Re: LF: 9kHz: soundcard RX

["Ken" <ken.h.wright@btinternet.com>]

 

----- Original Message -----

From: M0FMT

To: rsgb_lf_group@blacksheep.org

Sent: Thursday, March 04, 2010 10:51 PM

Subject: Re: LF: 9kHz: soundcard RX

If I have understood the issue, it is that you are saying sound cards are very venerable to damage when fed with an external antenna to the mic socket?

If that is the assertion then I am say that I have had a good survival rate when doing just that over a relatively long period of time. Also other pieces of kit are connected to antennas like very very expensive transceivers and modems connected to antenna like telephone wires... there is potential hazard to all these devices. So we do take a risk when connecting any sensitive electronic device to an external antenna but the risk can be mitigated by ensuring the antenna is removed when not in use and especially during lightning storms and / or by adding some form of static bypass arrangement. And yes a pair of back to back diodes appear to prevent damage because of their voltage limiting characteristic. It is a precaution I would recommend as a minimum protection but you can never be sure how well they would actually work. Its a risking business play with high external antennas but that's what we do.

 

That is my point and nothing else. 

73 es GL petefmt

--- On Thu, 4/3/10, Chris <c.ashby435@btinternet.com> wrote:

From: Chris <c.ashby435@btinternet.com>
Subject: Re: LF: 9kHz: soundcard RX
To: rsgb_lf_group@blacksheep.org
Date: Thursday, 4 March, 2010, 16:25

Not sure what your point is, surely you're just saying the diodes are doing their job?

Chris, G4AYT.

----- Original Message -----

From: M0FMT

To: rsgb_lf_group@blacksheep.org

Sent: Thursday, March 04, 2010 7:07 AM

Subject: Re: LF: 9kHz: soundcard RX

never blown a sound card up yet in over almost ten years of use. Two back to back diodes on the antenna lead close to the input plug. Don't leave it connected during thunderstorms. Most modems are left connected day and night to very very long over head telephone wires for years with out problems. Vastly over hyped problem.

73 es GL petefmt

--- On Wed, 3/3/10, Horst Stöcker <horst.stoecker@web.de> wrote:

From: Horst Stöcker <horst.stoecker@web.de>
Subject: LF: 9kHz: soundcard RX
To: rsgb_lf_group@blacksheep.org
Date: Wednesday, 3 March, 2010, 9:32

>And what about a simple band pass filter to supress the 50Hz and it's harmonics? Necessary or dispensable?

You can hear (!) the difference. I just took a 10mH coil from Reichelt to improve my soundcard-RX before one of the last SAQ activities.

Despite of more or less excellent digital filtering of SpecLab it's a good idea. One should not keep the soundcard busy with unwanted signals.

What I am not sure about is the use of an audio transformer. It might have some influence to the signal. As it just has to keep the soundcard from beeing blown it might be a good idea to take a cheap soundcard instead of the audio transformer - and maybe a second in spare.

Stefan, what USB-soundcard you bought for 10 EUR ?

Horst DO1KHS
___________________________________________________________
GRATIS für alle WEB.DE-Nutzer: Die maxdome Movie-FLAT!
Jetzt freischalten unter http://movieflat.web.de