go wrong and hinder communication. Is this good in an emergency situation when it misses synch and gives you noise when SSB would have been readable?

Is it an open standard? I wouldn't want to support a proprietary system that may well be usurped by a better open standard the next month.
Digital Voice Over HF  
by KG4RUL on October 29, 2003 Mail this to a friend!
Let's see.

$550 a copy for the box. If you have a net with 20 participants, the investment is $11K. Of course, you also have to already have the HF rig and antennas.

I think I will wait until this concept is implemented in shareware, for use with a computer soundcard. More like $20 investment if you don't already have the rig-to-soundcard interface.

Dennis - KG4RUL
00101 11001 11100 01111 !  
by WB9GKZ on October 29, 2003 Mail this to a friend!
All I can say is: 01111 10110 01010 01110 01110 11010
01111 and also 10001 10100 10100 1000 0001 01000.

So there,

Analog Pat WB9GKZ
Digital Voice Over HF  
by N4VNV on October 29, 2003 Mail this to a friend!
I will gleefully purchase one when the bugs are worked out. My sub-division has no patience with antenna farms and high power amps.
I wonder if the negative comment about "ECHOLINK" was from a person who thinks the Earth is Flat! Since he is ashamed to give his call sign. IF he has one.
RE: Digital Voice Over HF  
by N3HKN on October 29, 2003 Mail this to a friend!
Will this work with my loop antenna?? Just kidding..

Given the spending habits of Hams this mode will have to become more affordable in the realm of cost/benefit. Right now that does not seem to fit. Cost recovery needs of commercial vendors will keep prices high for awhile. Eventually some talented ham will create the system on a breadboard and be able to sell it based upon the cost of the hardware by "donating" the development costs. Rather like some of the kits that come from QRP clubs.

Some will become very annoyed at tuning across the band and picking up S9+ sections of noise. Thus the question, should digital voice be operated within a seperate portion of the band INITIALLY. This would allow those who can afford the stuff to be able to find someone to talk to and keep the complaints about "noise" down. At some point the new mode could become free to operate anywhere in the normal phone bands. Of, course this would be a voluntary ARRL sponsored bandplan.

The little boxes are too costly now given the small benefit of somewhat better fidelity - maybe. Different voices bring different results. When they approach $200.00 they MAY become attractive IF there is sufficient population to talk to. Where they will begin to come into their own is being able to exchange digital information. As an example APRS like position reports, WX, station profile, signal reports, QTH, and so on.. All of this can be sent with the depression of a button in a few seconds and either appear on a PC screen or be displayed on a low coat LCD display in the unit (optional). Emergency applications will be developed. Before you go to assist in a flood scenario you would download the appropriate form into your "modem". A cheap PC keyboard could then fill out the form in the field using cheap voice response, or low cost LCD, from the modem to guide you. Press a button and it is sent with error correction to insure 100% accuracy.

In my opinion the value of this modem is that it will be able to transmit data faster and more accurately than if given by voice. Voice may become a supplement to the data mode in field situations. Casual use will be a balance with voice being used for the usual chatter and the data being the mundane signal reports, QTH, etc... Thus it becomes much like the Harris field radios used by the military as Software Defined Radios merge with digital voice and data.

Dick N3HKN
RE: Digital Voice Over HF  
by G5FSD on October 29, 2003 Mail this to a friend!
>I wonder if the negative comment about "ECHOLINK" ...

It wasn't negative, you're too ready to take offence. I like VOIP (Echolink/eQSO/IRLP etc) and the way it breathes life into otherwise stagnant VHF and UHF, but FM quality on HF just doesn't seem right somehow, and to my mind smacks of Echolink. I hope you see my point.

Digital voice removes you from an awareness of what's going on in the spectrum you're using. If QRM pops up you'll have no idea what's happening other than the link failing, whereas on SSB you'd HEAR what's happening (and probably be able to mentally filter it out too, often). It's like putting up the shutters and ignoring the rest of the world apart from the one station you're talking to, and seems a bit antisocial. Also, what happens on shared/secondary bands if another user wants to tell you to QSY?

73.. and long live Echolink :o)
Digital Voice Over HF  
by KC8VWM on October 29, 2003 Mail this to a friend!

Great Article Brian!

This is what it must have been like for Amateurs when SSB was about to take over HF back in the good 'ol days of Amplitude Modulation.

Eventually SSB was accepted as the norm. I suspect that "digital" too, will soon be accepted.

I bet there is a cheaper version of this technology by linking your soundcard to your radio equipment to somehow process the digital signals.

I have seen similar "digital decoder" programs for PC's and soundcards that are intended for scanner & SWL listeners to decode digital signals.

Any ideas ?



Digital Voice Over HF  
by OBSERVER11 on October 29, 2003 Mail this to a friend!
what ever happened to that add on box from about 20 years ago??

Wasn't that supposed to give FM quality in SSB bandwidth too?
RE: Digital Voice Over HF  
by WB2EWB on October 29, 2003 Mail this to a friend!
I would like to see more work on HF digital voice before spending big $$... Any protocol used by amateurs should be open, published and unrestricted by licensing fees allowing enhancements, PC based implementations and market driven cost pressure. There is alot of technology available at low cost for us to innovate with: lets get inventing!
Digital Voice Over HF  
by WB8ROL on October 29, 2003 Mail this to a friend!
Sounds really exciting! Don't think I can afford to buy into it right now because of finances BUT I sure would if I had the extra bucks. I'm sure most currently active hams will NOT buy into it -- at least not right away. Many will adopt a prudent "wait and see" attitude, while others may not have the money, and a large number will reject it because it doesn't fit their image of Ham Radio.

After all ..... there are many who still operate on AM and haven't accepted SSB yet ..... and the "If it don't have a CW key hooked to it - I won't use it" crowd ... well they think a technology breakthrough means a better straight key.

Exciting stuff, though. The real question, to me, is whether it will really improve the state of communication art. If it does at least as good as SSB (eventually) and provides readily available standardized digital data transfer capability ... then that is something worth having. If it actually does better than SSB, as far as getting voice transmissions through more reliably, then it really will be a keeper. However, despite new compression algorithms and such, I am very skeptical that it will out perform SSB. Time will tell.

RE: Digital Voice Over HF  
by K0BG on October 29, 2003 Mail this to a friend!
I can only speak for myself, but paying $500 (more if you get the video option) for a device which is admittedly buggy and attaching it to my $1,300 transceiver just doesn't make sense to me. The only question I might have is; what do the folks at the FCC think about its use?

Alan, KBG
RE: Digital Voice Over HF  
by K3UD on October 29, 2003 Mail this to a friend!
Maybe it is the cutting edge.

The initial resistance will revolve around the high cost, limited installed base, and the need to replace your power supply if you are using a switching unit. Anyone remember when the cutting edge for voice communications on HF was considered to be Narrow Band FM? Again the problems were cost, special adapters, and lack of installed base.

