Ok, I have some theroies, but I need confirmation from someone that
is like good with math and formulas and stuff as you know I flunked my
high school pre-algebra class.
Anyway I want to make a 2 meter duplexer economy style as the person
who is building the repeater cannot afford a trip to the Zoo let alone
a set of big cans. So I wan't to build either a 6-pack or a 8 block
of cavitiys, like the UHF mobile duplexers only longer. 2 - 3dB of
insertion loss would be acceptable
Doing some coaxial theory and using air as a di-elelctric. Will an
inner conductor with a outter diameter of 3/8" and the outer
conductor with an inner diameter 1" yield 70 ohms impedence? If not
what would the impedence be? And what would the dimensions of the
outter conductor need to be if the inner is 3/8"?
The present idea of mechanical construction is to use 3/8" copper
solid ground rods cut to length for the inner conductor and encasing
in either 1" or 1 1/4" pipe. Then there would have to be a bushing
fabricated that has allen set screws to adjust the length of the
center conductor. This design should be ideal for any frequency
asuming the materials are big enough.
I am planning for a Notch only style duplexer to keep costs down.
Without design software I cannot acurately predict band pass or BpBr
"Q" if the cavities have more than one connector.
Also loop construction ideas are welcome as I currently am planning
BNCs on the top with 12 ga straight down from the top and soldered to
a hole in the side of the can.
I am also considering a Teflon disc at the end of the tuning rod to
act as a spacer for mechanical stability if the set is lied flat.
On 4/22/05, Mathew Quaife <[EMAIL PROTECTED]> wrote:
>
> Yes I agree on that one, I locked them down and one of them moved on me,
> check each one indivually.
>
> Mathew
>
>
> Dave VanHorn <[EMAIL PROTECTED]> wrote:
>
> At 07:22 AM 4/22/2005, Mathew Quaife wrote:
> >If these are like my TX/RX duplexers, the slighest movement of the
> >tuning rods makes a huge difference, especially on the tx
> >side. retune would be a good idea. Take them slow, they are fun to
> >tune. Enjoy!
>
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