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| To: | [email protected] |
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| Subject: | LF: Re: Phase meter for propagation experiment |
| From: | [email protected] |
| Date: | Wed, 10 Apr 2002 17:46:56 EDT |
| Reply-to: | [email protected] |
| Sender: | <[email protected]> |
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Hi Stewart and group,
Thanks for the suggestion. The SNR of the LORAN lines in the receiver's passband makes it difficult to track them, and as I understand it I need two of them separated by a couple of Hertz to use them to calibrate both sample rate and LO drift. Stewart wrote- >> (...) turn on the TV and the flyback's ninth harmonic of 15625 will be at 140.625 kHz. It may be somewhat out of the receiver's passband, but should be strong enough to be trackable. For calibrating the sample rate, use the field rate modulation inevitably present. << I am not sure what the field rate modulation is; in german we have the "Bildablenkfrequenz" (~ frame rate?), I guess it has something to do with the field rate modulation. Looking at the spectrum radiated from my TV set: sidebands at 15575 Hz and 15675 Hz, about 25dB weaker than the main peak at 15625 Hz. The 140.625 kHz TV sync harmonic received with a TS850 tuned to 136kHz is very weak, and the 'sidebands' are too weak to be useful (may be different in other parts of EU where a wider IF filter can be used, but impossible here - almost in DCF39's neighbourhood). But the idea is great and I will try it on other frequencies, for example on 60 kHz to compare the phase of MSF against 4*15.625=62.5 kHz (asked Mr Fourier why the 62.5 kHz signal from the TV is so strong, he said 'because your TV flyback transformer does not produce a square wave' ;-) >> If one has a GPS with a 1 PPS output, you can get really accurate results. Again, no special hardware is needed. Couple the 1 PPS directly into the Rx antenna input (along with the desired signal) and do the rest in software (G3PLX algorithm). << The GPS method sounds very interesting, it looks like Andy's info about the cheap GPS modules came at the right time, in fact I received it directly after posting the 'propagation experiment' suggestion. Though I don't know Peter's algorithm (except for the fact that he is experimenting in that field), I guess the maximum 'LO error' must be significantly less than 1 Hz, and the drift only very slow - may be tough for some receivers, especially the older ones with a couple of independent oscillators affecting the conversion. Regards, Wolf DL4YHF |
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