Re: LF: noise mitigation, 8970 reception Ewew etc

[uwe-jannsen@kabelmail.de]

congrats Laurence, so one problem has gone.

I have got home made problems: feed back from the transmitted signs into the sound cards Im using.

so Im playing around with groundings and shieldings.

GL
Uwe/dj8wx

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Von: rsgb_lf_group@blacksheep.org
Gesendet: 19.03.2013 14:10
An: rsgb_lf_group@blacksheep.org
Betreff: LF: noise mitigation, 8970 reception Ewew etc

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Thanks Ewe - the interference  is confirmed as coming from an Alpha XM2 cable head end "switched mode sort of" 60V PSU unit anout 1 Km from my home -
 
The interference is common mode on the coax distribution system but coupling to the AC line directly and also being coupled into DSL telephone lines - all of which are underground here. Made interesting DFing -
 
I spent the morning out with the  cable lineman who were very supportive - I used an SDR IQ and baby bottle Eprobe and portable laptop out in the field supplmented by a live "view" of the rx system at KL 1 X via Teamviewer and rx audio via Iphone from SAQ RX - pretty impressive when they swityched off the suppy and the audio and screens went quiet "Oh" said the engineer....
 
Now they  have to figure out what to do about it (hopefully as I think its more than Part 15 allows for) as there are a number of these devices out there in the local area -
 
I can actually hear this one a mile away and not close to utility lines
 
For info here is group of products that appear to be the offenders - note the pseduo square wave output :-(( in the specs
 

http://www.alpha.com/outside-plant-power/cableups-power-supplies/item/xm2-series?category_id=105

I dont think its affecting 8970 too much, but I can see multiples up and down the spectrum and given its nature it isnt helping
 
If you scroll down to the Wideband VLF youll see the interference signature at 19KHz - yuck -  http://kl7uk.com/Alaska.html
 
Still looking for you and praying it dries up at your end - lovely weather here though cold is a little biting holding the laptop and balancing the SDR IQ and probe/psu in my jacket pockets at -25C with 20 knots  :-)
 
Oh and HF LF and MF conditions are very poor of course ....
 
Laurence KL 1 X  we 2 xpq Wasilla AK

 

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Date: Tue, 19 Mar 2013 22:02:23 +0100
From: uwe-jannsen@kabelmail.de
To: rsgb_lf_group@blacksheep.org
Subject: Re: RE: LF: Decca 5501 mod, conditions, noise mitigation, 8970 et al;

thanks Laurtence,

the WX here is not so pro VLF TXing: it snows and rains without interruption.

kill that cable amp.

GL
Uwe/dj8wx

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Von: rsgb_lf_group@blacksheep.org
Gesendet: 18.03.2013 17:22
An: rsgb_lf_group@blacksheep.org
Betreff: RE: LF: Decca 5501 mod, conditions, noise mitigation, 8970 et al;

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Grabber on line Uwe - we have some qrm from a local cable company which Im working on - looks like one of the Cable amps up the road is oscillating at 19KHz - ouch - look at my wideband snapper and youll see what I mean - 40dBm

- but it looks clear on 8970 - running now 238uHz Bucket bin - dang VLF reference station keeps on going off and GPS twinking up here with all this Aurorally stuff....

We are now at 12 day 12 hours night increasing at 5 mins 46 secs per day.....but still -28C last night

Laurence KL 1 X

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Date: Mon, 18 Mar 2013 14:18:53 +0100
From: uwe-jannsen@kabelmail.de
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Decca 5501 mod, conditions, noise mitigation, 8970 et al;

Hi  Laurence,
last days I made some tests on 8970Hz, mode CASTLE, shift 0,002Hz transmitting the letter “W” in 5000sec/dot. Pse see:
http://abelian.org/vlf/fbins.shtml#p=1363442400&b=080&s=sp
the signs could be seen on all grabbers I know.
Now I changed the speed and the shift to 10000sec/dot and 0,001Hz,
I`ll give the PA some coal extra.
 <VLF
<If anyone wants to spark up on 8970Hz again from Eu Im looking at slow QRSS's and shoving the results out on the web site.
<The s/n noise is now vastly improved down there too using the E field L400B.
 pse, Laurence, let us have an other try.
GL
Uwe/dj8wx/jo43sv

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Von: rsgb_lf_group@blacksheep.org
Gesendet: 02.03.2013 09:00
An: rsgb_lf_group@blacksheep.org
Betreff: LF: Decca 5501 mod, conditions, noise mitigation, 8970 et al;

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Decca 5501 mod -

I think I recall that the late G3AQC, maybe others  had a clever way of installing mods allowing it to be "switched"  between 137 and 500 - if anyone has any details Id like to hear or see them - with thanks.

Conditions -

Well - its been a very poor LF season up here to date - with only a couple of Eu openings, obviously my stars havent been aligned, or moreover the Coronal holes have been.  At least the nights are getting shorter

 - HF conditions are very poor too at this time. Still its good X country skiing weather and the Aurora are pretty.

VLF

If anyone wants to spark up on 8970Hz again from Eu Im looking at slow QRSS's and shoving the results out on the web site.

 The s/n noise is now vastly improved down there too using the E field L400B.

QRM

I spent yesterday after noon with our local power utility linesman tracking down a noise source(s) pulsing away at 9Khz prf from 50kHz to 5MHz - traced one to a house about 0.4 miles from here, and I have a second one with the same sort of signature which is proving more difficult to DF.  I havent approached the owners yet, but heck sitting outside the offenders house on the road in the car with the SDRIQ and another L400B magmount the pulses were stronger than local NDB and some MW broadcast signals and a huge amount being re radiated from the underground power lines - so you can imagine something fairly meaty shoving out this do doo, especially as I can hear the same signatures (but maybe not the same source) on overhead HT power lines some 5 miles away - Im guessing home automation, but it might be a wayward lighting switch or blender :-) . If your interested theres a visual capture of the interference source covering the MF band at

http://kl7uk.com/Screen7.png

or on WSPR water fall   http://kl7uk.com/MEA1.png


Cheers





Laurence KL 1 X  WE2 XPQ