CB Issues - Exhausted all research

2419 Views 16 Replies 8 Participants Last post by Bobby Boucher, Dec 28, 2015

Bobby Boucher

Discussion Starter · Mar 4, 2015 (Edited)

First off, I HATE posting questions, stuff like this is a pet peeve. But I can't find what I need.

I installed a CB back in December, and I love it except I can't get it tuned correctly. In other words it will not stay tuned. Some stats with the engine OFF:

Best SWR I got was 1.9 on 1, 2.2 on 40
Then it was at 2.8-3.0 on channels 1 and 40 after no changes
Then SWR was at 2.8 on 1, and at 6.0+ at channel 40 after no changes
I didn't know the SWR could go that high!!

I have no idea why these readings would be so far off, and change so much without me touching anything. Any ideas from anyone?

Location of the CB. The radio is wired directly from the battery, which gives the "cleanest" form of power. The coax goes under the floor mat, and runs under the panels of the driver side and then out the rear of the cab.

Mounting point, between tool box and the cab directly center. There is no ground wire because the mount uses the bed as the ground. But is the bed grounded to the frame?

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olds88

· #2 · Mar 4, 2015 (Edited)

well first off how big is the antenna and how do u have the coax ran also here is some good reading CBRadioMagazine.com - CB Radio Articles

oh and here as well been on here for a few years http://www.worldwidedx.com

08Canyon

· #3 · Mar 4, 2015

It has been forever that I've matched an antenna. Doesn't it have something to do with the length of the whip though? If you aren't able to get it more stable I mean, then the length isnt right? Last time I had a CB was mid 90's. I used them and matched them in late 80's/early 90's. I have a radio in the attic if 17 years of California garage attic heat hasn't fried it. LOL

Do you have an alternate base? Mount it elsewhere as a test to see if you can get better readings?

olds88

· #4 · Mar 4, 2015

ya i have no problems lol

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Bobby Boucher

Discussion Starter · #5 · Mar 4, 2015

olds88 said:
well first off how big is the antenna and how do u have the coax ran

I mentioned how I ran the coax above and the whip is 4". I forgot to mention it.

08Canyon said:
It has been forever that I've matched an antenna. Doesn't it have something to do with the length of the whip though? If you aren't able to get it more stable I mean, then the length isnt right?
Do you have an alternate base? Mount it elsewhere as a test to see if you can get better readings?

It does, but between the differing SWR reading I did not change the length of the antenna. I don't have an alternate base right now, and I won't be able to get one for a while.

olds88

· #6 · Mar 4, 2015

I ment coax does not coiled up and tight

olds88

· #7 · Mar 4, 2015

what grade coax u got i don't think it would be a bad ground plane as many others here have a same ish mount also check again make shure the antenna is grounded

if any thing that antenna could be to short to go there thats a lot of steel the bounce back

6651

· #8 · Mar 4, 2015

Is the the SWR still fluctuating? Often the best practice is to run wide braided copper from the antenna mount to the bed wall nearest the antenna and then to the floor of the bed and onto the frame, 2 connections each would be good. It cannot be assumed that the existing mount will remain RF and DC continuous without adding the braided straps, there are too many points of wear, movement and corrosion to consider. The end result would be intermittent ground plane connection to the antenna mount--drifting SWR. Also check the PL259 connections. Then trim the antenna for best match. Works for me.

Supermodulation

· #9 · Mar 4, 2015

First, your antenna is located is the wrong place. Your getting bounce back.
Your antenna is called an end feed which is high Q. Any close metallic objects will de-tune it.
Either mount it on the roof which is the best for omnidirectional or the rear of the bed which is aiming forward great for skip.

If your getting ignition noise or alternator wine. Run your power + and - directly from the battery. If your still getting noise then add an inline filter. In worse case conditions I have had to use RG-8/RG-213 shield coax cable for the power wire.

Bobby Boucher

Discussion Starter · #10 · Mar 4, 2015

olds88 said:
what grade coax u got i don't think it would be a bad ground plane as many others here have a same ish mount also check again make shure the antenna is grounded

I don't know what grade I am, and I could not find one. I know the shielding is 95%.

BillyC said:
Is the the SWR still fluctuating? Often the best practice is to run wide braided copper from the antenna mount to the bed wall nearest the antenna and then to the floor of the bed and onto the frame, 2 connections each would be good. It cannot be assumed that the existing mount will remain RF and DC continuous without adding the braided straps, there are too many points of wear, movement and corrosion to consider. The end result would be intermittent ground plane connection to the antenna mount--drifting SWR. Also check the PL259 connections. Then trim the antenna for best match. Works for me.

I haven't checked in a few days, but I assume it is. So is the bed not grounded to the frame then? If braided cable worked for you I'm more than willing to try it!

Supermodulation said:
First, your antenna is located is the wrong place. Your getting bounce back.
Your antenna is called an end feed which is high Q. Any close metallic objects will de-tune it.
Either mount it on the roof which is the best for omnidirectional or the rear of the bed which is aiming forward great for skip.

If your getting ignition noise or alternator wine. Run your power + and - directly from the battery. If your still getting noise then add an inline filter. In worse case conditions I have had to use RG-8/RG-213 shield coax cable for the power wire.

Never heard of bounce back before but it makes complete sense. So the strength of the radio waves depends on the antennas location on the ground plane? No ignition noise, + and - are coming directly from the battery.

93nav

· #11 · Mar 5, 2015

You are getting different results. Is the pickup always in the same spot, facing the same direction etc when you test? I know nothing about radios, but just a thought that occurred to me (limit the variables).

olds88

· #12 · Mar 5, 2015

yes because of the size and placement it favor's off the rear of the truck same can be said when running a duel antenna also 90* front and rear

really the info in cb radio mag is every thing you would need to know that's why I linked it

Bobby Boucher

Discussion Starter · #13 · Mar 23, 2015

Re: CB Issues - New Mount!

Heeding the advice from this thread, I purchased and installed a Firestik doorjamb mount. That almost singlehandedly solved all my problems!! I don't want to be premature at all, but lets see what happens after a week or two!

SWR: 1.1 on ch.1 and 1.4 on ch.40

It's just a steelmark, but :steelers:

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Slow & Wide

· #14 · Nov 16, 2015

Her is a little interesting info I found on antenna placement

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Bobby Boucher

Discussion Starter · #15 · Nov 16, 2015

Link? I believe it has something to do with where you ground the antenna but I'm not sure

Dubfire98

· #16 · Dec 23, 2015

using ground straps to "tie" your body panels together is also a good idea. There are a hundred things that could throw your swr off. When you tune anything you want to be in as wide an open space away from anything as you can get

Bobby Boucher

Discussion Starter · #17 · Dec 28, 2015

Right now the stupid thing isn't even transmitting. But before it started acting up my new position was giving me a near perfect ratio.

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