[Lowfer] 630m overnight

Michael Sapp wa3tts at verizon.net
Thu Dec 28 10:36:38 EST 2017


John (& the Lowfer Group):  Interesting observation overnight, I was able to decode K9FD with another station reporting being on the same frequency at the same time---although with some drift...

This event occurred once over 10 K9FD decodes.  The other evening I saw the same thing happen with the same stations when watching the waterfall in real time. At the time I thought it was a

fluke, but it has happened again last night, so I thought it may be noteworthy.

10 spots:
Timestamp Call MHz  SNR Drift Grid Pwr Reporter RGrid km az
 2017-12-28 07:30   K9FD   0.475615   -20   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 07:24   K9FD   0.475615   -22   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 06:50   K9FD   0.475615   -24   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 07:42   K9FD   0.475615   -24   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 07:20   K9FD   0.475615   -27   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 08:16   K9FD   0.475615   -28   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 08:38   K9FD   0.475615   -28   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 06:54   K9FD   0.475615   -29   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 08:20   K9FD   0.475615   -29   0   BL11je   1   WA3TTS   EN90xn   7439   54 
 2017-12-28 07:06   K9FD   0.475615   -30   0   BL11je   1   WA3TTS   EN90xn   7439   54 


 2017-12-28 07:20   KC4SIT   0.475615   -2   -1   EM85tg   5   WA3TTS   EN90xn   623   18 
 2017-12-28 07:20   K9FD      0.475615   -27   0   BL11je   1   WA3TTS   EN90xn   7439   54


Given the current WSPR2 situation on 630m, I decided to turn lemons into lemonade and focus on some high dynamic range tinkering over the past few weeks.

For several months my LO driver amp was out of service and I simply bypassed it and made do with the +15 dBm coming out of the 
3.0 MHz IsoTemp OCXO.  When I decided to test RF, LO, and IF diplexer filters on all mixer ports in an attempt to improve IMD and dynamic range,
I decided it was time to repair the LO driver.  In the above decodes, the LO drive was at +23 dBm to the Mini-Circuits RAY6 Level 23 double balanced mixer. 
All 3.0 MHz LO harmonics are at least 60dB down through the LO diplexer as observed on my HP141T spectrum analyzer.

So apparently I have enough dynamic range in my receiver converter to handle 2 WSPR stations that are nearly right on top of each other.

The diplexer filters are simple series and shunt LC combinations with 50 ohm terminations at 3.0 MHz (LO Port), and 3.3 MHz (Mid IF range for LF/MF band).  

I had a 475 kHz IF diplexer on the mixer RF port, but it seems to make more of a dynamic range improvement in front of my single-ended 2N5109 preamp.  So the next step is to build another
475 kHz diplexer for RF mixer port testing.

An explanation of how the diplexers work is here... https://www.youtube.com/watch?v=AMPbG8MfoNI


Data Sheet on the RAY 6 Mixer is here...   https://www.dropbox.com/s/8rvksgql313j7kj/RAY6.JPG?dl=0

The RAY6 is a non catalog model that I picked up an Nebraska Surplus Sales a few years ago.  A similar Level 23 production-available mixer would be the RAY3 for

those who want to experiment with high dynamic range mixers...


73 Mike wa3tts



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