"Richard Clark" wrote in message
...
On Thu, 09 Sep 2004 19:42:41 GMT, "Jimmie"
wrote:

This equates to about 40 ohms
impedance seen at the antenna base. This also agrees with my antenna
analyzer. Antenna is a full length 1/4 wl antenna on 20m. I was figuring
37
or soo for this.

Hi Jimmie,

So you have no radials?

Yes I alreaady described it once in this thread.
73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Thu, 09 Sep 2004 19:42:41 GMT, "Jimmie"
wrote:

This equates to about 40 ohms
impedance seen at the antenna base. This also agrees with my antenna
analyzer. Antenna is a full length 1/4 wl antenna on 20m. I was figuring
37
or soo for this.

Hi Jimmie,

So you have no radials?

Described the radials once but that text has been snipped.

12 12f t wires, Center ground stake 10 ft long, far end of each wire has a
stake about 3 ft long. These are used more to just hold the wires in place.
73's
Richard Clark, KB7QHC

On Fri, 10 Sep 2004 14:25:15 GMT, "Jimmie"
wrote:

12 12f t wires, Center ground stake 10 ft long, far end of each wire has a
stake about 3 ft long. These are used more to just hold the wires in place.

Hi Jimmy,

Modeling concurs with your description, measurements and conclusion.

73's
Richard Clark, KB7QHC

Jimmie wrote -

12 12f t wires, Center ground stake 10 ft long, far end of each wire has a
stake about 3 ft long. These are used more to just hold the wires in
place.

===============================

Jimmie, For amusement and my education, would you mind letting us have a few
more crude details of your ground radial system please.

TYPE OF SOIL

(A) Is it high quality, fertilised garden loam, perhaps very slightly sandy
which can grow flowers and shrubs of which you can be proud when you try.
Perhaps used to be farm or orchard or agricultural land.

(B) Is it slightly gritty, stoney, but ample body which can still make a
nice flower garden. Quite fertile even though it may be overgrown with
profuse, dense, robust weeds. (Like mine.)

(C) Is it sandy, clayey, with small stones or pebbles? Needs attention with
fertilisers to grow nice flowers. But a lawn might do very well.

(D) Does it contain stones, sand, grit and small rocks with only 75% of
good soil but still needs hoeing and weeding to keep looking presentable.?

(E) Is it poor soil, smewhat infertile, difficult to manage as a flower
garden? Could be turned into a rock garden. Even the weeds don't do very
well.

(F) Thin layer of mediocre soil over bedrock.

MOISTURE CONTENT

(G) Fairly wet.
(H) Nicely moist.
(I) Slightly damp.
(J) Well drained, dry.
(K) Dusty.
(L) Arid.

ROUGH DEPTH OF WIRE BURIAL.

In tenths of an inch if very shallow.
Zero if just trodden in, in good contact with soil surface.

Thank you.
----
Reg.

"Reg Edwards" wrote in message
...
Jimmie wrote -

12 12f t wires, Center ground stake 10 ft long, far end of each wire has
a
stake about 3 ft long. These are used more to just hold the wires in
place.

===============================

Jimmie, For amusement and my education, would you mind letting us have a
few
more crude details of your ground radial system please.

TYPE OF SOIL

(A) Is it high quality, fertilised garden loam, perhaps very slightly
sandy
which can grow flowers and shrubs of which you can be proud when you try.
Perhaps used to be farm or orchard or agricultural land.

(B) Is it slightly gritty, stoney, but ample body which can still make a
nice flower garden. Quite fertile even though it may be overgrown with
profuse, dense, robust weeds. (Like mine.)

XXXX (C) Is it sandy, clayey, with small stones or pebbles? Needs
attention with
fertilisers to grow nice flowers. But a lawn might do very well.

(D) Does it contain stones, sand, grit and small rocks with only 75% of
good soil but still needs hoeing and weeding to keep looking presentable.?

(E) Is it poor soil, smewhat infertile, difficult to manage as a flower
garden? Could be turned into a rock garden. Even the weeds don't do very
well.

(F) Thin layer of mediocre soil over bedrock.

MOISTURE CONTENT

(G) Fairly wet.
(H) Nicely moist.
X (I) Slightly damp.
(J) Well drained, dry.
(K) Dusty.
(L) Arid.

ROUGH DEPTH OF WIRE BURIAL.
1 inch

In tenths of an inch if very shallow.
Zero if just trodden in, in good contact with soil surface.

Thank you.
----
Reg.


