Pretty much you want an electrical 1/4 wavelength or 3/4 wave of coax cavity to cavity and from the cavities to the antenna tee.
This should be the distance measured to the center of the Tee including connectors. You will need to know the velocity factor of the coax and calculate it in. But no one ever said what the velocity factor of the connectors and Tees are, so your going to have to dead recon it the rest of the way. I'd calculate both sides for 146.00 length wise and it should be close enough to cover the whole ham band, if you calculate to exact frequencies you cn probably get .5dB of additional rejection. for ultimate precision you can use a line stretcher, but then you get additional cable and connector loss. http://www.repeater-builder.com/wacom/wp6xx-vhf-tuning-instructions-remec.pdf http://www.repeater-builder.com/antenna/duplexer-cabling-lengths.html On Tue, Nov 10, 2009 at 5:26 PM, Kris Kirby <[email protected]> wrote: > > I'm working on re-fitting a Wacom WP-639 for re-use. There are two > remaining jumpers on this four cavity filter set, located between the > cavities on each respective side; there is no coax between the High side > of the Low side, only coax between each of the two low side cans and the > two high side cans. > > Due to the age of the jumpers, and with parts available on hand, I am > replacing the jumpers with RG-142. My questions are these: > > Are the side pieces frequency specific or "middle of the road". (i.e.: > 146.01 and 146.61 MHz for each side or 146.31MHz for both)? > > How much length does a connector add to the length of the cable when > making a frequency-specific or critical jumper? > > Is the distance between the high-side and the low-side of the duplexer > 1/2 wavelength? I believe that from the "tee" in the middle of the set, > there should be 1/4 wavelength to the first high-side can, and 1/4 > wavelength to the first low-side can. Is this correct? > > I know that I have to factor for velocity factor, but I am at a loss as > to what to add or subtract for crimp N-type or PL-259 connectors. > > Thoughts, comments, information are greatly appreciated. > > -- > Kris Kirby, KE4AHR > Disinformation Analyst > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
