[222mhz] 220 duplexer

[Dr. Gerald N. Johnson]

On 10/18/2010 6:52 AM, Chris Boone wrote:
> Came across (2) items what looks to be a 216-220MHz duplexer used on the
> Inland Waterway Communications System (IWCS) and it looks a lot like a DB
> Products; has their tan color on it, 5 cavities of what LOOKs like Band
> Pass/Reject design PER leg inside a weatherproof fiber box (obviously to be
> mounted close to the antenna)..but there is no model number, etc on it....I
> have tried Googling and still no joy...anyone have any model numbers or info
> on this??
>
> BTW I have retuned one set to the highest 220 rptr pair (out 224.98/in
> 223.38)....WOW!! with only 3 cans tuned, I get little insertion loss and
> 100+db notch on my IFR1500 in the tracking gen mode...cant wait to get all
> 10 cans tuned and see how it works as a 220 duplexer!

Be sure the notch you see is only from the cans and not from the signal 
passed by the cans canceling the signal leaked between source and 
indicator coax cables. That happens with singly shielded cables in the 
test setup and connecting the cans. That can also come from signal 
generator and detector with some RF leakage even with good double 
shielded braid coax or modern corrugated foam insulated partly flexible 
heliax.

73, Jerry, K0CQ
>
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