75 to 50 ohm

[Alex Fraser]

I'm using 3/4 " hardline.

John Teller wrote:

> It's a wash, pretty much.  CATV coax (RG59) is so bad at L-Band that any gains you may come up with by improving the match are more than offset by the losses.
>
> We use RG6 at work to connect the LNB and antenna on the roof to the receiver inside.  The LNB converts the Ku-Band satellite feed down to L-Band for the benefit of the receiver.
>
> --- JST
>
> -----Original Message-----
> From: Alex Fraser <beatnic@home.com>
> Date: Wed, 24 Oct 2001 11:45:51 -0400
> To: tacos@amrad.org
> 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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>
> --
>
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--
<<***********************************>>
~~~~~~~~ Alex Fraser  N3DER ~~~~~~~~~~~
--------- beatnic@home.com ------------
~~~~ http://members.home.com/beatnic ~~
>>***********************************<<