cb question

[Lor]

I read/search the forum and didn't find anything similar to my problem.

Here is my problem. I have a Cobra 29 LTD installed in my truck with the 4' Wilson fiberglass antenna. The SWR is about 1.5 or less on all channels. The antenna is mounted near the windshield on the driver fender side.

Here is the problem. When I communicated with my friend during close range (few yards away), everything is fine. As soon as one drove more than 1/4 mile away, I started to loose reception signal. I had to lower the squelch to get some noise in order to hear him. I can do this to about 1.5 miles and completely lost the signal. When I transmitted, he can still hear me find on his.

What could be the problem? Any idea? I had another unit that I tried and it was the same. I am going to swap out the coax to see if it will make a difference, but I just want to see if anyone had experience this before.

 

[Brentbba]

1.5 miles could be about all you are going to get from a CB. Ham radio is the next step for much, much longer range.

 

[Lor]

I do understand it's limitation. But like I said, as soon as we were about 1/4 mile away, I'm loosing signal quickly. I can bearly hear, but his was loud and clear. His cb is the Cobra 25. The terrain is flat. When I completely lost reception signal, he can still recieve from my transmission. He even had a shorter antenna (2') mounting about the same location. Any idea?

 

[Brentbba]

Since you know your SWR readings, you've obviously tuned your antenna. How well grounded is it?
You're right - flat terrain you should be able to get more than 1.5 miles and hear much clearer from 1/4 mile. Just a bad radio perhaps? Can you swap with your friend to see if the same thing occurs in your truck with his radio and visa versa w/o much difficulty? Give that a try to eliminate the radio itself as the problem. Also, check the coax for kinks, cuts and loops. If you've got excess coax coiled up somewhere, that becomes the coil for the antenna and can affect performance in both cb's and ham radios.

 

[Lor]

I didn't swap radio with him, but I did swap with another 29 ltd that I have. It's the same problem. Like I've said, I'll check the cable and/or replace the cable for now. If anyone experienced this before, please let me know how you fixed it. Thanks.

 

[Miescha]

Brent's got all the answers .

Where is your friend's antenna mounted?

The location you mention for your antenna is a relatively poor image plane for transmission and reception. You can actually see (hear) this if you have your friend park on one side of a large parking lot (think walmart/sam's/mall of america) with nothing between you and your friend but flat terrain (parked vehicles shouldn't matter much for this test). You park on the other end of the lot trying to get the same 1/4 mile distance. Transmit with your cruiser parked so that the antenna is closest to your friend, then move the cruiser around and transmit with the antenna farthest from your friend's truck with your cruiser blocking the antenna as much as possible). You'll notice a difference. This is why mounting your antenna in the center of your roof is best (height, clear transmission/reception, and a nice image plane).

You can overcome some of the poor image plane from your mounting location by bonding the various pieces of your cruiser to create a better image plane. You'll need to attached 1/2 - 1" braided ground wire from the body to the hood, from the body to each of the doors including the rear upper/lower hatch.

I've been in situations where I couldn't hear the transmit of the truck directly in front of me on the trail (maybe 10 yards) when they had a mag mount 2' cb antenna stuck on their front ARB bumper such that the tip was only abut 1' above the hood and fully block by the windshield and truck. Once the truck turned, I could hear just fine.

Your DC ground connection is probably good given your SWR (a bad or non-existent DC ground will generally cause a pegged needle on the SWR meter - so way over 3).

The fix is a different antenna mounting location followed by a better (taller) antenna. Of course, the next step is a move to Ham radio where you can blast out 2m transmissions at 100w and reach much further than the 4w your legal cb puts out (not to mention the generally better component build quality of most ham radios).

Good luck!

 

[Lor]

Hmm... My friend's antenna is mounted in the same location as mine.

 

[Miescha]

That's helpful to know, but even with the same antenna in the same location on the same model vehicle with the same coax and the same radio connected, the location can still result in poor reception and/or transmit that is only noticed when the body of the vehicle is blocking the transmitted/received signal.

Or maybe I just need to stop offering suggestions for tracking down problems - my record is 0 for 2 (on the last two attempts).

Hope you get it figured out!

 

[fieldsken1]

buy a linier lots of power that always works