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LF: RE: RE: Static protection when using a soundcard as an Rx

To: <rsgb_lf_gr[email protected]>
Subject: LF: RE: RE: Static protection when using a soundcard as an Rx
From: "g3zjo" <[email protected]>
Date: Mon, 14 Jun 2010 09:33:13 +0100
Importance: Normal
In-reply-to: <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Hi All


I think I will add a 600ohm 1:1 transformer to my sound card LF set up in
addition to the diodes I have at present.


Incidentally it has suddenly struck me what a loose term 'back to back'
diodes is. It could be confusing for an enquirer. What is being referred to
here is 2 diodes in parallel across the input, one of them one connected one
way round and one the other.

Back to back diodes is also a term for two diodes in series connected + to +
or - to -, putting the open ends of this combination across the input would
do nothing to protect the circuit. Joining the open ends and placing that
across the input would not be right either.



Eddie G3ZJO


-----Original Message-----
From: Stefan Schäfer [mailto:[email protected]] On Behalf
Of Stefan Schäfer
Sent: 13 June 2010 23:54
To: [email protected]
Subject: AW: RE: Static protection when using a soundcard as an Rx


Hi Brian and also welcome :-)


I would combinate back to back diodes with a isolating transformer for
audio. A combination of the hints you heared before ;-) The transformer
prevents galvanic coupling (could become a problem even if your wire is
grounded for high voltages by the diodes) and the diodes on the soundcard
side are an additional safety factor that reduces voltage spikes. But the
diodes start to conduct already at some 1/10 volts (depending on the
temperature) so you may use 2 in series each...


73 es gl becoming QRV!!





Von: [email protected] im Auftrag von James Cowburn
Gesendet: So 13.06.2010 20:09
An: [email protected]
Betreff: LF: RE: Static protection when using a soundcard as an Rx

Hi Brian


Welcome to the reflector.   Back to back diodes are good option to limit
surges and spikes, but others are more qualified than me to advise





With best regards






Dr. James Cowburn  G7NKS

E [email protected]


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From: [email protected]
[mailto:[email protected]] On Behalf Of Brian Reay
Sent: 13 June 2010 17:38
To: [email protected]
Subject: LF: Static protection when using a soundcard as an Rx


Hi All, 


My first post to the reflector.


I plan to try using a sound card and a "long wire" (well as long as I can
fit into the garden) antenna and later a kit lofted antenna but I'm
concerned re static. 



Normally I'd add a "dc short" with an inductor but at 10kHz than is a big
inductor. A resistor is another options.


Does anyone have any other suggestions, please.





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