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CB Radio Squeal after stereo amplifier installed ?

B

blaze one

NAXJA Forum User
Location
N.Delta British Columbia Canada
I have a uniden pro510 cb radio installed . it was not tuned , but was in working order prior to the installation of a sony stereo amplifier .

Now that I have the amplifier installed - everytime i press the mic button to talk , I get a loud squeal from the stereo speakers .

I have tried disconnecting the amplifier and the squeal goes away . So it is the amps fault for the squealing .

I have tried several different grounds for the amp as well . No improvement .
All the amp wires are insulated and proporley installed .

the power for the CB Radio is not connected to the stereo in any way .

the amp is grounded under the rear seat .

the antenna is mounted to the roof rack .

What am i doing wrong !!! ???
 
the cb coax is 4 feet away from the speaker wire , that the furthest they can be away from each other , cause a xj is only so wide ...

-- as for the ground ... how else do you ground 2 different devices then ???? currently they are both grouned to the body of the jeep .
 
blaze one said:
-- as for the ground ... how else do you ground 2 different devices then ???? currently they are both grouned to the body of the jeep .
Click to expand...

It's not necessarily related to the grounds; it could simply be that something in the Sony amp does not like having four watts of RF in close proximity to it when you key up the mic. That's not to say that the grounds shouldn't be checked, but that they're very possibly not the only factor at play here.

How is the CB receiving power? Directly from the battery, or is it spliced through to the harness? Is the amp using factory wiring, or is it a custom install? What are the chances of swapping the amp out for a different model and seeing if the same behaviour occurs?
 
I am an Amateur radio operator and I think I can help.

Your amps have line level inputs and these inputs are extremely low voltage and are amplified many, many times and are very sensitive to any RF (radio Frequency) signals.

With that said, there are a couple of things that you can do:

1- Make sure everything is well grounded, including your antenna unless it's a magnet-mount antenna, nothing you can do about that)

2- Make sure that you are using a good quality coax for your antenna.

3- Make sure that your SWR is as close to 1:1 as is humanly possible.

4- Use the best quality input cables from the music source into the amps. The more shielding, the better.

5- Wind the input cables, and power supply cables for the music source and amps through ferrite cores.

6- And lastly, if all else fails, use a good quality low pass filter after your
2 way radio equipment and before your antenna. The low pass filter must be the last thing in line before the antenna and must be well grounded.
 
blaze one said:
the cb power is spliced off of the power mirror harness ( it was close to where i wanted it mounted )
the amp is wired directly to the battery and grounded under the back .
Click to expand...

Power mirror harness? I don't think that power source can reliably power a radio transmitter. You need a higher amperage power supply source than that.
 
blaze one said:
the cb power is spliced off of the power mirror harness ( it was close to where i wanted it mounted )
the amp is wired directly to the battery and grounded under the back .
Click to expand...

I would start by getting a different power source than the mirrors. Wiring up its own power source is a good start.
 
Sorry, accidental double post.
 
Last edited:
Warlock1 said:
6- And lastly, if all else fails, use a good quality low pass filter after your
2 way radio equipment and before your antenna. The low pass filter must be the last thing in line before the antenna and must be well grounded.
Click to expand...

While I'm in agreement with you on everything else you've listed, if the problem is that the amp does not like absorbing the RF his CB is generating, I don't understand how a low- (or band-) pass filter will necessarily help in this case. While it would certainly aid in eliminating the possibility of spurious emissions outside of the CB band being the problem (and may even clean up reception a bit), it doesn't change the band that his CB is operating in - i.e., his basic frequency remains the same. Since this is where the majority of the RF energy is going to be concentrated, it's the most likely cause of the RFI at the amp.

the_weirdo said:
I would start by getting a different power source than the mirrors. Wiring up its own power source is a good start.
Click to expand...

Straight to the battery with an inline fuse would be best. Also, since the antenna is mounted to the roof rack, be sure to check the roof rack to body mounting points are clean and secure.
 
Last edited:
casm said:
While I'm in agreement with you on everything else you've listed, if the problem is that the amp does not like absorbing the RF his CB is generating, I don't understand how a low- (or band-) pass filter will necessarily help in this case. While it would certainly aid in eliminating the possibility of spurious emissions outside of the CB band being the problem (and may even clean up reception a bit), it doesn't change the band that his CB is operating in - i.e., his basic frequency remains the same. Since this is where the majority of the RF energy is going to be concentrated, it's the most likely cause of the RFI at the amp.
Click to expand...


This one was strictly if the problem lies in the front end of his music source, ie; if the music source (AM/FM receiver) was picking up the signal through the AM or FM band that he might have been listening to at the time through spurious emissions or harmonics . I just wanted to cover all bases without having to resort to a Q&A session or lengthy descriptions to try to keep my response post as brief as possible. :wave:
 
Warlock1 said:
This one was strictly if the problem lies in the front end of his music source, ie; if the music source (AM/FM receiver) was picking up the signal through the AM or FM band that he might have been listening to at the time through spurious emissions or harmonics .
Click to expand...

Gotcha. I was actually wondering why he had the amp on at the same time as the CB - it seems to me that from at least the standpoint of practicality, having the stereo playing at the same time as you're trying to use the CB is self-defeating.

I just wanted to cover all bases without having to resort to a Q&A session or lengthy descriptions to try to keep my response post as brief as possible. :wave:
Click to expand...

Understood, makes sense now. I'm a ham as well, so when I read the original post I had a, "hang on a sec" moment.
 
Yea, I probably would have done the same thing.
 
Warlock1 said:
I am an Amateur radio operator and I think I can help.

Your amps have line level inputs and these inputs are extremely low voltage and are amplified many, many times and are very sensitive to any RF (radio Frequency) signals.

With that said, there are a couple of things that you can do:

1- Make sure everything is well grounded, including your antenna unless it's a magnet-mount antenna, nothing you can do about that)

2- Make sure that you are using a good quality coax for your antenna.

3- Make sure that your SWR is as close to 1:1 as is humanly possible.

4- Use the best quality input cables from the music source into the amps. The more shielding, the better.

5- Wind the input cables, and power supply cables for the music source and amps through ferrite cores.

6- And lastly, if all else fails, use a good quality low pass filter after your
2 way radio equipment and before your antenna. The low pass filter must be the last thing in line before the antenna and must be well grounded.
Click to expand...
All great suggestions. I'd even go a step further and make that choke into a pi filter by putting a capacitor to ground on both ends of it. Use the largest ferrite core you can find, old "ignition condenser" type capacitors, or any 20+ volt, 1uF (not very critical on the capacitance) ceramic or foil capacitor if you can't find those.

(I'm a ham also - W1KAS)
 
all of this talk of filter , capacitors ... etc . is getting a bit to techie for me .

I may just put a switch in the amp power wire so I can switch the power off / on . That way I can totaly isolate the amplifier from the truck .

I also have noticed that the squeal on happens when i key the mic with the antenna attacted . If i remove the antenna , and go to tx . no squeal .

I will move the power supply for the cb from the mirror splice to the battery tonight .
 
blaze one said:
I may just put a switch in the amp power wire so I can switch the power off / on . That way I can totaly isolate the amplifier from the truck .
Click to expand...

That's probably your quickest and easiest option.

I also have noticed that the squeal on happens when i key the mic with the antenna attacted . If i remove the antenna , and go to tx . no squeal .
Click to expand...

This really isn't something you want to do habitually; running your CB for long enough without an antenna can burn it out. How quickly depends on a few factors, but as a rule of thumb: not a good idea to do that.
 
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