[amsat-bb] Re: Avoiding statics on helix antennas

[i8cvs]

Hi Lars, OZ1BXM

The shorted quarter-wave coax line suggested in the ARRL Handbook 2008 and
2009 pages 23.20-21 will work great because it is a short circuit for the
static electricity and a theoretically infinite impedance at the resonant
frequency so that for the RF input signal it is completely ignored by the
input stage of a converter or preamplifier.

Remember that a quarter-wave transmission line when shorted at one end
shows an infinite impedance in theory at the open end as you can see using
the Smith Chart.

If you enlarge a shorted quarter-wave by any even or odd number of  1/2
wavelenght of coax line thing do not changes because a 1/2 wavelenght of
transmission line represents a full turn of the Smith Chart.

Do it as suggested by the Handbook !

73" de

i8CVS Domenico

----- Original Message -----
From: "Lars Petersen" <lars.petersen at pobox.com>
To: <AMSAT-BB at amsat.org>
Sent: Tuesday, August 04, 2009 6:01 PM
Subject: [amsat-bb] Avoiding statics on helix antennas


> Hello AMSAT list,
>
> I have a problem caused by static electricity building up on my two helix
> antennas (23 cm and 13 cm). Two converters have already been zapped, so I
> have to do something about it.
>
> What measure would you recommend to avaoid statics building up on helix
> antennas?
>
> Does anyone have experience using the shorted quarter-wave-stub mentioned
in
> "The ARRL Handbook 2008" pages 23.20-21?
>
> Vy 73, Lars Petersen, OZ1BXM,
> AMSAT-Member 36222,
> oz1bxm at pobox.com
> www.oz1bxm.dk
>
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