nuckolls.bob(at)aeroelect
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 Posted: Tue Mar 31, 2015 8:17 am Post subject: Handheld transceiver alternate antenna |
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At 11:22 2015-03-30, you wrote:
Found this article in kitplanes archive which describes a $2 antenna diplexer.
http://tinyurl.com/nz6q8qb
This would more properly be called a 'switch', a
system whereby a single antenna may be routed to
any one of two or more transceivers. A 'diplexer'
is a device that allows two activities to share a
single resource. WAyyyy back when, television receivers
had both UHF and VHF antenna terminals on the back.
One was expected to have both UHF and VHF antennas
on the roof with separate feed lines brought into
the house. A 'diplexer' would combine two signals from
separate antennas for transport into the house on one
feed line. A similar device was hooked up in reverse
at the receiver to feed UHF and VHF signals to their
respective inputs.
Later on, wide band tuners would accept UHF and VHF
signals into a single antenna jack . . .but a diplexer
was still a useful thing to use for combining the
two spectrums into one feed line on the roof.
A duplexer is a bit more sophisticated. It's generally
used to allow simultaneous use of a single feed line
for both receive and transmit. Repeaters of
all stripe will make good use of a duplexer to
watch a single antenna and feed line for
sub-microvolt signals coming down then separating
that signal out to a receiver while simultaneously
allowing a 100 watt transmitter to squirt a signal
up the same feed line to the same antenna.
Real magic stuff. I've tuned dozens of such devices
and built a few for both commercial and amateur
radio applications. They save you a lot of money
for feed lines and antennas when your antenna
site is hundreds to perhaps a thousand feet
up the side of a tower. But they can be a 'horsy'
beast. The legacy duplexer for 146Mhz was 4 to
8 "stove pipes" about 20" tall.
UHF duplexers are proportionately smaller but still
substantial pieces of equipment.
There is good application for a diplexer/spltter in aircraft
where a single VHF VOR antenna can be pressed into
service to drive either multiple VOR receivers or
even multiple GlideSlope receivers.
What good man Jim has described in his article
is a clone (along with evaluation of performance)
of the Icom hand-held antenna jack and SWITCH
that we discussed earlier in this thread and
at some length years ago.
[img]cid:.0[/img]
^^^^ Icom Product ^^^^
[img]cid:.1[/img]
^^^^ AEC DIY project ^^^^
Bob . . .
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