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Hello Manuel,
sorry, nothing here at locator JO40KA last night. I grabbed the whole night
the range from 136317 to 136325 Hz with DL4YHF's Spectrum Lab, but I got only
noise. Not even traces from your signal :-(.
Last week (10.12.06), I received PE1RRF at the same frequency with a nearly
perfect signal. You may have read my answer here at the group.
Anyway, I've to admit that my actual rx isn't very sensitive. I've an
passive low pass (edge frequency approx. 140khz) with 20dB amp in the next
stage. This signal is then going to be mixed through a symmetric transformator
with an CD4016 and TCXO controlled 135khz down into the baseband. Similar to the
design of Jean-Pierre's rx, but without bandpass filter. So I receive the mirror
frequencies (like 133679 in your case) as good as the desired frequencies...
which is not a big problem (there's not much here from 132 to 134kHz) but at
least a waste of 3dB sensitivity.
But the real problem with this approach is, that I'm located approx.
4 wavelengths from Mainflingen / DCF49, so if I increase the amplification,
the output of the mixer is going to be clipped due to the 128.830 kHz
of DCF49 (which produces nasty distortions all over the band).
I experimented with several bandpass filters to suppress the undesired DCF
signals, but all my filter approaches produced additional noise that wastes the
gain of selectivity. I even tried an nf-peak filter between the output stage
(low pass with small amplification) and my PC's soundcard, but I only got
more noise instead of sensitivity.
So I'm now designing a new rx, around a very good 1.4MHz ssb-crystal filter
(from a commercial marine rx), which will use two (TCXO
controlled) DDS synthesizers. Then I'm going to get rid of DCF49 and even
DCF39 (which still has a very strong signal here).
vy 73 to you and the group de DL3FCH
----- Original Message -----
Sent: Tuesday, December 19, 2006 10:16
AM
Subject: LF: RE: Re: EA4BVZ MC
At wich speed/mode are you going to
transmit, QRSS3/10/30/60 ?
At QRSS 60.
Many Thans Stephan
EA4BVZ
I will have a look at 136321 Hz tonight.
Greetings from DL3FCH, Stephan
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