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[aprssig] Helmet Antenna - dont bother.

Marsh James w9nje at sbcglobal.net
Mon Mar 7 23:03:46 UTC 2005

What gauge foil should be used for this body wrap?

Keith - VE7GDH <ve7gdh at rac.ca> wrote:Scott N1VG wrote...

> Perhaps you weren't doing it right. Here's a reference:
> http://zapatopi.net/afdb.html#BUILD.

I think that Abba (see the above site) might have actually been on the right track after all. Instead of just coating the head with aluminiumiumium foil, wrap the entire body in foil - shiny side out of course!. As well as warding off mind control, it will be an even better ground plane and will shield the user completely from RF on the outside. In medieval times, the aluminum foil wasn't needed. Just stick a mag-mount on anywhere!

All kidding aside, Bob went above and beyond the call of duty in performing this dangerous experiment! Also when it comes to antenna performance, you can't beat actually testing the antenna in the field to so how it does. Perhaps on the next ride, he could use one of the aerodynamic racing helmets that project out the back. Then there would be room for a parasitic element then that could provide some directivity! 

Just to change the subject slightly, has anyone done any experiments with antennas running the length of the bike jersey from one of the back pockets? I'm looking for an antenna for APRS use that won't be attached to the bike and won't get in the way when I bail from my mountain bike. I'm not sure if my spine will act as a reflector or if it will absorb lots of RF. For night rides, there will also be a cable running from one of the pockets to the helmet mounted headlamp, so perhaps I should be looking at dangling a quarter wave flexible wire antenna instead of going up towards the helmet - as long as it can't get caught in the spokes. Hard to say if my nether regions will absorb more RF than my head. I don't have any APRS on the bike yet. It's a future project that will probably include a helmet mounted GPS (probably GPS18 LVC just taped to the top of the helmet) and a PocketTracker. Right now, I'm riding with a GPS mounted on the handlebars and download it into a mapping program
 when I get back.

73 es cul - Keith VE7GDH
"I may be lost, but I know exactly where I am!"

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