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[aprssig] Helmet Antenna - dont bother.

Ian ik7565 at verizon.net
Mon Mar 7 03:05:49 UTC 2005


Icom's T-81A quietly disappeared even though it was the only game in town
for 1.2GHz HTs. Some lawyer must have advised Icom after figuring out that
our eyes resonate just below 23cm that this was product liability in the
making.

73 de Ian
N8IK

-----Original Message-----
From: aprssig-bounces at lists.tapr.org [mailto:aprssig-bounces at lists.tapr.org]
On Behalf Of Gerry Creager N5JXS
Sent: Sunday, March 06, 2005 9:25 PM
To: TAPR APRS Mailing List
Subject: Re: [aprssig] Helmet Antenna - dont bother.

Simply put, Rich's comments are on-target.  HT's are made the way they 
are for convenience and tradition.  That they're not the safest 
configurations in the world isn't a major concern to the radio 
manufacturers.

A.J. Farmer (AJ3U) wrote:
> When you hold an HT up to to talk, you have the antenna right in front of
> your face and close to your head.  What's the difference? 
> 
> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org
[mailto:aprssig-bounces at lists.tapr.org]
> On Behalf Of Rich Garcia
> Sent: Sunday, March 06, 2005 8:50 PM
> To: TAPR APRS Mailing List
> Subject: RE: [aprssig] Helmet Antenna - dont bother.
> 
> Bob... I hate to preach but let me see here you have a 1/4 wave antenna
> right at the VHF frequencies somewhere near 1/2inch or less from your head
> at 5W.
> Foil or no foil Bob please do yourself and your family a favor don't take
> the risk however small it is. I have not taught RF Safety in several years
> but take a look at some of the ARRL Tech License publications, they point
> out several things about VHF vs. Microwave and how many people are so much
> more afraid of MW than VHF and it should be the other way around.
> 
> That is not something I would be mentioning out in public. Actually for
some
> time I saw a lot of geeky hard hats with BNC connectors on the top of them
> sold at hamfests, I think everyone got the message long ago since I no
> longer see them for sale.
> 
> Rich
> 
> 
> 
> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org
> [mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Robert Bruninga
> Sent: Sunday, March 06, 2005 7:25 PM
> To: aprssig at lists.tapr.org
> Subject: [aprssig] Helmet Antenna - dont bother.
> 
> 
> Today I was tail-bike on a marathon.
> Lesson:  Dont bother with a helmet antenna
> for voice.  (APRS maybe, but not for just voice).
> 
> I took one of those tiny 19" mag mount
> whips with a small base (like a kisses chocolate piece)
> stuck it inside the helmet protruding up through the
> air holes, covered the inside with aluminum foil and
> then let a can lid stick to the bottom of the magnet.
> 
> I also, carried an identical HT with its own
> long whip.  Conclusion was generally no difference
> after lots of side-by-side tests...
> Therefore, dont bother.
> 
> An HT held to my mouth with a similar 19" whip is
> going to work similarly as a 19" whip on the helmet at
> the same height.  I had just hoped that the slightly
> better ground  plane might work better than the HT with
> no real  counterpoise.... dont bother.
> 
> Now, for APRS where you are not holding the HT to
> your mouth, then maybe the extra height and lack
> of body blockage is worth it.
> 
> Just 2 cents...
> Bob
> 
> 
> 
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-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
Page: 979.228.0173
Office: 903A Eller Bldg, TAMU, College Station, TX 77843

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