Topband: base loaded vertical
George (K8GG) & Marijke Guerin
gmguerin at voyager.net
Wed Jun 27 07:33:31 EDT 2007
Roy, K6XK wrote:
----- Original Message -----
From: "Roy" <royanjoy at ncn.net>
To: <topband at contesting.com>
Sent: Tuesday, June 26, 2007 9:30 AM
Subject: Re: Topband: base loaded vertical
> "Which has better bandwidth for matching this antenna, an L-L step-up L
> network with two coils that are *not* coupled to each other, or the
> tapped-coil scheme that I used?"
> In general, the fewer components, and the simpler the circuit, the more
> broad the antenna will be. The old motto applies: 'simplicity is
> 73, Roy K6XK
In this case, I think I have to disagree with Roy.
I was modelling verticals in the 60 - 87 foot height range for a recent
expedition, and some inverted-L antennas for a ham new to 160 and repeatedly
I was led to the solution with two separate coils:
The first in series with the feed point of the antenna to eliminate the
capacitive reactance of the short antenna and
The second across the coaxial cable from center conductor to ground to act
as "half of a hair pin match" to bring the low antenna impedance up to 50
It is much easier to not have interactive taps on a single coil.
Incidentally, on 160 meters, the value of the shunt coil across the coax is
approximately 2 uHy for most antenna impedance values from 10 - 30 ohms.
Also, Array Solutions makes a tuner for a 60 foot vertical, model AS80 that
clearly shows the separate match and loading coils on their website:
I have no reports on how well it works, but I guess Jay has done his
homework and this unit will do its job well.
73 & GL
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