[TenTec] Estimating receiver passband responses.

[Gary E. J. Bold]

Hi All,

I write the morse column in the NZART Journal "Break-In".  Recently, I've been 
comparing and publishing the passband responses of various commercial 
transceivers.  

I do this by 

1. tuning the receiver to HF noise only (empty frequency on 20m say);
2, digitizing the audio noise from the receiver;
3. finding the power spectral density of this digitized audio noise, which is 
   the response of the complete radio.  

For digitizing, I use GoldWave, which is shareware software obtainable from

  http://web.cs.mun.ca/~chris3/goldwave

This samples using a standard PC soundcard.   I sample for 10 seconds at 8 kHz, 
digitize to 16 bits.  Because most of us listen to CW via the speaker, I sample 
through that, with a high-quality microphone.  

I produce the spectral responses using Matlab.

I don't own a Ten-Tec radio (one day) but (of course) I read frequent glowing 
reports of the Ten-Tec passbands.   I (and my readers) are very keen to see 
what they look like, and compare them with Yaecomwoods.

Is there somebody out there who

1. uses GoldWave,
2. Has a Ten-Tec rig,
3. Is prepared to digitize a record as above, and email me the resulting 160 kB 
   file to me as an attachment?  

In return, I'll email you back (or post on the reflector if there's any 
interest) the spectral response either as a PostScript file, as ASCII numbers, 
or some other mutually agreed format.   

Naturally, I'm particularly interested in the "CW filter" position responses.
If you know GoldWave, it helps to save the file as a .MAT (Matlab) file, but 
not essential.

This method is used in various branches of acoustics (I am an underwater 
acoustics scientist and signal processor) but seems to have been rarely applied 
to Ham rigs.   It has the advantage of being fast, estimates the response 
of filters without removing them, includes all transfer functions that 
contribute to the overall response, and also any effects due to 
intermodulation, since all frequencies are interrogated simultaneously with the 
psuedo-white RF noise.

Please let me know if you're interested, or just digitize and attach me a file.

Regards,
Gary, ZL1AN.



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