Topband: Trees (not the N6TR kind)

[Lew Sayre]

On Tue, Jan 1, 2013 at 4:13 AM, Richard Fry <rfry at adams.net> wrote:

> As for the affect of trees on EM waves, below are the results of some
> simple measurements I posted earlier on another board.
> ___________________
>
> Recording the relative readings on the dBµ and S/N displays of a Tecsun
> PL-310 tuned to a directional station about 52 miles east of me on 790 kHz,
> radiating about 1 kW in my direction:
>
>        Location                                     dBµ                S/N
> (dB)
>   (Tecsun 4-1/2 ft AGL)
> Area clear for 50 ft around                    32                       15
> Pin oak tree, 3' diameter trunk,             42                       24
>  east side against trunk
> Ditto, but west side of trunk                  34                      14
> Gnd Wire of 50' utility pole                    48                      24
>   (Tecsun 9 ft AGL)
> Gnd Wire of 50' utility pole                    50                      24
>
> These locations were all within 100' of each other, in my back yard.
>
> (later)
>
> I just went back out to my pin oak tree, tuned in the 790 kHz station east
> of me, and found that the field improvement when the rx is held against the
> east side of the trunk is completely gone when the receiver is moved to the
> east about 15 feet.  So this is quite localized, and probably wouldn't have
> much of an affect on a DA unless an MP was poorly located.
>
>
>
    Yo 160M People,
      This discussion about trees is important. Primarily because I live on
the top of a somewhat narrow ridge where I've already planted several
towers. (50'-180' tall)  I have several fir trees that range up to 130'
tall,  Several years ago I attempted to feed a 120' tower on 160M with
various schemes but was not not successful for a variety of reasons. I then
decided to use a pneumatic air gun to launch some wires over 2 tall firs
that were angled at 20 deg/ 200 deg keeping in mind to keep them as far
away from the closest tower possible. (About 120' from the most northern
tree).
     I placed 60 non-measured but roughly 130' long radials around each
base and fed this "array" via a 2 port Comtek box.  Seemed to work as only
was getting 0.5 watt into the dummy load with 100 watts from the radio.
These 2 trees are spaced about 186' apart so theoretically am not sure what
kind of pattern I'm supposed to have when changing the phasing through the
box. That is about a 3/8 wave separation.  In practice it doesn't seem to
matter which phasing through the box I use as I can't tell any difference
on Rx. I purposefully let the 12GA stranded wire sweep out over the
branches rather than try to pull it taut as that allowed more wire to be
nearly vertical and makes wire survival better in the winds up here on the
ridge. The very tops of the wire may actually have a short "L"
configuration to them as I can't see those ends.
     Anyway I was trying to come up with some non-anecdotal way to assess
whether these trees hurt my signal.
What I came up with is not very accurate or elegant method but maybe a step
in the right direction.
    During the recent Stew Perry contest N9RV in Montana, N6TR in Boring,
Oregon and W7EW, me in Salem, Oregon were all calling CQ. What I did was to
go to  www.reversebeacon.net  look under DX tools, put in those 3 calls,
add the date of Dec. 30 and then looked at the different skimmer reports
around the country and KH7LC.
I think we were all running 1.5 KW and verticals.
    There is wide variability in reporting from minute to minute from some
nodes but overall I don't think the use of  trees as antenna supports has
hurt my signal out there in DX-land as compared to a somewhat peer group
out west with similar working conditions.
   Sure there are a huge bunch of uncontrolled variables but this may be as
good as it gets for a comparative experiment where 2 controls ( no trees
used as wire supports but tall trees are around) are compared to the index
case (trees are used to support the wires with other tall trees around.
     I invite comments, suggestions and interpretations regarding this
feeble attempt to see if trees are a detriment to the 160M situation.
  HNY!!
    73 and I remain,
   Lew    W7EW