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@pobox.com To: AMSAT-BB@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@pobox.com www.oz1bxm.dk
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