I had a set of home brew copper pipe duplexers that used regular steel
threaded rod for the plunger rods. After the frustration of not being able
to keep them tuned, I took them apart and put two nuts above the plunger
and two nuts below the plunger on the threaded rod. I tightened these
against each other (top two and bottom two) allowing about a 1/16" slop in
the connection. I then tuned the cans. This was the difficult part
because, if you past the peak or null, you had to back up and pick up the
slack and tune the other way. When I was done, I turned the rod 1/2 the
distance of the slack so that the plunger was centered equally between the
two sets of nuts. This stopped the rod from pulling the plunger up and
down as temperature changed. I never got any noise from this loose
connection that I could hear, but I was only running about 40 watts.
We Yankee's are parsimonious, don't you know. 73, Joe, k1ike
At 11:57 AM 8/4/2004, you wrote:
>reliable repeater performance and operation; it will require some very
>special materials (like threaded invar rod) and access to a well out-fitted
>machine shop.
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