Questions about AM mode

Discussion in 'Amplitude Modulation' started by KI5OMM, Jul 2, 2021.

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  1. KI5OMM

    KI5OMM Platinum Subscriber Platinum Subscriber QRZ Page

    If this need to be moved to the AM category, my apologies. There's not a lot of activity there so I am asking a general question here.

    I have AM and AM narrow on my Yaesu FT900. I've never used it except tuning up sometimes. Can I just switch over to AM and talk on the phone bands? I suppose only folks on AM also could understand me? It seems to be really wide in the bandwidth department too, which can clog up a crowded band and get me in trouble with those talking on SSB.

    Just exactly what is the procedure for talking using AM?
    Bud- KI5OMM
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    There are popular "AM user" frequencies on each band except where it is prohibited, like on 60 meters and 30 meters.

    AM is still fairly popular, but usually on or near specific frequencies on each HF band.

    Lots of AM action on 160 meters, a fair amount on 75 meters, a bit less on the other bands. It's "legal" anywhere voice modes are legal (but not on 60m). If 10m is open pretty well, there's almost always action above 28.8 MHz on AM (in the 28.8-28.9 region or so).

    There are "AM nets" on 75m coast to coast. Our local ones are on about 3850 kHz or so and some really "booming" signals eminating from guys using really good antennas abound. Some may think those guys all run several kilowatts, and perhaps a few do, but mostly it's just "big antennas" used by guys who have substantial property. If they ran 20W, they'd still be strong.:p
  3. W4HWD

    W4HWD Premium Subscriber QRZ Page

    Find one of the established AM frequencies on 75 or 40m (there's also AM on 160 if you have the antenna) and join in. 3885kHz seems to be a popular frequency here on the east coast with AM roundtables going on nightly.

    Now there are some rather anal "purists" on AM that think plate-modulated vacuum tube AM transmitters are the only way to go, and that solid-state rigs sound horrible. Ignore them. Another tip - don't use any compression on AM. Just set the mic gain just below your rig's ALC threshold and you'll be fine. Set the carrier to 25w and go for it.
    N3RYB likes this.
  4. N1BCG

    N1BCG Ham Member QRZ Page

    You'll find the most AM activity around 1880-1890, 3870-3890, and 7280-7300 although there is also activity in the phone portions on other bands.

    Check your manual for the proper settings for operating using AM. The maximum carrier output will be 25% of your sideband PEP capability since the PA stage needs to include a carrier and second sideband. Some rigs automatically account for this but verify your actual carrier power without modulation to be sure.

    It's important for both AM and SSB ops to understand each mode when operating in close quarters and how receive filters and sidebands interact.

    You can find considerable operating information toward the bottom of this page:
    Last edited: Jul 2, 2021
  5. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Also at the top end of 160, 1980-1985.
  6. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    AM resources:

    The AM community has a number of subcultures-
    -Boat Anchors, restored old radios, primarily tube types
    -High Fidelity AM with new radios or modified BA's
    -Home brew Pulse Width Modulated (PWM) radios
    -'Tall Ships"; stations with high power and maximized antennas and Hi Fi audio.
    Note: Modern solid state radios are capable of quality AM transmissions. May require some minor adjustments to obtain optimum modulation.

    AM radio's allure is its ability to convey the natural speech tones. As a community it is oriented towards rag chewing and relaxed operating. Round table operations are common. The lower bands tend to attract the bulk of operating. Deep winter late nights without static can yield true arm chair copy and satisfaction of personal contact.

    AM is several orders of magnitude less efficient than SSB. While amplifiers are not strictly necessary, they are quite helpful. Low modulation significantly decreases intelligibility. Caution: in round table ops, a weak signal or low modulation may make you unheard by distant stations. Some Tall Ships may be less than tolerant when this happens. shrug.

    There is some times friction between SSB'ers and AM'ers over frequency usage and adjacent ops.

    -Dirty Secret of ham radio: There is a lunatic fringe that often jams AM'ers. The best way to deal with them is completely ignore them. Do not mention their interference. They thrive on attention. Ignore them.

    Jump in, AM is a fascinating part of AR. bill.
    Last edited: Jul 2, 2021
    N5HXR, N1BCG and (deleted member) like this.
  7. KI5OMM

    KI5OMM Platinum Subscriber Platinum Subscriber QRZ Page

    Thank you all for the great advice! I'll look into experimenting with it a bit. I have no amp at the moment, so I will just have to run barefoot.
  8. W3SLK

    W3SLK Ham Member QRZ Page

    KI5OMM said:
    That being the case, I would recommend the top end of 40M. Pending band conditions, a small signal is heard just as well as a big signal. 'Riceboxes' can sound just as good as the 'olde' rigs of past. I remember a fellow on 75 who ran a Kenwood -440. He bypassed the speech processors by not using the mic input of the rig but by bringing line audio into the phone patch input. He had a very FBOM audio and fooled a lot of people with it, including me!
    N1BCG likes this.
  9. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Somewhat less efficient, but I wouldn't say orders of magnitude less. If two numbers differ by one order of magnitude, one is about ten times larger than the other. If they differ by two orders of magnitude, they differ by a factor of about 100.

    100 watts carrier output of 100%, voice-modulated AM, yields 50 watts peak sideband power. 100 watts average/mean power of SSB (what really counts in terms of signal loudness), yields anywhere from 200 to 500 watts peak power, depending on the peak-to-average ratio of the speaker's voice and degree of processing in the rig. Thus 6 to 10 dB more "talk power" for SSB for the same average power output; that's maybe one order of magnitude.

    The unprocessed human voice has a very high peak-to-average ratio, typically about 10-to-one, or 10 dB. A clean SSB transmitter running the "legal" 1500 watts peak power with no audio processing, actually transmits about 150 watts of average sideband power on voice syllables at best.

    Both AM and SSB require some method of compression and/or peak limiting to bring up the average power. SSB ops often achieve this effect simply by hard clipping, that is, driving their linear amplifier to flat-top on voice peaks, resulting in buck-shotting and a broad signal. With AM, the same thing (splatter) occurs when the modulation capability of the transmitter is exceeded, or in any case when negative modulation peaks exceed 100%.
  10. W7TFO

    W7TFO Premium Subscriber QRZ Page

    Clean audio and a good antenna mean more than anything else.

    A quiet RX level is very important to be able to hear. Lots of modern conveniences make a lot of RF hash.

    As I said, a good antenna can make more RF in the air than lotsa' Watts into a mismatch.

    Get a good scope, and learn how to read your modulation level with it. Proper mod will go a long way for you.

    W2VW and W3SLK like this.

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