Topband: Steeply Sloping Ground

[Guy Olinger K2AV]

If you are in a quiet location, you may find it difficult to hear
better than your TX antennas, simply because they are not
disadvantaged by the normal issues over flat ground.  Vertically
polarized signals do not bounce well off dirt.  Essentially not at
all, even with the best dirt found around.  For most people dirt and
clutter obscure the lowest angles, for ANY antenna.

Your hearing well in a particular direction will have a lot to do with
NO CLUTTER or obstruction in your way at the lowest usable angle.
That is why aiming a direction sideways across the hill to have level
ground in front of it is not a good idea.  If I understood your
terminology correctly, beverages aimed downhill did best.  You will
find that to be true with ANY RX antenna, as the no obstruction
quality of looking  in the clear at a very distant horizon will trump
any other consideration.

Modeling beverages, flags, pennants, yada, yada, all of them
significantly improve pattern up 10 or 15 degrees vertical.  This
angle is formed above the immediate ground slope.

At your QTH, it may not be possible to improve over 280' downhill
beverages.  Placing two of those (or two of anything)  aimed downhill,
equal phased side by side for best horizontal pattern may be the best
possible.

73, Guy.

On Thu, Jul 28, 2011 at 10:58 AM, Charlie Young <weeksmgr at hotmail.com> wrote:
>
> I am about to configure antennas for my 3rd Topband season here in WV.   The terrain is very irregular.  My house sits atop a conical shaped hill, with sides which slope off steeply in all directions.  All of my transmit antennas are on top of the hill, overlooking the steep slopes including the 160 inverted L's, which are configured with the vertical portion of the radiator right at or just over the cusp of the hill, with the ground falling away steeply in the desired direction.  Last year, I used four of these L's, each positioned to cover a direction favored by sloping ground.  Switching between them exhibited noticable directivity on rx and tx, so I am convinced we are on the right track with the tx antennas.
>
> I am not sure what to do about the rx antennas.  They can't be placed on the high ground, due to space and driveway constraints.  The first season, we tried several short beverages and last year we added four  dual flag antennas.  There are not many options for the beverages.  To cover desired directions with my property layout and the terrain, these must be placed on the sides of the hill, some running upslope, some downslope and some sideslope.  They seem to work OK, some directions better than others.  Generally, I found that an upslope beverage is the poorest performer.
>
> My real question regards the best way to orient the flags in relation to the sloping ground.  I have some choices.  In some cases, we can go sideslope, so the antenna is both level and parallel to the ground surface in the primary target direction.  In other cases, I am faced with the choice of either making the antenna array  level, which puts one end significantly higher above ground surface than the other or placing the antenna array parallel with the earth surface, which makes  the whole array tilt downhill in relation to the horizon.
>
> The  flags I am using are 21' high by 30' long, thus making the double flag array about 63' long.
>
> My intuition with these antennas says to avoid putting one upslope entirely, and when possible to make it sideslope.  However there are some directions where we must go downslope, and my instinct is to follow the earth surface and have the array tilt down in relation to the horizon.  Anyone got any experience with this, or any thoughts about it making any difference in the real world?
>
> 73 Chas N8RR
>
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