[Fwd: LF: Radio 4 in ZL]
Sun, 31 Jan 1999 09:57:54 -0500
Steve Olney wrote:
> G'day Marco, Bob, Dave, Geri and all
> As Marco has pointed out frequency accuracy/stability is in terms of ppm at
> the frequency of interest. An earlier post of mine (12/11/98) indicated
> that the sampling frequency at 11025Hz of my SB was a little over 6ppm low.
> I have applied a correction in my software for this. If a correction
> wasn't made this would be only an error of 0.0036Hz for a sidetone of
> 600Hz. As Marco has pointed out the accuracy/stability of the receiver is
> most likely much higher than this.
> I had another look at DBF39 but couldn't identify the mark frequency
> (actually there was a little bump) but once again it would be right down in
> the noise. The problem is that the longer the record the more drift and
> the more the signal spreads across the FFT bins negating any gain from the
> longer record. The limit with the present temperature stability of my
> receiver is at best 2 hours and at worst 30 minutes before drift starts to
> be a problem. I can do a decimation in time for a wider FFT bin BW and
> average the spectrums but this only give gains as a function of the square
> root of the number of averages which very quickly gets you into the world
> of diminishing returns.
> I also took a longer record of 198kHz. I couldn't identify the 12Hz phase
> mod sidebands for the same reason as above. However, the longer record
> shows six carriers within 0.2Hz of each other around 198kHz. The image can
> be seen by going to:-
> and clicking on the "Other LF signal source" link and then clicking on the
> six carriers on "198kHz" link.
> Sorry I can't do any better at the moment. I am disapointed to have to say
> there will have to remain a question mark over the identification of the
> carriers until I can upgrade the stability of my receiver.
> 73s Steve Olney (VK2ZTO)
> email: email@example.com
> Web Page: http://www.zeta.org.au/~ollaneg
> LowFer: http://www.zeta.org.au/~ollaneg/lowfer.htm
> LF Receiving - FRG-100, 8-turn 10sqm Loop
> or Ferrite Loop + K0LR Preamp