What needs to happen is for Ten Tec, Yaesu, Kenwood, and Icom include this as a standard feature on their high end rigs to begin with. Of course, a look back at NBFM will show that the major receiver manufacturers also included NBFM as a standard feature until it was obvious that the mode did not gain wide acceptance among the ham community.

There are always a certain percentage of hams who will purchase the latest high end offerings for these companies and will certainly try out the DV over HF feature. As with almost anything else, the acceptance will come from the top down rather than from the bottom up.

Digital Voice Over HF  
by KD7KGX on October 29, 2003 Mail this to a friend!
Interesting application of technology. Evidently this modem is using 36 PSK carriers to transfer information... like running numerous PSK31 signals simultaneously to get the throughput up. It would be VERY interesting to watch a digital QSO on a waterfall display. It should also be possible for someone to write a soundcard app that could replace this modem.

If it is using PSK, then it should be subject to the same limitations that occur with PSK31... adversely affected by phase shifting. This means that DX across the poles would be a problem, and also that multiple ionospheric 'bounces' might cause problems. In other words, any situation where PSK31 degrades would also be a situation where this system might not work. I hope this is NOT true.

It should be fine for regional communications, but then regular SSB works fine for that too. The only advantage would be better audio quality (repeater-like?). The question for us hams is: is the advantage offered by this unit compelling enough to get a bunch of us to part with $550? If the unit provides good copy when SSB degrades, then the answer is a definite YES. If the only advantage is clearer copy under good conditions, while copy suffers compared to analog SSB under bad conditions, then I don't think it will do well. Only time will tell.

I think the cost is justified because I'm sure a lot of time and effort and money went into this thing... probably 4 to 5 man-years or a couple hundred thousand dollars of R & D... and AOR needs to recoup their investment. Figure their gross profit is a couple hundred dollars... so they'll need to sell a thousand or so units to break even on their investment. Evidently they have a similar unit with encryption for commercial use, and that should sell pretty well especially for the L/E and military market.

I think AOR deserves kudos for 'going out on a limb' here and trying something that is pretty daring. I hope their encoding method is robust enough to work well under adverse conditions. And I think that it will sell ONLY if it works BETTER than SSB, i.e., conditions where SSB is not copyable become S-5 copy when this unit is switched in.

Good luck, AOR!
RE: Digital Voice Over HF  
by AB2KT on October 29, 2003 Mail this to a friend!
Don't bet on HF digital voice taking over anytime soon. As has been remarked, HF is a very variable and digital-unfriendly medium. Unlike analog voice, digital voice degrades fast and badly as the SNR goes down or QRM goes up. And it's sluggish by comparison too, just as the digital text modes are by comparison with even semi-QSK CW.

However digital voice might be a suitable vehicle for hi-fi audio enthusiasts, since when conditions are right it does offer bandwidth advantages over single wideband. But a DX or contesting animal it ain't, and won't be, because what you're up against is information theory, not technological innovation. There's no clever end-run around Shannon's Theorem.

It's not a coincidence that the deepest RF penetration of digital voice has been at VHF/UHF where link quality can be fairly well guaranteed, either by proximity, line-of-sight, or systems of repeaters.
RE: Digital Voice Over HF  
by WB2WIK on October 29, 2003 Mail this to a friend!
Nice writeup.

For the time being, I'd rather spend the $550 on antenna improvements that I know for certain will net me more, longer contacts regardless of what the other station is using.

However, it's good to see technology advancing and hopefully this will pave the way to lower-cost and widely implemented use.

Digital Voice Over HF  
by W3DCG on October 29, 2003 Mail this to a friend!
FM quality over the low bands?
Bring it on.
It is not standard or inexpensive for now, I hope it becomes just another selectable mode on a transceiver, STANDARD.

Especially, if it will support FM quality CW on the low bands!

Then again, imagine all the audiophiles out there who have spent loads on audio processing and super microphones, equalizers, mixers...

FM quality over HF, at reduced bandwidth?
Maybe it will become widespread in time for me to retire in 25 years! I hope sooner.
Digital Voice Over HF  
by KE4ZHN on October 29, 2003 Mail this to a friend!
I find this technology very interesting. It has its bugs, which Im sure in due time will be ironed out. The concept of noise free, ultra quiet HF radio is intriguing, but it will lack the "personality" of analog HF radio. I think its tough to justify spending $500 on that little box of parts though, especially given the cost of modern rigs. Id be willing to bet that the folks at the big 3 will be incorporating this technology into the radios soon. If I had to make a prediction, Id say Icom will be the first to come out with one that has this all built into one box within the next couple of years. Probably cost will be an issue though, how many hams are willing and able to invest thousands of dollars in just one rig? Looking at this from another angle, this device would make it legal to use phone in the subbands. It transmits a digital signal, so its a data transmission, not actually phone, but it carries voice information. So, in theory, you can legally work a sced with your bud right in the middle of a subband with these things and be perfectly legal, and enjoy nice quality digital audio at the same time. The only downside I see with this is, as a digital mode, its vulnerable to noise as the author stated so you would have to have an alternate analog place to meet in case the digital link failed. Very cool technology though!
RE: Digital Voice Over HF  
by AB0ZE on October 29, 2003 Mail this to a friend!
K0BG sez:

>I can only speak for myself, but paying $500 (more if
>you get the video option) for a device which is
>admittedly buggy and attaching it to my $1,300
>transceiver just doesn't make sense to me. The only
>question I might have is; what do the folks at the FCC
>think about its use?

I am in total agreement with you on the bugginess, but as for the FCC's opinion, Part 97 currently states that any digital mode is OK as long as it complies with bandwidth requirements and is a published specification.

I don't have my copy of Part 97 with me (it's in the car right now, and I'm too lazy to run out and get it), but to the best of my recollection, that's what the requirements are for digital modes from my recent read-through of 97 for my Extra exam. The FCC made that mod to the regs because of the proliferation of digital modes.

Now, my question is this: Is this a proprietary protocol on the part of the manufacturer? 'Cause if it is, then they probably wouldn't publish it & it wouldn't be legal. But if it's just a piece of dedicated compression hardware that runs an algorithm like MP3 or one of the freely-available algorithms that's even better, there shouldn't be a problem.

Finally, one last question...with the accuracy needed to transmit compressed data of any type, wouldn't you need either an exceptionally low level of QRM/QRN or a totally gonzo error correction protocol?

