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Author Topic: HF AM???  (Read 30381 times)
KD0ILS
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Posts: 7




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« on: February 26, 2013, 05:33:44 PM »

I'll be the first to admit I'm rather new to HF i've had my ticket for 6 years and thought its time to venture away from 2m/440.  I know I'm only a technician and currently my bands are limited to 6 m and 10m ssb but the real question is concerning the two radios I have that could get me going into HF.  I have a hallicrafters HT-40 and a drake tr-4c and rv-4c that was given to me from a silent key and these radios havnt been touched since the early 80s.  I also have 2 astatic d-104 microphones to be paired with these radios but they just need to be rewired for the proper plugs.  The status of the HT-40 is unknown because i have no crystals and the drake doesnt seem to be transmitting on 10m ssb or measuring into a dummy load.  It could just be my lack of knowledge of boat anchors.  What this comes boiled down to is the question whether or not its worth to get the radios checked and re - tuned/aligned and when I do get the fixed does anyone work HF on AM anymore?  Which brings me to another question if anyone knows of a good place to take these radios to get a thorough once-over.  Cosmetically these radios look great and I'd really like to use them but i was just curious about other peoples opinions.  I know i could just buy a yaesu 857d and all my problems would be solved but i decided to go back to school and paying my way through college doesnt leave $900 in the budget.  thanks for the help
-73's
PETE
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N4NYY
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« Reply #1 on: February 26, 2013, 05:47:32 PM »

There is a group on 80M that does AM, and most use homebrew tube or boatanchor gear. Nice bunch of guys. I was once having a rag chew on their SSB side of their freq before their net started. When they informed me of it, we told them we would move and they said do not bother, and to just flip the switch to AM, and join them. But we did not, as I have a FT-950.
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WA2CWA
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« Reply #2 on: February 27, 2013, 12:43:21 AM »

You'll find AM operating on just about every major band (160, 80, 40, 20, 15, 10, 6, and even 2 meters). If you check the ARRL band plan you'll even find AM calling frequencies listed. And, since AM is "phone" you can find AM operating anywhere phone operation is authorized. Not only is homebrew and vintage equipment used,  you'll also find many AM operators using current state of the art rigs (Yaesu, Kenwood, Icom, Flex, Elecraft, Ten-Tec). Even the FT-950 can operate on AM. I've worked a number of stations using them on AM. The popularity of AM operating has been growing for years. There's even an AM page on the ARRL web site: http://www.arrl.org/am-phone-operating-and-activities

Pete, wa2cwa
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KB4QAA
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Posts: 2371




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« Reply #3 on: February 27, 2013, 06:58:25 AM »

Here are some starting points....

http://amfone.net/Amforum/index.php
http://amfone.net/ECSound/
http://www.amwindow.org/index.htm
http://www.ami-west.com/

Gratuitous radio porn:
http://www.radioblvd.com/
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KB5ZSM
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Posts: 70




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« Reply #4 on: February 27, 2013, 10:23:43 PM »

Hey Pete,
         Your question about AM on HF is one you can answer yourself with a decent Short Wave radio. You'll find quite a bit of AM activity, especially on the lower bands. I recommend a lot of listening to the HF bands while you study for your General ticket. It will help you find your niche and learn more about how it all works before you ever pick up that microphone and when you do get to operate in those regions you'll be able to attack them with more confidence.
         As for your Drake equipment, Your radio setup is the same as the first one I ever got to play with many years ago back in high school. It was our school station so I have vary fond memories of that radio I may even buy one someday just for the fun and memories it will bring back. As far as fixing yours up, I think the first thing I would do is buddy up with a local ham who has some boat anchor experience and let him look at it. See what he thinks of its condition. Do NOT just plug it in to see if it works. If it has set for many years with out power, you could do damage to it if you don't bring it up slowly.

Hope this helps & 73s,
Win (KB5ZSM)
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W2WDX
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« Reply #5 on: April 18, 2013, 09:18:44 PM »

Two things about AM operation and why it is still popular. Higher fidelity audio and less critical frequency tuning. The latter being less important, the former being the primary reason people still operate on the mode.

