The Truth About Sound Card Interfaces
For Amateur Radio HF Digital Modes

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PSK31/CW/ETC Sound card Digital interface question

You can build your own PSK31 interface very inexpensively. So why buy one?

They tell me that the Signalink is a good unit, and the Rigblaster is not bad either. However, I think that all the suggestions we read that we must spend money on a commercial PSK31 interface borders on the ridiculous, when we can quickly build something so utterly simple that will work just as well for almost no cost..

For PSK31, etc., all we have here is a very simple interface: It uses two audio transformers and about 4 resistors. No USB or serial port connection, no adjustments, and no PTT connection, either (it uses the transceiver's VOX).

What are the advantages (if any) of digital mode interfaces with their own sound card, such as the SignaLink, RIGblaster, etc.?
I haven't found many. Not that were worth the hassles, and especially the money. Have you?

I see people with these commercial units complain about (among other things):

If your transceiver has VOX (most do), then you do NOT need a separate PTT line to operate most digital modes.

99% of the schematics you see on the Internet tell us that we need to control the PTT line to put our transceiver into transmit mode, but that is NOT always the case. VOX works just fine to key the rig. I operate PSK31 using Fldigi, and I don't have a thing connected to my transceiver's PTT line.

The audio from your computer's sound card going into your microphone input is ALL you need to key the rig.

Turn on your radio's VOX feature, and play with the VOX GAIN and VOX DELAY controls.

Magic, isn't it? :-)

I posted this question on eHam and QRZ (stay tuned):

Some of these links suggest that we need to use the transceiver's PTT line to operate PSK31. However, this is the case only when the transceiver does not have built-in VOX capabilities. WHY do we need RSID to determine the mode?


Copyright © 2011 Comtech Research LLC. All Rights Reserved. - Last Edited July 16, 2013


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