[RTTY] Some basic RTTY questions

[Kok Chen]

On May 29, 2014, at 7:49 PM, Michael Rapp wrote:

> I'll certainly go pick myself up a decent card with a line in.  It seems
> silly not to.

Wait, did you just say that you have a SignaLink?  Why don't you just use it as a receive sound card?  The sound card in it is a Burr-Brown/TI 2902 series codec and is quite decent.

When I measured some of the sound cards that I owned, the SignaLink USB came in with about 2.5 dB better 3rd order IMD and about 1.5 dB better in 3rd harmonic distortion than the Syba UAUD (a "$5 Amazon special" :-)  

Granted, it is nowhere near a Presonus FireStudio Mobile which has another 30 dB better IMD and 3rd harmonics. 

For those interested, the MicroKeyer II input codec's 3rd harmonic distortion was noise limited by -12 dB full scale (very good performance for a 16 bit device), although it has 1 dB worse 3rd order IMD than the Signalink.

I had intended to publish the full measurements for the numbers I measured (5 different sound cards) but then I went the SDR route and no longer even use sound cards anymore.

73
Chen, W7AY