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| To: | [email protected] |
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| Subject: | Re: LF: w3eee.com -10dB |
| From: | [email protected] |
| Date: | Wed, 22 Jan 2003 16:45:37 EST |
| Reply-to: | [email protected] |
| Sender: | <[email protected]> |
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Hi Steve and LF-Group, thanks for inserting the 10dB-attenuation at W3EEE: last night's plot definitely proved it's value and allowed an evaluation of the path budget from Central Eu into the USA. During the -7dB-peak between 0630 and 0700, the noise curves apparently replicated the signal, supporting Steve's point that displayed SNR is actually limited (to about 30dB) by the modulation sidebands. An extrapolation of the noise during the nearest troughs (about -43dB) would have given 36dB SNR at the peak. Gaining 16dB by going from 0.4Hz to 10mHz and allowing some 3dB for the peak-maximum-type noise evaluation, SNR from DCF's 40kW EMRP was 55dB. A 1W E(D)RP amateur station would have produced 48.5dB less signal or 6.5dB SNR, good enough for an "M" report. But, as Alan has said, a UK-to-East-Coast path could have been significantly stronger. A detailed look on the sideband-spectrum during many FSK telegrams (see image) revealed a number of gaps where its intensity is another 30dB less than close to space frequency; good channels for noise measurements would be near 138563, 138634, 138765 or 138966Hz. Another approach might be to take a little advantage of the relatively short telegram duration by using true-rms averaging rather than peak-hold in the noise channels, although I'm not quite sure how to tell SpecLab to do just that. 73 de Markus, DF6NM
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