The normal operating practice on AM in Amateur Radio is a frequency response in the audio pass-band of about 6-7kHz, compared to about 2.7 kHz (sometimes slightly higher) for SSB operation. This gives a very pleasing sound for normal ragchewing. However AM is very inefficient because of this, which is why SSB is so prevalent especially for DX work. But AM is unbeatable for the local ragchew operation. The extra bandwidth allowed makes for very natural sounding speech and reduces listening fatigue.

The advantage of using older boatanchors is that you can get close to this bandwidth, sometimes, depending on the transmitter. A Yaesu like the 857 still uses its filters so your audio bandwidth is usually limited to under 4kHz, and most times to 3kHz. AM is an afterthought on most modern Japanese/Chinese radios. SDR's like FlexRadio can give significant audio bandwidth approaching that of broadcast standards, albeit this may be a bit broad for amateur use, but not uncommon nor in violation of FCC A3E mode specification.

Actually the designator used in FCC regulations is 8K00A3E which is an 8kHz audio bandwidth. The designator describes the first four characters as "necessary bandwidth required to transmit the desired information". So this is the bandwidth of the information being sent. Most Amateur operators do not use this full bandwidth however even though they can if they wished. BTW, broadcast AM is designated (8K00A3E or even as wide as 20K0A3E (with limits on higher modulated audio frequencies), for reference.

Incidentally, the SSB designator is 3K00J3E. The "J" determines it is a single sideband mode with a 3kHz information bandwidth. Since it is single sideband the radio signal is limited to 3Khz. J3E was brought into Amateur since it reduces congestion within the Amateur bands. The most common in Amateur use is 2K70J3E at 2.7kHz. However this does not preclude that A3E at full bandwidth is not allowed. It should be noted that while these designator appear nowhere in Part 97, they are only referenced there and actually appear in Part 2 Subpart C.

Another fact is there is no mention about "communications quality" for using A3E in Part 97, as is commonly argued. That term is only used in describing certain single sideband emissions "... shall not exceed that of a communications quality A3E emission". In fact, in Part 97 there is no limit mentioned specifically about A3E other than it adhering to emission type standards outlined in other Parts (Part 2 specifically). So in theory one could technically operate at a 20kHz bandwidth as long as you adhere to the standard for that emission type, specifically 20K0A3E, However, in Amateur practice while technically allowable it would simply be rude. So most AM operators have settled into operating using the 8K00A3E emission type on HF bands as good amateur practice.

So as far as "High Fidelity" audio is concerned AM is the way to go in Amateur Radio. Achieving that "Hi-Fi sound and experimentation and developing a station for this goal is what AM operation is all about. Of course, with the virtually "unlimited" bandwidth of the A3E emission type make this possible. If one tries operating true "Hi-Fi" on SSB you may find yourself operating an emission mode not allowable by either the FCC or the ITU. Of course, the true purpose and reasoning for SSB is not fidelity, but instead the goal is efficiency.

John, W2WDX
« Last Edit: April 18, 2013, 09:56:09 PM by W2WDX » Logged

K4KYV
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« Reply #6 on: April 26, 2013, 09:07:00 PM »

No specific bandwidth limitation is mentioned in the Part 97 rules. The rules vaguely prescribe "good engineering and amateur practice". The FCC intended it that way, in order to allow the amateur the maximum flexibility for experimentation and self-instruction in the radio art.

Therefore, if you decide, for example, to transmit on 160m in the middle of the day, or 75m in the wee hours of the morning when there are likely to be few if any other stations using the band, good amateur and engineering practice might not preclude running hi-fi audio with frequency response up to 10 kHz or more.  No harm done transmitting a "wide" signal when there is no-one else on the band to interfere with.  OTOH, under congested band conditions during prime operating hours, good engineering and amateur practice would suggest limiting the frequency response of the audio modulating the transmitter to 3500 Hz or less.

The same standards would apply equally to AM or SSB. Why would it be less permissible to transmit an audio frequency response up to 5 kHz on SSB, resulting in a total bandwidth of 5 kHz, than to transmit with the same modulation on AM, resulting in a total bandwidth of 10 kHz?

There is an important distinction between the bandwidth of the sidebands resulting from the frequency response of the audio used for modulation, and spurious sideband products resulting from distortion or non-linearity in the transmitter.  Excessive bandwidth due to overmodulation or spurious distortion products is poor amateur and engineering practice, regardless of the actual bandwith of the transmitted signal or the level of band congestion.

