[TowerTalk] Coax Switch Isolation

[don tyrrell]

Hi,
I noted that someone measured one of our coax switches with a 26.5 dB
isolation. Maybe I can clarify why this may have happened. The microstrip
cavities and isolation fins are die cast into the main housing casting so
there is little if any variation from unit to unit. We use a MIL spec RF
test house to measure these characteristics and they test for a minimum of
50 dB isolation. They say the most common reasons for comparative test
errors in non lab environments are: A. Improper use of, or faulty jumper
cable/connector assemblies. B. Improper or faulty test loads. These must be
exactly R50 plus J ZERO loads. C. In the case of the DELTA-4 family, the
case must be hard grounded to a proper ground system since the devices are
protected by an ARC-PLUG gas tube module. If grounding is not proper, the 1
pF of capacitance of the tube will throw off the readings, including the
VSWR specs.
Hope this clarifies the situation.
Thanks and 73,
Don,  W8AD, Alpha delta Communications
Don Tyrrell at d.r.tyrrell@worldnet.att.net


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