Topband: FW: Hi-Z Around Trees

Mon Nov 14 09:25:43 EST 2016

I have a Hi-Z 4 element array that is wedged into the only available space
I could figure out.  It breaks lots of rules:

1. Two of the elements are less than 60 feet away from the transmitting
vertical (a loaded tower).  One of them is about 40 feet away.
2. One of the elements is essentially in a tree and I noticed that some of
the small branches were actually touching the top of the element (was going
to trim them but haven't gotten to it yet).
3. Two of the elements are about 8 feet from an metal barb wire fence +
electric fence .

However, the array works just as I would expect it to.  Last Winter - I had
a 1200 foot Beverage going to the East and while I would say the Beverage
out performed the Hi-Z array - I would say it wasn't more than a db or two.

Certainly one should always do the best they can to isolate it as much as
possible - but don't let a less than optimal situation stop you from trying.

73 Tree N6TR

On Mon, Nov 14, 2016 at 5:07 AM, Michael Walker <va3mw at portcredit.net>
wrote:

> Same reply.  At our contest station, we have a 300M beverage just running
> through the woods and tree branches in Northern Ontario
>
> No scientific testing, but it just worked.
>
> Mike va3mw
>
>
> On Mon, Nov 14, 2016 at 7:49 AM, Paul Mclaren <paul.mcl at gmail.com> wrote:
>
> > On a similar note can I ask about beverages touching leaves and other
> > vegetagian.   Will this result in poor performance and if so is it
> > significant?
> >
> > Regards
> >
> > Paul MM0ZBH
> >
> > On 14 November 2016 at 12:41, Michael Walker <va3mw at portcredit.net>
> wrote:
> >
> >> For my 80CW and 160 verticals, I have wires suspended through 90 ft tall
> >> evergreens.  I have been doing that for years and I put them in place
> >> using
> >> a drone (long before everyone was doing it).
> >>
> >> I have radials underneath.  In fact, they are on a common feedpoint.
> >>
> >> Based on my 160M or 80M WSPR / JT65 testing, I would be hard pressed to
> >> say
> >> that much if any RF is being absorbed by the trees.
> >>
> >> In my case, I work with what I have available.  For me, they just work.
> >>
> >> Mike va3mw
> >>
> >>
> >> On Mon, Nov 14, 2016 at 12:54 AM, Lee STRAHAN <k7tjr at msn.com> wrote:
> >>
> >> >
> >> >
> >> >   Greetings Top-Banders, I have been away for a couple days, sorry for
> >> the
> >> > late comments.
> >> >     The fact is, for me there is no definitive answer to the effect of
> >> > trees on the Hi-Z arrays. I have made tests measuring phase shifts and
> >> > amplitude changes with a variety of objects around these elements. My
> >> > original thoughts after the tests were that any tree or large foliage
> >> would
> >> > have to a minimum of 5 feet distance from the elements. There are not
> >> many
> >> > trees where I live so this sort of test is very difficult. One of the
> >> > things I did was to measure the capacitance of the elements as a
> source
> >> > impedance to the amps. Changes in this capacitance would make
> amplitude
> >> > changes at the amplifiers. The only real changes I measured after
> >> numerous
> >> > tests were when I would approach the element with the capacitance
> meter
> >> in
> >> > operation. When a 6 foot person approached the elements I could see
> >> changes
> >> > in the element at about 3 feet separation. Nothing at 5 feet. This was
> >> with
> >> > a 24 foot aluminum element and a low capacity mounting insulator. This
> >> > capacitance test was more sensitive than my voltage and phase
> >> measurements.
> >> >    Mike NI7T installed a 4 square system in the forest behind his
> cabin.
> >> > Many pine and redwood trees were within 5 feet of the elements. We
> were
> >> > never able to discern any negative affects to his array. Front to back
> >> > rejection was well within nominal and front patterns seemed proper.
> The
> >> > array remained sensitive to weak signals. Larry K1UO had his array in
> a
> >> > brush patch. As I recall I suggested a 5 foot spacing which he did. If
> >> you
> >> > have not seen the DX Larry posts from Maine you are missing something.
> >> In
> >> > other words it was apparently adequate spacing.
> >> >    So with the 24 foot elements ¾ inch diameter that have around a
> 75pf
> >> > source capacitance I would say you are pretty safe at 5 feet. Shorter
> >> > elements with significantly less source capacitance would surely need
> >> more
> >> > spacing. A 12 foot similar element drops clear down to 42pf source
> >> > capacitance. I would hazard a guess that arrays using short whip
> >> elements
> >> > at around 25pf would be quite sensitive to close trees or foliage.
> >> >     Barring all this I am confident you would be absolutely safe in my
> >> > estimation at 10 feet distance of brush, tall foliage, and trees from
> >> the
> >> > elements.
> >> >
> >> > Lee  K7TJR
> >> >
> >> > >>Hello Jim
> >> >
> >> > My HI-Z 4 square has trees about 15 feet away from two of the elements
> >> (I
> >> > can make exact distance measurements if that would help you).
> >> >
> >> > I do not "think" the trees interact in my setup - but I am not 100%
> >> sure.
> >> > Even my HI-Z 8 circle has trees pretty close to 3 elements (10 feet).
> >> > Without measuring changes (impedance) to these elements due to
> >> location, I
> >> > am not sure how else to know. However, given Frank's comments - I will
> >> be
> >> > trimming some trees today!
> >> >
> >> > I am certain K7TJR is the expert on this has he has heard from users
> >> about
> >> > element location and performance for years.
> >> >
> >> > I wish you the best.
> >> >
> >> > 73
> >> > Tim K3LR
> >> >
> >> > ________________________________
> >> > From: donovanf at starpower.net<mailto:donovanf at starpower.net> [mailto:
> >> > donovanf at starpower.net]
> >> > Sent: Saturday, November 12, 2016 6:57 PM
> >> > To: jim at audiosystemsgroup.com<mailto:jim at audiosystemsgroup.com>
> >> > Cc: Lee K7TJR; k3lr at k3lr.com<mailto:k3lr at k3lr.com>; Joel Harrison
> >> > Subject: Re: Hi-Z Around Trees
> >> >
> >> > Hi Jim,
> >> >
> >> > My comments about short verticals not performing well near trees
> >> > applies only to high impedance verticals.   Low impedance are
> >> > little affected.
> >> >
> >> > 73
> >> > Frank
> >> > W3LPL
> >> > ________________________________
> >> >
> >> > _________________
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> >> >
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> >>
> >
> >
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