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Author Topic: FCC's limitation on 300 baud for HF, why not let us use MIL-STD 110A at 9600 bps  (Read 13905 times)
AA4HA
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Posts: 1434




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« on: August 15, 2012, 02:02:26 PM »

I keep to the letter of the law on what modes I operate, occupied bandwidth, power, gain, etc but it chafes me that we are forced to keep ourselves limited to 300 baud for digital modes. There have been so many advances in modulation techniques (eg, 39 tone modems), FEC (forward error correction) ARQ (data interleaving), all while still remaining in the occupied bandwidth of an SSB audio signal.

As long as we are identifying, not occupying too much bandwidth, encrypting our data and the other dozen or so "biggies" in the R&R to the FCC it should not matter what data rate we are running at. Let us be challenged to develop even better protocols where we can still remain in an SSB channel bandwidth but let us see how far we can go with data rates. Give the new generations of amateurs (teens, young adults) something to strive for. To push those boundaries.

I am a contrarian, I will not use PACTOR III because it is proprietary and way too expensive. For the same reasons I stay away from DSTAR (I wish that APCO-25 had made it to the forefront, it sounds much better).

I am not asking for spread spectrum or frequency hopping in HF (both very good ways to elude the obligation of the FCC to monitor and regulate us). We have packet networks, we have ALE. If we were MARS operators then we could run a STANAG 110A modem at 9600 baud. In support of MARS, faster data comms is always better but the FCC does not seem to recognize that maybe we can open up new challenges "to advance the art of radio" by letting us play with something faster than a teletype machine (exaggeration but you should get my drift).

I am not going to beat the EMCOMMS drum but it would make more sense for those folks as well. To be operating at higher data rates in HF. Imagine a HF digital contest where it was all rapid, 200 millisecond burst transmissions trying to work some distant contact point in an island way down by Antarctica? Automatic SNR reporting, link establishment messages, BER... just like real radio adults.

This may sound a little ranty and I am spun up by it all and just wonder if other ops feel the same way? Sometimes it only takes one pebble to start an avalanche and maybe our much vaunted "representation" in the ARRL could actually take on a challenge like this to revise CFR 47.
« Last Edit: August 15, 2012, 02:33:19 PM by AA4HA » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
NL7SX
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Posts: 39




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« Reply #1 on: August 15, 2012, 06:16:46 PM »

Interesting suggestion and lack of acceptance of speeds above 300 is a big handicap. Is thee a good reference for MIL-STD 110A?
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NL7SX
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Posts: 39




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« Reply #2 on: August 15, 2012, 06:20:55 PM »

Perhaps you meant MIL-STD 188-110A which might be on Multipsk at this time?

http://mt-milcom.blogspot.com/2009/07/multipsk-to-add-mil-std-188-110a.html
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AA4PB
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« Reply #3 on: August 16, 2012, 07:31:30 AM »

The FCC limits the "symbol rate" to 300 baud. If you are running standard FSK then that indeed limits your throughput. However, modern modulation techniques permit you to transfer multiple bits in a single symbol. This is what permits PactorIII to transfer larger amounts of throughput while still maintaining the required symbol rate. I think MIL-STD-188-110A has 39 tones with a symbol rate of only 44.44 baud so it should be legal.
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AA4HA
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« Reply #4 on: August 19, 2012, 10:22:26 AM »

You are quite correct that we could do more if we implemented phase shift keying more aggressively. That was the big difference between just FSK (frequency shift keying) where a tone like 2000 Hz would represent a digital 0 and 2300 Hz might represent a digital 1. That is how the older bell 202 modem standard worked and was ok for things up to around 1200 baud across a radio link.

When you wanted "more" but to still stay with roughly the same tone frequencies you went to PSK (phase shift keying) where you created Q-bits based upon what part of the sine wave you shifted from one frequency to another. (0 degrees on the sine was a didbit of 00, 90 on the sine had a didbit of 01, 180 on a sine had a didbit of 11 and 270 on a sine had a didbit of 10. (just an example)). This was known as the Bell 212 standard modem and was at first, good up to 2400 baud.

