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VK3ABK > TECH 15.09.04 07:33l 40 Lines 1700 Bytes #999 (0) @ WW
BID : 23590_VK3KAY
Read: GUEST OE7FMI
Subj: Re: Pawsey Stub Coax Baluns.
Path: DB0FHN<DB0THA<DB0ERF<DB0SHL<DB0SON<DB0MRW<DB0WUE<DK0WUE<DB0RES<ON0AR<
ZL2BAU<VK3KAY
Sent: 040915/0610Z @:VK3KAY.#WEV.VIC.AUS.OC #:23590 [Wendouree] $:23590_VK3KAY
From: VK3ABK@VK3KAY.#WEV.VIC.AUS.OC
To : TECH@WW
Hello all VHFers
Just a variation on a previous bulletin 'to HFers'!
John, G8MNY, (again!) has sent an interesting bulletin about a 'Pawsey Stub'.
This pleases me, as I have some reservations about the increasingly common
(split infinitives aside) use of 'choke baluns'. A 'balun' is supposed to
convert a 'BALanced' connection to an 'UNbalanced' one, and at the same time
to limit the radiation from the feedline. It makes a compatible connection
between two incompatible RF circuits, one an antenna, and the other a
transmission line. (There are other uses for a balun in RF transmission, but
we usually talk about antennas (insects have antennae) and transmission lines.
The 'Pawsey Stub' is a 'text book antenna, as John reports, and has been a
favourite in VHF and UHF for many years. Any good antenna book will give
examples of its use and construction details. I have the impression that a
'choke' balun is more concerned with choking back any RF that dares leak
out of the antenna and runs down the coax! Whether it does the job of the
eponymous 'BAL-UN' is another matter.
It may be of interest to say that Joseph Pawsey was an Australian Physisist
who worked in Australia for the CSIRO (Commonwealth Scientific and Industrial
Research Organization, pronounced locally as 'siro') after working in England
on "...transmission lines and aerials for EMI"... television. At CSIRO, he
was a group leader working in radar and radiophysics, with an interest in the
work of Karl Jansky and Grote Reber, both pioneers in detecting radiation
from the 'Milky Way' galaxy.
Something old that keeps coming back to help us!
73. Dick. VK3ABK.
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