Sorry post was too short there!
Does the factor of 234 equal a full wave or partial wave like 1/4? 3.3"
sounds shorter than I'm used to seeing. Is there any reason, other than the
result being too tall of a device, to use an antenna that is not a full
wave?
Or to put it another way, if I build a di-pole ant. for 850 mhz what part of
a wave length will result in the best reception? Would there be any harm in
tuning for 2 wave lengths? See where that question is headed, if 2 is OK
then it will work on another freq as a 1(full) wave length antenna.
I seem to remember that 850 mhz was full wave at 13.8" so a half wave for
425 mhz is 13.8" too, is this right?


"Dxluver" wrote in message
...
try a homemade vertical di-pole with one element for each band you
want to receive soldered to some good coax. For protection from the
weather
you can seal it in a suitable length of PVC pipe with endcaps.

For the bands you mention above, your elements would be: 17", 6", and
3.3".
One of each soldered to the center conductor and another of each
soldered
to
the shielding. This is not a transmitting antenna so no impedance
matching
mechanism is necessary and the coax can run down alongside the lower
half
of
the di-pole.

To calculate other lengths: FEET=234/MHz (i.e. 17'=234/160.000).

Hey Frank,
That is interesting and I know of the thinking behind it. Have you or
someone
you know (maybe someone in this group) ever run an antenna like that
and
what
are/were the results. {?}

This might sound silly, but you wouldn't need a switch box would you
to
switch
to each 'antenna.'?? You mean you could use this 'one' antenna and
just
run it
straight to your scanner and as you searched different parts of the
spectrum
the cut antenna would automatically work for the part/areas you were
scanning?

Thanks for any reply by anyone. :-)

**I know in SWL you'd have to use a switchbox for a setup like that.

His idea is similar to the antennas that RS and maybe others sold. The
ones
with "3" vertical radials one for VHF low, one for VHF Hi and one for
UHF -
3 distinctly different length vertical elements - all mounted to a
center
plate and connected to a SO239 with ground radials to boot. I made one
like
it once out of a block of wood, 3 clothes hangers and 4 curtain rods -
to
work in a pinch. I used 50 ohm coax. It worked quite well when made to
center of the bands they were to receive. No switch box needed. L.