Cobra 200 noisy RX

Discussion in 'CB Radio Forum' started by PtownBubba, Feb 12, 2021.

  1. PtownBubba

    PtownBubba Bobtail Member

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    I have this Cobra 200, it is a few years old,, but has less than 10 hours on it,, it seems to boom out,, but the receive is pretty weird. There is like 3-5 noise on RX meter, no matter what vehicle, or where I am,, even in garage,, where RX on meter should be almost "0". I have both leads going direct to battery,,, was thinking about putting an additional ground tap on ground lead to a metal surface in cab. this noise, has pretty much always been like this, that is why I never used it much,,,, sure is a sharp looking radio,,,,, can the RF be tuned to clean up the white noise,,, and still get good RX ? Just love the look of this radio,, really want it to work,, hate to just throw it back on the shelf. Cobra 200.jpg
     
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  3. Crude Truckin'

    Crude Truckin' Alien Spacecraft

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    Does it have that noise in a different setting? ie a different vehicle or house? Might be your vehicle
     
  4. PtownBubba

    PtownBubba Bobtail Member

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    Yes,, noise stays with radio,, in any vehicle, any antenna, any outside location,, mobile or base setup,,,, driving me nuts,, always been this way,, older radio, with very little use ,, but looks great,,, really sad,,
     
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  5. Night Stalker10

    Night Stalker10 Heavy Load Member

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    What's the noise level on the meter with the coax disconnected? Is it worse with motor running or off. I would disconnect ground cable from battery, and ground the radio to the vehicles frame as close to the radio as you can. I wouldn't have a receive alignment done until you determine if it's the radio or the antenna system.
     
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  6. Night Stalker10

    Night Stalker10 Heavy Load Member

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    I see you added additional information before I posted. Since the radio has always had noisy receive in any vehicle or antenna, it sounds like someone has turned the RF gain pot all the way up inside the radio. This will drastically bring up the noise floor in the receive circuit of the radio.
     
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  7. PtownBubba

    PtownBubba Bobtail Member

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    Ok,, thanks,, if this pot is turned back,, will that kill the rx input as well,, but guess it does not matter,, any signal less than 4-5 on meter does not come in well anyway,,,I can turn the RF gain down of course to kill white noise,, but that also blocks the incoming RX signal,,, correct ?
     
  8. Night Stalker10

    Night Stalker10 Heavy Load Member

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    Yes, if it's turned down too much, it will effect the radios receive. I have seen some radios where this pot was turned all the way up. Maybe because the receiver alignment wasn't done correctly, or someone just messing with the adjustments. You really need the proper test equipment to do a proper receiver alignment. Also the service manual has you adjust the receive cans for maximum receive voltage or gain. This isn't good because it just allows the noise in the radios receive section (the noise the components generate), to be amplified and then your radios receive is noisy. Basically like what your radio is doing. Thats what happens when you watch people on ytube videos who claim they can tune a radio by ear.
     
    Last edited: Feb 13, 2021
  9. Ridgeline

    Ridgeline Road Train Member

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    There is no adjustment inside the radio for the receive strip.

    To the op, here are my questions.

    has anyone messed with the radio? Meaning you had it peaked and tuned?

    try this ... take off the coax from the back to see if it still has the noise.

    if the level of noise is still there, but reduced it may environmental around you, i had at my old house cable leaking and killing 15, cb and 10 meters.

    Try this too, put it into another vehicle, drive somewhere where there is no power lines and seen if you still have the noise.
     
  10. Night Stalker10

    Night Stalker10 Heavy Load Member

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    Ptown, it's looks like I was wrong about the gain pot. After looking at the schematic and service manual, the 200 doesn't have one like the AM cobra 25 and 29 radios. Sorry for mis-leading you. Have you tried removing the coax from the radio yet? Since you've said you've had this radio for a few years, and it always been noisy in different vehicles, it may just need an alignment done. Unless the noise drops significantly by disconnecting the coax.
     
  11. PtownBubba

    PtownBubba Bobtail Member

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    Discovered something interesting,,,,, with any radio , I have ever had,,, I seemed to always have the RF gain set to full,, just sort of an automatic thing,,,,never gave it much thought,, just all were set all the way,,,,and adjust the white noise with squelch,,,,, today,, I backed the RF gain down,, thinking well, that eliminates some noise, but also restricts the incoming voice traffic,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,it really sorta' did not,, I was talking to my buddy,, now this radio booms out,,, he said my signal did not lessen the further away I got, so that part is great,,,but with fine tuning the RF gain and squelch,, it seemed to work pretty decent,, well enough, that 4 miles away,, and IN my garage,,, with the door closed,,, I could still hear him,,, and he could hear me,,, now his audio was pretty weak,, but doable,,, again inside the garage,,,,,,,,,, I have never done that before,,,,,,,,,,,really weird,,,,,so,, right or wrong,, maybe the radio is doing the best it can, with all features,,, I was just to dumb to work with it,,,,,, I got this radio,, who knows how long ago,, new,, from Sparky's CB in Illinois,,, got a lot of stuff from this guy,, he always took care of me,, until he started slipping as his age increased,,,, so he may have tuned it to the max,,,,anyway,,,, still doing some playing around,,, again,, always before I gave up, and put it back on the shelf,,,, but always tried it later,cause it is just a cool looking radio. So,, sorry to put you guys into The Twilight Zone,,, maybe I am the one out of tune,,,, Thanks all,,,be safe, be well,, from Bubba in NW Illinois,,,, p.s. I really like the old Turner mics,,,, I just put a new cord on this one,,, got a couple more to re-cord,, and have a really nice one ,still with a nice original cord,,,they were /are great mics,,,,since I may keep this radio installation, I will clean up the wiring and stuff,,

    Cobra 200 1.jpg
     
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