re: Circulators and Isolators.
Hello all...
My turn...
:The so called ISOLATOR is a name given to a three port CIRCULATOR with
the
:third port terminated in a load. Port 1 goes to the transmitter. Port 2
to
:the antenna. Port 3 to the termination.
Pretty much, but there are multi port units made, very common at VHF and
above.
: At UHF and microwave these are
: usually made using strip line and ferrites.
The strip line is mostly Microwave... the VHF/UHF versions are ferrites
made slightly different.
: I do not recall seeing too many ISOLATORS at HF.
I have one at 24 MHz, it's the size of a large shoe box. About 50MHz
they look like a large 12 power supply heat sink, 150MHz about the size
of a Ham Sandwich... UHF takes them down to the size of an instant camera
for a dual unit.
:I think Collins and Chu did build some using lumped
:constant networks for the phasing networks. When I was with RANTEC we
made
:some at VHF using lumped constants. They were pretty big and very
narrow
:band.
They should be tuned for the frequency of operation. Adjustments are
often offered on higher quality, higher power units. Below 30MHz often
finds them with lumped constants.
:The purpose of these gems was to divert reflected power (or incident
:power from collocated transmitters) from the transmitter. They did
nothing
:to change the SWR of the transmission line or the antenna.
They are a must have at busy locations to prevent mixing problems in PA
stages of adjacent transmitters.
The diversion is most often done to an external load "off" the third port
on single stage units used in two-way radio communications.. Dual stage
units have two terminations, the closest unit to the output port has a
larger termination for the majority of reflected power.
Very common to commercial communications transmitter power combiner
setups on mountain tops. A science project to build and adjust... one of
my "other fun hobbies."
:Yes -- a nice attenuator in the transmission line will reduce the
reading of
:reflected power --- but it will not "match" the antenna system.
:Harv K6EXO
Doesn't stop some folks from trying though... If anyone requires help
setting one up, Email me for the information. Telewave is one of many
companies that sell them. They can be found on their web site... very
expensive toys.
cheers
skipp
nospam4me@juno.com
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