Chris Markus et al thanks - I did another middle of the day recording using an omni eprobe -
http://kl1x.com/alaskaloran0042z.wav 28th Feb 10 - Excuse some of the common mode noise burbles.
Unfortuately I leave for Oklahoma in a few hours so this will be it for a while
Laurence WE2 xpq kl1X G4dma
> From: [email protected]
> To: [email protected]
> Date: Sat, 20 Feb 2010 11:21:05 +0000
> Subject: Re: LF: Loran A and C
>
> Dear Markus, Lawrence and others,
>
>
> Thanks for your interesting comments on this theme.
>
> > The slow phasing effect is caused by pulsegroups of these very similar rates, walking through one another in time.
>
> I think I can hear two effects which might be described as phasing.
>
> One is due to the different GRIs (Group Repetition Intervals, i.e. pulse group rates) which Markus describes. This appears a a change in the chittering sound. When the groups coincide you hear it as "chit chit chit" and the pulsiness is more pronounced: you can hear this about 1/5 to 1/4 of the way through the recording. When they fit in each others' gaps you hear "chitchitchit" and the sound seems smoother: you can hear this just before half way through the recording.
>
> The other effect is a change in the relative strengths of higher and lower audio frequencies. You can hear this from about 4/5 of the way through to nearly the end, where the sound cycles between treble and bass. Presumably this is cancellation in some part of the 90-110 kHz spectrum, though the treble will be represented by both the parts just above 90kHz and those just below 110 kHz, so presumably it is subtler than that*. Maybe this is caused by frequency-selective fading, presumably what Lawrence described as the "musical sounds they made as sky waves did their thing". Could someone more knowledgable than me comment on that?
>
> * Unless Lawrence was demodulating as SSB, in which case he would see only one half of the spectrum.
>
>
> For those who have deleted the original message, the recording is at
> > http://kl1x.com/loranalaska.wav
>
>
> 73,
> Chris G4OKW
>
> -----------------------
> Dr Chris Trayner
> School of Electronic & Electrical Engineering,
> The University of Leeds,
> Leeds LS2 9JT, United Kingdom
> Tel: +44 113 34 32053
> Fax: +44 113 34 32032
>
>
>
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