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Old April 4th 07, 09:56 PM posted to rec.radio.amateur.antenna
Pete[_3_] Pete[_3_] is offline
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First recorded activity by RadioBanter: Apr 2007
Posts: 7
Default Non technical antenna question

Michael Black wrote:
"Larry Gauthier \" ) writes:

If you find yourself with two radios that are similarly-equipped in
terms of antennas, but one gets your favorite stations while the
other does not, then the one that does not is either broken or has
designed-in lousy sensitivity.

Actually, it might be the reverse, depending on what exactly is
happening.

I have a all in one stereo I got at a garage sale. It had lousy
reception of a non-local station that is always receivable here on
other radios, even lousy ones. I naturally thought the antenna was
the problem. But I did something and realized I likely was
attenuating the signal, and the issue wasn't "not enough antenna" but
too much. I took off the whip antenna, and that thing gets perfect
reception on that non-local station, whereas before it
was noisy.

Clearly, the stereo was being overloaded by local signals, which
impacted
on it's ability to receive the strong but comparatively weaker
non-local station. Removing the antenna attenuated the local
station(s) enough that the stereo didn't overload, but the non-local
station was still strong
enough to be received fine.

Most consumer broadcast receivers are too sensitive if anything,
because
they don't handle strong signals that well, yet the strong signals
overloading them make them useless for receiving distant signals. A
less sensitive receiver wouldn't be as good for distant reception, but
the local signals wouldn't mask those distant signals with overload.

I don't know if this is the case here, but it is worth looking into
since it's the last thing people generally expect. I notice when I
got a Grundig portable sw receiver at a rummage sale in September, the
manual specifically states to keep the whip antenna shorter when on
the FM broadcast band (the antenna being longer for the shortwave
bands), and having been prompted by the manual and experience, I do
notice that not so great reception on the FM band is improved when
I shorten the whip antenna.

Michael VE2BVW


Michael...you were absolutely correct (100%) about shortening the whip for
FM broadcasts. I shortened the whip to its fully collapsed position and it
worked, and the station I wanted came in at an acceptable level. Great
info. So now my logical question is why are the FM whip antennas even
extendible if they play better fully collapsed. I guess it depends on a
bunch of variables such as power of the transmitter and location of where
the signal is being transmitted from. I know from past experience that
extending the antenna can help sometimes.

But shortening it worked - what is the quick logic if you don't mind. I
know that everything is frequency and wavelength and they are inversely
proportional. I would have never thought that shortening the antenna would
have solved the problem - I even thought I tried that before, but I must not
have stayed with it long enough. Thanks again to you and everyone else for
all your help :-) .

Pete