An effective height of 300 ft. is 4 WL on 20M, 6 WL on 15M,
and 8 WL on 10M. W3LPL and others with antennas at 200 ft
indicate that nulls tend to 'wash out' when the lobes are
very narrow, especially over uneven ground.
At 4 WL, the - 3dB points on the lobes are as follows:
2-4 degrees, 8-11 degrees, 15-18 degrees, 21-24 degrees,
29-32 degrees, etc.
Nulls greater than 10 dB are at 6, 13, 20, 27 degrees
and extremely narrow.
At 6 WL, the -3dB points on the lobes are as follows:
1-3 degrees, 6-8 degrees, 11-13 degrees, 17-19 degrees,
21-23 degrees, 26-28 degrees, etc.
Nulls greater than 10 dB are at 5, 9.5, 14.5, 19.5, 25 degrees
and are extremely narrow.
My printout does not include antenna heights of 8 WL.
For antenna heights below 4WL, the lobes (and nulls) are
much wider, requiring high and low antennas to fill in
the respective pattern nulls.
My understanding of the W7RM beech antennas was that
those were used for RECEIVE only, to block out interference
from N.A. For receiving, pattern is more important than absolute
gain so feedline loss was not much of a concern.
Tom N4KG
On Tue, 12 Mar 2002 10:49:09 EST K7LXC@aol.com writes:
> In a message dated 3/12/02 7:36:40 AM Pacific Standard Time,
> n4zr@contesting.com writes:
>
> > It would be interesting to look at the various antennas at that
> QTH in YT or TA -- given the effective height of those antennas,
> I'd expect them to be too high for some paths (like JA).
>
> Too high? Just ask the guys on mountain tops if they're too high.
>
> Actually for JA they had 'beach antennas' mounted at the bottom
> of the bluff aimed up Puget Sound. The 300' bluff behind them added
> LOTS of attentuation to those pesky W6's and W5's trying to work
> the same path.
>
> The first time they sent in a score with a huge number of JA
> contacts, the League said that working that many JA's was
> impossible and deducted lots of Q's and points from their score.
>
> Cheers,
> Steve K7LXC
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