Batboard

Hello all

I have a customer who wants a VHF rubber duck type antenna for their VFD ATV. I'm using a Antenna Specialists Part#
HP12 . The radio will be a 45 watt M1225. Anyone have any ideas if this will work ?????
thanks
steve w

I can't find the antenna you're talking about (can you post a link?) but problems might be the VSWR of the helical is so bad the M1225 may go into shutdown or the VSWR is OK but the top of the helical may catch fire. Don't laugh I've seen it happen with just 25W.

Thanks for the info !
The antenna is for portable radios but just checking to see if it might work or not.
steve w

You are better off with a good 1/4 wave antenna. Comtelco A1511A.

Do not forget you need a good groundplane for the antenna, 19 inches radius. Even with the ruberduck you need a groundplane for it to work correctly and not feed back into the radio.

Because there is nothing between the radio and the antenna except air, you may have to fold power back to less than 10W. Otherwise, you may find the radio does strange things like no xmit audio, distorted PL or DPL, xmit whine, etc. That series was not meant to operate in it's own near field.

On atv's I use fiberglass marine antennaes just like on a boat. They don't need ground planes and they can put the orange marker flag on top of it

What HLA said.... They used to make no ground plane fiberglass antennas for motorcycles. The marine antennas would work as well. I'd kick down the RF too. Human body proximity in a ATV is too close for 50 watts!

I'm thinking about a Shakespeare 36" marine antenna (model # 5240-R) with the rail mount. I believe this might work well.
steve w

Stay away from ANY portable antenna for mobile use, especially at the power rating you described.
H.T antennas are not designed for that power level, the RF current melts connecting joints, warps field patterns, and will cause damage due to radiation resistance of the antenna itself.

Portable antennas are designed to carry minimal RF current, and will cause an impedance imbalance due to the physical size(power limiting factor), and also size/form factor to relieve mechanical stresses on the antenna connector on the radio itself.

RF burns for a portable antenna are bad at 5 watts, you can get a deep burn at 45 watts with your configuration, so carry plenty of gauze and ointment!

The HEAT buildup will also be greater due to the mechanical design of the portable antenna, and I will bet you melt the cover in a few short minutes. That RF MUST go somewhere, and if not radiated, it is wasted in heat.

Mount a 24" square or round 'plate' on top or under the roof if you have a canopy, and use wither a 1/4 wave or 3dB gain whip. You can also use the 1/2 wave feeds, and forego the ground plane. Just SCRAP the H.T antenna idea, poor choice!

Thanks for info !!!
Looks like a marine antenna is what I am going them.
steve w

I usually use the Shakespere 8 footers mostly for height for a marker flag but the height definately helps with coverage too. Plus if i'm not mistaken it's a 3db gain antennae so you can cut power down and still get the same range