Enquiring minds want to know!
RE: Digital Voice Over HF  
by AB0ZE on October 29, 2003 Mail this to a friend!
A quick PS to my previous comment... If you want to check out the specs for this item, here's a link to a spec sheet:
Digital Voice Over HF  
by KD6NXI on October 29, 2003 Mail this to a friend!
Great now we can add the din of noise this will create to the 1000s of other barking dogs also known as contesters... Does anyone realize how much shril noise is going to eminate from the HF bands when this starts up???
RE: Digital Voice Over HF  
by KD6NXI on October 29, 2003 Mail this to a friend!
Buddy just because it's digital doesn't somehow mean you now miraculously can get away with ultra low power and a sub standard antenna. It's just a different mode and like the advent of digital cellphones doesn't work when conditions are bad. Analog phones kept on trucking but digi's just disconnect completely at the slightest hiccup,, it's the same with this thing.
Digital Voice Over HF  
by K7LZR on October 29, 2003 Mail this to a friend!
I think that I'll wait until it (hopefully) appears as another mode on transceivers. I'm with that G5 fellow who said that he LIKES to hear band noise, etc. - He's right - that is part of the magic and it can have a cozy sound to it. Regarding high end audio, I am lately hearing some SSB stations which sound really good despite their bandwidth limitations. Unless this technology offers some significant improvements over traditional SSB other than snazzy audio and noise reduction, I don't really need it yet.
RE: Digital Voice Over HF  
by WT0A on October 29, 2003 Mail this to a friend!
I was going to comment but G5FSD and N3HKN pretty much mirrored my thoughts. K0BG and AB0ZE also brought up good point regarding encryption. I don't recall if this was in ARRLs last list of accepted "published" specifications.
RE: Digital Voice Over HF  
by W9WHE on October 29, 2003 Mail this to a friend!

The whole world has gone digital, except for hams.

As a group that once led the way in communications, we hams have fell far behind the average teenager with a digital phone. All I can say is, its about time!
Digital Voice Over HF  
by K0RGR on October 29, 2003 Mail this to a friend!
I read the details on their web site, and it sounds very exciting.

The unit does use a published protocol, so hopefully, we will see some competing units appear, and the price will drop. If it works as well as advertised, I think it will eventually become a big part of ham radio - increasing our immunity to RFI and reducing our RFI impact on other devices.

FM-quality voice in a mode with a power advantage over SSB is very attractive. With some changes in the rules, we might have another shot at creating a reliable, medium-speed digital network on HF, with built in voice and picture capabilities! If we are confronted with BPL problems, we may find that 1500 W of this digital mode gets through very nicely.

Hopefully, AOR will work to encourage other manufacturers to provide compatible gear by licensing any proprietary technology they may have developed. So far, the dealer price cuts AOR expected have not happened.
Digital Voice Over HF  
by N8PPZ on October 29, 2003 Mail this to a friend!
While I don't see myself buying this device in the near future, I think it's great.

SSB, CW have their place, just as digital voice has it's place. As more and more people experiement with it, more manufacturers will take interest and bring products to the market.

Much in the way they did with packet radio. Many older radio had to be modified for packet operation, now many newer radios include packet modems built in or easily connectable.

Yaesu jumped on the internet linking bandwagon, and Alinco has a APCO 25 radio out.

Once they work out the bugs, and inneroperability I think it will be a great thing to have.

However I think of how crappy my digital cell phone is, and any flucuation of signal causes packet loss. I think packet loss on HF will be major problem due to propogation.

I think Digital voice may be more well suited for VHF/UHF operation. Or for local groundwave communication on HF instead of skywave propogation.

Just a thought.
RE: Digital Voice Over HF  
by NA6Z on October 29, 2003 Mail this to a friend!
Another amateur and I had the opportunity to play with the AOR modem at the ARRL Southwest Convention. The audio improvement was, in a word, stunning! We were impressed enough to ask AOR to demo their equipment at our next club meeting.

Like many of the other commenters, I'm not ready to be an early adopter. The price would need to come down quite a bit and market penetration would need to go up quite a bit. But it is a big step in the right direction.

No, I'm not associated in any way with AOR.
Digital Voice Over HF  
by WA0ZZG on October 29, 2003 Mail this to a friend!
Thanks for the report on this new product. QPSK
modems, with some form of CODEC have been around
for a while. I use something like this, at work,
to put a T-1 data carrier on to an analog point-
to-point microwave system. The price for this
class of equipment has always been high. $500 each
isn't bad compared to the $10,000 my employer pays.
I suspect if you were to look at your transmitter
output on a spectrum analyzer, it would look like
a rectangle. I only have three quextions:
1. The filter ripple in some amateur transmitters
isn't that good. Will this degrade the carrier?
2. How close can the top of the rectangle get to
the noise floor before one begins to hear pops
in the audio?
3. Any way to be able to delay, or repeat the
sending of the sync tones?
BTW...go read an old QST at about the time
SSB was first introduced. Looks like history repeats
All the white noise you hear may not all be
RE: Digital Voice Over HF  
by AA4PB on October 29, 2003 Mail this to a friend!
A primary driver of digital voice's success will be whether the protocol is documented, open source or not. If the various companies each develop their own proprietary protocol so that, for example, AOR units only talk to other AOR units then digital voice will fail for general amateur radio use.
Digital Voice Over HF  
by NH2CW on October 29, 2003 Mail this to a friend!
I work with an international broadcaster looking at digital HF using the DRM system (no, not Digital Rights Management). It's Digital Radio Mondiale ( There are currently many HF broadcasters in Europe using digital with a few others scattered elsewhere. As always with digital, the results are breathtaking when it works and dismal when it doesn't. The good news is that it works more and more as it is being used and perfected. The same could have been said with any new mode in its infancy. We of the older set can easily remember CW transmitters that sounded like chiping birds and yooping aliens. You rarely hear that nowadays. I congratulate those hams who have to have the newest toy. They are paving the way for others to follow when the technique improves and the prices come down.

The big issue with international broadcasters going with DRM is the fact that only a few thousand DRM-capable receivers exist on the planet, none particularly small and portable unless you like carrying a computer around. Right now the cheapest solution is to have a receiver with a 12 kHz IF output and to use it to drive a soundcard. The software does the heavy lifting. Perhaps we'll see the same thing done with ham HF digital voice. For broadcasters to use this technology, small and inexpensive receivers must be made available. A number of broadcasters are betting this will happen. They figure that no one will want a receiver if there are no signals to listen to. So they are broadcasting largely to the wind for now.

Another big issue, and the one where this modem interests me, is the great cost to a broadcaster going DRM. To conceive of a usable HF modem that "only" costs 500 bucks is amazing to me. For a broadcaster to do this will cost six figures, assuming his transmitter won't have to be replaced.

This particular modem may or may not be the box that takes ham radio into a digital future. But you can be sure that it represents a coming trend. I enjoy CW, SSB, FM, PSK31, and I grew up under some of the best AM practitioners in ham radio, like the late W3FDY. It's not a zero-sum game, gentlemen. Let's use ALL the modes, and more as they come out, to make ham radio vibrant and new as time unfolds.

