[SOC] G5RV

[JMcAulay]

At 12:58 PM 06/14/2003 +0100, Chris G4PDJ wrote:
>Agreed Jim, and nice to hear from u.
>
>1. Yes Jim, spot on, you need a 1:1 balun (50 Ohms unbalanced co-ax in - 50
>Ohms balanced twin out), not a 4:1 (which I think is for feeding folded
>dipoles, but correct me if I'm wrong).

You are right on.  Other than feeding folded dipoles, 300R polyethylene
(polythene) jacketed parallel line (called "Twin-Lead") is popular here for
connecting television antennas.  It's *much* less expensive -- and offers
lower loss -- than coaxial line.  Some hams have used it for long feeder
runs, especially at higher frequencies.  A 4:1 balun gives a nice
transformation between 70-75 ohm coax and 300 ohm line.

Some seem to have the idea that a 4:1 balun is more appropriate for a G5RV,
because of the characteristic line impedances -- but it is NOT.  If one
studies the theory of operation of the G5RV, this may become clear.  The
1:1 should be used.

>2. A 1kW Balun for 20 bux. I believe you...we often refer to our country as
>"rip-off Britain". Tourists notice that prices for the same item are about
>the same number of dollars as pounds. USA tourists to the UK don't
>understand why we put up with it.
>I'll post-up some UK rig prices from Radcom and you can compare them with
>the prices in QST.

It's been too many years since I was in Britain, but I've been told
recently that what you mention seems true:  that for most purchases, the
prices in =A3 are pretty close to those expected in the US in $.  It's also
been a very long time since I priced a 1 kW balun, so $20 may be 'way out
of date there.

Most commercially available baluns are designed for QRO, which is one
reason the prices are as they are.  For QRP, winding your own balun
transformer on a small toroid core will cost little and require just an
hour or so, even for the dexterously challenged. =20

73
John WA6QPL  SOC 263