To summarize:

1. Obtain information about the allegedly-offending station: power,
location,
antenna mode (ND or D) and if D, the pattern and where YOU are in its
footprint;

The offending station is KARR ( 1460).

I have a friend living in next county north (appox 20 miles) of me has same
problem
on a 1940's Scott Receiver. I used to live 15 miles north-west of the
station and
now live 1 mile south of station.

In a later post, Bob provided information about the station in question:

To summarize:

1. Obtain information about the allegedly-offending station: power, location,
antenna mode (ND or D) and if D, the pattern and where YOU are in its
footprint;

The offending station is KARR ( 1460).

I have a friend living in next county north (appox 20 miles) of me
has same problem on a 1940's Scott Receiver. I used to live
15 miles north-west of the station and now live 1 mile south of station.

By "same problem", I take it that he too gets a splattery signal at about 5 Mhz,
that you can relate to KARR's programming by its general resemblance. It comes
in on a tube radio, and various solid-state ones; it is heard from 1 mile, to 20
miles from the station. Is this a good summation?

This would suggest that there *may* be a spur from the transmitter of KARR *if*
your observations are all well-controlled.

It is not a third or fourth harmonic: they'd fall at 4380, and 5840, well away
from 5 MHz. It could be a spur, somehow related to an internal transmitter
oscillator frequency if there is frequency multiplication involved; but since
the division of the interference signal (5 MHz) by the KARR carrier frequency is
an odd value (3.42) that does not seem at all likely to me. What may be
happening is a randomly-oscillating transmitter stage -- maybe with bad
neutralization -- whose spurious radiation is somehow passed into the antenna,
and radiated. But an AM broadcast station antenna is a highly resonant device;
way up at 5 MHz it will be quite inefficient. And there are other constraints:
the impedance of matching networks, or the complexities of phaser components,
reducing the likelihood that a really strong signal can be radiated this far
from the cx frequency. BUT IT *CAN* HAPPEN!

Perhaps, as I've suggested, if the signal is REALLY being propagated into space,
over a wide area, AND IF IT GOES AWAY WHEN KARR IS OFF THE AIR (!), then you'd
have to start looking at the possibilities that (a) the station is in terrible
shape; you should inform them!; (b) it's a strange cross-mod problem with
another station; (c) it's caused by a re-radiation effect in the near-field of
the KARR antenna system, at a hot spot where the signal is strong, and is
causing corroded metal surfaces to act as an RF mixer and passive radiator.

Once again, if the problem at 5 MHz is NOT eliminated by notching out the KARR
signal at 1460 at your antenna input (by a simple two-component series LC
filter), then (after exhausting all possibilities that you could be in error)
you probably should inquire from KARR's management and engineer if they are
interested in the phenomenon, and if they can assure you that THEY aren't
responsible for it.

I say "after exhausting all possibilities that you could be in error" with no
disrespect; I'd do the same myself before I'd contact the broadcaster.

AUTEUR

--
Ce message a ete poste via la plateforme Web club-Internet.fr
This message has been posted by the Web platform club-Internet.fr

http://forums.club-internet.fr/