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Hi Stefan & All,
Thanks for your comments & suggestions, I like the cheap GPS idea best as running more & more app's on the PC causes more & more hiccups. I presume the GPS module would be a stand alone device, any help with this method would be appreciated.
Thanks & 73,
Gary - G4WGT. 2011/9/24 Stefan Schäfer <[email protected]>
Hello Gary,
About sound card locking on LF: Actually its the same like on VLF
except the need for injecting a reference frequency.
If you decide to receive VLF in a separate SL instance and maybe even
separate soundcard (e.g. a 3 EUR USB soundcard from amazon) then you
lock that soundcard as usual to your VLF reference signal such as GQD
and generate e.g. 10 kHz on the output, which will be locked too then.
Then you can inject this 10 kHz ref signal to the LF soundcard...
Or buy such a cheep GPS receiver instead, as often suggested here. My
whole VLF RX, LF RX and LF TX system is based on that 10 kHz reference
signal from the GPS module...
73, and thanks for the grabber! :-)
Stefan/DK7FC
Am 24.09.2011 21:12, schrieb Gary - G4WGT:
Hi Marcus, LF,
Pleased it provided useful feedback.
I am hoping to optimise the system, both from the receiver
stability & SpecLab. The receiver is quite good but does show
temperature stability issues at these narrow systems. I am considering
trying a similar sound card receiver to the one Stefan DK7FC has
recently posted in his mails.
I am not at all sure about sound card sampling correction at
this frequency range, I have no problem at the 8.970kHz range with
using the MSK transmissions at VLF but with the narrow bandwidth of the
system at 137kHz it presents a different situation for me.
Thank you for your suggestions, I will try them in due course.
73, Gary - G4WGT.
On 24 September 2011 17:55, Markus Vester <[email protected]>
wrote:
Hi Gary,
this is excellent, and much
appreciated! I had basically tried to provide a readable signature on
Chris' grabbers, but in the end QRSS 1200 turned out to be a bit fast
for those. I guess the general concept is more suitable for straight
unmodulated carriers...
Your screenshot reveals
my transmit instability near the end of the "N", when my (DHO-based)
samplerate locking temporarily failed, and the audio frequency
jumped by 20 mHz. Do you have plans
for further optimization? The Loran line visible on 137780.419 (Anthorn
et al) may come in handy to evaluate sensitivity and stability
during development.
One thing I would perhaps
suggest is to activate the "one pixel per FFT bin" option in Speclab.
If you don't, and zoom in instead, the brightness of each pixel is
driven by the highest power from a number of adjacent FFT bins, which
in effect increases the visible noise level significantly. Of course the downside is that the visible range
becomes quite narrow, requiring TX stations to cuddle closely around a
prescribed QRG to be seen on the grabber slot. On the other hand, you
can still move the slot around a posteriori, and manually search for
possible missed activity.
Best 73, and thanks
Markus (DF6NM)
Sent: Saturday, September 24, 2011 12:26 PM
Subject: LF: DF6NM 23-09-2011
Hi Marcus, LF,
Please forgive the frequency accuracy & stability on my
experimental very slow (2 mHz) SpecLab screen but the signal is clearly
visible.
Receiver - JRC NRD-345
Antenna - PA0RDT Mini-Whip at 9 metres
73
Gary - G4WGT
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