CB tuning help

[adamb95]

I just installed a new CB radio and have been trying to tune it using a SWR meter I got off Amazon. My SWR reading on channel 1 and 40 are both around 2.5. I sanded all the paint off underneath my mount to ensure my antenna is grounded properly. I have an 18' coax and I have looped the small amount of extra cable into a figure 8. I have no idea why the SWR reading is so high. It seems like I have done everything right. The only reason I can think of is maybe there is some interference or feedback between the Jeep body and the antenna. I would appreciate any thoughts or advice.

[adamb95]

I forgot to mention that I was testing the SWR in an open area with no trees or power lines nearby.

[TerryD]

Where were you checking it? What brand antenna do you have? Is it adjustable?

[adamb95]

I drove to research center drive near the airport to check it. I was more than 20 feet away from any tall objects. I have a 3' firestick firefly with a tuneable tip.

[Collison]

You will get a better reading if you don't loop the extra length up in circular patterns, if i remember correctly that can create magnetic/electrical interference. Try just stretching it out in a S type shape or try to find a longer route between the antenna and the radio.

[TerryD]

I meant where in the line were you checking it? That can sometimes make a difference. As for looping or what ever, it has very little effect on it and several ~6" coils will actually help reduce noise. I have this done at the back of my K5 and have a perfect 1:1 match. The "have to have 18' of coax" thing is a bunch of bunk based on some faulty math.

You need to check to make sure your antenna is isolated from the ground. I had an issue once where I got the plastic washer in the wrong spot and the antenna was shorted to ground. Easy fix once I found it.

Here's my CB thread:

viewtopic.php?f=3&t=2319

[adamb95]

When I was testing I tried unraveling the coils in my coax and it didn't make a difference. I have also used a multimeter to make sure my antenna is isolated from the ground. I have only tested the swr at the cb. I think I'm going to try wiring the cb directly to the battery. If that doesn't make a difference then I'm going to move the antenna to the front fender.

[TerryD]

The CB being hooked to the battery shouldn't make a bit of difference in SWR. That is to help isolate noise coming in on the DC line. Does moving the tip of the antenna make any difference at all in the SWR reading?

[adamb95]

Yes, moving the tip does make a difference. I have been able to match the swr reading on channel 1 and 40 at around 2.5 by moving the tip. The reading on channel 20 is about 1.5-1.7. Do you think that adding a spring could improve my reading on channel 1 and 40?

[TerryD]

Is you reading on CH 20 highest or lowest when the tip is all the way extended? If the reading is highest, adding a spring should only serve to make it higher as it would seem the antenna is too "long" at that point already and the spring just makes it longer. If it's lowest with it all the way out, buy a "heavy" spring (not the big super coil thing you'd use for a 102" whip) and give it a try. They are fairly inexpensive and you can toss it in your toolbox for later if it doesn't work on this application.