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