75 to 50 ohm

[John Teller]

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 ~~
> >>***********************************<<
> 
> 
> _______________________________________________
> Tacos mailing list
> Tacos@amrad.org
> http://www.amrad.org/mailman/listinfo/tacos
> 

--