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CB weak at close range

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cbjet52

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Just recently installed 2 Cobra ultras in my off road vehicles. I used firestik antennas and tuned them. My problem is when the vehicles are 3-5 car lengths apart the signal is quiet or weak. At about 100 feet to 5 miles the signal is perfect.

While on the trail offroad vehicles stay fairly close.....

Do I need to tune them differently since the vehicles are never going to be more than 100 yds apart?

Thanks.
 

cbjet52

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no rf gain option,

I did install smaller antennas, which helped a little but not much. They also reduced my range from 5 miles to about 3/4 miles.

I'm thinking I might have to de-tune these antennas to make them weaker but not so much where in puts the radio in danger.
 

com501

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Yup, RF overload. Get a decent radio with an RF gain control if you don't have one now.
 

cbjet52

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Just bought 3 of these cobra radios, getting another radio is not an option. If that's the only fix then thanks anyway, i'll live with it the way it is.

Figured someone on here might be able to explain why it's doing this.
 

WA0CBW

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I don't think you can de-tune the antenna enough to fix the problem. The problem is in the receiver. The receiver front end overloads from the strong signal causing the the radio to not hear. I haven't looked at the specifications of that particular radio (if they actually print them) but I would guess the dynamic range is pretty low and the bandwidth pretty wide. Along with little 2nd IF filtering makes it a poor radio to use in a high (or close) RF environment.

BB
 

com501

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If you want to get techinical, the detector circuit is being swamped. You can go into the front end or in front of the 1st mixer and decouple it by about 60db, that would fix it. Of course, it would also limit your range to visual contact...

This is why expensive radios have gain control.
 

zz0468

QRT
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I'm not sure I understand why you think there's a problem. If they work good at a distance, then LEAVE IT ALONE! If you're 3 feet away, turn the radio off, turn the vehicles off so you don't have to shout, and talk to the guy next to you.
 

zz0468

QRT
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After re-reading the OP a bit closer (coffee helps!), I understand the concern. But I would still suggest you do nothing to diminish the range of the radios. Being able to get out better is a safety feature that I would think over rides having the ability to communicate over a few car lengths. A CB radio with an RF gain control is preferable to detuning the antenna, since the problem is on the receiver end, not the transmitter.
 
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JayMojave

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Dec 13, 2007
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Mojave Ca
Hello CBJet52:

I agree it sounds like a reciver overload problem. I believe some of the older CB radios had two diodes crossed and solderen in some were in the receiver RF Amp to reduce the overload problem.

Also the RF Gain Control is a great thing to have as already menationed, and a good noise elminator, called the NB Switch, is also a good call.

Good Luck

Jay in the Mojave
 
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