[Motorola] Isolator tuning ??

[Eric Lemmon]

Jay,

If you need to retune a ferrite circulator/isolator more than 2% away from
its original center frequency, it will need to be re-manufactured to operate
properly on the new frequency.  This is not a hard and fast rule, but it
generally is true.

One of the radio clubs in my area was given a Sinclair dual isolator that
was manufactured and labeled for a frequency in the 162 MHz band, and the
club wanted to use it for a 2m repeater in the 147 MHz band.  When I tested
this isolator on my network analyzer, it worked perfectly at the labeled
frequency.  However, its performance rapidly deteriorated as I tuned it per
the Sinclair instructions, and by the time I reached 159 MHz it was almost
useless.  A call to Sinclair tech support uncovered the fact that the
catalog listing for this isolator, 138-174 MHz, does NOT mean that any unit
will tune over that band; it only means that Sinclair can make an isolator
for any transmit frequency in that band.  The fine print in the tuning
instructions reveals the fact that a VHF isolator is tunable over a very
narrow range about the delivered center frequency.  Most of the internal
parts require machining or replacement when the unit is moved to a new
frequency more than a few MHz away.  The radio club sent the isolator to
Sinclair for rebuilding and tuning to the 2m frequency, and paid about $250
for the service.  Since that is about 1/3 the cost of a new dual isolator,
they were happy.

Contact RFS/Celwave at <www.rfsworld.com> and Telewave at <www.telewave.com>
for information about isolator and circulator remanufacturing.  I do know
that Telewave will rebuild isolators made by others, so be sure to ask about
that service.

73, Eric Lemmon WB6FLY


-----Original Message-----
From: motorola-bounces at mailman.qth.net
[mailto:motorola-bounces at mailman.qth.net] On Behalf Of Coote, Jay
Sent: Wednesday, April 11, 2007 11:11 AM
To: motorola at mailman.qth.net
Subject: [Motorola] Isolator tuning ??

Looking for tuning instructions for VHF isolators:
1. RFS/Celwave model CC150-AA
2. Telewave T2200B
 
Thanks
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