AB-15 /MS 116-117-118 antenna fail

[ramcatdoc]

Update

Well, I used my VOM to check the resistance through the antenna and base alone (disconnected from the antenna cable). Extended, the resistance is around 1 ohm, but tied down, it is around 300 ohms! HUGE and very reproducible difference!

The "antenna fail" message on the radio screen only occurs at lower channels, say below channel 10. This is where my SWRs are also higher, around 2. They are just above 1 at the middle and higher channels. I noticed the SWRs are the same whether the antenna is vertical or tied down, though.

I don't know if this means there is a problem with the new base or what. Does anybody use an AB-15 that transmits well on all the channels when tied down? I'm really not up to replacing the base a second time.

Right now my "solution" is to transmit with the whip extended. A pain in the neck if I am off-roading through low-hanging trees!

 

[Cleveland Iron]

Antennas can be tricky. Part of the problem is how the antenna reacts to the metal of the truck body. As you bend the antenna over, you may be changing the operating frequency of the antenna. If you can get your hands on the MFJ analyzer, you could see just what is actually happening. Good luck. Oh, if you want to understand what I am talking about, check out a copy of the ARRL antenna handbook. ( Just a thought. )