wow - 75 down to 32?! Was that with no radials (the 75 ohm)? I hope that
wasn't after you had the 32 down - I'd think 32 would bring it down to being
asymptotic. With poor soil I believe the literature would say there's no
need to go out to 1/4 ... 1/5th would be fine (and this isn't taken in to
account the VF question).
g.
-----Original Message-----
From: John Santillo N2HMM
Sent: Wednesday, November 30, 2016 1:41 PM
To: StellarCAT
Cc: tower
Subject: Re: [TowerTalk] radial lengths ...
Depending on the conductivity of the earth the VF will change the length
of the radials. Poor soil has a VF of ~72%. My soil is very poor!
What I did with my Inverted-L is I put down 32 x 1/4 wavelength (~130
feet) long radials in close to circular pattern around the feed point.
Then I put down an additional 8 radials ~40 feet long to help with the
near-field currents in an attempt to increase the radiated energy. As I
was putting down the radials i could see the impedance of the antenna go
from ~75 ohms to ~32 ohms which is what I was hoping for.
I'm pleased with the performance and it's the best I can do with the
topography of the yard and the height of the trees.
73,
John
N2HMM
For the ‘experts’ out there ...
So question.... in ON4UN’s book it is stated in abundance that one
should use typically 0.25 wl radials... the length of course varies with
the properties of the earth and the desired end results but somewhere
around 32 1/4 wave radials seems to be within about 1 db of 100+ of the
same length ...
but he also states, kind of “on the side†in one sections only (it
seems) due to the velocity factor attributed to the earth that 1/4 wave is
actually physically only 0.14 waves in length!
So which is it – when it is stated 32 1/4 wave is that physically 1/4
wave or is it physically say 1/7th wave (and still electrically 1/4
wave)?!
so for example on a 160 meter vertical are we looking at 32 ~130’
radials or more like 75’ radials (with the end of each of those not
having enough current in them to contribute appreciatively to the current
distribution)... ?
I know most will respond with 1/4 wave.... but I’d bet most would be
going by the generic statements of “1/4 wave radials for verticalsâ€...
if indeed the VF makes going beyond about 1/6th wave of very little value
(again talking about 32 radials here – not 120) ... then why go through
the effort?
if this is (more) clearly stated in John’s book please let me know
where.
Gary
K9RX
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