Uniden 520XL - 102 whip on mazda wagon

[fuzzydroid]

I've been smacking my head on the dash for a week trying to get my install to work properly. First of all, I'm still guessing I have a ground plane problem, but let me spell out the details of the install before we get to that.

Radio is directly connected to battery. Starting from the mount/antenna back to the radio. An isolated roof rack with a 6g wire attached to chassis ground (~10" long with ~2ohm resistance to battery) with a steel tube and plate custom designed mount. It's sturdy! A stainless steel antenna mount with a 102 whip antenna attached to it without a spring. 18 foot of RG8 cable attached to workman SWR meter, and then small patch cable from SWR meter to radio.

The problem is, I'm still getting and SWR 3+. I don't have another person around me that has a CB setup, so I've taken it out near a highway and I have randomly heard people on it. I'm worried about transmitting due to the high SWR. I've done continuity tests between all equipment, and it it's fine. I've tried my best to educate myself by reading forum posts/old books/articles on CB setup, and I just don't know what to do for the next step. I may try mounting it directly on my roof, but it doesn't have anywhere near sturdy enough to support that antenna. If that works I guess it rules out the crazy fabricated roof rack mount I've designed. Was hoping that would work.

Anyone out there know how to solve my problems, or give me some additional steps to troubleshoot?

 

[byndhlptom]

102 whip

A couple of thoughts....

1) A quarter wave at 27 mhz is nominally 108inches. Most 102 in whips were intended to be on top of a 6 inch coil. So your antenna is probably a little short.

2) the "isolated" rack is probably not a good RF counterpoise (ground ref) for the whip. The whip wants to see a quarterwave ground (108 inches/9 feet) for 360 degrees. Any deviation from this affects radiation patterns and swr. An automobile is actually a poor ground reference at 27Mhz (and lower). A DC ground is not the same as an RF ground. There are several references that help explain the difference (search rf ground and counterpoise). The ARRL has several antenna books that go into depth on antennas and ground references (look at HF mobile antennas in paticular).

3) If you get the SWR below 2:1, you should be able to use the radio safely. Most modern radios self protect and you would not believe the SWR swings while a whip is moving in the breeze.

good luck

 

[milkman21218]

The spring is really needed with the 102" whip!