Hi Jim, I guess that could be frustrating to some who maybe do not
understand the limitations enough, but would seem to work ok within them.
The ideal method at 136 as you say was to use Loran sidebands of known
frequency. A better method would be to generate a 1Hz comb by injecting 1PPS
tickes from a GPS receiver into the antenna (very small cap) as with Peter
Martinex's "ClickLock" this can be done on the band you require to monitor.
For those not having a GPS 1PPS available the best solution my be to
generate one from MSF (or Droitwich), but this is not a
trival bit of hardware development, thought it is not too difficult I would
think...... 1 sec "ticks" are provided by MSF. I suppose you may need to
lock to those to generate the missing tick at the minute, but that would not
really be a problem for comb generation. Maybe kickoff a retriggerable mono
set slightly long to clean up the pulses.
All you then require is a receiver that enables you to distinguish which 1Hz
you are using
:-))
For Droitwich....mmmm how about a limiting carrier amp, a divide by 99 in a
CD4040 (maybe a 74HCT4040) followed by several 74HCT390s down to 1 sec. It
would not satisfy the purists with 40 to 100nS of jitter but would be good
enough for WOLF.
..and not so much daunting math to use :-))
Cheers de Alan G3NYK
----- Original Message -----
From: "James Moritz" <[email protected]>
To: <[email protected]>
Sent: Thursday, October 01, 2009 6:09 PM
Subject: LF: RX and Sound Card
> Dear LF Group,
>
> I have just uploaded "RX_Soundcard_cal_v1.pdf" to the files page at the
> UK500kHz group web site (go to
> http://groups.google.com/group/uk500khz/files - it is down at the bottom
of
> the list). This describes a way of calibrating receiver frequency and
sound
> card sampling rate using an off-air standard frequency such as MSF or
198kHz
> R4, without requiring an accurate audio frequency to calibrate the sound
> card. This is addressed primarily to WOLF mode transmission and reception,
> where this calibration has to be done fairly accurately in order for the
> mode to work properly, but could also be generally useful where sound card
> sample rate calibration has to be done, and there is no precision audio
> frequency source available in the shack.
>
> Any comments would be welcome,
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>
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