CB Tuning: Bad SWR Meter, Bad Antenna, Bad CB?

Beowulf

Expedition Leader
#1
I bought a SWR meter and tried to do tune my CB setup.
  • Cobra C75WXST: CB Radio
  • SWR Meter Workman SWR2T
  • Jumper Cable RG58A
  • Firestik antenna on a push and twist disconnect
I am not really able to talk well with another vehicle even 100yrds way. Emergency weather seems to pull in on at least one channel even without the antenna. When scanning I usually only get one channel and can never really hear it well.

I attempted to tune the setup, but could not get the SWR meter to register anything. I jumped the CB module to the SWR and hooked the antenna cable to other side. Tried to take a reading pressing the PTT button. Nothing!

I followed this video's instructions from Right Channel Radios, but sadly nothing.

It is as simple as having a bad SWR meter, or is there something more sinister at play? Is my antenna so out of whack that it does not even register?

It worked ok for a few years and was tuned when I first set it up with my brother's SWR. I just figured it was time I have my own SWR. Maybe I'll borrow his again and test it out.
 
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#2
If his meter is readily available, certainly worthwhile to give it a try.
I'd lean towards the radio itself being the likely problem as the PTT button should register something on the meter even if the antenna was not there or connected.
 

J!m

Active member
#3
Usually, the main problem is ground.

So, you need a ground plane for the antenna to pick up (or transmit) correctly. If the firestick (generally decent antennas- I use them) is for instance mounted on a mirror, (trucker-style), it may not have much ground plane to reflect off. Think of the antenna as a satellite dish- you need the "dish" part (the ground plane) to bounce/focus the signal to the antenna. That's why cheap magnet mounts on the roof tend to work so well (unless you have an aluminum roof, but that's another story). Line of sight in all directions and a good plane under the antenna. Also why those trucks run "twin ears" with an antenna on each mirror- if they are broadcasting/receiving with someone off the antenna side, they won't pick up (or transmit).

Further re ground: if the center conductor of the mount is grounded, it won't transmit (or receive usually). Typically there are two nylon top hat washers to isolate the center stud of the mount from the mount bracket. If there is a short here (dirt, never-sieze etc.) that's a problem. Be sure it remains clean, particularly after, oh, going to the arctic circle in winter... Use silicone dielectric grease, not a conductive one. And use an OHM meter for testing- disconnect the coax from the mount, touch the center stud where the bayonet mount goes and the other test lead to a known good ground (or the mount- a poor ground will still impair performance). It should show an open circuit. Now, while it's apart, check the coax- the shield should be near zero resistance to ground, and the center conductor should be open to ground.

Check all connections at the radio end as well. Make sure you don't have a bad cable- Check all from shield to center, and make sure all are open. Also check continuity end to end of the shield and center conductor. Just because it's a new cable(s) doesn't mean it's not bad...

Finally, be sure you have full voltage to the radio, and the electrical ground for the radio itself is good. I'm not a fan of the hand held ones, but probably not an issue...
 

FlipperFla

Active member
#5
I agree with the above posts about checking the ground. I had a similar problem ( not with the meter not moving at all) but with the firestick. Cobra radio, workman SWR meter and RG8X cable and jumper cable for the meter. Good ground on the radio, and a gutter antenna mount which was screwed directly to the body of the truck. Ohmed both to make sure. I just couldnt get a good low SWR with the Firestick. Switched to a Tram steel antenna and had no issue at all with the SWR. I know Firesticks are great antennas but it just didnt work in my application. With no output at all it sounds like you have anothet issue as Wirenut and Jim stated in their posts.
 

DaveInDenver

Expedition Leader
#6
If you don't move the meter at all I suspect a bad radio
It's possible if the antenna is shorted, not grounded, bad coax or something other major issue the radio will see a short or open circuit and the output will fold back, meaning the output amp will reduce it's power to zero in order to protect itself. You may see the power blip or jump and go to zero, you may see nothing.

Not sure how this particular Cobra works in this respect, if it even has output protection at all, so just generally speaking. One way to test this is replace the antenna with a dummy load and see if the radio output stays on. A dummy load is a purely 50 ohm resistive load to the radio. It's a terrible antenna but an ideal electrical load, so the radio will work as though you have a perfectly tuned antenna.

The other troubleshooting steps are covered in other posts, check grounds, check connections, check cables.
 
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#9
Just remember Workman products are not know for high quality..... Do you have another radio to try it on? because if you can talk to somebody 100 yards away, I'm going bad radio.
 
#11
I have a similar setup, except my needle is moving too far into the red. My first time trying to tune a CB, my original install worked perfectly right off the bat so I got lucky and didn't have to work through these challenges. I have changed to a different mount and location (off the side of the hood), bought a new cord and am about to start testing for shorts in the system. I keep getting a 3-4. I am watching this thread to hear all the good info! I have taken this opportunity to learn more about electrical circuits and whatnot as well. Good luck!
 

J!m

Active member
#12
The Ham GUY’S are far more knowledgeable than I am, but since I was a little kid Dad had a wicked CB rig in the house and in whatever car he was driving. He worked about 45 minutes drive from home and we could chat on that CB rig pretty much right away.

So by exposure/default I know CBs. I also installled old junky ones in my friends cars and we’d play hide n seek with cars...

Re that fire stick that just wouldn’t work- I’d check to see if it hit something and broke the wire. Alll they are is coated copper wire wound around a fiberglass stick and shrink wrapped. On the older radios (without internal tune) it was always an event piling the rubber cap and trimming the wire to dial in SWR. Stainless whips had to be cut at the base. Good times.
 
#13
I have a similar setup, except my needle is moving too far into the red. My first time trying to tune a CB, my original install worked perfectly right off the bat so I got lucky and didn't have to work through these challenges. I have changed to a different mount and location (off the side of the hood), bought a new cord and am about to start testing for shorts in the system. I keep getting a 3-4. I am watching this thread to hear all the good info! I have taken this opportunity to learn more about electrical circuits and whatnot as well. Good luck!
Make sure the mount is well grounded to the body of the vehicle. If the antenna mount it painted or powder coated remove any of it where the mount touches the body and where it touches the bottom of the antenna stud.
 
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