[amsat-bb] Re: RF Quiet my digital recorder

Patrick STODDARD (WD9EWK/VA7EWK) amsat-bb at wd9ewk.net
Fri Apr 15 19:16:18 PDT 2011

Hi Bill!

> I am using an Olympus digital audio recorder for logging LEO passes,
> because I can directly transfer a .wma to my PC from it (versus the
> tape recorder I used in the 90's).
> I am using an extension clip-on mic. I am finding that it generates a lot of
> RF crud on 435, enough to swamp the RX if I am not careful.
> Beside a torroid on the mic cable, and maybe a foil/mesh cover over the
> recorder
> (maybe one of those new-fangled RF-ID protecting wallets),
> anything else I should try?

Have you tried recording with just the mic on the recorder?  Do you
hear the crud without the extension mic?  Have you tried using a Y
cable and patching the audio from the radio to your recorder's mic
jack and an earpiece or headphone?

With the way electronic items are manufactured these days, you may
find that you aren't able to sufficiently cut down on the interference you
hear around 435 MHz.  Can you borrow another make/model of digital
recorder and try it in place of your Olympus recorder?

I have used Sony digital audio recorders over the years, and now use
the ICD-PX820 recorder.  It may still be in production, or replaced by
a newer model - something Sony, like other manufacturers, tends to
do frequently.  It has a mini-USB jack, works like a USB thumb drive
with many computers (Windows, Mac, Linux) without using special
software, and stores recordings in MP3 format.  I have never had RFI
issues with these recorders when working the satellites in the past
5+ years.



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