It would be interesting to recreate the measurements at other locations. My
location has 500 feet of sand below me. It would be a great improvement just
to have poor soil.


"Walter Maxwell" wrote in message
...
Hi Reg,

You've presented a very interesting way of measuring soil characteristics.
When
I return to Florida in November I'm going to use your method of measuring
the
soil underneath the dipole whose impedances I measured over the frequency
range
14 to 15 MHz at various heights above ground, including one set of
measurements
with the dipole lying on the ground.

One of the reasons I offered to distribute the data from my measurements
is to
see whether anyone can deduce any soil characteristics from the changes in
impedance with height. The changes are significant. For example, the
terminal
impedance with the dipole on the ground runs from 470 + j250 at 14 MHz to
570 +
j132 at 15 MHz. The inductive reactance doesn't become capacitive until
the
dipole is 2 ft off the ground. In addition, except at zero height, the
resistance component decreases with height, but for every height the
resistance
increases with frequency. Do you think any of the soil characteristics
could be
determined by such data?

Would you like a copy of my data, just fer the helovit?

Walt, W2DU

Fred W4JLE wrote:
It would be interesting to recreate the measurements at other locations. My
location has 500 feet of sand below me. It would be a great improvement just
to have poor soil.

Depends on your objective. For NVIS operation with a horizontal antenna,
where you need the reflection, that's probably true. But for a vertical
or for DX with a horizontal antenna, you're better off with the sand.
Perfect ground has no loss; free space has no loss. There's an
intermediate quality of ground at which the loss is maximum at a given
frequency. Unfortunately, this happens to be in the range of ordinary
ground characteristics in the HF range. Your ground should be very low
loss. And your pattern should resemble free space, with a very strong
field at very low radiation angles.

Roy Lewallen, W7EL

Anecdotally, I have noticed, I have no problem working Europe, ZS, VK, and
ZL on 75 running 90 watts. I am typically 5-9 or better in to Great Britain.
My antenna is 38 feet in the center and 20 feet on both ends. Actually I
have two 132 foot dipoles that are orientated 90 degrees from each other.
They share a common relay box for switching in additional ladderline. That
is the input to the relay box is selected by a separate relay. The unused
antenna is grounded. I have tried it both grounded and ungrounded and it
"seems" to be better when the unused antenna is grounded.

My next set of relays will tie them both together as a big capacity hat on
160. Have not got around to doing it yet.

I can push a 10 foot ground rod into the ground by hand. If I don't wet it
down, I can rotate it by hand when it is 9.75 feet in the ground. If a
rabbit gets in the garden, one is in dire straits trying to find a rock to
throw at it.

A sand pit down the road from me is over 200 feet deep and they have not hit
anything other than sand in over 20 years of digging.





"Roy Lewallen" wrote in message
...
Fred W4JLE wrote:
It would be interesting to recreate the measurements at other locations.
My
location has 500 feet of sand below me. It would be a great improvement
just
to have poor soil.

Depends on your objective. For NVIS operation with a horizontal antenna,
where you need the reflection, that's probably true. But for a vertical
or for DX with a horizontal antenna, you're better off with the sand.
Perfect ground has no loss; free space has no loss. There's an
intermediate quality of ground at which the loss is maximum at a given
frequency. Unfortunately, this happens to be in the range of ordinary
ground characteristics in the HF range. Your ground should be very low
loss. And your pattern should resemble free space, with a very strong
field at very low radiation angles.

Roy Lewallen, W7EL