Sunday, August 18, 2013

New Season Approaching Pt II

Well I was wrong. The noise I experienced on the 50 degrees beverage had nothing to do with insufficient grounding. The noise just happened to be gone when I tested after the grounding work. It later returned, and was present almost every time I checked the past week. Before noon on Saturday however the band was quiet again, and it is still quiet on Sunday morning. Problems of intermittent nature are indeed difficult to pin down. And conclusions are easily made on insufficient evidence.

During Friday evening (when the noise was definitely there) I analysed it to the best of my ability. It appears to start around 400 kHz, and above 4 MHz it's not noticeable. It has its peaks and nulls as can be seen from the 4 MHz DDC spectrum below but they are not completely evenly distributed. What was really quite surprising was that when I engaged the G33DDCs Noise Blanker, it all but removed the noise. Alas, the Perseus NB is much less effective so unless I'm able to remove the source, the G33DDC is the only SDR I can use with the 50 degrees beverage.
Noise floor when disturbed. Vertical lines are "proper" signals.
I am now 100 % certain that the source is not within my house or any of my equipment. There aren't many possible sources within a reasonable distance here, but 3 km away on the back lobe of the beverage there is a power plant transformation station. I walked around the station on Saturday with a Degen DE-1103, but its ferrite antenna didn't pick up any particular noise.

The 310 degreees beverage was erected in beautiful late summer weather yesterday and works as expected. The hope for early trans-atlantic signals was shattered by two M-class flares yesterday evening followed by a proton event.

The dual-340 beverage will wait until OJ Sagdahl comes around in early September.


Chuck said...

Although it is not directly related to your noise problem, I wanted to tell you that you have at least temporarily lost the position as "best DXpedition cuisine" for 2013. I believe Victor's curried chicken with rice noodles in August has given us a temporary lead.

Fire back at will, Bjarne.


Bjarne Mjelde said...

That's cool! Curry chicken is great stuff. Mind you, I will not enter the 2013 competition until October 11 ;-)