AM on 160m using old "Boat" radios

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

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  1. W7IMM

    W7IMM Premium Subscriber QRZ Page

    Howdy all,

    I have an old Pearce Simpson Bimini 550 MF marine radio that I have modified for use on 160. I even use the original "telephone" handset and integral carbon microphone

    It's crystal controlled and I have it "channeled" on 1925, 1945, 1975 and 1992KHZ. I've had it for many years and bought those crystals when they were fairly inexpensive. Now, crystals would cost more than the radio is worth!

    For those not familiar with it, There's pictures here: Ban.../Pearce-Simpson/Pearce-Simpson_Bimini 550.htm

    Mine puts out about 50W (carrier) and seems to work pretty well.

    Anyone else out there doing 160m with a "boat" radio?

    W2VW and KA0HCP like this.
  2. VK3YE

    VK3YE Ham Member QRZ Page

    W7JMP likes this.
  3. WA3VJB

    WA3VJB Ham Member QRZ Page

    Somewhere in the attic of the garage I have a Pearce-Simpson Islander 90 crystalled up on 3885. Picked it up for $25 about 45 years ago at a hamfest near Annapolis. At the time, the new VHF-FM allocation was coming into favor, and a lot of the old 2Mc marine radios were going for cheap. The final tank had enough to get me up to 75 meters, and I had a base loaded 6 meter whip antenna on the back bumper of my '71 Capri to go mobile with it. I think the only station I worked was Pete, WA1SOV, which wasn't a bad haul from Maryland to Connecticut. But the carbon mic, mobile electrical noise, and the poor antenna combined to make it not worth filling up the passenger footwell with the dang thing.
  4. WB1GCM

    WB1GCM Ham Member QRZ Page

    I have put boat radios on 160 meters with reasonable results; most recently using a SONAR marine radio. I'm a bit sentimental, as I grew up sailing and used a Pearce Simpson quite a bit aboard our family's 40 foot yawl, using an insulated backstay as the antenna and grounded to the lead keel. 1975 was the last year these marine radios were used, before the change to VHF was mandatory. These 2-3 MHz boat radios work best on antennas that are short, but I found that an inverted L, 88 feet overall, directly attached to the antenna post, worked fine. Best contacts were to Florida and Wisconsin from Connecticut. The crystals are the issue, so if one can furnish a VFO for the needed flexibility, go for it.

    One can develop quite a collection of these, as no one seems to want them anymore. I bought the SONAR for $5, but had to grind crystals for 1.885, plus 1.885+455 kHz. Still cheap fun, though. This thread makes me want to hook it up again! Good thread!
  5. W2VW

    W2VW Ham Member QRZ Page

    Fun until the little modulator melts.

    That's what happened to my last Sonar on 3885 at the boarder of North and South Carolina in 1995.

    Otherwise great fun but lately I scarf the nice ceramic switches and coil stock for use elsewhere.
  6. K5UJ

    K5UJ Ham Member QRZ Page

    Those little rigs are fine for local communications. There are pockets of low power 160 m. activity, sometimes fostered by clubs who started things with low power kit building activities. About 100 miles southwest from me is an area where local hams have a post-sunrise 160 m. net on Sundays. The local club had interested hams build 160 m. phone rigs in the past, that put out 10 or 20 watts. I've tried to hear them up here but get nothing but band noise. It's a very local ground wave activity. Probably a lot of this has died out over the years, replaced by off the shelf VHF FM.

    The problem is when operators of low power stations fail to realize their limits and repeatedly attempt to contact distant tall ships at night, thinking there is reciprocity in readability between their 25 watts and the other guy running a broadcast rig, audio processing and a vertical with a complete ground system.
    WA3VJB and K4KYV like this.
  7. W7IMM

    W7IMM Premium Subscriber QRZ Page

    I get on 160 with mine fairly frequently. It puts out 50w of carrier and seems to be modulating to nearly 100% (although I have not set up a scope to check)

    I did remove the L-network from the radio and set it up as a more standard Pi-network output.

    It does more power output than a Ranger or AF67 so I wouldn't necessarily call it "low" power . It is probably low power if you're used to running A KW-1 or a Johnson Desk Kilowatt. But there's almost no one around here running more than 100w.

    Most all of the people I am talking to around the NW (ID, WA, OR, NV, Ca) are running less than 100w carrier using either Kenwood, Icom, or other newer stuff driving linear amplifiers .....

    And I would call them low level modulated.... No one seems to be able to tell much difference between my 50W (high level modulated) and the others.
  8. W2ILA

    W2ILA Ham Member QRZ Page

    I am using a Simpson 55 on 1885, 1945, 3885. It was given to me in new in the box along with a receipt from the late '60's. The output is about 30 watts and the carbon mic works pretty well.
    These are fun rigs to put on the air.
    WA3VJB likes this.
  9. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    I have a Kaar transmitter-receiver that mount in a standard 19" rack. The receiver covers the broadcast band plus up to around 2400 kc/s. It may extend up through 75m, but I'm not sure. The transmitter is crystal controlled and takes old style round crystals that fit in a 5-pin tube socket, but the receiver uses standard tuning like any other AMBC receiver. I'm not sure, but the receiver may have the option of crystal control. It looks like a high quality broadcast receiver from the late 30s.

    The transmitter uses a pair of 807s modulated by another pair. The output stage is not pi-network nor is there a coupling link; it uses taps on the tank coil. Probably an L-network. As I recall it uses a carbon mic.

    I haven't tried to fire up either transmitter or receiver since I picked them up years ago at a hamfest. That's a project for 'one of these days'.

    With a few modifications to make it more amateur-friendly, and necessary changes in the audio (likely to be stock 'communications quality'), it should make a nice 160m station in the 100-watt class when used with a good antenna*.

    *I DON'T mean an inverted-L or short vertical with no ground radials, or dipole/inverted vee/G5RV/long wire, 18-20' off the ground.
  10. W7IMM

    W7IMM Premium Subscriber QRZ Page

    They are indeed!!:D

    It's amazing that the one I have using a 12JB6 final tube will put out 50w carrier and with 100% mod, would do approx 200w PEP!

    For those that are not familiar with the 12JB6, it's the 12v filament version of the 6JB6 ( DRAKE T-4X B/C) and of course the Drake TR-3 uses three 12JB6's.

    Even at 50w carrier, the tube doesn't seem to get prohibitively hot ........presumably because it's being operated Class C (17w plate dissipation)
    With reasonable efficiency, it appears that at 50W output, the input power would be a little less than 70w or so. (I haven't actually measured it though)

    Also interesting is the solid-state modulator (2 high power push-pull PNP germanium transistors with a small but seemingly effective modulation transformer, All running on 12vDC.

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