Later they began detecting at 45 degree phase angles, then 30 degree phase angles and so-forth. Then, doing that across radio became difficult due to multipath in an RF environment and how it sort of chews up phase angle detection. It could good work good on a telephone modem but was a problem across radio. You would end up with some where a single phase angle shift would represent a byte 0000 and eventually a word 00000000.  This was in the 80's when dial up computer modems were getting much faster, up to around 64 Kbps.

They began to incorporate different parallel paths of tone sets with closely spaced pairs and very good PLL circuits and pushing the limits. Also, along came QAM (Quadrature Amptitude Modulation) and "constellations" that were all run through multiplexers and demultiplexers. Unfortunately that really made bandwidth really wide as they were pushing the limits of "Shannon's Theorem" on how many bits per Hz you could push at a certain SNR level (if interested, look up the formula, it is pretty easy to understand).

I just know that we amateur operators and experimenters still have some room to contribute to the art of radio by working in this area. Even the most complex waveforms they use today still have room for improvement to work in a poor SNR environment and at higher data rates.
FCC, give us that challenge. Let us see just how fast we can push things in the bandwidth of an SSB signal. We will not encrypt data so you cannot decode it. We will publish the waveform data so all amateurs can do some homebrewing with hardware or software on a PIC.

Today we know that it can be done with MIL-STD-110A at 9600 bps. Let us try to get it working at 19.2 kbps or higher or make it so it works with forward error correction (FEC) and theoretically with adaptive modulation and adaptive power levels that are negotiated on a lower bandwidth side-channel buried in the data-stream. Let us be able to do things like SNR, BER, link quality and stuff like that on side channels inside of the data stream.

Let us work in a sandbox instead of telling us that a matchbox should be more than enough room for us to play in.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
N5PVL
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Posts: 210




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« Reply #5 on: September 02, 2012, 05:47:32 AM »


Since it appears to be missing, I will inject a note of common sense, here.

Higher baud rates are a non-starter on HF because they also entail wider signals.

Wider signals may be a good idea on commercial or military spectrum that is channelized and tightly regulated. - On amateur radio's shared spectrum though, less regulated so that experimentation may occur, wider signals have not been found to be suitable for long-term or regular use.

Occasional experiments with wider signals by well-informed, responsible amateurs are unlikely to generate spectrum pollution - just as widespread use of wider signals by large numbers of uninformed, irresponsible amateurs is absolutely certain to generate spectrum pollution. - This point regularly shoots over the heads of supposedly clever wide-signal and spread-spectrum devotees whose IQ's take a sudden nose-dive when it comes to the basics of responsible, thoughtful operation within shared spectrum.

Duh.

73 DE Charles, N5PVL
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N3QE
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« Reply #6 on: September 02, 2012, 06:53:04 AM »

I keep to the letter of the law on what modes I operate, occupied bandwidth, power, gain, etc but it chafes me that we are forced to keep ourselves limited to 300 baud for digital modes. There have been so many advances in modulation techniques (eg, 39 tone modems), FEC (forward error correction) ARQ (data interleaving), all while still remaining in the occupied bandwidth of an SSB audio signal.

Unless you have an exceptionally noise-free channel you are not going to be pushing 9600 bps over a voice bandwidth on HF. Google "Shannon Hartley Theorem".

The efforts toward MFSK with FEC and interleaving is there in ham radio for sure: e.g. Olivia.

Overall the trend in HF ham radio is towards low data rates comparable with human typing and with very robust performance. e.g. PSK-31 and variants. I think this is fine direction. I still think there's too much automation and turnaround time in PSK-31 but that's mostly me looking at it from my DX+contest+ragchew standpoint.

If I had a gigabyte of data to send to a ham in the next state over I would probably use a CD and USPS rather than ham radio.

I too despise proprietary modulations/protocols.

Tim.
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N9AOP
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Posts: 144




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« Reply #7 on: September 02, 2012, 03:29:21 PM »

Ms. Hayes,
I use 110A on the army MARS nets.  Using software to emulate a modem produces a thruput of no more than 600bps under the best of conditions.  Under the usual band conditions at this time, 300 or 150 can be a challenge except for very short exchanges.  The sync bits are sent at the start of the message and if sync is lost on the receiving end, anything from that point on is totally lost.  Also, 110A is not a true ARQ mode.

