[SOC] G5RV

Thu, 12 Jun 2003 22:40:19 +0100

No it's not, Paul. Mine's the same antenna, and it's just a black plastic
drum with nowt in it. Only consider lashing out for the balun if you have
electrical noise (try switching to AM and having a listen). But if you do
have EMC or timebase noise then the balun I mentioned will kill the problem
stone dead.
I often listen to overseas broadcast stations on AM for a change, and there
is S9+10db switched-mode shite here in the evenings. The balun just loses
the noise completely.
All the best
Chris G4PDJ

----- Original Message -----
From: "Paul Bartlett" <[email protected]>
To: <[email protected]>
Sent: Thursday, June 12, 2003 7:36 PM
Subject: Re: [SOC] G5RV

Hi All,

Thanks for all the helpful comments. I've been dumb.

I just looked a little more closely at the G5RV (purchased from Maplin but
built by Moonraker). It terminates in a PL259 connector and what's just
behind it looks suspiciously like a balun with the 300R ladder feed coming
out of the back. Doh!

Paul :-)

----- Original Message -----
From: "Chris Redding" <[email protected]>
To: <[email protected]>
Sent: Thursday, June 12, 2003 7:18 PM
Subject: Re: [SOC] G5RV

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, �24.95 + �6 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 -----
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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