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 trifila wound 8
or nine turns. This one works
from 80 through 15 meters.

I also tried a Quadrifilar winding on a #67 and #61 core as multi
impedance transformer, still
narrow band with bad or high VSWR from 10mhz to 30mhz.

I tried another one with #61 material and did not have much success.

I then tried a auto transformer type primary 9 turns secondary 44
turns using a Amidon 61 core.
This produced a nice low frequency UNUN .5 mhz to 10 mhz.

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

On Fri, 31 Jul 2009 17:57:04 -0700 (PDT), Greg
wrote:

I am trying to build a broadband UNUN 9:1 from 1.8 mhz to 30mhz.
,,, what core do I use?

Hi Greg (signing as Bob),

It might take a combination of two, or three.

73's
Richard Clark, KB7QHC

Greg wrote:
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 trifila wound 8
or nine turns. This one works
from 80 through 15 meters.

I also tried a Quadrifilar winding on a #67 and #61 core as multi
impedance transformer, still
narrow band with bad or high VSWR from 10mhz to 30mhz.

I tried another one with #61 material and did not have much success.

I then tried a auto transformer type primary 9 turns secondary 44
turns using a Amidon 61 core.
This produced a nice low frequency UNUN .5 mhz to 10 mhz.

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

Type 43 or a 70-series ferrite is a better choice for that frequency
range, and 70 series is probably better for the relatively high
impedances you're dealing with. And as Richard said, you might have to
do the transformation in more than one step.

Roy Lewallen, W7EL

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

Question is: Where are you going to find an antenna that
exhibits a feedpoint impedance of 450+j0 ohms from 1.8 MHz
to 30 MHz? Here is a Z0=450 ohm ladder-line-fed all-HF-band
antenna that exhibits a feedpoint impedance at my QTH
between 40+j0 and 87+j0 ohms on all HF bands and needs
a 1:1 balun with no conventional tuner.

http://www.w5dxp.com/notuner.htm

Would you mind describing the antenna system that requires
the specified balun?

The question is simply how do I build a broadband UNUN or
Autotransformer from 1.8mhz to 30mhz and what core do I use?

It's extremely difficult to build a balun that functions
properly over a 16:1 frequency range. It is relatively
easy to build one that functions properly over a 4:1
frequency range. I would suggest building two baluns and
switching between them, one for 160m-40m and the other
for 30m-10m.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

"Greg" wrote in message
...
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 trifila wound 8
or nine turns. This one works
from 80 through 15 meters.

I also tried a Quadrifilar winding on a #67 and #61 core as multi
impedance transformer, still
narrow band with bad or high VSWR from 10mhz to 30mhz.

I tried another one with #61 material and did not have much success.

I then tried a auto transformer type primary 9 turns secondary 44
turns using a Amidon 61 core.
This produced a nice low frequency UNUN .5 mhz to 10 mhz.

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

You don't state what shape the core is. Have you tired a binocular core? I
wound up a 9:1 on a 43 binocular core and see under 1.5:1 from 500KHz to
30MHz on an Agilent network analyzer.

Dale W4OP

"Greg" wrote in message
...
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/~mcdona..._4_1_46_05.pdf
http://standards.ieee.org/reading/ieee/ept/trans.pdf

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

Mike

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" wrote in message
...
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/~mcdona..._4_1_46_05.pdf
http://standards.ieee.org/reading/ieee/ept/trans.pdf

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

Mike

On Aug 2, 5:50*am, Greg 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" wrote in message
...
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/~mcdona...ck_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