> Regardless of L or T format it is important to keep the vertical portion
> as
> far away from any metal or conducting objects. This would include trees.
The effect of trees is very murky and poorly researched (for cause). They
certainly do not respond in the same manner as metal conductors. Some where
in the archives of this or the TowerTalk reflector is a long post by W8JI
where he took a section (8' by 1'?) live green sappy tree trunk and tried to
measure it's conductivity, etc. The fuzzy answer was that it really wasn't
a conductor in the ordinary sense, and behaved differently at RF than at DC,
exhibiting a resistance in thousands of ohms per foot. I went out and drove
two nails at spaced points on a live tree trunk during "sap season" and saw
similar readings on my ohmmeter.
There are reports of seasonal variation in performance of antennas out in
the "woods", but the most likely villian for that is variation in ground
moisture. For flat surfaces vertical performance varies enormously with
changes in the ground in the near quarter mile, particularly at the lower
angles.
> In the L antenna the inverted horizontal portion radiates some in the
> horizontal plane. When that element slopes towards earth there is some
> small
> net gain in that direction.
Might be read two ways. If the top is east and the bottom is west, the
favored direction is west.
> Further with the T portion as top loading
> the feed point radiation resistance will be greater for a given vertical
> height. This when coupled with an excellent ground system of 1/4 wave
> radials
> will make the antenna substantially more efficient than other types of
> loading.
Amen. Really the main issue for a vertical antenna of any sort on 160.
Teddy's Top Ten Tips for understanding a top ten signal from a vertical on
160.
0) Over salt water (Yeah, I know, I can't live there either...)
1) Radials at all
2) Two Radials instead of One
3) Four Radials instead of Two
4) Eight Radials instead of Four
5) Sixteen Radials instead of Eight
6) Thirty Two Radials instead of Sixteen
7) Condition of ground beyond radials
8) Other conductors in area.
9) Sixty Four Radials instead of Thirty Two
11) Amount of Horizontally polarized radiation.
17) Ease of matching to 50 ohm coax.
Riley's Rule for understanding contest scores on 160 meters: 95% of 160m
antennas in a contest stink.
Charlie's corollary to Riley's Rule: 50% of 160m antennas in a contest
REALLY stink.
(I want to see W8JI run QRP one year, not tell anyone, and see how many get
their b*tts whipped by a 5 watt signal. on a professional grade antenna)
73, Guy
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