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Dave Oldridge · January 25th 07, 03:28 AM posted to rec.radio.amateur.antenna

(Michael Black) wrote in
:

"R. Scott" ) writes:
80 is basically useless. 3400 and 4000 I have a Pegged meter WFM
signal from 1380kc station here. I have mini harmonics ever 200kc
that basically makes 80meters unusable Its really annoying and the
station says they had their equipment recertified 2 months ago

This is hardly an antenna issue.

You do realize that it may not be the transmitter?

If your receiver (and you don't specify what it is) hasn't got
good strong signal-handling, the station may be overloading it
and causing the junk. And at first glance, it wouldn't be
obvious whether it's the receiver or the transmitter.

Try a different receiver.

Put an attenuator between your receiver and antenna, and see
what happens to those signals when you increase attenuation. If
it's overloadig, there will be a point where the unwanted signals
go away that can't be accounted for by the actual attenuation.

An attenuator is the best and easiest test. Lots of ham receivers
actually have attenuators in the front end, so it may be just a
measurement thing. Basically if an in-band amateur signal is attenuated
significantly less than the spurs, then they are, indeed generated in the
receiver. The quick cure for that is to put a filter in the line to
remove the big signal on its own fundamental. Just make sure the filter
is either ONLY in the receive line or is capable of handling the output
power of the transmitter on any ham band.

Borrow a spectrum analyzer, which should stand up well to strong
signals since it wouldn't be much use otherwise, and see what signals
are arriving at your antenna. If you do see signals that are
traceable to the broadcast station, then likely they do have a
problem. But if not, it's your receiver.

Even then, there could be rectification in nearby clotheslines, fences,
etc., etc. I've cleaned up a couple of problems just by bonding a fence.

And it may not even be the receiver. There could be something acting
as a rectifier, that is picking up the transmiter signal and
generating harmonics for your receiver to pickup. A rusty rain
gutter, or a bad connection on an antenna, obviously something nearby.

Yep...usually that type is from a fairly nearby source.

Of course there are genuine spurs from broadcast stations. I remember
once, we had a big wide-band FM signal on 2182khz. DOC (at that time the
relevant authority) quickly tracked it down to a station running many KW
about 12 miles from our receive site (and made them fix it--interference
with hams is one thing, interference with a marine distress frequency
totally another thing in their books).

--
Dave Oldridge+
ICQ 1800667