New set up prblems

Joined
Jul 12, 2018
Messages
3
Location
London, Ontario
#1
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.
 
Joined
Jul 12, 2018
Messages
3
Location
London, Ontario
#3
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?
 
Joined
Jun 30, 2006
Messages
7,194
Location
So Cal - Richardson, TX - Tewksbury, MA
#4
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.

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.
 
Joined
Jul 12, 2018
Messages
3
Location
London, Ontario
#5
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?
 
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