Message-id: <A68345795F2C4AF9847E111520C3F1A4@MichaelSappPC>
From: "Michael Sapp" <wa3tts@verizon.net>
To: <rsgb_lf_group@blacksheep.org>
References: <1934937394.20160518170418@chriswilson.tv>
In-reply-to: <1934937394.20160518170418@chriswilson.tv>
Date: Wed, 18 May 2016 12:48:48 -0400
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Subject: LF: Re: Can LF damage a mains input filter?
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Chris: John, W1TAG, has an LF mains filter on his web site, but it is 
designed for 120VAC service, so you have to rate components appropriately

for your higher EU mains voltage....(usual X1/Y2 X2/Y2 capacitor precautions 
apply).  I had a noisy APC uninterruptible power supply and John's filter 
design helped my situation on 137 kHz...

http://www.w1tag.com/SWITCH_FIL.htm

Consider the possibility of RF rectification occurring on either the input 
or output side of the TV preamplifier, possibly at the antenna connections, 
coaxial connections to preamp input, etc., as oxidation could be the 
culprit.  Coaxial "F" connectors can be prone to center pin and outer 
threaded barrel oxidation.  I use 75 ohm RG6 coax and F connectors for my 
LF/MF EWE antennas and regularly apply some intermittent DC "sealing 
current" (24V through 100 ohm resistor) to keep the connector resistance 
low.  I see a few ohms difference before and after if I leave the antennas 
alone for a week or so without sealing current treatment. Any time I notice 
some IMD products at LF it is usually F connector oxidation that is the 
culprit....

Connectors with gold or palladium center pins (and shells) help in that 
regard...

73 Mike wa3tts


----- Original Message ----- 
From: "Chris Wilson" <chris@chriswilson.tv>
To: <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, May 18, 2016 12:04 PM
Subject: LF: Can LF damage a mains input filter?


> 18 May 2016
>
>
> Long story, but since stopping LF 136kHz TX for a while in lieu of
> some HF working all the digital TV's in the house freeze or totally
> blank on all bands above top band, up to 50MHz when I transmit at more
> than about  5 or 10W. I have a loft mounted UHF TV aerial feeding an
> amplifier cum distribution box. It has an internal mains PSU. Without
> it we receive hardly any channels. It's been fine for years, and I
> have never had TVI. My HF set up is unchanged from when I had no
> issues. I put the TV antenna co-ax direct into my SA and on circa 531
> MHZ see a broad digiTV signal that's strong. If I TX on say 20 meters
> at high power into my antenna I see zero change in the TV signal. I
> have also fed the output of my HF TX (TS-590 Kenwood) into the SA via
> an attenuator and the output looks spotless on all bands. However, if
> I connect the TV aerial amp / distribution box up and look at the
> output from it the TV signal immediately drops into the noise when I
> TX.  My neighbours have no issues at all.
>
> This seems to have occurred since I have been active on LF, and I had a
> stage  where  full power would trip the main RCD in the consumer unit,
> so  RF  was  getting  into  the mains. Is it conceivable something has
> occurred  to perhaps a mains filter in the TV amp? I looked inside the
> plastic  case  and  it  has  a small mains transformer that feeds feed
> throughs  into  a  screening  can  with all the RF stuff within it. If
> there is any mains input filtering it must be on the low voltage side
> of the transformer. The unit has a moulded on three pin mains plug, but
> with a plastic earth pin, so the unit is not grounded.
>
> Is  it  possible to make a mains input filter for a piece of equipment
> that would filter 136kHz but not affect normal 50Hz mains operation?
>
> Has anyone experienced anything like this?
>
> I  have  ordered  a  new amp / distribution box of known make, and will
> just  try  replacing it, but would also like to know if my LF activity
> could have done this?
>
> Thanks.
>
>
>
> -- 
>
>
> Best regards,
> Chris  2E0ILY                           mailto:chris@chriswilson.tv
>
> My        part        time        LF        grabber       is       at
> http://www.chriswilson.tv/grabber.html
>
>