RE: Digital Voice Over HF  
by K5TED on October 29, 2003 Mail this to a friend!
Time for some entrepreneurial programmer to develop a piece of software to do this work, rather than rely on a hardware device. That would allow much beta testing and tweaking. The cat is out of the bag.

Considering the review points, I'd say it's not ready for primetime. price:functionality ratio is off.
RE: Digital Voice Over HF  
by NI0C on October 29, 2003 Mail this to a friend!
In some of the responses to this article, I've seen comments like "reduced bandwidth," and "phone in the sub-bands." You don't get something for nothing. According to the specs for this device, it uses 36 tones separated by 62.5 Hz in the audio band of 300 Hz to 2500 Hz. That means it will occupy approximately the same bandwidth as an SSB signal. As such, it is unlike the very narrow RTTY, PSK, and CW modes, and would certainly not be allowed in the CW and digital portions of the bands.

RE: Digital Voice Over HF  
by AA4PB on October 29, 2003 Mail this to a friend!
Pactor III uses approx the same bandwidth as a SSB signal and it operates in the data sub-bands. Digial voice is one more example showing why the FCC rules need to be changed to assign sub-bands by occupied bandwidth rather than content. Is digital-voice data (belonging in the data sub-bands) or voice (belonging in the voice sub-bands)? How about if I record a WAV file and transmit it via Pactor - is it data or voice? How about a GIF file - is it data or image?

Digital Voice Over HF  
by AB0TA on October 29, 2003 Mail this to a friend!
Neat-ohh . Unfortunately I don't think digital voice will ever be embraced as well as SSB for the simple reason that it doesn't work in pileups . Can you hear more than one transmission at a time ????

Digital Voice Over HF  
by IS0IEK on October 29, 2003 Mail this to a friend!
I know not much about digital voice ; other things apart, will it improve S/N limits on HF, that is lower LUFs and power requirements ? Needs it particular frequency stability and/or precision, in other words needs only PLL / DDS to work, or a classic VFO may fit ?
About costs ... wasnt the same for SSB gear in the early 60s, when SSB came up ?
Best 73s de Emilio Is0iek
RE: Digital Voice Over HF  
by AE6IP on October 29, 2003 Mail this to a friend!
Hmm... According to AOR, their device uses an AMBE 2020 chip, and relies on the AMBE proprietary format. Apparently, to talk to this system, you have to either use the AMBE 2020, or license the technology.

Digital Voice Over HF  
by WA8VBX on October 29, 2003 Mail this to a friend!
Sounds interesting but probably a few years off yet to be within the average ham's budget, and maybe by then the bugs will be worked out. Will it help with the QRM, that is to be seen.
How many remember Spread Spectrum Radio that came out in the 70's (I think it was a Tempo), that the ARRL was pushing to help relieve some of the QRM.

For the guy who talked about the APCO 25, it is not 100% reliable, and still has bugs in it, I know I work with it 8hrs a day/5 days a week a least, for the last 3 yrs.


Digital Voice Over HF  
by AI4CG on October 29, 2003 Mail this to a friend!
In the FAQ for the AR9800 it does say that this modem doesn't infringe on FCC limitation because it uses an open and publicly available protocol for digital voice transmission, namely G4GUO's. Looking up G4GUO's on Google, I found this interesting page:
where G4GUO explains how this modem works; it looks like the last time he worked on it was about 4 years ago on 10/29/99, and the AOR picked up from there on 9/4/03. Since his modem only uses 16ms tones in the range 312.5-2500Hz (as per, I think it should be relatively easy to use a standard soundcard to encode/decode his protocol, and I may work on it. On the other hand, if some protocol for digital voice on H.F. should be adopted some time in the future, why not have a look at all the options out there (G4GUO's, MP3, Ogg Vorbis, or others) and make a well thought decision based on technical advantages of each approach and then build some sound card software to encode/decode it.
I was also wondering this: if a 'FM-like' 15kHz bandwith voice signal can be compressed down to about 2.5kHz, it means that a regular SSB signal at 2.5kHz must have some redundancy; well, could it be possible to somehow 'use' that redundancy to send/receive the bandwidth between 2.5kHz and 15kHz? In other words, could we think of a 'pseudo-digital' mode that when listened through a regular radio would sound like and old regular SSB signal, but has some 'components' that a special digital radio (or a radio + soundcard) would detect and allow to restore the higher frequencies to have a 'FM-like' signal? This would be a better approach, I think, because it would allow some sort of continuity with old modes/old equipment, similar to what happened when color TV was introduced and it had to be somehow compatible with the old B/W TV sets (I don't think this applies to the new digital TV though).
Just my 2 cents.
73, Franco Venturi, AI4CG
RE: Digital Voice Over HF  
by N3HKN on October 29, 2003 Mail this to a friend!
Just another "two cents" - I believe that the best way to market this is not the compressed digital voice. That really carries little value for the average Ham. It is the variety of digital pieces of info that can be sent concurrently with the voice transmission. As I said before APRS(GPS), QTH, small digital picture, wx, etc. are easily sent during pauses from the speaker. A cute thing to do would be to display your position on the receiving person's PC screen while you are HF mobile. The "Hams" who seek various artifical awards for talking to people in a vehicle that is stradling a county line would love it.

This is not a new basic mode, as was PSK, but another improvement for SSB voice. It may be more pleasent to listen to than SSB BUT when the signal drops below the decoding threshold it just disappears (cell phones). Today, your "SSB ear" can usually dig into the noise and still make some sense of what you hear. Digital is not that good - yet.

Dick N3HKN
Digital Voice Over HF  
by K0RGR on October 29, 2003 Mail this to a friend!
Here's an interesting URL with much more information:

It looks like the AMBE2020 is the same chip being used by Alinco, and the researchers mentioned in this article. The AOR unit is supposed to be compatible with the G4GUO published protocol, and it sounds like they are cooperating with others to make the technology more available. When TAPR comes out with a kit for $200, I'll be ready to try it.
RE: Digital Voice Over HF  
by KC6F on October 29, 2003 Mail this to a friend!
Compression technology has limits for HF voice. The better the compression, the greater the non-causal aspects of the system--usually. Thus, better compression usually requires more "old information" which is used to represent future information. Therefore, if their are frequent errors (as with the harsh conditions of HF), the decoder will have a dificult time accurately decoding the signal.
Digital Voice Over HF  
by W9JCM on October 30, 2003 Mail this to a friend!
Did you see the Price OUCH!! I think I will wait there is always something that comes out later down the line more refined and better priced.
RE: Digital Voice Over HF  
by W9JCM on October 30, 2003 Mail this to a friend!
" You don't get something for nothing. According to the specs for this device, it uses 36 tones separated by 62.5 Hz in the audio band of 300 Hz to 2500 Hz

Thats not that great audio...So what if it mutes out the static. A Hi FI signal is much fuller even in a 3K bandwidth.. try under 100Hz and right to the wall at 3K. Much better sound.
Digital Voice Over HF  
by W9LBB on October 30, 2003 Mail this to a friend!
All I wanna know is, what is this fancy little box gonna do when it winds up sharing a hunk of spectrum with a big, fat AM signal?

