Answers from the experts on www.eham.net on the duplexer question.
This is the question I posted on eham.net
Posted By KG8ID
Does cold temperatures (0-32 degrees F) cause duplexers to de-tune?
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These are the answers I received - thanks guys for the great information and
thanks to eham.net
Posted By WB2WIK
Depends on the duplexer. What kind of duplexer are you referring to?
The high-Q cavity-type, commercially made and sold duplexers are very stable over
large temperature ranges because the tuning screws are normally made of Invar, a
metal having a zero temperature coefficient. Homebrew duplexers would typically
drift a great deal more.
WB2WIK/6
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Posted By OBSERVER
Comment.
Nothing has a ZERO temperature coefficient or more commonly termed as Linear
Coefficient of Thermal Expansion. Invar in nothing special, it’s simply a Ni/Fe
alloy with what appears to have a low CTE. Some materials have very low CTEs
however everything expands and contracts at a specific rate.
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Posted By AC5E
Hi Perry: Temperature related detuning of the Tx-Rx "cans" we have is measurable
but negligible. At least from 130 degrees to 5 degrees F measured at our repeater
shack. I am reasonably sure yours will have essentially the same performance.
73 Pete Allen AC5E
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Posted By KE4MOBIn all reality, every environmental change causes the duplexers to detune a little bit...rain/ice on the antenna, temperature, relative humidity, etc. If you are using commercial (not homebrew) duplexers, I wouldn't worry about it, though. If your repeater performance measurably drops when the temperature changes, I'd be willing to bet it's either a problem in the radio, antenna, or feedline and not the duplexers.
Steve, KE4MOB