Re: UNUN Cores?How To Wind?

On Aug 2, 5:50 am, Greg <bluehyh...@xxxxxxxxxxx> wrote:
Thanks  for all the information.

The 9:1 works with 8 turns trifilar, on the FT240-67 from 80 through
to 10 meters. Its poor on 160 meters.

All the cores are FT 240 size from Amidon or Bytemark. I can get the
transformers to work but only over a narrow frequency range for the
higher impedance ratios.

I notice that the Sevick UNUN  thats sold by Bytemark, a 18:1  ratio
is narrow band and wont cover  1.8mhz to 30 mhz. Anyhow i dont have
the magic recipe yet but I will keep experimenting.

Bob



amdx wrote:
"Greg" <bluehyh...@xxxxxxxxxxx> wrote in message
news:22e47242-3660-4bb4-9406-fab7333e915f@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi

I am trying to build a broadband UNUN 9:1 from  1.8 mhz to 30mhz. I
have had no luck.

The first one the that I built, I  used #67 material
snip

The question is simply how do I build a broadband UNUN or
Autotransformer from 1.8mhz to 30mhz and what core do I use? I am
coming to the conclusion that  these auto transformers  or high
impedance UNUN's are narrow band devices?

I am playing  around with a terminated  T2FD type antenna trying
different impedances, 450,600,800 and 1000 ohms termination resistors..

Bob

 Here are some papers that may help.
http://www.hep.princeton.edu/~mcdonald/examples/EM/sevick_hfe_4_1_46_...
http://standards.ieee.org/reading/ieee/ept/trans.pdf

These came from here, there are others.
http://unjobs.org/authors/jerry-sevick

                              Mike- Hide quoted text -

- Show quoted text -

This guy seems to have made one work. See the middle of this page

http://g8jnj.webs.com/currentprojects.htm

UKM
.

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