If DRM experience is any indication, that "FM - like" audio is going to squelch into dead silence.

RE: Digital Voice Over HF  
by KE2IV on October 30, 2003 Mail this to a friend!
Nice thread.

Congrats to AOR for "kicking off" the game.

But no one has asked. Will digital voice HF "work" in a BPL environment?

I dunno.

Anyone out there have some useful info whether hams going digital voice will "overcome" likely BPL interference?


P.S. I don't think so....RF is RF....
RE: Digital Voice Over HF  
by KE6I on October 30, 2003 Mail this to a friend!
Maybe we'll need to go to some kind of Spread Spectrum HF system -- where the signal covers the entire band, after BPL wipes out traditional ham radio.
RE: Digital Voice Over HF  
by N3EVL on October 30, 2003 Mail this to a friend!
W9JCM said:

"...Thats not that great audio...So what if it mutes out the static. A Hi FI signal is much fuller even in a 3K bandwidth.. try under 100Hz and right to the wall at 3K. Much better sound..."

Errrr, actually, that's not any kind of 'audio' - that's data - which in this case happens to be a highly compressed digitized audio signal, but could be anything so I don't understand your comment regarding the tones and SSB HiFi???

Pete, N3EVL

RE: Digital Voice Over HF  
by W3JXP on October 30, 2003 Mail this to a friend!
From my point of view, digital audio brings very little to the table. The main points for it is FM like audio and little or no noise. To me that is not much. When SSB was first brought to ham radio, it had several things going for it. It took up less room.It made more efficient of transmitter power than AM does. It changed the way many Hams operated, with the fast back and forth replaceing AM monologs. I can't see digital audio changing Ham radio all that much. My guess it will fill a need for those who don't want to work DX or contests or join nets and like "high quality" audio. This not all a bad thing and I think it will find a spot in ham radio, like slow scan TV does now.

John W3JXP
State College, Pa
Digital Voice Over HF  
by AG4CI on October 30, 2003 Mail this to a friend!
I don't see it going as far as predicted. Prime case
digital AM broadcasting AM broadcasting in stereo.
The pushers behind it talk a good game but always
seem to fade away when they can't producee what they've been clamoring. Look back in communications
history for similar things that came on the scene.
RE: Digital Voice Over HF  
by KC8VWM on October 30, 2003 Mail this to a friend!

>>>>According to AOR, their device uses an AMBE 2020 chip, and relies on the AMBE proprietary format. Apparently, to talk to this system, you have to either use the AMBE 2020, or license the technology. <<<<<

Sounds a lot like Microsoft when users were "forced" to use "their" brand of web browser.

Digital Voice Over HF  
by K6TLA on October 30, 2003 Mail this to a friend!
Interesting product but way too expensive. Surely there will be authors who will implement this or something similiar in software with a pc/soundcard and likely existing computer/radio interfaces used to couple the two. As DRM has done commercially in as much bandwidth as an AM channel it would be nice to see amateur digital voice modes come in several flavors including an FM like high quality mode.
RE: Digital Voice Over HF  
by K6TLA on October 30, 2003 Mail this to a friend!
One further comment. We've recently been playing around with COFDM digital television transmission versus analog fm transmission in a 2 ghz microwave channel. With weak signals as analog becomes noisy and unusable the digital signal remains completely usable and noise free over a range of 4 or 5 db. When one hits the cliff it is the end of the story. During HF radio fades there will be alot of falling off the cliff. Performance with QRM and QRN might just be quite surprisingly good with HF digital voice. Our experience with digital television in conditions of less than optimal signals, many reflections etc. has shown excellent performance under conditions where an analog signal is completely unusable.

K6TLA KTLA-TV Hollywood
RE: Digital Voice Over HF  
by AB2KT on October 30, 2003 Mail this to a friend!
One question to ask is, what's the symbol rate of the signal vs. the channel capacity of the link? In other words, how much data are you trying to pass through how big a pipe?

If you're trying to pass a small stream of data through a big fat pipe, you leave yourself a lot of room to correct errors. That's what many digital encoding schemes do: protect themselves against degraded channel conditions by including heavy error correction, which means, basically, sending data redundantly. So it's not surprising there are many situations where digital channels outperform analog channels. But HF digital voice as currently constituted isn't exactly one of those situations.

In the case of HF digital voice, you're grinding the necessary symbol rate (how much data you need to send) up against the channel capacity (how big the pipe is) and as a result there isn't much room left for error correction. As long as there are fairly tight bandwidth constraints on HF digital voice signals, with the resulting small budget for error correction, the digital voice signals are going to be playing dangerously close to the edge of usability.

That's one reason spread spectrum would be so desirable. It would allow higher single channel capacities while minimizing the impact on the entire set of channels competing for the same frequencies. But amateur HF equipment and practice would have to change a lot in order to capitalize on these advantages.
RE: Digital Voice Over HF  
by N3EVL on October 30, 2003 Mail this to a friend!
AB2KT - Some of the information you were asking about is presented in the specs either on the AOR web site given in the article or on the documents ref'd there. The nominal symbol rate is 20mS (50 baud) and FEC is used.

73, Pete, N3EVL
RE: Digital Voice Over HF  
by VE7RF on October 30, 2003 Mail this to a friend!
DRM may not be all that's it's cracked up to be. go to 'guy', and read all the drivel. Seems that DRM may or may not be broadcast simultaneously with regular AM.

There is a 2nd digital method that may well be used for AM broadcasting in the 550-1700khz range, that WILL handle both digital format, AND the reg AM format.(broadcast at the same time).

The problem with this AOR unit is the software is allready obsolete. If I remember correctly, it was 1st developed by a young fellow in the UK (amateur/engineer). AOR ran with it. The fellow in the UK has since made vast improvements to it.

Selective fading, phase shift, group delay, etc, can screw up these new modes real fast.

I too like the sound and feel of real ssb, complete with background noise, and zero dynamic range in the recovered audio. Heck, since all my rack gear is dual channel, I use all the right channels on TX, and all the left channels on RX. I feed the resulting enhanced RX audio into a 100w per channel amp, then into a pair of speakers on upper shelf, towed in a bit... images right in front of my face.

You would be amazed at what you can do with audio rack gear on RX. EG: like these weak buried in the muck ssb sigs.... just a little bit of carefull eq, and they pop right outa the noise... amazing.

The downward expander (similar but different than a noise gate) works superb on RX. Everybody stops talking on ssb, and the downward expander takes over, and hiss just fades away to any level you desire. Blows away any of these ssb squelch systems hands down.

