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From: John Andrews <w1tag@charter.net>
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Date: Wed, 25 Nov 2015 17:22:52 -0500
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Subject: Re: LF: EbNaut and The Cat / Take 3
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Andy,

I recall doing a series of 137 kHz experiments with Peter Martinez using 
PSK, with the sending end being triggered by 1PPS interrupts from my HP 
GPS receiver. Somewhere here I have the 8051 code I kept modifying. We 
were using bit timings of 30 seconds or so. If memory serves, there were 
no wildly successful results, but he certainly copied my signal on some 
nights that would have been rough for QRSS30.

John, W1TAG

On 11/25/2015 4:32 PM, Andy Talbot wrote:
> Its a pity we no longer have 73kHz
> Back in the early 1990's when that band was being proposed, one of the
> ideas put forward as an argument for getting it  was a link budget
> worked out showing how TA might be just about possible using coherent
> PSK with low symbol rates - something that would have been very
> difficult for amateurs in those early days of DSP.
>
> The TA path was managed eventually once, or perhaps twice AFAIR,  by
> very slow QRSS at high power and, I think, a period of enhanced
> propagation.   Suspect it would be easy enough on EbNaut now.
>
> The PIC 1kHz bandpass digitiser is a very neat way of doing the back end
> of an LF narrowband SDR, allowing embedded GSP timestamp and completely
> independent of all the nasties associated with soundcards
>
> Andy  G4JNT
>
> On 25 November 2015 at 20:42, Paul Nicholson <vlf0403@abelian.org
> <mailto:vlf0403@abelian.org>> wrote:
>
>     Markus wrote:
>
>      >
>
>     take long to exhaust the permutations.
>
>     And what are the limits at LF?   How far do amateur signals go?
>
>     For that matter, how far does this mailing list reach?
>     How to interest more experimenters... away from Europe and
>     North America.
>
>     Was reading about lowFER, severe limits on antennas and input
>     power.  Now that could be interesting.   Do lowFER signals
>     reach Europe?
>
>     Lacking DX stations, the only option is some serious QRP.
>
>     Can we think of something interesting enough to drag Andy
>     away from his GUI?
>
>     --
>     Paul Nicholson
>     --
>
>