75 to 50 ohm

[Bob Bruhns]

Hi Alex,

If you can machine the materials, I would think a gradual tapering
over a few wavelengths from 50 ohm dimensions to 75 ohm dimensions
should do it, with nice broadband properties.   And smoothing is the
way to go, I think.  FWIW.

  Bob, WA3WDR


----- Original Message -----
From: "Alex Fraser" <beatnic@home.com>
To: <tacos@amrad.org>
Sent: Wednesday, October 24, 2001 11:45 AM
Subject: 75 to 50 ohm


> I want to use some 75 ohm CATV hardline at 2.4 gig (DSSS lan
card). A
> matching piece of coax is recommended in the ARRL handbook, but
not
> specifically  at this high of frequency. I understand the square
root of
> the sum of squares to find the value of the matching section. I
was
> thinking  a length of 6061 aluminum home made coax made to slip
over and
> clamp to the CATV hardline on one end and have a flange for an "N"
> connector at the other. I can  figure out the dimensions to
machine to
> get the matching section's impedance in the ballpark, but wonder
what
> shape the ends should be for low loss and little reflection?
Should I
> taper the ends to blend the change in diameters or leave the edges
> square? Or for that matter should I taper the whole section? If I
need
> to have a constant taper how could I calculate its dimensions? And
> finally am I causing more losses by trying to match than by
ignoring the
> mismatch and getting on with it?
>
> --
> <<***********************************>>
> ~~~~~~~~ Alex Fraser  N3DER ~~~~~~~~~~~
> --------- beatnic@home.com ------------
> ~~~~ http://members.home.com/beatnic ~~
> >>***********************************<<
>
>
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