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.
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