[RFI] FW: Common mode choke on 4 Square feedlines without skewing phasing?

[Jim Brown]

On 1/29/2019 12:55 PM, Paul Christensen wrote:
> Don't rule out surplus RG-303.  It's not too common but it can be found with
> some searching.  RG-303 is similar in construction and power handling to
> RG-142/RG-400 but with a slightly smaller diameter that makes winding
> easier.

But he's looking for 75 ohm coax, and 303 is 50 ohms. Pasternak's RG179 
is 75 ohms, center is seven strands of CCS, silver-coated copper braid. 
0.4-in bend radius. 0.1-in o.d. Harbour Industries lists the same 
characteristics.

If someone wants to send me some, I'll wind some chokes and measure 
them. I'll need about 60 ft to do both 4-in and 2.4-in o.d. toroids. 
(Because these chokes are pretty high Q on 160 and 80, I need to wind on 
four cores at the limits of specs for Rs and Xs, and base my guidelines 
on worst case of those four sets of data). As noted in an earlier post, 
I'd say that chokes wound on 2.4-in o.d. cores are plenty good enough to 
use at the feedpoint of each element of a 4-square.

73, Jim K9YC