Dear OMs,
I am pleased to see this question raised for all the praise of ON4UN's book
this coverage of radials and their length leave a great deal to be desired.
The treatment is to say the least confusing and not very explicit.
73 Doug EI2CN
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
StellarCAT
Sent: 30 November 2016 18:47
To: John Santillo N2HMM
Cc: tower
Subject: Re: [TowerTalk] radial lengths ...
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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