I sent my previous post too quickly...

In fact wiring is totaly different, but the question remains anyway :
what will be the best desing between
http://www.m0ukd.com/Magnetic_Long_Wire_UnUn/index.php
and
http://www.hard-core-dx.com/nordicdx.../9_1balun.html
??

Thanks

Charly

On 1/17/2011 9:20 AM, Charly wrote:
I sent my previous post too quickly...

In fact wiring is totaly different, but the question remains anyway :
what will be the best desing between
http://www.m0ukd.com/Magnetic_Long_Wire_UnUn/index.php
and
http://www.hard-core-dx.com/nordicdx.../9_1balun.html
??

Thanks

Charly

The second link is in error, that is not a balun, it is an
autotransformer ...

Regards,
JS

On 1/17/2011 9:20 AM, Charly wrote:
I sent my previous post too quickly...

In fact wiring is totaly different, but the question remains anyway :
what will be the best desing between
http://www.m0ukd.com/Magnetic_Long_Wire_UnUn/index.php
and
http://www.hard-core-dx.com/nordicdx.../9_1balun.html
??

Thanks

Charly

A properly constructed balun/unun is a TLT (Transmission Line
Transformer.) And, there are in variations in how to wind these ... use
a search engine and research for further info ...

Regards,
JS

Charly wrote:
In fact wiring is totaly different, but the question remains anyway :
what will be the best desing between
http://www.m0ukd.com/Magnetic_Long_Wire_UnUn/index.php
and
http://www.hard-core-dx.com/nordicdx.../9_1balun.html


There a lots of designs for 9:1 transformers, some work better than others,
and in practice none works better than all of the others all of the time.

You don't need a toroid, although they have become popular these days, a
ferrite rod will do too. You can buy them on eBay from various Warsaw pact
countries, where they were obtained from Russia. The price depends more on
the quantity and postage method than anything else.

If you look at the transformer, the simplest method of connecting it is to
connect the antenna to the primary and the recevier to the secondary.

9:1 transformers are usually used for random wires with the other end of the
antenna being a ground rod. This is good for electricaly safety because the
transformer appears as close to zero resistance to static and lightening,
making it a long wire connected to ground.

At RF frequencies the transformer is not a direct short and the signals
go across it to the receiver.

The other end is connected to the receiver and eventually connected to ground.
Many places (e.g. the US) require the coax to be grounded (and that ground
bonded to the electrical system ground) where it enters the house.

Whether or not grounding the antenna end of the receiver coax will improve
things or not is questionable. In some cases it does, in others it does
nothing and in even different cases it makes things worse.

In any case, the best way to mount a transformer in a plastic box is so that
the bottom is empty and a small hole is drilled in it to allow moisture to
exit. Eventually humidity or even water gets in and the drain will help.

Note that there is no recent research on the use of these devices. There is
an article that has been referenced here several times. It was written 14
years ago, and commented that the need for a 9:1 transformer was lessend
(and maybe eliminated) by a modern receiver.

The author did mention that it was needed for a "Sky Buddy", but I'm not
sure there were many of them in use then or now.

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
Those who cannot remember the past are condemned to misquote it.

On 1/17/2011 9:28 AM, John Smith wrote:

...
A properly constructed balun/unun is a TLT (Transmission Line
Transformer.) And, there are in variations in how to wind these ... use
a search engine and research for further info ...

Regards,
JS


This page:
http://www.physics.princeton.edu/~mc..._3_2_48_04.pdf

along with the choice of proper toroid material, wire and size of core,
should allow one to design and construct a proper unun. If you are
using a balanced antenna, a balun ...

Regards,
JS

On 01/17/2011 09:49 AM, Geoffrey S. Mendelson wrote:

Note that there is no recent research on the use of these devices. There is
an article that has been referenced here several times. It was written 14
years ago, and commented that the need for a 9:1 transformer was lessend
(and maybe eliminated) by a modern receiver.

The author did mention that it was needed for a "Sky Buddy", but I'm not
sure there were many of them in use then or now.

Geoff.


If you want to use coaxial cable with a random wire you need a
transformer. The only reason some people notice no difference is because
they are listening to absurdly high power transmitters. Impedance
matching (or at the least proper bridging) makes a big difference when
DXing weak signals like Utes and Tropical Band 50 Watters, Ham Radio, etc.

If all you're trying to hear are =/ 50 thousand Watt stations it's not
as critical. Good operating practice dictates you try to follow the rule
whenever practicable.

On Jan 17, 9:20*am, Charly wrote:
I sent my previous post too quickly...

In fact wiring is totaly different, but the question remains anyway :
what will be the best desing betweenhttp://www.m0ukd.com/Magnetic_Long_Wire_UnUn/index.php
andhttp://www.hard-core-dx.com/nordicdx/antenna/feed/9_1balun.html
??

Thanks

Charly


CHARLY,

Which is ever easier for You to Visualize and Build.

Basically take a Ferrite Toroidal and wrap two Winds
of Wire around and through it.
* Toroidal Ferrite Core {Donut}
http://www.goldmine-elec-products.com/images/G6683B.jpg
* Antenna & Ground Winding : 30 Turns of Wire
http://www.mwcircle.org/images/mw/loop/coil.jpg
* Coax Cable Winding : 10 Turns of Wire
http://www.qrp.pops.net/images/before%202008/UNUN-3.JPG
* * The Wire can be Enameled Solid Magnet Wire
-or- PVC Insulated Stranded Copper Wire
http://www.ure.es/yabbfiles/Attachments/Balun_1a9.gif

On Jan 17, 1:08*pm, John Smith wrote:
On 1/17/2011 9:28 AM, John Smith wrote:

...
A properly constructed balun/unun is a TLT (Transmission Line
Transformer.) And, there are in variations in how to wind these ... use
a search engine and research for further info ...

Regards,
JS

This page:http://www.physics.princeton.edu/~mc...sevick_hfe_3_2...

along with the choice of proper toroid material, wire and size of core,
should allow one to design and construct a proper unun. *If you are
using a balanced antenna, a balun ...

Regards,
JS

Sevick actually wrote a whole book on this subject . Very
interesting,by the way .