RadioReference on Facebook   RadioReference on Twitter   RadioReference Blog
 

Go Back   The RadioReference.com Forums > Commercial, Professional Radio and Personal Radio > CB Radio Forum


CB Radio Forum - Discussions regarding Citizens Band Radio (CB)

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 07-12-2018, 9:03 AM
Newbie
   
Join Date: Jul 2018
Location: London, Ontario
Posts: 3
Default New set up prblems

This is my second vehicle that I am installing a cb radio and experiencing problems.
Bearcat 880 radio
Fire stick 2 4' fibreglass antenna
Jeep JK with antenna mount on back by tire carrier ( powder coated mount and yet I sanded off the coating where the stud makes contact)
18' Wilson super mini 8 coax cable with FME and pL-259 connectors

Confirmed continuity from coax hot tip at radio to tip of antenna
Confirmed coax ground from radio to mount
No continuity between hot tip and ground
Continuity confirmed between antenna mount and vehicle ground and even to battery negative terminal

Very high SWR on all channels
1: 4.55
40: 8.5

Antenna diagnostic passes on channels 1-16
RF out diagnostic fails on all channels

Confirmed tight connections
Confirmed no shorts
Confirmed proper stud installation

Wire is new
Antenna is new
Stud is new
Radio is new

Now what????

I am welcome to any advice / help.
Reply With Quote
Sponsored links
  #2 (permalink)  
Old 07-12-2018, 9:53 AM
iMONITOR's Avatar
Member
  Premium Subscriber
Premium Subscriber
 
Join Date: Sep 2006
Location: MACOMB, MI.
Posts: 6,731
Default

Have you tuned the antenna with the adjustable tip and a good SWR meter?
Reply With Quote
  #3 (permalink)  
Old 07-12-2018, 11:01 AM
Newbie
   
Join Date: Jul 2018
Location: London, Ontario
Posts: 3
Default Tuning antenna

I haven't tried too much as I was concerned since SWR is >3 on all channels.

BUT...I was under impression that antenna is too short if SWR is lower on channel 40 vs 1 and too long if channel 1 SWR < channel 40 SWR.

I didn't think that it was even tunable at this point given the high SWRs to begin with on all channels. I can certainly try but should I be worried about damaging radio with such high SWRs, even if momentarily (but repeatedly) pressing PTT button during tuning process?
Reply With Quote
  #4 (permalink)  
Old 07-12-2018, 4:13 PM
prcguy's Avatar
Member
   
Join Date: Jun 2006
Posts: 6,743
Default

This exact problem has come up several times in the last year as the tire carrier mount does not provide an adequate ground plane under the antenna to match it. Try temporarily connecting about 9ft of wire, any kind, to the ground side of the mount and stretch it out sideways away from the vehicle. If that provides a good match then you will know its the ground plane problem.

You can try adding a 25pf or 50pf ceramic disc or dipped silver mica capacitor across the hot and ground of the coax at the base of the antenna. A 50v rating would be more than adequate for a stock CB and a 500v rating would handle more power than you could probably come up with. This capacitor will fool the antenna into having some ground plane around it and it should match ok with one of the two values I mentioned.

Quote:
Originally Posted by Bjmatush View Post
This is my second vehicle that I am installing a cb radio and experiencing problems.
Bearcat 880 radio
Fire stick 2 4' fibreglass antenna
Jeep JK with antenna mount on back by tire carrier ( powder coated mount and yet I sanded off the coating where the stud makes contact)
18' Wilson super mini 8 coax cable with FME and pL-259 connectors

Confirmed continuity from coax hot tip at radio to tip of antenna
Confirmed coax ground from radio to mount
No continuity between hot tip and ground
Continuity confirmed between antenna mount and vehicle ground and even to battery negative terminal

Very high SWR on all channels
1: 4.55
40: 8.5

Antenna diagnostic passes on channels 1-16
RF out diagnostic fails on all channels

Confirmed tight connections
Confirmed no shorts
Confirmed proper stud installation

Wire is new
Antenna is new
Stud is new
Radio is new

Now what????

I am welcome to any advice / help.
Reply With Quote
  #5 (permalink)  
Old 07-12-2018, 8:59 PM
Newbie
   
Join Date: Jul 2018
Location: London, Ontario
Posts: 3
Default

Wow...this is awesome information. I will give this a try and post my results.

If I go with capacitor route, will that decrease performance / range of CB?

Can I increase ground plane by adding a metal plate / strip to the mount. Will ground plane be better enhanced with size of mass of metal? I.e. Thin strip of say a 9" x 1" vs a thicker strip of same size?
Reply With Quote
Sponsored links
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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



All times are GMT -5. The time now is 6:28 PM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
All information here is Copyright 2012 by RadioReference.com LLC and Lindsay C. Blanton III.Ad Management by RedTyger
Copyright 2015 by RadioReference.com LLC Privacy Policy  |  Terms and Conditions