tv antenna isolation transformer design help needed

[Andy]

Hello:

I would like to build a simple 1:1 galvanically isolating transformer,
for insertion into the 75 Ohm TV antenna path, for the band between
45MHz and 870 MHz.

There is a design available at

http://www.epanorama.net/documents/groundloop/antenna_isolator_building.html

but it uses a ferrite core. The core materials that I've come across are
not rated for more than 200MHz, so I have some doubts about the design.

Would a coreless winding work? Any help with the choice of the core
material, L, compensation network would be appreciated.

Thank you.

 

[Leon Heller]

http://www.kasamba.com/viewExpert.asp?conMemID=105725&Catid=1111&banID=2100
"Andy" <andy@nodomain.nod> wrote in message
news:41c58470$0$22307$8fcfb975@news.wanadoo.fr...

Hello:

I would like to build a simple 1:1 galvanically isolating transformer, for
insertion into the 75 Ohm TV antenna path, for the band between 45MHz and
870 MHz.

There is a design available at

http://www.epanorama.net/documents/groundloop/antenna_isolator_building.html

but it uses a ferrite core. The core materials that I've come across are
not rated for more than 200MHz, so I have some doubts about the design.

Would a coreless winding work? Any help with the choice of the core
material, L, compensation network would be appreciated.

It's a transmission line transformer, the material need only be suitable for
the lower end of the band.

Leon

 

[Winfield Hill]

Andy wrote...

The device that I am looking for is a real transformer, with
the energy transmission by flux linkage. ...

Why?


--
Thanks,
- Win

 

[Andy]

Winfield Hill wrote:

Andy wrote...

The device that I am looking for is a real transformer, with
the energy transmission by flux linkage. ...


Why?


Well, this is to break the ground loops in the TV antenna feed. I

believe that I need to isolate down to tens of Hertz, and this looks to
me difficult to achieve with a kind of a UHF TLT. Maybe I am wrong. I am
ready to experiment.

 

[Fred Bloggs]

Andy wrote:

Winfield Hill wrote:

Andy wrote...

The device that I am looking for is a real transformer, with
the energy transmission by flux linkage. ...



Why?


Well, this is to break the ground loops in the TV antenna feed. I
believe that I need to isolate down to tens of Hertz, and this looks to
me difficult to achieve with a kind of a UHF TLT. Maybe I am wrong. I am
ready to experiment.

Well- the epanorama page also shows the dual DC-block- you might try
that one. The capacitors are in series with the load so that the low
frequency cutoff becomes F= 1/(2 pi R C/2) and for 45MHz at 75 ohms this
becomes 100pF.