[Elecraft] QRP Antenna

[Ron D'Eau Claire]

Clark, KE4RQ, asked:

I installed a commercial multiband inverted V at my QTH and have had poor
results for DX. It looks like a Windom design with the feedpoint off-center
and comes with a balun to allow for coax feed.  According to the specs, it
should provide a match at 80, 40, 20, 17, 12, and 10, and the ATU within my
K1 matches fine on 40, 20, and 17.  (I've also had no problems matching
other rigs using their ATU to the other frequencies).  I am using a low loss
coax from Davis RF and the rig(s) are grounded to a ground rod just outside
the shack.
   
  The apex of the antenna is about 40 ft with each leg at the approximate
height about ground that the manufacturer's specs require.  It is strung in
a NE/SW direction -- broadside to southern Africa.  The antenna seems to
'hear' fine; it's in the transmitting that it appears to be deficient. I've
tried to check into the Elecraft net with no luck.  I tried to contact Peter
One  (using 100W I must admit) with no luck at all times of the day and
night.  
   
  Standing on my deck looking at the antenna and wondering what, if anything
could I change, it occurred to me that perhaps my problem is that the
antenna is significantly BELOW the housetop.  How can that be, you ask?
Well, here in Atlanta, I have what we call a 'ravine back yard'.  My house
is below street level and the back yard has a deep slope.  The tree to which
the antenna is strung is in the backyard and while the height above ground
is 40', it is also at the eye level of my first floor (2 story house).  The
longest leg of the V is well below the house level and actually facing (for
half its length) the concrete basement that holds up the house.
   
  Sooooo.....how much impact on the take-off angle would you think this
configuration would have?  Should I replace the V with a flat-top doublet at
the same 40' height which would result in most of the antenna being at 40'
but still below the roof level? 
   
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Expect your strongest signals to be opposite the direction of the slope.
That is, the ground sloping up to the house will act as a reflector.
Actually, below a wavelength or two above ground, the ground ALWAYS acts
like a reflector. That's why horizontal antennas at the right height - about
1/2 wave up - enjoy 4 to 6 dB gain over a vertical for fairly low angle
radiation. Closer to the ground horizontal antennas see that gain straight
up for short skip  propagation. That's why folks currently call as a NVIS or
near-vertical incidence system. 

In your case the ground isn't horizontal, but it'll work just the same. At
40 feet, the major lobe from your antenna will be opposite the  ground,
especially on 40 and 20 meters. Only in this case it's off at an angle
opposite the slope of the ground instead of straight up. That's good for
working stations in that direction, particularly DX and lousy for working
stations in other directions beyond short-skip range. 

"Mountain topper" portable operators often try to duplicate your situation
on purpose, erecting a low doublet or dipole off the side of a steep cliff
to get low angle radiation from a horizontal radiator that is not very high
off of the ground. 

Bottom line: your propagation will be greatly affected by that slope.
Hopefully it points your signal in interesting directions even if that
doesn't include Oregon for the ECN.

Ron AC7AC