Topband: FW: Hi-Z Around Trees

[Michael Walker]

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
>> > ________________________________
>> >
>> > _________________
>> > Topband Reflector Archives - http://www.contesting.com/_topband
>> >
>> _________________
>> Topband Reflector Archives - http://www.contesting.com/_topband
>>
>
>