The best operating practice would be to use a receiver with variable selectivity or several filters with a variety of bandwidths, and to adjust the audio response of the modulation so that the bandwidth of the transmitted signal is the same as the optimum receiving bandwidth under the given set of band conditions.
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W2WDX
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« Reply #7 on: September 23, 2013, 03:24:41 PM »

Just to be clear and this is often misunderstood by Hams, Part 97 should never be taken in isolation.

It is not the only Part of the FCC regs that apply to Amateur radio. When a specific emission type is mentioned in Part 97 it refers directly to other Parts, specifically Part 2. Amateur operators are bound to apply those other parts as well, since it deals with the specific emission types allowed for Amateur use as prescribed by Part 97.

A 5kHz SSB signal is not allowed according to specific emission type allowed for use on the Ham Bands (specifically 3K00J3E) as outlined in Part 97. However, an 8khz AM is allowed (8K00A3E), though I agree not a good idea or good practice in peak band use periods.

These detailed designators are specifically referenced in Part 2 for the Amateur bands. So Amateur use regulations appear in other Parts, not just in Part 97. Licensed US Amateurs are required to adhere to " ... all FCC regulations for Amateur use". Not just Part 97 in isolation.
« Last Edit: September 23, 2013, 03:31:39 PM by W2WDX » Logged

AC5UP
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« Reply #8 on: September 23, 2013, 04:13:41 PM »

...just flip the switch to AM, and join them. But we did not, as I have a FT-950.

And your ALC diode was clipped.

 Cheesy
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Never change a password on a Friday                
G3RZP
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« Reply #9 on: September 24, 2013, 12:43:08 AM »

8K3 means 8kHz overall bandwidth. As 'necessary bandwidth' is so ill defined in the ITU Radio Regulations, common practice is to use the occupied bandwidth, which is the bandwidth containing 99% of the energy - usually, but not necessarily, the bandwidth at 20dB down from the maximum.

As it is AM with two sidebands, the audio bandwidth is limited to 4kHz, not 8kHz.
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VE3FMC
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« Reply #10 on: September 24, 2013, 12:14:43 PM »

There is a group on 80M that does AM, and most use homebrew tube or boatanchor gear. Nice bunch of guys. I was once having a rag chew on their SSB side of their freq before their net started. When they informed me of it, we told them we would move and they said do not bother, and to just flip the switch to AM, and join them. But we did not, as I have a FT-950.

You should have switched to AM because that FT-950 sounds very good on AM if you set the mic gain properly. Any of the new rigs should sound good on AM if they are operated properly.

I have run my FT-950 on AM while driving an AL-80A and was told the audio sounded very good, after I did some tweaking.

Get it set up properly and don't tell them what you are operating unless they ask!  Grin
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W2WDX
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« Reply #11 on: September 27, 2013, 08:33:19 PM »

Some folks are intimidated by the way many of the guys sound, (particularly on the East coast of the US). Many guys on AM are running QRO level using sophisticated homegrown ClassE technology, which is very high fidelity. Many run retired and converted Broadcast AM transmitters.

However this should never discourage anyone from operating AM. Due to the high quality audio and ease of tuning it is pleasing to the ear for ragchew, with little fatigue. Most of the folks running AM are either ol' timers with a vast amount of knowledge or younger folks with an understanding of newer AM technologies. Mostly all are very technically accomplished. The conversations can be very educational, interesting, sometimes a little crude maybe, but always different.

Most of the AM operators can very easily discern a radio like the FT-950 from a higher-end AM transmitter. Anyone using one may get a little friendly "ribbing". However if operated properly they do sound quite good on AM. Apparently, Yaesu decided to make some changes and realized AM is certainly not dead and that the modes main attraction is the higher fidelity audio. Yaesu realized AM should not be an afterthought mode.

And Peter, you are correct about the audio bandwidth at 4kHz on AM of course. I was refuting the assumption by others that one could operate a wider SSB signal, which is not correct. Many US hams misinterpret the vague "good engineering and amateur practice' clause that exists in Part 97 of the FCC regulation here in the States. There is a reason why manufacturers use 2.7kHz filters in SSB transmit modes. This is to gain type acceptance certification for amateur use. Any wider, taking into consideration the slope of these filters, and the transmitted signal would be beyond the specification of 3K00J3E limits set forth for Amateur use in Part 2. Many Hams do not understand this "practice" clause as meaning adhering to standards set forth in other sections, outside of Part 97, which define in detail the specifications of what is good engineering practice.

