Rob wrote:

John S wrote:
On 7/26/2016 8:20 PM, Allodoxaphobia wrote:
In rec.radio.amateur.antenna, you wrote:
On 7/26/2016 9:13 AM, Allodoxaphobia wrote:
On Mon, 25 Jul 2016 15:18:14 -0700, Robert Smits wrote:
Hi. Can anyone recommend a source of 36:50 ohm ununs?

I'm adding an inverted L for 160 meters and would like to add an
unun of 36
ohm to 50 ohms to reduce my SWR. EZNEC shows it would lower it
substantially and when you're running barefoot on 160 you need all
the help
you can get.

Just run two sections of 1/4 wavelength 72 ohm coax in parallel as
a matching section. KISS.

Where does the transformation to 50 ohms occur? If you have a 36 ohm
antenna and you build a 36 ohm transmission line with the paralleled 72
ohm lines (doesn't have to be 1/4 wavelength) you still have 36 ohms at
the transmitter end to deal with.

Ahhh... You are so correct!
I read the OP "intently" and then went off half-cocked.
Apologies!!

So, for a revised "suggestion" I would try parallel sections
of 93 ohm coax -- RG-62 -- and see how that plays out.

73
Jonesy W3DHJ


Errr... how does that help? Paralleled 93 ohm coax results in a 46.5 ohm
transmission line. It might as well be a single 50 ohm line instead.

The line needs to be sqrt(Zi*Zo) = sqrt(50*36) = 42.4 ohm.

Paralleled 93 ohm is probably the closest you can get using off-the-shelf
cable.

How about 75 ohm in parallel with 93 ohm giving a theoretical 41.5 ohm?
Or doesn't this work?

--

Roger Hayter