CB to GMRS Conversion?

Discussion in 'CB Radio Forum' started by russbrill, Jun 11, 2021.

  1. handlebar

    handlebar Heavy Load Member

    Yo, PJ -- was that Advanced Electronics that was formerly in Carson, CA (mailing address in Gardena) and presently in Redildo Beach or Manhattan Beach or one of those beach towns? I worked at Advanced at Broadway & Victoria in what had been a CHP post. Started out in the Portable Shop -- a 5-station screen room, and moved to SP under Gene Friese WA6MPV (SK) for the last year I was there. He knew I was planning to move back to Alaska, now that I had my 2nd Phone w/Radar, and wanted a more rounded experience beyond radios that could fit into a pocket.
    Motherola sold a huge DVP system to the IRS CID, and I got to have a hand in aligning them and doing mountaintop repeater installations. This was WAAAAYYY before AES & other fancy encryption methods.
    I was there from 1978 to 1981, when I moved back to Alaska, worked for Industrial Electronics in Anchorage (a GE, RCA, and Icom warranty dealer). I then got hired as a paramedic/firefighter in Soldotna, and retired 16 years later (I had 5 years under my belt in Fairbanks, and Alaska was a "20 and out" retirement state.
    Way cool to meet meet another "ExMO" :)
    diddly dahdidah
    dit dit
     
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  3. handlebar

    handlebar Heavy Load Member

    Powder Joints is right -- you can only filter out so much hash & noise at the receiver end without taking out all of the desired stuff you wanna hear.
    Might be worth putting a couple of RF chokes in the reefer's power lines -- as close to the refer as is possible. If its ground lead is running aaaalllll the way to the battery (and the battery posts and leads are all shiny bright) you might be able to shorten the ground path by finding a shorter path to a good, solid ground.
    I must admit to bafflement that the noise is *only* on Ch 19. AND that it's on FM.
    Now I'm just spitballing here, but unless there are literally thousands of drivers using GMRS on Ch 19, mayhap a few judiciously placed posts on forums (like here, f'r instance) to suggest Ch 16 (the old, old SSB channel for 23-channel radios -- and yes, I'm that old -- or some other easy to remember channel (just make sure it's a full-power channel). BTW, how many channels either side of 19 are you hearing any noise at all. And is the noise pulsing, or varying up and down (like a non-musical siren) ? Remember discriminator noise ("FM squelch noise") is much louder than AM background noise. FM receivers have couple of amplifiers to remove all AM variations so that the only signals left "modulation" are in frequency. Hence the term "frequency modulation." Speaking of which, FM signals DO NOT get stronger with higher "modulation". No amount of modulation on an FM signal will make the transmitted signal stronger. All it does is cause adjacent channel splatter, which is outside the range of a properly designed receiver. I.F. filters in at least two stages keep all the A.M. fluctuations out of the detector stage (called either a discriminator or phase detector, depending upon the design) so that the only audio that comes out is the result of the minute changes in frequency, which were impressed upon the transmitter's carrier. All that junk in between the mic jack and the volume control on the receiver is just a way to vary the transmitter's signal and sucking it out of the received signal.
    If you can find any variation in the signal you hear on your radio at start up, running, or shutdown of the refer, or if you can hear it "drift" up or down in frequency by following with the channel selector, that would be good to know. It *could* be something in the temperature sensor circuit that tells the refer to turn on or off. Perchance its manufacturer can suggest a fix, or maybe even substitute a part or assembly....maybe as a freebie to free them up from any future complaints or lawsuits.
    If you go into their headquarters (assuming it isn't in the Philippines or Madagascar) and speak nicely with records of what you've seen, what you've tried, and what the results have been they're likely to receive you more cordially than, "Hey, your ### refer is killing my truck!"
     
  4. handlebar

    handlebar Heavy Load Member


    Try going to GMRS.net
     
  5. Timin770

    Timin770 Road Train Member

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    Thanks HandleB. I think I've ascertained that the radio needs to be fairly close to the reefer control panel to cause trouble. It's only channel 19.

