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Author Topic: HF Stationary in a Jeep Grand Cherokee  (Read 948 times)

Posts: 227

« on: March 01, 2006, 07:52:19 PM »

I want to set up a HF while stationary station in my 96 Grand Cherokee. It will be for emergency communications use. I am mostly interested in 80M,60M and 40M. I have an FT757GXII which can do all three bands. I already have power from the battery available at the front and rear diver's side of the vehicle as I now have an FT8900 with the radio behind the spare on the drivers side rear quarter. I can tap the wiring going to the rear of the car at an existing Anderson Powerpole connection in the drivers side front kickspace and install power to the front console area. I picked up a genuine GE ballmount at a hamfest and was thinking about mounting it in the quarter panel and using a long whip on the ballmount or maybe a telescoping fiberglass pole to support a wire vertical. Can I get away with a length of high quality coax from the passenger seat area to the antenna location with the radio and a manual tuner located in a module seatbelted or solidly webstrapped to the passenger seat? Would it be worth the considerable cost to locate an automatic antenna tuner at the ballmount?

What do you think of the approach and choice of antenna mount?

73 de Walt N2IK

Posts: 10248


« Reply #1 on: March 02, 2006, 06:02:41 AM »

You need to be careful for several reasons.

First, the voltages can be VERY high, in the order of 10 to 15 kilovolts. The backing plate will not take this sort of stress. The voltage rating of the coax may be exceeded, and the loss through the coax will be excessive.

If you with to use a coupler, it should be mounted as close to the base of the antenna as possible, and all of the leads must be short! Read that as inches, not feet! And it can't be coax.

While using an auto coupler has advantages (rapid QSY, and no tune up worries if done correctly), you'd be better off with resonant antennas. You have to remember, an HF mobile antenna is a compromise among compromises; there are better alternatives when stationary operation is the objective.

Alan, KØBG


Posts: 246

« Reply #2 on: March 05, 2006, 06:51:32 AM »

If you only want the 3 bands you can go with a hustler system or get 3 of the mono band antennas and switch them for whatever band you want. Depending on how long and where your staionary you might want to look at one of the mast system and just erect a tower and put up a dipole, yagi or whatever you want. K4TMC over at the The Mast Company (as well as several people on ebay) sell a mast system, fiberglass or aluminum 45ft mast with base and guys. TMC also sells a 32 telscopic mast. Kanga and MFJ sells versopns of  DK9SQ  mast system.

Lots of options depending how stationary you need to be.

Posts: 17411

« Reply #3 on: March 10, 2006, 03:33:00 PM »

Presuming your emergency communications will be NVIS, you
will do best with a horizontally polarized antenna, not
more than 30 to 40 feet high.

My suggestion would be a lightweight antenna support such
as a fishing pole or painters extension handle in the
12 to 20 foot range with some way to mount it so it stays
upright - perhaps a flat plate mount that you can drive
one wheel onto.  Then hang a set of pre-cut dipoles from
the mast - no tuner required.

If you really insist on using a vertical whip on a ball
mount, when you are stopped quarter-wave clip-on wires to
the top of it and run them out horizontally.  That will
not only keep the voltages down on the mount and the tuner,
but will make the system much more efficient and give you
the high-angle radiation you want for local communications.
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