[Elecraft] Balun

[Geoffrey Mackenzie-Kennedy]

Rich,

I would like to second Ron's (AC7AC) comments about tuners. Personally I
would stay away from 'T networks' for use in antenna tuners, and use the old
fashioned link coupled form of balanced tuner. T networks can be mistuned to
provide a 50 ohm load for the transmitter, but not deliver much power to the
antenna, in other words become a fairly good dummy load. Quite a lot has
been written about this.

Although some commercial 'old fashioned' balanced tuners might run out of
steam, there are ways to cure this problem - without modifying the tuner. If
of interest to you, we could discuss this off list at a later date. The
other option is to build one!!

About the antenna, and assuming centre feed. As Ron has said, reducing the
length of the wire even down to a quarter wave has little effect on the
radiated signal at the frequency where the length is a quarter wave, less
than 0.75db down from a full size halfwave dipole at the same frequency. The
radiation resistance does decrease quite a lot, but is still manageable. The
important thing is to keep the antenna wire away from tree branches, roof
and other objects. The same applies to the feeder. If you feel happier with
the longer wire and bend the ends downwards, the radiation pattern on the
higher bands could be quite different from that of a straightforward flat
top depending on how much wire droops. This comes about because the drooping
ends at some frequencies become 'elements' of a broadside (or end fire)
beam, whose radiation adds to (or subtracts from) the radiation from the
horizontal wire. Murphy's law states that the high gain lobes will always
point in the wrong directions! Dog legging the wire will have some effect,
although not as much perhaps if gentle. Personally I would stick with a
straight doublet, hung clear of other objects.

Good luck,

73
Geoff
GM4ESD


----- Original Message -----
From: "Richard Soennichsen" <richard at fdatasystems.com>
To: <elecraft at mailman.qth.net>
Sent: Thursday, June 09, 2005 9:30 PM
Subject: [Elecraft] Balun


> Hi All,
>
>             I (a Ham to be) am planning to buy a K2 in the future.  I am
> planning my antenna now and am going to borrow a radio in the mean time.