I DON'T like the 100% duty cycle requirement for this AOR unit. (100% duty cycle on your xcvr + linear). Double the average power on a ssb rig, and tank coil heat goes up by 4 x etc.

S meters are peak reading devices. Mo pwr is mo betta.

Somebody please explain to me if SEVERAL stations equipped with this AOR unit, can all sit in a round table taking turns in rapid fire sequence, running VOX ????. It appears that you gotta 'key the rig' 1st, establish a protocol with another station, then start talking ??

Sounds too much like IRLP/echo link/2M-FM to me.

I like the sound of my 'enhanced ssb' sig with my much modified FT-1000D and mountains of rack gear. I can rapidly switch it to contest/dx mode if needed.

Stock ssb audio sounds lousy cuz it simply needs some help. Mine runs 50hz - 3050 hz... sounds like a FM broadcast station, and doesn't burn up the amp like FM/RTTY/Digital voice.

All these digital modes have come and gone like amtor-sitor- pactor-pactor2 HF packet, etc. All hell breaks loose when there is a big RTTY contest on...RTTY is still around.

IMO, you would be better off to spend the money on more tower sections, LMR-1200, YC-256's, Dahl plate xfmr's, 4CX-10,000's, sockets etc.
RE: Digital Voice Over HF  
by VE7RF on October 30, 2003 Mail this to a friend!
Stereo broadcasting in AM bombed.

My new Stereo FM tuner has this 'RDS' mode, that displays station ID, name of show etc. Outa 45 FM stations on the dial (totally full from 88-108), only 3 use it. RDS bombed too.

Broadcasters TX and DON'T RX. They don't have T/R relays, qsk, work dx contests etc... so it's apples and oranges.

I'm sure DRM for international SW broadcast use will run just fine.... esp since they all got 50-500kw and 21-dbi curtain arrays to start with.

Who the hell am I gonna talk to on 75m, at midnight on a wed, with this AOR unit ??

Will it work on 75M during the summertime static crashes ???
RE: Digital Voice Over HF  
by W5HTW on October 30, 2003 Mail this to a friend!
I can see that the need for "armchair copy" throughout ham radio could make this indeed the apple of the future.

I wonder about adjacent channel rejection, for one thing. Could this mean we could no longer tolerate signals close to our own? Would we be able to adjust the passband to one side or the other in order to reject a signal on the skirt of the filter, and still maintain solid copy on the digital signal of choice? Would we need better channel spacing and regulation? In fact, would we NEED channels? With sideband we can tolerate a significant amount of interference within the passband and still communicate. Will digital radio have the same capability?

Can it tolerate selective fade? QSB? Some of the comments I'm reading here suggest it cannot. That, like FM, it will suddenly drop out at certain thresholds, an "either all or nothing" type of signal.

In discussions of digital radio, we are almost always (as already noted by others) talking about one-way transmission, not two-way contacts. I wonder how different the technical and operating requirements will be to make it work in a two-way setting. Obviously it can be done, or this device would not be now on the market. But how well can it be done?

Would one be able to instantly switch to normal SSB, to regain control of the contact in progress? And if so, that would limit this to standard amateur voice bands, not the digital bands.

I think a lot of people will also greet this with narrowed eyes for another reason, and some of that has already been voiced here; it takes away the asthetics of having to copy through difficult conditions. "The challenge of ham radio." It may not "sound like" ham radio, but more like the phone or VoiP.

As an old dinosaur myself, I'm not sure that particularly bothers me personally, for two reasons. One, I'm probably going to get out of the hobby in the next year or two anyway and find something less frustrating, (am considering it now, if I could unload the radio equipment without too much of a beating!) and, two, I doubt digital radio would be the "only" mode available on the bands for quite some time.

Also, the price factor has been mentioned. Actually I don't see that as much of a block, if we look back in the history of the hobby. There have always been hams with the bucks to buy the latest, from the best sideband equipment in the 50s and 60s to the TNCs of the 70s and 80s, the multi-kilobuck HF rigs on the market today.

I think the questions are, at least for now, who are you going to talk to, and how well are you going to talk under current band conditions? How will you find, on the air, others using this or a similar device?

Certainly I will never have such a device, but I'll be watching as others acquire them. I suspect it IS the future.

Digital Voice Over HF  
by W4LGH on October 30, 2003 Mail this to a friend!
You know, its really amazing to read thru the comments about this new mode. Why HAMS are so slow to make any changes is way beyond me. But as in the past, nothing has changed. They (HAMS) always wanna bitch about losing band space, say we need to do something to keep from losing what we have, but then something really new and exciting comes out, something that just might intrigue someone new to get into the hobby (hence mose useage) then they go back into "bitching" mode about how BAD it is. Ham radio is like everything else in life, its all relative. Everything has to grow and change to survive. Digital mode HF is just another one of these growing spurts, and with growing spurts, comes growing pains.

I think its a great idea and should spur some new activity on HF. I aso think it will add some additional fun into playing radio. I personally can't wait to get started in it, but will have to sit back awhile and wait for prices to come down, and useage to go up.

Think about it as just another MODE to play and experiment with... Just like CW in the begining, AM Phone, SSB, FM, RTTY, etc. Open your eyes and minds and accept it. You don't have to play with it, just accept it.

I say, HATs off to AOR, and others for working the kinks out and giving us another way to enjoy our life long hobby.

Alan Jones -W4LGH
_._ _.
RE: Digital Voice Over HF  
by N8MMZ on October 31, 2003 Mail this to a friend!
What an excellent opportunity for hams to once again become relevant as the tinkerers and pioneers in the RF field on the HF bands (as we once were with the birth of SSB and FM). It sure would be a nice change as we explore and push to the limits new modes of operation - we can then make our findings known and pass on our insight to the next generation! We can also have another reason to legitimize our vast spectrum holdings on HF (we need all the help we can get on that)!!

What a far cry from talking about our last brush with the proctologist on ancient, analog SSB!!! We have the opportunity to work all of the bugs out of new digital voice modes, utilizing whatever published CODEC parameters that we can imagine. Once we have perfected that, then we can slip back into RF obscurity and resume delightful QSO's about our hemorrhoids on the digital HF bands!

I would love to help out in such an endeavor, but I'm too intimidated by those new fangled gadgets!! Now back to winding my coils for my spark gap transmitter - I'm going to be up all night caluculating the number of turns on my Versalog slide-rule!

