[Lowfer] 630m overnight

[Michael Sapp]

JD wrote...

>The band of noise just above XIQ also faded into view as the QRN decreased, 
>and a batch of faint lines returned that I noticed for the first time 
>yesterday.  They encompass the entire WSPR band and beyond, and are spaced 
>at roughly 10 Hz intervals.  Very prominent on Argo (though not strong 
>enough to cause problems) and faintly visible on the WSPR waterfall. 
>Wonder if anyone else is seeing those?


    I see the "band of noise" above XIQ frequently.  I have observed others 
refer to the 10Hz lines
as "plasma lines" from plasma TVs. I had a collection of those 10Hz lines 
when listening on the NE
 xfmr end of my EWE antenna, but none when listening on the SW xfmr end of 
the EWE antenna.
 (I swap termination and receive ports in the shack to change rx reception 
direction).  I frequency scaled  one of
W1VD's preselectors for the 475 kHz a few years ago, and those 10Hz lines 
came right through it ---
 confirming they were not intermod products.

I few weeks ago I was able to almost eliminate my local 10Hz plasma lines. 
I replaced my CM chokes on the
 two RG6 cables to the EWE on the antenna end with "new&improved" choles, 
added new ground rods at each xfmr end of the antenna,
 and grounded the cables at about the mid-point of their length with a dual 
F grounding block like those used
 on Ku sat TV dish systems.  I also relocated where the RG6 cables enter my 
house to minimize parasitic
 capacitance, as they shared a common exit with my VHF/UHF antennas.

The result was the 10Hz lines largely disappeared when listening on the NE 
antenna xfmr.  There are now only
two lines at the upper and lower ends of the 475.7 wspr2 window. But the 
remainder at barely noticeable under
quiet conditions.  I'm not certain if relocating the RG6 cables with a 
separate entrance to the shack to minimize
stray capacitance coupling or the reworking of the feedline grounds & CM 
chokes made the difference.  However. the source
appeared to be local and coupling to my feedlines versus my antenna---as the 
antenna is a few hundred feet away from my shack
and two adjoining neighbor's houses.

   One sidebar note is the RG6 cable run pair from the midpoint grounding 
block back to the shack is about 100ft.  The cables in the shack are not
grounded to the service ground when receiving. I realized the two outer 
jackets of the RG6 running parallel along the ground and close to each other 
could act line
 a balanced feed line.  A quick look with my O-scope across each RG6 outer 
jacket showed 150mv at about 1MHz being induced from the 1020kHz
 50KW AM station 4 miles away.  Tying the two RG6 outer jackets together 
appears to have solved that problem.  I'm somewhat leary about grounding 
those RG6
cables closer to the house, as the noise on my utility ground is substantial 
and fear that noise may couple ground rod to ground rod...especially at 
VLF...

I do ground the RG6 rx antanna cable pair to the service ground in the shack 
when the antenna is not in use.

Mike wa3tts