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VK3ABK > TECH 14.09.04 15:32l 48 Lines 1997 Bytes #999 (0) @ WW
BID : 23546_VK3KAY
Read: GUEST OE7FMI
Subj: Re: A Nest of Dipoles for HF.
Path: DB0FHN<DB0MRW<DB0HOT<DB0ERF<DB0FBB<DB0BI<DB0NOS<DB0EA<DB0RES<ON0AR<
7M3TJZ<SP7MGD<VK3KAY
Sent: 040914/1320Z @:VK3KAY.#WEV.VIC.AUS.OC #:23546 [Wendouree] $:23546_VK3KAY
From: VK3ABK@VK3KAY.#WEV.VIC.AUS.OC
To : TECH@WW
Hello all Hfers.
The recent bulletin from John, G8MNY, 'A Nest of Dipoles for HF' gives an
excellent multiband antenna design for HF. This 'antenna' has the advantage
of being resonant on each band of operation, and does not require matching
to a tranceiver as other multiband antennas do.
Like John, many of the 'new' HFers of 50 years ago used this design as it
could be made with available components, long before beams became easier to
build. Beam type aluminium, and rotators were not as readily available as
they are today. When I first used these "nest(s) of Dipoles" they were called
'multi doublets', a fashionable name for a dipole!
The antenna (antennas?) worked well on all bands and were usually fed with
clear plastic (figure 8) lighting flex which was cheap and available. This
feeder was later replaced with 75 ohm two wire RF feeder sold under the
trade name 'Telcon' which may be the same as John has used. I still have a
length of this black plastic covered, twin 0.88 mm solid copper conductor
feeder, apparently as good as new, after about 40 years in all weathers.
The individual antennas are not affected greatly by a common connection at
the feed point, or proximity as long as they are kept separate by nylon
fishing line, and small weights that usually stop the antennas twisting in
a strong breeze. At each resonant frequency, the respective antenna will be
shunted by a much higher, and reactive, impedance of the other antennas.
I still have the arrangement described by John; a 75 ohm (Telcon) balanced
feeder (also fixed to a fence!) leading to a balun and coaxial cable which
gives a low radiation connection to the tranceiver. (Important today with
our problems of RFI in a computer based environment). The advantage of having
a matched feed point, and so, dispensing with an ATU, should be considered.
Thanks John, for the reminiscent bulletin of a very useful antenna system.
73. Dick. VK3ABK.
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