Soil is kind of a strang brew. when the house was built there was quite a
hill here that was leveled off. When the top soil was put back they put down
the top soil with about a foot of clay over it. So I have a foot of clay a
foot or so of top soil and more clay. Top layer of clay can get faily dry
while the layer of topsoil and underlying clay stay fairly moist. Grass and
trees grow fairl well and I never have to water them. Sometimes the grass
browns when we have drought conditions but the fruit trees always seem to do
well. I susppect this is because they can reach the underlying moisture.

On Fri, 10 Sep 2004 14:25:15 GMT, "Jimmie"
wrote:


"Richard Clark" wrote in message
.. .
On Thu, 09 Sep 2004 19:42:41 GMT, "Jimmie"
wrote:

This equates to about 40 ohms
impedance seen at the antenna base. This also agrees with my antenna
analyzer. Antenna is a full length 1/4 wl antenna on 20m. I was figuring
37
or soo for this.


12 12f t wires, Center ground stake 10 ft long, far end of each wire has a
stake about 3 ft long. These are used more to just hold the wires in place.

Hi Jimmie,

My last post responding to this included a mistaken analysis. I had
picked up the sample vertical and did not notice it was using MININEC
ground, which is unsuitable for this question.

On using the particulars you supply above, the results are very much
different.

With the default ground (0.005/13):
Impedance = 57.96 + J 0.1116 ohms

With extremely poor ground (0.001/3):
Impedance = 65.24 - J 0.1441 ohms
SWR (50 ohm system) = 1.305

With poor ground (0.002/13):
Impedance = 55.64 + J 0.1153 ohms
SWR (50 ohm system) = 1.113

With "Pastoral" ground (0.01/14)
Impedance = 56.62 + J 0.1475 ohms
SWR (50 ohm system) = 1.132

With very good ground (0.0303/20)
Impedance = 54.38 + J 0.3596 ohms
SWR (50 ohm system) = 1.088

For each change of ground I drove out reactance by trimming the
radiatior to

On Fri, 10 Sep 2004 14:25:15 GMT, "Jimmie"
wrote:


"Richard Clark" wrote in message
.. .
On Thu, 09 Sep 2004 19:42:41 GMT, "Jimmie"
wrote:

This equates to about 40 ohms
impedance seen at the antenna base. This also agrees with my antenna
analyzer. Antenna is a full length 1/4 wl antenna on 20m. I was figuring
37
or soo for this.


12 12f t wires, Center ground stake 10 ft long, far end of each wire has a
stake about 3 ft long. These are used more to just hold the wires in place.

Hi Jimmie,

My last post responding to this included a mistaken analysis. However,
it has been now thrice plagued. Originally I had picked up the sample
vertical and did not notice it was using MININEC ground, which is
unsuitable for this question. Then in doing the suite of grounds, I
had truncated the radials by half in a frequency translation. Then I
fumbled the wrong key -sigh-

On using the particulars you supply above, the results offer the low
end of ground resistance by your estimate. However this depends on
several things (not surprisingly - ground). Does your analyzer read
real resistance, or simply SWR? What does it read with a 50 Ohm
resistor (taking the average of several, all with close trimmed
leads)?

Anyway, by your SWR reading it appears your situation corresponds to
an "extremely poor ground." Curious thing about the nature of
"extremely poor," is that what does this mean? There is every
indication that it offers the least loss, and yet it also offers the
poorest signal out (at 10° as an indicator of DX).

With extremely poor ground (0.001/3 Zground = 209 Ohms):
Impedance = 39.46 + J 0.234 Ohms
SWR (50 ohm system) = 1.267
-6.01 dBi @ 10°

With poor ground (0.002/13 Zground = 104 Ohms):
Impedance = 42.34 + J 0.1014 Ohms
SWR (50 ohm system) = 1.181
-3.25 dBi @ 10°

With the default ground (0.005/13 Zground = 99 Ohms):
Impedance = 43.64 + J 0.03538 Ohms
SWR (50 ohm system) = 1.146
-3.36 dBi @ 10°

With "Pastoral" ground (0.01/14 Zground = 87 Ohms)
Impedance = 44.93 + J 0.515 Ohms
SWR (50 ohm system) = 1.113
-3.00 dBi @ 10°

With very good ground (0.0303/20 Zground = 57 Ohms):
Impedance = 44.5 + J 0.3779 Ohms
SWR (50 ohm system) = 1.124
-1.11 dBi @ 10°

For each change of ground I drove out reactance to less than one Ohm
by trimming the radiator to what you describe as a full size
quarterwave antenna.

