Connecting up FM aerial

[patrick j]

Hello

With a certain degree of predictability now that I have my FM (or VHF or Band II) aerial erected I wish to enquire about connecting it up.

Before you get to those questions you can if you wish admire the aerial in this 34kb jpeg:

It will be connected to two tuners, an Arcam one in my living room and a Tivoli clock radio in my bedroom. The signal strength is high so I don't think I'll be needing an amplifier, instead I'll just use a splitter.

The Tivoli clock radio has an F type socket and the Arcam tuner has a standard sort of a socket which has been used for TV aerials and radio aerials here in the UK for years.

I believe the F type socket is a 300 ohm connector whereas the standard type of aerial connector is 75 ohms.

I've read somewhere that for the Tivoli clock radio I'll need a 300 ohm to 75 ohm Balun transformer. Is this true and how should this be configured?

An additional question is that the splitter I've got is an F type one, which presumably won't make any different to either tuner?

TIA

[mike ring]

patrick j wrote in news: [e-mail]:

I can't see a flashing red light on top, this could be a danger to passing astronauts.

mike r

[John Rumm]

Very pretty ;-)

That would be unusual since most F-Types I have seen are designed to attach directly to 75 ohm co-ax (in fact the centre conductor of the co-ax usually forms the "pin" of the plug. 300 ohm feeders are usually of the "balanced pair" type rather than co-ax.

If it does have a 300 ohm input then you could use a balun. Configuration is just a case of unbalanced co-ax connects to one side and the balanced feeder to the other.

Having F-Type connectors is a "good thing" in most cases since it preserves the screen integrity. The actual quality of the splitter itself will have more effect than anything else. (something like the fully screened inductive splitters by Labgear (available from CPC) will do the job nicely for anything in the 5 MHz to 5 GHz range!)

[patrick j]

On Fri, 16 Apr 2004 4:08:58 +0100, John Rumm wrote (in message ):

Thank you. In fact I've looked at the socket on my Tivoli clock radio and it clearly states 75 ohm :)

I don't know where I got the notion that F-type sockets are usually 300 ohm.

[Dave Plowman]

300 ohm suggests a balanced input - so the connector is usually symmetrical, even just a pair of screws - rather than a co-ax type.

[The Natural Philosopher]

Yes. The flatt ribbon feeder with two condicutors is charcteristic at

300 ohm, but coax tends to be in the 50-75 ohm range.

ISTR that qarter wave antennae match 75hohm, and half wave are better suited to 300, but my theory is very rusty..

[Andy Wade]

And is pretty-well obsolete now in the UK (& probably the rest of Europe).

OOI, does anyone know whether 300 ohm balanced inputs are still being used on TVs in the USA (for VHF) - or have they gone over to coax at last?