CB tuning problems - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

Reply
 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 09-05-2002, 07:54 PM Thread Starter
 
Join Date: Mar 2002
Posts: 232
Thanks: 0
Thanked 0 Times in 0 Posts
 
CB tuning problems

Hey All

I am trying to get my CB squared away, it is giving me fits.

I set it up and tuned it all with the top off. It tuned right away to a SWR of 1.4 all the way across. I figured that would do fairly well for a first shot and then see where it was from there.

Now that the hard top is on, I can't get any sort of consistent results out of the tuning. The SWR numbers are all over the place. It seems like I can't get the same reading twice in a row.

First, the antenna was too long, then too short, then too long, etc, etc etc.

There was a crazy amount of engine noise when I started it up. I went through all sorts of mess trying to get it settled down. Nothing made any difference.

What are the characteristics of a dead coax cable? What would it do if I tweaked it when the top went on? It just seems like I should not have to fight this thing so hard.

Suggestions out of the HAMs and CB folks?

Thanks

John
truckjohn is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 09-05-2002, 07:58 PM
 
Join Date: Dec 1999
Posts: 5,140
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CB tuning problems

unhook coax at the radio, them use a volt/ohm meter check teh coax from tip to ring, there should NOT be continuity.

if there is youve crushed teh inner into the outer, or the mount is a dead short to ground.

also make sure the mount is grounded well.

there should be continuty from the outer of coax to the vehicles body and the antenna mount, but the center conducter should only have continuity with the antenna itself

check out firestik.com

lots of good trouble shooting tips
ozarkjeep is offline  
post #3 of (permalink) Old 09-05-2002, 08:07 PM
Keyboard Implanted
 
Smokngun's Avatar
 
Join Date: Sep 1999
Location: Palmyra, WI
Posts: 2,209
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CB tuning problems

One more thing to check if you are having inconsistent SWR results is the coax connectors themselves. I had the solder on ends on mine and couldn't get it to tune. Same problems as you, up and down on the SWR readings. I switched to the ends that tighten as you screw the connector together around the cable. I haven't had a problem since! I know it was just a bad solder connection, but I re-soldered them twice and no dice so i gave up.
Smokngun is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 09-05-2002, 08:29 PM Thread Starter
 
Join Date: Mar 2002
Posts: 232
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CB tuning problems

My antenna cable is a Belden RG-8 cable, but the short jumper on the SWR meter is just radio shack special RG-8.

I get the feeling that the stupid radio shack cable is no good....... It seems to be too sensitive to the cables being screwed in tight or loose.

Interesting that when I switched the two cables around, I went from SWR all over the place to infinite/ off the scale SWR. That might be a hint that one or both of those cables may have gotten tweaked.

I will ohm it out tonight and see what I get. Maybe I will get lucky and only have a bad cable.

Best regards

John
truckjohn is offline  
post #5 of (permalink) Old 09-05-2002, 09:31 PM Thread Starter
 
Join Date: Mar 2002
Posts: 232
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CB tuning problems

Unlucky again....

Ok, Ohm'd the cables all out -- no breaks. They both check out like they should.
Checked the ground continuity to the outer shield cable -- good.

I had it setup earlier tonight to ~1.6 or so. I would have been happy to leave it there. Checked it again, 2.5-3 and up. This makes no sense to me.

I will probably just take it over to the CB guy and let him try out his magic on the system. *sigh*

If you can think of anything, post it for me.

Thanks

John
truckjohn is offline  
post #6 of (permalink) Old 09-05-2002, 09:40 PM
Keyboard Implanted
 
TOM85CJ7's Avatar
 
Join Date: Sep 1999
Location: Austin, Texas
Posts: 2,072
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CB tuning problems

This may be a stupid question. Are you reinstalling the end cap after each adjustment on the antenna? If not, I have heard that you will make yourself crazy trying to get the proper SWR without the tip on. Just a suggestion.

Tom
TOM85CJ7 is offline  
post #7 of (permalink) Old 09-05-2002, 11:06 PM
 
Join Date: Aug 2001
Posts: 395
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CB tuning problems

It really sounds like a short between the antenna and ground, at least an intermittent one. Here's what I'd do: remove the connector at the back of the radio and be sure there is no continuity between the inner and outer conductors. Have someone push/pulling on the antenna mount while you do it to see if it may be something intermittent.

If no continuity ever, then move on to the cable.
Testing good with a DC meter doesn't mean it is passing RF. You can crush a large portion of the dielectric and kink the inner conductor pretty good without having any outward signs of the damage and good DC continuity. The connection on the connectors can be munged too. Try swapping another cable and see if that helps.
80sCJ7 is offline  
post #8 of (permalink) Old 09-05-2002, 11:26 PM
 
Join Date: Jun 2002
Posts: 138
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CB tuning problems

Put a noise filter on the power supply, it helps w/ the engine noise.
Reverend26 is offline  
post #9 of (permalink) Old 09-06-2002, 07:25 AM Thread Starter
 
Join Date: Mar 2002
Posts: 232
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CB tuning problems

Today I am going to get some new coax. Today at lunch I will get some and see what happens. There are a couple of good pinch looking places in the one I have on there now. It could have gotten boinged pretty good when the hard top went on. Mental note: route cable on the bottom of the roll-bar.

As for the intermittent ground -- I have checked and checked for that. Wiggling cable, tweaking this and that, antenna mount, etc. No continuity between the center pin of the antenna and ground.

The other thing I am wondering about it the antenna's matching lead. I have a Wilson fiberglass. It has the matching lead deal that you don't hook up unless you really need it. I am wondering if the matching lead was pinched or is making contact with the antenna lead in there somewhere it should not.

I tried hooking it up figuring it would drastically change the SWR, but it really didn't. It just made the SWR higher and made the antenna think it was a little shorter. I could not get it under 2.5 with it hooked up so I unhooked it again.

If I had another antenna handy, I would try it out to see if I can figure out where the real problem is.

We will see what the coax does first, though.

Best regards

John
truckjohn is offline  
post #10 of (permalink) Old 09-06-2002, 08:42 AM
thejunker
Guest
 
Posts: n/a
Re: CB tuning problems

Another note on engine noise. If you do not want to buy a noise filter, then here is how to remove 99% of your engine noise.

Run the positive to the battery, the more direct the better, and run the ground to the closest ground point to your CB head. My ground wire is like 4 inches long (no dirty thoughts here), and I get very little interference...

My $0.02
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome