Topband: 160 Meters Mobile Antenna Suggestions

[Bill Turner]

On Tue, 06 May 2003 21:37:27 -0500, you wrote:

>In a perfect world, I'll use the same antenna for AM BCB DXing
>while on my lengthy drives at night. I've got some 102 inch
>fiberglass and stainless steel whips with the standard 3/8
>inch mount, so I'd thought about adding a base loading coil
>for use with one of these.

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A 160 meter mobile antenna is going to have a very narrow bandwidth so
it may not be effective for BCB unless you are able to tune it
somehow.  2:1 SWR bandwidth typically will be on the order of 20-30
kHz.  Less bandwidth is better for transmitting since it indicates
higher Q and therefore less loss.  Beware of "wideband" loaded
antennas.  :-) 

Avoid base loading for mobile if the coil will be near any sheet
metal.  Eddy currents will be induced in the sheet metal dramatically
increasing losses.  Center loading is preferable because it gets the
coil away from sheet metal and also increases the feed point
impedance, making matching a bit easier.  

Whatever else you do, get a MFJ-259 SWR analyzer or the equivalent.
It will save countless hours of cut-and-try.  For an antenna
experimenter it is the most valuable single piece of equipment you can
own.

Let us know how it works out.

-- 
Bill, W7TI