Elecraft RFI Problems

[Martin.Evans]

Hi Guys and many thanks for all the responses both on and offline. I've
some excellent advice and plenty of things to try. To recap, problems are
on 20m with HI FI and AM radio and on 80m with PC modem. I did a bit
fiddling around with the feeder on Sat with some surprising results.

Firstly out of curiosity I wound about 8 turns of the coax feeder into a
coil (about 6 inches diameter) not at the feed point (didn't fancy getting
the ladders out on a wet day) but at ground level (about 30 feet from feed
point). The breakthrough on the HI FI on 20m got much worse (seriously
worse) but it did at least indicate that the feeder was a big factor. I
then remembered that because there was a bit of slack in the feeder where
it meets the ground (at the base of the old apple tree) I had taken to
coiling up a few feet of it (say only 2 or 3 turns) and hanging it on a
branch. So I straightened out the coax so that there were no coil turns at
all. This produced a dramatic improvement on 20m, with 100W (CW BTW) the
50HZ hum on the HI FI was almost inaudible.

The 80m breakthrough on the PC modem has been reduced by disconnecting a
long length of elevated internal telephone line (all on the same circuit)
which isn't used any more and by winding the line on a ferrite at the PC,
don't know which measure did the trick but I can now use at least 50W on
80m without any probs.

Have also re-routed the feeder to come away from the dipoles at 90 degrees
for as far as poss before turning back towards the house.

The AM radio is still a problem but will try a ferrite on the mains lead.

So I have a temporary working solution whilst I try some of the ideas
raised on this reflector.

I will try coiling the coax at the feed point when I get the time and
checking for RF on the rig (touching rig when looking at SWR).

Thanks again for the wealth of advice.

Martin
M0KWV
K1 #1534 feeding TS520 Tube PA to multi dipole.


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http://www.simoncarves.com

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