AM on 160m using old "Boat" radios

Discussion in 'Amplitude Modulation' started by W7IMM, Feb 22, 2020.

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  1. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    BTW, here's a schematic of the Kaar receiver.

    Attached Files:

  2. AC5JM

    AC5JM Ham Member QRZ Page

    This thread is old but whatever. I also have a Pierce Simpson Bimini 550 AM marine radio that I bought at a local electronics store. I also converted it to 160m but have never tried making any contacts with it. What amazes me most about it is the low current draw of the recevier- 0.45 Amps even using a tube in the front end for all of the mixing/local oscillator duties. That's better than any late model MPU controlled radio I have. I have a crystal for 1885 KHz.
    -Jerry AC5JM
  3. AC5JM

    AC5JM Ham Member QRZ Page

    It has been probably 3 years since I looked at that radio so I took another look and it is actually a Bimini 50, not 550. The only difference is that the 50 does not have the AM Broadcast tuner built-in. However, I used that slot to connect a home-made VFO. There is a TX/RX slide switch where the AM dial is on the 550 that lets you turn off the transmitter tube filaments to conserve power. Mine puts out about 40 watts AM carrier.
    WA3VJB likes this.
  4. W7IMM

    W7IMM Premium Subscriber QRZ Page

    The 550 also has a filament switch. The only thing it really needs is squelch.
  5. G3YRO

    G3YRO Ham Member QRZ Page

    Some are saying that these low power AM rigs are a waste of time . . .

    But here in Britain we were only ever allowed to run 10 watts INPUT on AM & CW on 160m . . . with a decent Class C PA you might get 8 watts output.

    I always used simple Valve homebrew VFO-based transmitters, with a single-ended Class A Modulator Valve . . . but others used small commercial transmitters, like the Codar AT5, or KW KW One-Sixty.

    Yet we still worked all over the country . . . I even worked across the pond running a genuine 10 watts !

    Roger G3YRO
    AC5JM and W1BR like this.
  6. W7IMM

    W7IMM Premium Subscriber QRZ Page

    I suspect that in the next 5 to 10years 160 evening propagation will improve over previous years!
    That will make all these "low power" rigs work well!
  7. W4KJG

    W4KJG Subscriber QRZ Page

    Oh, I wish I hadn't seen this thread. I just wasted the last hour looking to see if anyone had any 1960s AM Ray Jefferson, Bimini, etc.for sale.

    I repaired and installed dozens, probably hundreds, of those vintage radios. The ones from the late 1950s to late 1960s were pretty solidly designed and built. I'd love to find a 25-50 watt AM marine transceiver at a yard sale price to put on 160 meters. Somewhere I think I still have a box of 2-3 MHz crystals left over from that period of time -- which would be rather useless these days. If I were to find the box, I'm thinking that about half the crystals would be for 2182 kHz from units we trashed.

    If I found one, I'd just buy a cheap digital synthesizer like one from QRP Labs for use in place of crystals.
  8. W7IMM

    W7IMM Premium Subscriber QRZ Page

    I used to see the Pearce Simpson Bimini 550 on ebay about 1 every 3 or 4 months.
    They always started with a $10 initial bid and in almost all cases no one (except me) bid on them!!

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