Amplitude Modulation

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KC9UDX, Aug 25, 2014.

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  1. KC9UDX

    KC9UDX Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    The VHF and UHF bands are a great place for AM.

    A lot of hams seem to have VHF AM gear, and would like to use it but don't have anyone to work. If this is you, you may find AM activity in your area that you didn't know about. If not, you can drum up activity with a little effort.

    Get that Twoer or Communicator on the air! Even if you have a modern all-band-all-mode rig, try it out!

    Don't forget, if you have an AM rig, you can work a station that only has FM gear: Your AM rig will likely demodulate FM just fine. The only caveat is the other station needs a way to receive your AM. But, most wide-band-receive handhelds will do this. So do some scanners. In fact, Yaesu handhelds will allow you to transmit in FM and receive in AM, very easily. I assume other makes of handhelds and some mobiles do this also.
  2. KM3F

    KM3F Ham Member QRZ Page

    I occasionally work 6, 2 and 432 AM just for something different.
    First rig used a 2m Transverter and solid state amplifier.
    Presently I use a Kenwood TS2000 for all the bands.
    Most ops won't go to the expense of 2m/432 AM due to the investment in equipment and antennas unless they are highly motivated to do so otherwise the bands are mostly empty except for Repeater use and contest times.
    On the Kenwood 2000, the use of memory control program can set up transmit in AM and receive in either AM, FM or SSB or any combination you like..
    The advantage of setup for TX AM on 80M and 40m and Rx in SSB is getting the use of more filtering than AM mode usually offers.
    Good luck.
  3. KA8MNP

    KA8MNP Ham Member QRZ Page

    Thread is a couple of weeks old but.....interesting. Just wondered if there is somewhere on those bands that is set aside for AM, in other words where to look for a qso.
  4. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    It used to be 50.400 - assuming it probably still is. I've heard anyone though, not that
    I have it parked there all day or anything though. I've not ever heard of a standard
    on 2 meters - probably is one though.

  5. KC9UDX

    KC9UDX Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    I researched everyone's opinions on a place for 2m AM for a while before deciding the best place is in the slice marked "miscellaneous/experimental". Reading the verbiage behind the bandplan that was the only place that actually made sense. Unfortunately, I don't have the information in front of me so I can't repeat it here right now.

    There are groups operating AM in different parts of the band in different places. If you are in one of those places, that's where to go, else I'd recommend the miscellaneous/experimental section. I can tell you 145.52 and 145.63 are within the range, but I don't know the limits of the range offhand.

    The other question everyone has is about polarisation. I think vertical is best: most everyone that has 2m capability has a vertical antenna. Even those who have horisontal antennas, numbers-wise, also have vertical antennas. Commercially manufactured (and kit-made) dedicated 2m radios that came with the provision to directly attach an antenna have vertical antennas. Also, when AM was the mode to use mobile, obviously everyone must have been using vertical.

    But these are just my findings and I know there are some who disagree, so, don't take what I say as an attempt at authority.

    And, 50.4 is the de facto standard for AM on 6. I spend a lot of time there, but if I don't hear anything in the SSB portion, I tend to call CQ in AM there. I expect anyone who normally operates SSB won't likely be parked on 50.4 listening. This works: I have a crystal for 50.315 and have made quite a few contacts there, and everyone I've worked appreciates my tactic (at least that's what they tell me:)).
  6. KI6MPU

    KI6MPU Ham Member QRZ Page

    I love 440 AM, have found it hard to get anyone else to use it
    to many people just don't have the hardware,
    way easier to find 6M AM
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It's sad that it's now a "niche" thing.

    When I was first licensed, 6m and up AM was extremely popular. 6m SSB didn't become very popular until maybe 1968 or so, and 2m SSB around 1972. The higher bands were even a bit later.

    I used to come home from high school and get on 6m or 2m AM and the bands were actually crowded, so you'd have to find an open frequency to call CQ. I ran 250W DC input power plate modulated on both bands with a Clegg Zeus transmitter (4CX250B modulated by push-pull 811As) and with good beams had a big signal on AM. By '68, I ran a TX-62 into a Johnson Thunderbolt 6n2 at 500W output carrier power and lit up the neighborhood with the 15L Telrex on 2m and 6L Telrex on 6m, on a roof tower over the top of my parents' house.

    Sadly, those days are just memories. But I won a lot of VHF contests. In a few cases, #1 high score nationally. Still have those certificates, although they're pretty faded now.
  8. WA2CWA

    WA2CWA Ham Member QRZ Page

    That analogy only works if you keep the radio vertical.

    When mobile, back in the "good of days", many of us used 2 meter halo's and turnstile antennas, which were horizontally polarized antennas. Made working base stations a lot easier.

    Pete, wa2cwa
  9. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Especially on 6-meters, and to a great extent on 2-meters, horizontally polarized antennas were very popular for mobile use. These were generally "halo" or "squalo" configurations.

    The frequency of 50.400 MHz has been "the" AM calling frequency on 6-meters since the band was made available for amateur radio use in the United States. This was largely due to the widespread availability of 8400 kHz surplus crystals which, times 6, come out to 50.400 MHz.

    For 2-meter AM, the frequency of 144.400 MHz was tried because of the similarity to 50.400 MHz. Unfortunately, APRS operation on 144.390 MHz renders virtually all AM operation on 144.400 MHz difficult, if not impossible. In many areas, the 2-meter AM activity has migrated to 144.350 MHz.

    However, except for nostalgia nets and some very sparse operation during band openings, AM activity on the 6-meter band and higher frequency bands just doesn't exist these days.

    For anyone around Dallas, Texas, who wants to try 70 cm AM, I can hook up my Vocaline AT-30 AM transceiver. It is tunable anywhere from 420 MHz to 450 MHz. However, the frequency stability is dismal! It is pictured on page 3 at:

    Glen, K9STH
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