As I said earlier, SSB was a mode adopted by the amateur service to help alleviate the very congested Ham bands as they were in the 1950's. It is a power efficient narrow bandwidth mode with the smallest possible band "footprint" yet still allow for intelligible phone operation. However, this does not mean this can be changed during low activity periods. The limits set out by the specification of 3K00J3E for amateur use are clear, and short of an experimental exemption, are not open to interpretation; this would be seen as a misinterpretation of the "good practice" clause. However, it should be stated the FCC has little interest in enforcement of such things, unless of course a formal complaint is made.

In informal conversations with people such as Riley Hollingsworth, former FCC enforcement head, and Laura Smith the current FCC enforcement chief, the development and operation of newer types of AM transmitters for personal use, such as ClassE rigs and its derivatives and variants (and other types of transmitters), comes under the special exemption for experimental transmitters. Therefore the view is the emission limits are exempted, within reason. However simply modifying a type accepted commercially produced radio to allow it to operate outside its normal 3K00J3E emission limits is not generally considered experimental nor good engineering practice.

I find it fascinating how the oldest mode AM is the one where more sanctioned Amateur experimentation is going on then in any other mode, short of digital modes. In fact, newer Broadcast AM transmitters are using the technologies developed in Amateur radio since these developments have lead to smaller size, higher power, easier control and maintenance, and lower operating costs for Broadcasters. This is a revitalization of one of the primary functions of Amateur radio and why it exists.

AM is a wonderful mode. And some of the newest and most effective technologies also happens to be one of the easiest to experiment with. That being solid-state FET based AM transmitters like ClassE rigs and others. This of course should not discourage anyone from using commercially produced transceivers on AM. Just read the manual and understand how to operate the radio in this mode, and I guarantee you will have a great time.

This is a recording of two AM stations, on 160m I believe, of two well known East coast stations. The one station in the distance is using a Collins Broadcast transmitter converted to Amateur use. The loudest of the two is using a older boatanchor (I believe it may be a Hallicrafters HT-37 but I may be wrong). However, he is using only a 20 watt carrier. The recording was made off a Hammarlund SP-600 boatanchor receiver. These two fellows are typical of the types of technically accomplished (One is a Technical Director of a major broadcast national news program). They also exemplify the type of gentlemen you will find operating on AM. And yes indeed, it is an AM QSO between New Jersey and Virginia near D.C.

http://www.vikingvintage.com/NBC-K2DK.mp3

John, W2WDX
« Last Edit: September 27, 2013, 09:22:48 PM by W2WDX » Logged

W8AAZ
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« Reply #12 on: September 28, 2013, 11:54:11 AM »

I suppose some AM on the bands is beneficial as casual SWLs can tune you in easily.  Maybe good PR.  It does have a pretty wide footprint on 75 and 40, which are crowded bands to begin with.  And it seems to be the mode to be if you are a gear freak, as someone is always trying to out hi fi everyone else with vintage transmitters, studio mics, and audio processors galore.  I guess sounding like a broadcast would attract more SWLs than some of those noxious SSB roundtables on 75.  I would prefer to work AM on 160 if I could.  Activity is spread out alot up there and not so much chance of having someone right up against your freq.  I have heard that there are AMers on 10 and 6, using old rigs or converted CBs.  Especially 10 would be fine as there is alot of elbow room like on 160.  Except I have not heard them on 10.  Being that propagation is scarce these days, and a local net would be cool but none around here. My SSB rig can AM, but pretty low power, like 25 watts max carrier.  What is the point of being hi fi if your weak and in the noise?   
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WA2OLZ
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« Reply #13 on: September 28, 2013, 04:53:00 PM »

C'mon on down to 7285 or thereabouts. All of the regulation QRM and broadcast type audio requirements go away - fast! It's great to get into a QSO 1:1 or roundtable with a bunch of guys (and gals) that like to ragchew about every subject under the sun. You won't find contesters or "5X9, 73" contacts here, however. Pull up an armchair, sit down and relax with friends. That's what it's all about.
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GW3OQK
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« Reply #14 on: September 29, 2013, 02:31:56 AM »

There's an AM net in UK on 3615 many mornings. Talk about being relaxed, I heard one guy speaking for more than 15 minutes on his over.
73, Andrew
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