Are those small 300/75 ohm tv baluns. voltage or current type?

I've taken a couple of those apart -
those were voltage baluns - transformers
I've used them for transmitting low power on 10 meters
(so I could use 300 ohm cable for the antenna run)


"puns" wrote in message
news:jzuoe.940$KQ2.679@trnddc08...
Are those small 300/75 ohm tv baluns. voltage or current type?

I never paid much attention, now that you mention it though, I seen one
busted open once... this particular one had a binocular core...

Warmest regards,
John
"Hal Rosser" wrote in message
. ..
I've taken a couple of those apart -
those were voltage baluns - transformers
I've used them for transmitting low power on 10 meters
(so I could use 300 ohm cable for the antenna run)


"puns" wrote in message
news:jzuoe.940$KQ2.679@trnddc08...
Are those small 300/75 ohm tv baluns. voltage or current type?

excuse my inexperience - what do you mean by "binocular core" ?
is that like a figure-8 ferite core ?
One that I opened up used a ferrite bar about twice the thickness of a
toothpick.



"John Smith" wrote in message
...
I never paid much attention, now that you mention it though, I seen one
busted open once... this particular one had a binocular core...

Hal:

I have heard others describe them (tv 75/300 baluns) as a normal, albeit
small, toroid--I don't know, would have to get some and open 'em
up--sounds to me like all sorts of designs could be being used....

But, if you look at the end of a binocular core, it does indeed have a
outline much line a figure 8... however, all I have ever heard 'em
called is binocular cores.... I have "duplicated" this design with two
toroids, side by side before (and winding through "one side" of each
independent core, touching at a "side" on each toroid--kinda hard to
describe), and seemed to work for my purposes--but since I haven't seen
anyone else doing it--so wouldn't recommend it at this point unless you
like to experiment... have purchased binocular cores for use in mosfet
linears before, they are out there...

Warmest regards,
John
"Hal Rosser" wrote in message
. ..
excuse my inexperience - what do you mean by "binocular core" ?
is that like a figure-8 ferite core ?
One that I opened up used a ferrite bar about twice the thickness of a
toothpick.



"John Smith" wrote in message
...
I never paid much attention, now that you mention it though, I seen
one
busted open once... this particular one had a binocular core...

In article jzuoe.940$KQ2.679@trnddc08, "puns" wrote:

Are those small 300/75 ohm tv baluns. voltage or current type?

Hello, and these broadband 4:1 (impedance ratio) baluns most often are
voltage type using two transformers. At the lower end of the operating
frequency band the balun appears as a 4:1 autotransformer while at higher
frequencies the transformer windings appear as transmission lines (ideally
each line would have a Zo of 150 ohms). FWIW, the broadband operation of
these types of devices were initially described in detail in C.L
Ruthroff's 1959 IRE paper, "Some Broadband RF Transformers." Sincerely,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

On Mon, 06 Jun 2005 07:31:32 -0400, J. B. Wood wrote:
In article jzuoe.940$KQ2.679@trnddc08, "puns" wrote:

Are those small 300/75 ohm tv baluns. voltage or current type?

Hello, and these broadband 4:1 (impedance ratio) baluns most often are
voltage type using two transformers. ... ... ...

Only the 'quality' ones. I've seen too many that were simply
resistor bridges. More like a 6dB insertion loss per leg than
the 'ideal' 3dB loss in a quality transformer-built version.

Jonesy
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK

Allodoxaphobia,
you must be talking about a tv 'splitter', rather than the balun
(remember, the balun has a 300-ohm cable on one end and a place to screw
coax on the other side.)
it wouldn't (normally) have 3db loss like a splitter would.


"Allodoxaphobia" wrote in message
...
On Mon, 06 Jun 2005 07:31:32 -0400, J. B. Wood wrote:
In article jzuoe.940$KQ2.679@trnddc08, "puns"
wrote:

Are those small 300/75 ohm tv baluns. voltage or current type?

Hello, and these broadband 4:1 (impedance ratio) baluns most often are
voltage type using two transformers. ... ... ...

Only the 'quality' ones. I've seen too many that were simply
resistor bridges. More like a 6dB insertion loss per leg than
the 'ideal' 3dB loss in a quality transformer-built version.

Jonesy
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK

On Mon, 6 Jun 2005 17:29:06 -0400, Hal Rosser wrote:

"Allodoxaphobia" wrote in message
...
On Mon, 06 Jun 2005 07:31:32 -0400, J. B. Wood wrote:
In article jzuoe.940$KQ2.679@trnddc08, "puns"
wrote:

Are those small 300/75 ohm tv baluns. voltage or current type?

Hello, and these broadband 4:1 (impedance ratio) baluns most often are
voltage type using two transformers. ... ... ...

Only the 'quality' ones. I've seen too many that were simply
resistor bridges. More like a 6dB insertion loss per leg than
the 'ideal' 3dB loss in a quality transformer-built version.

Allodoxaphobia,
you must be talking about a tv 'splitter', rather than the balun
(remember, the balun has a 300-ohm cable on one end and a place to screw
coax on the other side.)
it wouldn't (normally) have 3db loss like a splitter would.

Yep. You are correct -- I was misreading what my eyes were taking in.
Tho' it would not surprise me to see some cheap 'balun' consisting
of 100ohm-75ohm-100ohm in series with the coax tacked across the
75ohm resistor....

Jonesy -- who needs more skills in Reading-For-Comprehension...
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK

ok - cool.
I never saw one - I guess I just lead a sheltered life.

"John Smith" wrote in message
...
Hal:

I have heard others describe them (tv 75/300 baluns) as a normal, albeit
small, toroid--I don't know, would have to get some and open 'em
up--sounds to me like all sorts of designs could be being used....

But, if you look at the end of a binocular core, it does indeed have a
outline much line a figure 8... however, all I have ever heard 'em
called is binocular cores.... I have "duplicated" this design with two
toroids, side by side before (and winding through "one side" of each
independent core, touching at a "side" on each toroid--kinda hard to
describe), and seemed to work for my purposes--but since I haven't seen
anyone else doing it--so wouldn't recommend it at this point unless you
like to experiment... have purchased binocular cores for use in mosfet
linears before, they are out there...

Warmest regards,
John
"Hal Rosser" wrote in message
. ..
excuse my inexperience - what do you mean by "binocular core" ?
is that like a figure-8 ferite core ?
One that I opened up used a ferrite bar about twice the thickness of a
toothpick.



"John Smith" wrote in message
...
I never paid much attention, now that you mention it though, I seen
one
busted open once... this particular one had a binocular core...