Anyone using FM yet???

Discussion in 'CB Radio Forum' started by russbrill, Mar 17, 2024.

  1. russbrill

    russbrill Medium Load Member

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    Both Cobra and President have FCC compliant CB radios for AM/FM/SSB. Has anyone been using FM?

    73,
    Russ
     
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  3. NightWind

    NightWind Road Train Member

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    It depends on who I am running with and if they can
     
  4. Timin770

    Timin770 Road Train Member

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    I haven't heard anybody on FM
     
  5. Ex-Trucker Alex

    Ex-Trucker Alex Heavy Load Member

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    I hear that there's no static at all!
     
  6. Ridgeline

    Ridgeline Road Train Member

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    FM …
     
  7. Ex-Trucker Alex

    Ex-Trucker Alex Heavy Load Member

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    (no static at all....)

    Give her some funked up muzak, she treats you nice
    Feed her some hungry reggae, she'll love you twice
    The girls don't seem to care tonight
    As long as the mood is right.......
     
  8. handlebar

    handlebar Heavy Load Member

    Well, when folks are close enough together to achieve what's called "full quieting" in each others' receivers, you're right: there's no static. But tune to a channel where nobody is talking and switch to FM with the squelch all the way, off you'll hear massive "static" -- what's called "discriminator noise." It comes from the receiver trying to amplify the incoming signal so greatly that there's no perceived changing in the background noise.. Once all that A.M. noise it "limited" by a circuit called, you guessed it -- the limiter, then the receiver can listen for just changes in the incoming signal's frequency. Hence the term "frequency modulation." When everybody's strong enough in everyone else's receiver on FM, then yup, it'll sound as good as typical police & fire radio systems.

    Sometime when you've got idle time, tune across your "be-bop radio's" dial on FM. In places where there are only weak stations, a built-in FM squelch circuit will typically mute (or "squelch") said diiscriminator noise until the received signal has suttidient strength to overcome the weak signal squelch, and you'll hear your station(s).

    Seems like it qood idea to start to establilsh some calling and working channels on FM. That'll save a lot of frustration from 'FM users only barely being able to hear traditional AM (or SSB) transmissions, and FM transmissions on the agreed-upon channels will be heard best by other FM stations. FM on an AM radio sounds like just so much noise. And AM heard on an FM radio will be really faint (even with a strong carrier; the AM modulation will only be discernible by a handful of skillful listeners who can recognize someone trying to talk "crossmode,".

    So FM can make a lot of conversations more pleasant to the ear. It'll just take a little discipline in its use. And for heaven's sake, please don't let some Golden Screwdriver go inside and start twisting pots like "FM Deviation" in the incorrect assumption (or sales pitch) that "louder FM will carry farther." FM is a whole differrent animal from AM & SSB. If a shop doesn't have a "for real" service monitor bench gear, there's no way to set FM parameters right in your new Super Whizbang Phartblast 9000 multi-mode radio., It might mean taking your radio to a professional Land Mobile (commercial radio) maintenance facility and paying them for a minimum charge to optimize your rig(s) with an ear towards using FM. If your "tech" tunes your transmitter by whistling loudly into the microphone while watching the power output on FM, the output power *should not change" with modulation. If all the tech does is turn up the "FM Deviation" (max frequency excursion with loud input) the power should stay exactly where it was with a "deak key." This ain't rocket surgery, folks, but it's a #### sight closer to it than just clipping an AM mod pot or diode and sending trash out all over the band. And since proper service monitors, and the years of experience to use them properly take years & $$$, expext to have to pay a littlle more than a trip to a "snip & shout" so-called CB tech. But, after it's set, don't keep dinking with it. Short of a piece of the transmisster in an FM rig failing, there shouldn't be any need to go removing TX Limiter or FM Mod compoments.
    Fifty years experience as a commercial Land Mobile Radio and navigation radar tech here. I've got no do in the fight about getting y'all's radios running right, but ask around to see who to trust. Might even be worth biting the bullet and asking a ham (shudder!?) where they go for work on their VHF & UHF FM ham gear to help. After all, it can't hurt......and you don't even have to admit to having taken your CB rig to a ham for help./ We're not all ########.
    73 to all.
    Handlebar: 61 year ham, 55 year CBer, 53 year commercial tech, 15 year GMRS repeater system owner & tech.
     
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