[Lowfer] EAR rx experiments & other with ZLW-1 DBM

[Michael Sapp]

Hi All:  Below is a capture of lowfer EAR from this afternoon with my EWE antenna, HD-1420 VLF converter and FT-817 with the Yeasu TCXO9 "high stability" master oscillator option. 

http://i1296.photobucket.com/albums/ag19/wa3tts/earh1420_zpsa07567ad.jpg


Next capture was done a few days ago using the following:  EWE antenna (NE) feedline to 1:1 RF isolation transformer, to my VE7BPO "NDB filter" to Mini-Circuits ZLW-1 +7dBm double balanced mixer. Unfiltered and switch selectable 5MHz TTL output from my Spectracom WWVB receiver to the ZLW-1 via a 2dB attenuator.  RF and IF ports swapped on ZLW-1 to take advantage of DC-500MHz IF port specification....the VE7BPO filter and a different isolation/stepup transformer are used with my HD-1420, so the setup is essentially similar for both rx-converter setups.  The Spectrcom WWVB receiver no longer phase locks to WWVB (WWVB format change in March 2013), but the internal reference oscillator is still reasonably accurate....(10^-10 range...)

http://i1296.photobucket.com/albums/ag19/wa3tts/capt00021_zpsa6dc20ed.jpg


So I get my desired "flat line" response, although the noisy 5MHz TTL signal takes a toll on the coherence of EAR on the mixer output.  I expected that to happen.  On this EAR capture I had to reduce the visual gain a few times before the "dits" would resolve.  The HD-1420 3.5MHz LO sine wave makes for cleaning mixing with the MC-1496 active balanced mixer, even though it has no bandpass or lowpass LO filtering in that basic LF converter circuit.

EAR makes a good weak signal source for this test. The effect of the noisy TTL LO wass less obvious on a stronger signal like MP here in EN90xn.  Also tried both the 1MHz and 5MHz TTL outputs for the LO signal on MP, 1MHz seemed to be a bit cleaner result.  

1MHz LO capture of MP

http://i1296.photobucket.com/albums/ag19/wa3tts/MP1MHZ_zps074ed6b9.jpg

5MHz LO capture of MP

http://i1296.photobucket.com/albums/ag19/wa3tts/MP5MHZLO_zps2fa4893e.jpg


Also copied MLS with this 5MHz LO & ZLW-1 setup....

http://i1296.photobucket.com/albums/ag19/wa3tts/MLS5MHZ_zpsb9d04c49.jpg


No luck with DK7FC using the TTL LO's, but I did capture traces of Stefan's 136.172 signal with the 10MHz reference sine wave signal as the LO with the ZLW-1....

http://i1296.photobucket.com/albums/ag19/wa3tts/capt00022_zps00150f6d.jpg


Finally, a photo of the Spectracom rx & ZLW-1 setup....


http://i1296.photobucket.com/albums/ag19/wa3tts/speccom_zps66d95f78.jpg


Interesting to note all captured signals were only down in level by approximately the conversion loss spec of the ZLW-1 compared to the HD-1420, which is 6~7 dB range.  If the antenna captures enough uVs/m, one has to wonder if a preamp/IMD generator is necessarily a requirment for weak signal work at LF....(also gets me thinking about a Zero Volt thresehold diode xtal set project that was in QST a few years back :).....

Thanks for the bandwidth......73  Mike wa3tts