Topband: FW: Hi-Z Around Trees

[Paul Mclaren]

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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