(Actually, I've got plenty of DSP homework to do and a nice copy of MATLAB loaded with the DSP toolkit to do it for me - what a far cry from my analog days when I was in undergrad many moons ago)



P.S. ---> AM stereo was pretty cool! It just wasn't commercially viable -- It came along in the consumer market just as many AM music stations were folding up. AM stations started to pick back up in popularity with talk radio, news radio, and sports radio - who needs stereo for straight voice?? I also seem to recall a couple of different modes competing for the stereo market (a market which wasn't there for the above reasons). I did manage to catch some good AM country off of 540 KNOE in Monroe, LA in my 1990 Dodge Spirit - that was the only car I'd ever owned with a stock AM stereo. So there are still a few holdouts for AM stereo.
Digital Voice Over HF  
by ON4MGY on October 31, 2003 Mail this to a friend!
Looks very expensive to me. At this price it won't be used a lot I think. It might be a good evolution, but how about working "real" DX? I think a lot of stations in Asia, Africa and South-America, as well as a lot of ham's in Oceania, North-America and Europe, won't have the possibility to buy such a modem, so they won't use is. Too bad we can't work them.
Of course, this is just the first modem and some others will follow, so the price will eventually drop (I hope).
I think we should to see what's the evolution in digital voice, but no-one can stop evolution. When SSB was introduced lots of ham's were convinced AM would last forever and SSB was going to disappear fast. Who's working AM these day's?

73 de ON4MGY Nic
RE: Digital Voice Over HF  
by KC8VWM on October 31, 2003 Mail this to a friend!

Since we are on the topic you might try a few of these programs for digital communications using only a soundcard interface: (No I am not affiliated with them in any way)


Program for amateur radio digital communications via a sound card. Supported modes are RTTY (Baudot code), ASCII (7 or 8 bits), PSK31 (BPSK and QPSK) and AMTOR-FEC (SITOR-B, NAVTEX). SELFEC SITOR decoding is possible also. No additional hardware required, need only a sound card. Optionally you can use simple circuit fo PTT-control. Can cooperate with RZ4AG AAlog logger.

For the "Non Hams" that frequent this forum:


Easy to use Audio Spectrum and PSK31 decoding program specially designed for SWL's who don't need TX or for anyone who just like to monitor PSK31 or analyse signals. Adjustable DSP and Spectrum settings for audio and frequency spectrum to set for best decoding of PSK31.


MFSK16 is likely to be the next "hot" mode. While not as easy to tune-in as PSK31 it is very robust mode and performs even better than PSK31 under weak or distorted conditions. If you have your rig and computer already interfaced for PSK31, you are all set. All you need is the free software called STREAM


MFSK 16 sounds quite different from PSK31, it's tones have a musical sound to them. The best place to listen for MFSK16 is around 14080 to 14082. The mode is increasing in use and many DX stations are now trying it. You will not, as yet, always find a signal whenever you tune in but if you leave you rig parked around 14080 for 30 minutes of so, you will usually hear a station or two.

The quick and dirty version of what MFSK16 is ....

From the MFSK16 web site at

Also, I found some very extensive technical information about HF Modems here:

CHECK THIS OUT! - Digital Voice on HF

This person is currently working on a project to transmit digital voice over an H.F radio link. Although he doesn't believe this will ever become a mainstream Amateur mode it is interesting to investigate.

Intersting Article (.pdf file)"Practical HF Digital Voice"

High-quality voice communication is possible
without exceeding SSB bandwidth or
expensive broadcast studio equipment.


Charles - KC8VWM

Digital Voice Over HF  
by KG4RUL on November 1, 2003 Mail this to a friend!
W4LGH writes:

You know, its really amazing to read thru the comments about this new mode. Why HAMS are so slow to make any changes is way beyond me. But as in the past, nothing has changed.


I think this is a case where COST is the biggest stumbling block. Currently it takes an $1100.00 investment for two Hams to even try this mode. WAY to rich for my blood!

This is like the predictions that people would be so rabid for HDTV that there would be a shortage of sets. Have you ever seen people lined up around the block to buy $5,000.00 TV sets that they don't really want?

To blatantly parody a certain Baseball related movie: 'Make it affordable and they will come.'

Dennis - KG4RUL
Digital Voice Over HF  
by VA3DRL on November 1, 2003 Mail this to a friend!
all new ideas are interesting.
maybe it will provide a noise-free high quality method of sending dits and dats.

i have just signed up and am checking out this rolling messaging service to see what happens.

don, VA3DRL
Digital Voice Over HF  
by N5PVL on November 2, 2003 Mail this to a friend!

I'm always glad to see an new digital mode, and would like to hear more about using the modem to exchange data, though I realize voice is its main purpose.

The problem with station A hearing station B but B can't hear A is familiar to any old hand at digital HF communications. I hope you don't seriously think that it is a problem with the modem, because it isn't.

I seriously doubt that this modem can be replicated with soundcard software. Experienced digital ops are aware that many of the more advanced HF protocols cannot be cloned for soundcard use, because the protocols demand more performance then a computers' soundcard can offer. That may very well be the case here, as well.

One thing I am wondering about is where this mode should be operated... The digital segment of the bandplan seems to be the most logical spot, since the signals are digital and cannot be copied as voice without the use a special modem.

If the makers of this equipment are under the impression that an invasion of digital signals throughout the voice segments of the bands will be tolerated, they may find themselves in for a very rude awakening.

On the other hand, PACKET, PACTOR, RTTY and PSK enthusiasts would probably welcome the limited number of hams who will be inclined to buy these digital voice modems.

I hope the manufacturer of this new equipment encourages proper operating practice with this equipment, transmitting its digital signals only within the digital segments of the band.

Charles Brabham, N5PVL
RE: Digital Voice Over HF  
by G3RZP on November 3, 2003 Mail this to a friend!
I'm disappointed the data sheet says nothing about the SINAD out v. the SNR in.

You can manage (just!) an SSB exchange ina contest at an SNR of 6dB, and a Signal to Interference of -3 or 4dB. What can this device manage?

It's no use going digital if it needs a better SNR or C/I than the analogue it supposedly replaces!


Peter G3RZP
RE: Digital Voice Over HF  
by G3RZP on November 3, 2003 Mail this to a friend!
I'm disappointed the data sheet says nothing about the SINAD out v. the SNR in.

You can manage (just!) an SSB exchange ina contest at an SNR of 6dB, and a Signal to Interference of -3 or 4dB. What can this device manage?

It's no use going digital if it needs a better SNR or C/I than the analogue it supposedly replaces!


Peter G3RZP
Digital Voice Over HF  
by KN4LF on November 3, 2003 Mail this to a friend!
I heard that the FCC is going to mandate digital HF on the ham bands within 5 years with $10,000 rigs. Even CW will have to be digital. It will be much like what the FCC is currently doing with digital TV.

Thomas Giella, KN4LF
Digital Voice Over HF  
by N5VFF on November 4, 2003 Mail this to a friend!
Check out:

For a current look at implementation of a similar system. It also uses the AMBE2020 chip.

