Mobile Antenna Help

nr5a nr5a at RAP.MIDCO.NET
Mon Feb 4 22:14:41 EST 2008

Seems like there use to be a metal tape used for window alarm systems. It 
was about a 1/2 inch wide and stuck to windows. I've read about window 
antennas being made of it. Not sure where to get it but wouldn't something 
like that taped to the roof work??

Ok back to getting my Scrounger hooked up, almost there.

Jerry - NR5A - South Dakota
----- Original Message ----- 
From: "Richard Arland, W3OSS" <richard.arland at VERIZON.NET>
Sent: Monday, February 04, 2008 7:25 PM
Subject: Mobile Antenna Help

>I suppose you're wondering why I called this meeting!!
> Actually, I am in need of a solution for my mobile HF antenna. I got 
> talked
> into buying a High Sierra Sidekick screwdriver mobile antenna. It is
> extremely short (around 4 ft or so fully extended) but according to the
> folks at High Sierra, it is capable of 80-10M operation.
> Now I realize that this is all manufacturer's hype but as we all know if 
> you
> add enough capacitance and inductance in line with the antenna you can get
> it to  resonate almost anywhere. Radiation efficiency is something 
> entirely
> different, and much harder to realize.
> So, my situation is this: I have mounted the screwdriver antenna on the 
> rear
> cross member of the roof rack on my wife's Nissan Pathfinder SUV. I have
> tried the antenna on various HF frequencies including 80 and 40 meters.
> While it does resonate, my 100 watts of RF output doesn't radiate
> efficiently.
> I have thought about adding a ground plane to the roof rack in the form of
> copper or aluminum tape. In the days of slot cars, we  used copper tape
> which was positioned on each side of the "slot" in the track, and the 
> motor
> inside the slot car had a set of pickups that would contact the copper
> strips providing voltage for the motor. Unfortunately, there is a definite
> shortage of this copper tape. About as close as I can come to it is the
> aluminum duct tape used to seal heating duct work. It is conductive and I
> was thinking of placing this on the UNDERSIDE of the roof rack and
> connecting each end of it to the ground portion of the antenna mount. I 
> have
> anticipated adding a ground plane so I added some wing nuts to the lower
> portions of the antenna mount.
> My general question to this group is: Do you think that this is a workable
> solution to the RF counterpoise problem on this mobile installation?? If
> not, don't be shy, tell me what you have used in the past (or present) 
> that
> works for you. I am open to any and all suggestions (within reason, of
> course).
> I was wandering around Home Depot yesterday and spied a bunch of 3/4 inch
> copper pipe used for plumbing. The thought immediately crossed my mind to
> use this, along with some 90 degree elbows to form a tubular counterpoise,
> paint it black (to match the roof rack) and place it on the underside of 
> the
> roof rack, holding it in place with a few black plastic cable ties. The
> extra area might drastically improve the RF counterpoise and make the
> antenna perform as advertised. Just a thought.
> Comments, anyone??
> 73 Rich W3OSS
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