TopBand: RFC for balloon static discharge

Mark Mandelkern
Tue, 17 Dec 1996 21:55:25 -0700 (MST)

RFC for balloon static discharge

There have been several recent posts about static
discharge with balloon antennas, and matching.

When the wind permits, I use 1/4 wave on 160M with a
helium balloon. An auto-tuner (QST, 9/95, pp 46-49)
at the base of the antenna, in the center of the
elevated radial field, automatically maintains a 1:1
match during frequency changes and wind shifts. For
160M a low-Q LCL T-match is used. On 80M, at 1/2
wave, an L-network matches it very easily.

For static discharge I use an RF choke to ground, on
the xmtr side of the tuner. Not the little 10 cent type.
The coil is wound using 50 feet of 1/4 inch copper
tubing. Connecting this does not change the
matching, so it must be sufficiently high impedance
at RF. A smaller coil might be adequate - it depends
on what size lightning discharge you are expecting. I
just happened to have this coil on hand; several
others like it are used for actual tuning (see photo in

Thanks to those who put up the warnings. I wouldn't have 
thought of any protection, and a nasty shock while standing 
at the edge of the roof might have caused injury to the cactus 
plants below.


Mark, K5AM, DM62ni,

Mark Mandelkern      
Las Cruces, New Mexico, USA 

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