Batboard

I'm partway through putting a Spectra and an MCS2000 (both VHF) in my 05 F150. I'm using those NMO L-brackets that screw in where the hood meets the fender. I've tried using a 5/8 wave Larsen on the one going to the MCS (the spectra isn't in yet) and the performance is quite a bit down from mag mounting the same antenna on the roof. There's a bit of fender metal directly below the antenna but I'm not sure it's enough to make the 5/8 wave work right. Could a no ground plane antenna help things a bit, or do you really lose that much gain from going from the roof to the hood?

The antennas are mounted pretty far down the fender, I'd say probably 12-15 inches back from the front edge of the hood to lessen the RF in the cab. And I can't do a roof install; it's too tall even with a 1/4 wave up there...the stock FM antenna almost hits a parking structure this truck goes in.

Short answer - yep.

Long answer - an end fed half wave vhf ground planeless antenna will recover some of your lost coverage, but it will be long. They exhibit gain with sufficient ground plane, and approach unity without. However, the longer rod will help your rcvr at the bottom of performance no matter what ground plane it has. In my experience, you need to make a coaxial cable balun at the base of the antenna to match them properly - two to three wraps of the RG58 feedline as close to the base as possible depending on the freq of operation. Wrap the cable around your fingers to make an approximate 3 inch circle. Use two tiewraps to hold it together. You'll have to experiment with the number of wraps needed by watching your wattmeter.

Dale,

What about trying a plain old quarter-wave vertical instead of the 5/8 wave? Of course it all depends on how much power you're able to run, how much distance you must cover, etc. etc. but it might be the easy way out of the problem.

Tom in D.C. wrote:Dale,

What about trying a plain old quarter-wave vertical instead of the 5/8 wave? Of course it all depends on how much power you're able to run, how much distance you must cover, etc. etc. but it might be the easy way out of the problem.

I'll give a 1/4 wave a try. I just got one for another project and I'll try driving around with that on for a while and see what happens.

is there a ground strap from the hood to the fender? Don't depend on the hinge/prop for a good rf ground