The OD of the center conductor on a TX-RX 4" diameter 900 MHz cavity is
0.877" (probably 7/8" before silver-plating). It tapers slightly where the
"fingers" are cut into the bottom (open) end to grip the plunger.
The plunger will recede far enough up into the center conductor to allow for
resonance at 1.2 GHz once the center is cut down. The fixed length of the
center conductor only allows it to get up to about 1080 MHz before
modification, i.e. you have to cut back the center conductor tube far enough
to get it to tune up to 1.3 GHz. This also requires cutting the "finger"
slots deeper after cutting off the excess, and likewise forming/tapering
them inward so they make good contact with the plunger. The OD of the
plunger is about 1/16" smaller than the ID of the center conductor (just to
give you an idea of how much taper there is to the fingers).
If you want a pic of the center conductor/plunger assembly email direct.
--- Jeff
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Jeff DePolo
> Sent: Monday, July 13, 2009 8:08 AM
> To: [email protected]
> Subject: RE: [Repeater-Builder] Re: 3/4 wave cavity operation
> at 1296 MHz
>
>
>
> >
> > I wonder what the diameter of the center element, or plunger, was?
>
> I think I still have one with the rivets drilled out, I'll
> measure when I
> get a chance.
>
> --- Jeff WN3A
>
>
>
>
>
> Checked by AVG - www.avg.com
> Version: 8.5.375 / Virus Database: 270.13.12/2234 - Release
> Date: 07/13/09 05:56:00
>
>
>
