Message-ID: <573CBC68.5080307@lineone.net>
Date: Wed, 18 May 2016 20:03:04 +0100
From: LineOne <dhchurch@lineone.net>
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References: <1934937394.20160518170418@chriswilson.tv>
In-Reply-To: <1934937394.20160518170418@chriswilson.tv>
Subject: Re: LF: Can LF damage a mains input filter?
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Status: O

I can't really help, for some years I've had 2 industrial 25A filters in 
the shack supply, one in the house and one in the shack to alleviate QRM 
from local, crappy power supplies coming through the overhead supply. 
These have twin toroidal filters and 1kV ac capacitors so are 
bomb-proof, designed to partner with single-phase, industrial motor 
drives which are particularly noisy.

Hugh, M0DSZ.


On 18/05/2016 17:04, Chris Wilson wrote:
> 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.
>
>
>