[SOC] G5RV

Thu, 12 Jun 2003 19:18:42 +0100

Paul,
Things seem to be running away a bit here. What you need is not a =
'choke' (which is a device for 'choking-off') unwanted currents, but a =
1:1 balun transformer. This takes its drive from the inner core of your =
co-ax and creates from it a second mirror image 'channel' of opposite =
voltage and current. The original signal from the co-ax core goes up one =
leg of the twin line, and the 'equal-and-opposite' signal goes up the =
other. In this way the twin feeder carries two 'equal and opposite' =
signals which cannot radiate until the feeders diverge into a dipole at =
the top.
What cannot radiate cannot receive either, and this will help with =
electrical 'spike' noise, which will be 'turned against itself' inside =
the balun and largely cancelled out.

The item you need is an MB-1 balun, =A324.95 + =A36 p+p from Moonraker =
(01908) 281705 ( or www.amateurantennas.com )

This is a little black box with a PL259 connector on one end and two =
terminals for the twin feeder at the other.
I have had one in my G5RV for four years now, and wouldn't be without it =
in my noisy location.

Every home should have one:-)

Regards, Chris G4PDJ

----- Original Message -----=20
From: "Paul Bartlett" <[email protected]>
To: <[email protected]>
Sent: Wednesday, June 11, 2003 8:15 PM
Subject: Re: [SOC] G5RV

Hi John,

Thanks for that. It all seems to make sense.

Would it be correct to say that they're not really baluns at all but =
rather
simply common-mode chokes reducing RF currents in the feeder braid? I =
think
you said as much in your last post; just trying to get a handle on it...

Would it make sense to attach the feeder braid to a 'good' RF ground
immediately prior to the choke? I.e at the far end of the feed from the =
TX
point of view but before the choke.

Best,

Paul M3CRQ :-)

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