Going back to the nature of ground, we return to the descriptions of
conductivity and how a "very good" conducting soil is NOT what you
want nearby in terms of matching. A "very good" conducting soil is
injecting several ohms more resistance into your feed than an
"extremely poor" quality soil. However, when we consider the Z of
ground, we observe that it is the ratio of this impedance to the æther
that is the better indicator of achieving good low angle launch
characteristics. Consistent here are the SWR of 6.6 for "very good"
soil compared to the SWR of 1.8 for "extremely poor" soil.

There is less conductive loss (but more capture of power) in the
"extremely poor" soil and there is more conductive loss (but less
capture of power) in the "very good" soil. Clearly it is the
REFLECTIVE attributes of the media interface that is the more
compelling characteristic than with the so-called boon of
conductivity.

Two more points of practical consideration he
1. With 12 radials laid out as you have, there is very little
variation over "average" grounds (no point in trying harder);
2. The DX angle is driven by ground characteristics many wavelengths
out (no point in worrying about ground either way).

73's
Richard Clark, KB7QHC

I have lost all previous contributions to this thread.

But Jimmie gave the description of his radial system -

12 12f t wires, Center ground stake 10 ft long, far end of each wire has
a
stake about 3 ft long. These are used more to just hold the wires in
place.

plus a brief description of type of soil and moisture content. I guessed at
wire diameters.

From which I deduce the following input impedances -

AT 1.9 MHz AT 7.0 MHz
---------------- ----------------
10 + j0 13 + j11 ohms.

Uncertainty = +/- 3 ohms which is adequate for the intended purpose.

The above figures have been obtained using programs ENDFEED and RADIALS2
(two different modelling methods) and averaging the results at soil
resistivities of 100 and 300 ohm metres. Programs can be downloaded in a
few seconds from website below. Calculating time no longer than needed to
enter the simple data.

In practice, only the resistances matter because the reactances are tuned
out simultaneously with the antenna, equivalent to minor readjustments of
the tuner. The resistance values, in conjunction with calculated radiation
resistance can be used to calculate radiating efficiency.

If Jimmie should ever measure input resistance with similar uncertainty (not
too difficult) then I should be pleased to hear his results.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

On Sun, 12 Sep 2004 16:31:12 +0000 (UTC), "Reg Edwards"
wrote:


From which I deduce the following input impedances -

AT 1.9 MHz AT 7.0 MHz

This is a 20M system.

"Reg Edwards" wrote in message
...
I have lost all previous contributions to this thread.

But Jimmie gave the description of his radial system -

12 12f t wires, Center ground stake 10 ft long, far end of each wire
has
a
stake about 3 ft long. These are used more to just hold the wires in
place.

plus a brief description of type of soil and moisture content. I guessed
at
wire diameters.

From which I deduce the following input impedances -

AT 1.9 MHz AT 7.0 MHz
---------------- ----------------
10 + j0 13 + j11 ohms.

Uncertainty = +/- 3 ohms which is adequate for the intended purpose.

The above figures have been obtained using programs ENDFEED and RADIALS2
(two different modelling methods) and averaging the results at soil
resistivities of 100 and 300 ohm metres. Programs can be downloaded in a
few seconds from website below. Calculating time no longer than needed to
enter the simple data.

In practice, only the resistances matter because the reactances are tuned
out simultaneously with the antenna, equivalent to minor readjustments of
the tuner. The resistance values, in conjunction with calculated
radiation
resistance can be used to calculate radiating efficiency.

If Jimmie should ever measure input resistance with similar uncertainty
(not
too difficult) then I should be pleased to hear his results.

I had really not given it a whole lot of thought unti gettin invovled in
this thread but I am beginning to think that my sort of unique soil
conditions may effect my ground system considerably. With the moist, top
soil and clay at the lower levels I am getting a good primary power ground,
but now I dont think my RF connection to earth is very good at all ass the
counter poise is in some fairly dry sandy clay. Wife says that when I
installed this thing back in '94 that she remembered me putting in some
longer wires than the 12 12 ft wires. At this point I am thinking maybe is
was 8 12 ft wires and 4 1/4 wl 20m wires. I know the origonal plan waas to
put in the 12 ft wires and 1/4 wl wires for several bands out to 80m with 3
or 4 wires for each band. I know I didnt do it for 80M but now I must admit
I am not sure about other bands. I may have put in other radials for 20 and
40 meters. Shortly after this I almost totally gave up radio until
recently.