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