Hey, guys. Just spent the day trying to set up a cb in my 72 duster. Wired the power cable to a cigarette adapter (worked flawlessly) ran coax cable from magnet mount on trunk all the way up to the radio through back seat. Followed antenna tuning instructions (cut-to-size cobra antenna) and channels 1 and 40 match in swr. I just can't get them to be below about 5. Definitely not a usable reading. Any ideas on how to fix this issue? Thanks in advance
Cobra 32XLR CB radio tuning problem
- Thread starter Dusty17
- Start date
-
OwdKasd
Well-Known Member
SWR's are normally adjusted by antenna length. Sometimes you can shorten the Coax and bring the SWR's down. Can you try mounting the antenna on the roof??? That would be a great start to diagnosing it.
67Dart273
Well-Known Member
I don't have a lot of faith in mag mounts at lower frequencies. CB is low enough to be suspect. That is, the mag mount may not offer a very effective RF ground.
Is this a new antenna? Did you put the connector on the cable? Sure it's OK?
I hope you cut the antenna LONG according to the chart, as obviously, once it's too short, it's "too short."
Do you for certain know how to use an SWR bridge? What does it measure on 1, 20, 40? There should be SOME difference.
Cutting coax is not really a legitimate way of reducing SWR. It gets complicated, but trimming the coax only changes SWR at one point on the cable. That may or may not be at the transmitter. The fact is, that with a a properly matched, or "flat" load at the antenna end, it doesn't matter how long, or short, the coax is.
How close to the car is any metal buildings, masts, or another CB antenna?
An old vhf trick is to either get a helper or prop up the power meter so you can see it, and tape the PTT down. Go back to the antenna and watch the SWR. Reach out, to keep your body away, and move your hand near the top of the antenna. Be careful NOT TO TOUCH it!!!!
When you move your hand near--- if the SWR goes up--- the whip is too long
If the SWR goes down--- the whip is too short
Is this a new antenna? Did you put the connector on the cable? Sure it's OK?
I hope you cut the antenna LONG according to the chart, as obviously, once it's too short, it's "too short."
Do you for certain know how to use an SWR bridge? What does it measure on 1, 20, 40? There should be SOME difference.
Cutting coax is not really a legitimate way of reducing SWR. It gets complicated, but trimming the coax only changes SWR at one point on the cable. That may or may not be at the transmitter. The fact is, that with a a properly matched, or "flat" load at the antenna end, it doesn't matter how long, or short, the coax is.
How close to the car is any metal buildings, masts, or another CB antenna?
An old vhf trick is to either get a helper or prop up the power meter so you can see it, and tape the PTT down. Go back to the antenna and watch the SWR. Reach out, to keep your body away, and move your hand near the top of the antenna. Be careful NOT TO TOUCH it!!!!
When you move your hand near--- if the SWR goes up--- the whip is too long
If the SWR goes down--- the whip is too short
Ok, i've re adjusted the antenna but it still doesn't seem to bring channels 1 and 40 down to a usable level. Ended up hearing a guy from Fortworth, TX all the way from here in jersey, but the SWR still reads 4 and over. I tried putting the antenna on the roof instead of the trunk but still no luck. Thinking along the lines of getting a ground wire to the trunk via inside of it. Does anybody have pictures or instructions on how i might do that? Maybe ground straps or some type of magnetic connector? Thanks
-