Hardware modems work very well for the STANAG modes and will interface with amateur equipment.  Even as used equipment, what is available (Harris, Codan etc.) are pricy and exceed the price of an SCS Dragon.

Art, N9AOP

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N1ZZZ
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Posts: 161




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« Reply #8 on: September 14, 2012, 02:01:19 PM »

I agree with Tisha on the premise of this debate.  I wonder why baud or symbol rate is the metric that the FCC uses as the limiting factor.  Obviously when the regulations were written and FSK was the modulation scheme, this equated to bandwidth.  As mentioned, this is a dated measuring stick to use.  Frankly, if you can squeeze more data in a certain bandwidth by increasing the symbol rate, why not do it?  You are using the same amount of spectrum.  I have spoken with hams in other countries that face no limitation and it hardly seems to be causing major problems on the world stage that is HF radio.  I would love to move image data at a comfortable rate while maintaining 500 Hz, but you can't do it at 300 symbols per second.

73
Jeremy N1ZZZ
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AA6CJ
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Posts: 22




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« Reply #9 on: September 17, 2012, 02:07:38 PM »

The IARU Emergency Coordinator and ARRL RACES folks may become champions for changing the regulations, if the case can be made that increase throughput could help in emergency situations.  It seems to me that it would.

73
Fred, AA6CJ
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N1EN
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Posts: 26




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« Reply #10 on: September 21, 2012, 07:28:45 AM »

I agree with Tisha on the premise of this debate.  I wonder why baud or symbol rate is the metric that the FCC uses as the limiting factor.  Obviously when the regulations were written and FSK was the modulation scheme, this equated to bandwidth.  As mentioned, this is a dated measuring stick to use.  Frankly, if you can squeeze more data in a certain bandwidth by increasing the symbol rate, why not do it?  You are using the same amount of spectrum.  I have spoken with hams in other countries that face no limitation and it hardly seems to be causing major problems on the world stage that is HF radio.  I would love to move image data at a comfortable rate while maintaining 500 Hz, but you can't do it at 300 symbols per second.

I could be mistaken, but I thought the 300 baud restriction arises from the need to be consistent with other FCC regulations (written in terms of baud rate) and the general regulatory notion that amateur radio should not be seen as competing with commercial telecommunications.  Once upon a time, dialup services were the norm and internet access was a novelty to most, and presumably the powers-that-be sought to promote the development of such commercial services.

Under that theory, given the pervasiveness of broadband net access these days, there isn't a real need to maintain that restriction.

I'd bet the FCC would be willing to entertain a proposed rulemaking to ease that restriction.  The trick would be in having that proposed rulemaking not get bogged down with other pet projects or criticized by folks with longstanding concerns.   I can see objections being raised by folks concerned with the width of M110A transmissions, for example; or proposed rulemaking drafting being sidetracked by other possible changes to modernize the rules.
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AA6CJ
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Posts: 22




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« Reply #11 on: September 21, 2012, 12:31:04 PM »

Back in 2007, ARRL's Chief Technology Officer Paul Rinaldo, W4RI w4ri@arrl.org, posted a Request for Information on "ARRL Invites Comments on New HF Digital Protocol".  Here's the link:

http://www.eham.net/articles/16035

From FCC Part 97 - Amateur Radio, it seems to me that (a) and (c) would be well suited for building a case that the 300 baud/symbols per second restrictions should be amended.

ยง97.1 Basis and purpose.-
The rules and regulations in this Part are designed to provide an amateur radio service having a fundamental purpose as expressed in the following principles:
(a) Recognition and enhancement of the value of the amateur service to the public as a voluntary noncommercial communication service, particularly with respect to providing emergency communications.
(c) Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communications and technical phases of the art.

So, I think a strong case can be made, (and perhaps championed by the ARRL?), to let us experiment in these areas.
73, Fred aa6cj
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