Digital Voice Over HF  
by KG4RUL on November 5, 2003 Mail this to a friend!
In the late 1970's, I worked for System Development Corporation (SDC - now folded into UNISYS after being acquired by Burroughs Corp.) as a Contractor to the Naval Ocean Systems Center, San Diego (NOSC - now SPAWAR West).

One of the projects was a system for voice recognizable, digitized speech, in extremely small bandwidths.

One of the participants in this process was a mathematician who was extremely adept at simplyfing equations. He got the encoding simplified enough so as to be able to send recognizable speech at 300 Baud. We had even worked out a hardware system using nine microprocessors in a cascaded configuration.

Unfortunately, in the wonderful way that the Government works, the project was cancelled. Seems we were taking money needed by larger, more visible projects.

Dennis - KG4RUL
RE: Digital Voice Over HF  
by W5LZ on November 5, 2003 Mail this to a friend!
So what's new? Just digital encription, as in
'voice scrambler'.
RE: Digital Voice Over HF  
by DUKE_THE_KING on November 5, 2003 Mail this to a friend!
The new what could come up would be new methods of digital signal modulation, maybe combinations of PWM (pulse width modulation) & phase shifting.

RE: Digital Voice Over HF  
by AB8RU on November 7, 2003 Mail this to a friend!
Hmm ! this is veeeerrry interesting ! I kinda want to see what this will lead to B4 I would plunk down my hard earned money on something, I am a wait to see what happens person.
Digital Voice Over HF  
by N4ARI on November 7, 2003 Mail this to a friend!
This mode is amazing. I just used one of the AOR units. I didn't expect that much. Well, in "dead" band conditions, the data signal was inaudible, down in the hiss somewhere. My ears could not pull out a CW signal BUT the AOR did pull out the data 100%, no break up, no loss of info. I was shocked. My ears heard virtually nothing but the voice audio was beautiful. Amazing doesn't describe it. You have GOT to hear it in action. Don't embarass yourself by knocking it until you hear it for yourself.
Oh yes, this is THE next voice mode.
RE: Digital Voice Over HF  
by KC8VWM on November 8, 2003 Mail this to a friend!

>>>My ears could not pull out a CW signal BUT the AOR did pull out the data 100%, no break up, no loss of info. I was shocked.>>>>

Really? great to hear your experiences with the equipment. I would like to hear more people share their experiences in this forum like this.

Charles - KC8VWM
Digital Voice Over HF  
by IW3HQG on November 8, 2003 Mail this to a friend!
Interesting system... But I wonder why a simple computer could not use a digital protocol (G4GUO) to send the same modulation to the rig... So a simple software, a simple rig connection et-voil yhou have Digital over HF... Why not? it is an inexpensive way...

73 De IW3HQG
Digital Voice Over HF  
by KE0ZT on November 8, 2003 Mail this to a friend!
As a life-long ham experimenter, I do find this idea very interesting. As an engineer who has spent his career developing DSP techniques, I also wondered when this would be tried out at HF. However..... wouldn't this really take a lot of the fun out of making ham contacts if it became widespread?

As a hobbyist, I still get a thrill from tuning the knobs and using my skills to pull in that weak signal. It's a thrill to contact someone on the other side who is also using his skills to make the contact under adverse conditions. As my wife says, "wouldn't it be like just picking up a cell phone and talking to a stranger if the link were perfect?" Well, yes, it would -- at least it would for me. There is something special about making that difficult analog connection via traditional radio methods that makes the person on the other side an instant friend and comrade.

Also, someone else has brought up the point that if most ham radio transmissions were encoded (encrypted), there would be nothing but buzzes and weird noises on the air for those potential hams (SWLs and youngsters)to listen to on the shortwave sets they constructed from a kit.

There is certainly room for pushing new technologies -- that's what hams have always done. But I guess my preference for a hobby will remain with traditional methods (well, plus RTTY and SSTV, too)!

Just my thoughts...
RE: Digital Voice Over HF  
by KC8VWM on November 9, 2003 Mail this to a friend!

>>there would be nothing but buzzes and weird noises on the air for those potential hams (SWLs and youngsters)to listen to on the shortwave sets they constructed from a kit. <<<

I was an avid SWL'er & radio experimenter long before I was a ham. I can't begin to remember how many longwire antennas I got myself tangled up in. Don't kid yourself, SWL'ers probobly have more info on this new "digital" technology for HF than we do. Some SWL's are even ARRL members. I have seen a few SWL websites lately talking about this new ham digital technology. They even explain how the average SW listener can modify thier existing equipment to recieve these new digital HF signals. I bet we could even learn a lot from them. They probobly figured out how to connect a SW radio to your PC soundcard to decode HF digital signals.

Gee, why aren't these SWL guys not hams?



Charles - KC8VWM
RE: Digital Voice Over HF  
by N6HBJ on November 9, 2003 Mail this to a friend!
I happen to very much enjoy the sound of HF. The hiss and crackle of the HF bands is music to my ears and and I much prefer it over the sound of FM type comunications. Ever since I was a kid, that sound permeated my bedroom as I spun the dial searching for stations in the night against the glow of my rigs.

If all you care about is "quality" audio, then go talk on the internet or the telephone. Is nothing sacred?
RE: Digital Voice Over HF  
by N7JS on November 26, 2004 Mail this to a friend!
It's a great technology. No doubt, in the future, the new Kenwood, Icom, etc. radio's will have a "Digital" mode button in addition to USB, LSB, CW, etc. Those without it on their radio will feel like you would now if your radio only had the AM mode on it. Some people only want an AM mode on their radio today so I suspect it will be the same with this - but the majority will embrace this and want what all the newbies are getting. Personally I look forward to it.
As for buying this AOR unit now - you can look at it like a computer. For example: There were plenty of people buying old 286's (or whatever comes to your mind that is old in computers) when they came out (and shelling out a bunch of bucks) - now they are worth less than the effort to toss them in the garbage. However, those people who bought these old machines when it was the "item" had alot of enjoyment from it, while the others who said "I'll wait until the price comes down and they are better" were sitting around waiting for the next best thing. Some by no choice due to finances. I still know people to this day who don't own a computer because they are still waiting for the price to come down and for it to be better. That's the nature of technology, you buy it, it gets old, it's probably not worth a tenth of what you paid for it down the road, but hey, you were cool while you had it initially and you were USING it while others were playing with their thumbs.
If you can afford the AOR device (or even if you can't) get it and ENJOY it. Believe me, there are PLENTY of people buying this item and I'm sure they are having a hell of a good time with it.
As for me, eh, I'll probably wait for the price to come down and for it to get better <grin>
73 Jim N7JS
Digital Voice Over HF  
by KF6CZG on February 22, 2006 Mail this to a friend!
The value of a network is proportional to the square of it's endpoints.

Translation: Sounds like great stuff, but I won't be buying a box until everyone else has one. It's only valuable if you have somebody to talk to.
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