They are definitely Sinclair, welded top, side loop BpBr cans. They are
an intermediate design between the old rounded top, spun aluminum cans
with side loop and the welded top, top adjustable loop design of the
modern Sinclair cans. They date from the late 50s or early 60s (by 1964
or so the top adjustable loop design had been adopted).
The stub hanging down is a coaxial capacitor that tunes the notch. The
cable going up would connect to the side of a Tee connector with the
signal path going thru the Tee connector. That cable will be an
electrical 1/4 wave at the pass frequency although it is not super
critical. They could also be part of a hybrid ring design although the
can is the same regardless of the type of filter.
Try them on the tracking generator over a much wider range (like
130-160MHz) You should see two notches, one above and one below the
pass. If you want a HPLR you will have to reduce the capacity of the
coaxial capacitor stub considerably. That will move the low side notch
up closer to the pass.
Good luck in your experiments.
Burt VE2BMQ>>>
Scott Zimmerman wrote:
> Fellows,
>
> I bought these cans at Dayton last year. I have no information on them.
> The interconnecting harness is butchered pretty badly, so I'm not sure
> of the correct lengths. I'm hoping that someone can recognize these and
> has some documentation and / or a set that we can use as a pattern.
>
> I think these are Sinclair, but I'm not sure. Kevin and I have put them
> on the tracking generator and have been able to get LPHR response out of
> them, but not HPLR. I think this is due to not having the correct cable
> lengths.
>
> Thanks in advance for any info and to you dial-up subscribers, sorry for
> sending pictures you may not need.
>
> Scott Zimmerman
> Repeater-Builder (the company)
>
> Scott Zimmerman
> Amateur Radio Call N3XCC
> 612 Barnett Rd
> Boswell, PA 15531
>
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