RadioBanter - View Single Post - Semi-related: FM Dipole Total Length

George Cornelius · April 2nd 17, 04:32 AM posted to rec.radio.shortwave

In article , writes:

30". My first dipole was about that
length per side. Got in only the upper
half of the band. Once I got up past
35" per side, I started getting in
stations below 97 FM.

Now I'm up to 80" total, and I get the
whole band in, but moderate static
throughout.

Oh, if both antennas behave the same way
then we have to look somewhere else for
the discrepancy.

And you can be sure there is one, or we
have done something astounding: we will
have overturned 100 years of experience
with building dipole antennas.

I found two more commercially made FM
dipoles today, and of course they are
all roughly the same length. One was
tacked to a piece of plastic trim -
basically quarter round - and behind my
old Harmon Kardon 330B receiver, which
I no longer use.

Attaching the antenna and moving the
speakers over from some other sound
system I had been trying out, I fired
it up, and what I found was:

o The public radio station at 91.7 I
had been having trouble with on the
other side of town, and closer to
the tower, came booming in and
read 8 points on the signal strength
meter. So low end of the band was
OK.

o Major stations both at low end and
high end of the band came in at roughly
the same reading.

o Did not go into further detail, say
with more distant stations, but from
just a few minutes of testing, the
standard dipole design is working like
a charm with no preference for any
particular part of the band.

I would start looking for problems at
your receiver end, and if that is not
the problem, put the commercial dipole
outside, into a 4:1 xformer, and use
ordinary CATV coax to feed back into the
house and into your F connector.

I expect that one or the other of these
will tell the story.

George