    I believe you are correct in the dIfficulties establishing a trucker channel on GMRS. I simply bought two handhelds for evaluation and for my own amusement. The fact that Wolcott now carries GMRS must be encouraging for GMRS proponents.
     
  6. handlebar

    handlebar Heavy Load Member

    There's another GMRS net, in some ways better than qrz.com (a site for hams) which is mygmrs.com
    There will be a couple of hoops to jump through -- name, callsign, whether you have any repeaters of your own that you'd like to list, etc.
    You can look up repeaters by frequency, access tone, state, city, private/restricted/public, and a map will display showing the repeater's reported location and approximate coverage radius. I'm a ham, but while my HF ham rig is kinda difficult to manipulate whilst in motion, it's great when I'm parked.
    I use 2m and 440 mobile, and usually listen on the unofficial "ham calling channels" -- 146.520 and 446.000.
    And, of course, the obligatory CB on 19 until the "filth festival" starts up near truck stops and highway interchanges.

    If stuff is too busy, I mute the 2m and 440 radios, and put in a couple of GMRS repeaters on the "other" UHF radio. I can nearly always raise someone there.

    so...... myGMRS.com - GMRS Repeater Directory

    Mounting a "for-real" UHF antenna on the roof or fender may help. If your roof is plastic, even though you can put up a a 12-inch diameter aluminum plate where you want the antenna to go, then drill through the center (and some gorilla snot to glue down the rest of it) you'll get way better range than the rubber duckie antenna on the handheld. And putting the antenna on a front fender will help the cab body shield some of the ick (technical term) from the refer from getting to your rig, it's still a handheld. Part of the way handhelds (and all teensy mobiles) save size and weight is by leaving out bulky components -- like interstage shielding, better & more shielding, helical receiver front ends, and the like.

    If the radios you bought to test with are 0.5 watt FRS radios, (some go to 1 watt on "official" GMRS channels) then your radio is likely to pick up all kinds of stuff -- including control circuitry in your refer. Suggestion: have another truck with a properly installed GMRS radio pull up next to yours, and see if you can hear *his* refer noise.

    If not, you may have found the cause(s) for your problem.
    Also, as far as short range is concerned, recall that your FRS radio is a "bunny radio" -- All ears, no mouth. (The opposite is an alligator radio, like 1500 watts and a receiver with a blown first RF amp transistor -- All mouth, no ears :)
    Enjoy!
     
  7. Timin770

    Timin770 Road Train Member

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    Are mobile GMRS antennas smaller than some of the behemoth CB antennas I see these days? Are they easier to get set up properly?;There must be 1000 posts on this forum re the trials and tribulations of setting up 11 meter antennas
     
  8. Powder Joints

    Powder Joints Subjective Prognosticator

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    I was there back in I think 1981 or maybe 1982 thru 1984, At Broadway & Victoria in Gardena. Had a little truckstop (Chinese I think) had great split pea soup. Worked with Dale a lot on IRS Installs, the base station end , installing dishes on rooftops, speedwrapping till mi fingers were f=going to fall off. Good Days indeed. I did the drywall in Teryy Adams house in Long Beach for him, I think I charges him a couple of beers.
     
  9. Night Stalker10

    Night Stalker10 Road Train Member

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    A UHF mobile antenna can be 12 to 34 inches long. It depends on the gain of the antenna. All mobile antennas have to follow the law of physics. Basically they work best on a metal vehicle.
     
  10. Powder Joints

    Powder Joints Subjective Prognosticator

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    In the commerical world the average uhf (450-512 ballpark) were between 4 and 5 inches, vhf (150 ) were around 18 or so. gain antennas were bigger (800 - 900) gain were around 14 inches or so aprox. Motorola factory nmo mount antennas were all we delt with. Low Band (42 mhz) we'd cut down 102 steel whips to freq requirement.
     
    Night Stalker10 Thanks this.
  11. Powder Joints

    Powder Joints Subjective Prognosticator

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    According to Gene thanks not what FM stands for, I was told it just Fn Magic
     
    Crude Truckin' and handlebar Thank this.
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