"Roy Lewallen" wrote
I can assure the readers that all the effects I've discussed are
soundly
based on very well known principles.

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

Roy, you seem to have forgotten proximity effect.

If one calculates the Q of a coil from HF skin resistance of the wire
and from coil inductance, one gets ridiculously high values of Q.

Other producers of coil calculators appear to have forgotten this too.
That's if they were ever aware of it.

I have a coil, about 4 inches long, about 1.7 inches in diameter, with
about 90 close-wound turns of 1mm diameter wire, which has an
inductance of about 100 micro-henrys. The measured value of Q at 1.9
MHz is about 240.

This makes the proximity effect about 3.5 or 4 times the effect of
simple HF wire skin resistance. This is a large amount.

This is the first time such information has been appeared on a
newsgroup or published in bibles anywhere else. They didn't have Q
meters 120 years ago, in Heaviside's time, when such factors were
first considered.

My findings are incorporated in program SOLNOID3 which estimates Q
(and other characteristics) for coils of various dimensions. There
are, of course, other factors which influence Q which is a relatively
unimportant coil characteristic.

What do you do with Q once you have taken the trouble to find it? The
other more important things will already be apparent.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

To extend from Ian's remarks:

In some critical applications, the use of coax cable with braided outer Cu
conductor can cause problems.

RF charge flow (current) in the braid experiences a non-linear circuit
resulting in harmonic distortion or IM or both. Just made coax can have a
very low level of non-linearity with the effect increasing with age (and
probable corrosion). Ag plated Cu braid seems to have less of the
non-linear effect - perhaps because of a poorer mechanism for current to
move from one wire to another.
The effects are small, but can be important in certain applications.
Solid Cu outer conductors have advantages beyond mechanical and
power-handling.
73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Ian White GM3SEK" wrote in message
snip


Then it gets worse. Even the thinnest film of corrosion can disrupt the
contact between copper strands in a braid. Unless the current density is
large enough to break down this film, it means the RF current is forced
to flow into the interior of the braid. Again the exact geometry is hard
to visualize, but again the physics dictate that if an isolated
'filament' of current is forced to flow beneath a conducting surface,
the voltage drop per unit length must increase - in other words, the RF
resistance must increase.

Scientific deduction has told us that all these effects must exist.
Whatit cannot tell us is how big they are in real braid, or how
important they are in practice. For that we'll need some measured
numbers.

You have two choices he either look for existing measurements from
people who have demonstrated their competence and scientific approach;
or do it yourself.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

These results were from Reg's c_poise program. The band is 75 meters and the
coils were about 70 uH. The coils were a relatively large diameter, on the order
of a meter. The wire lengths were about 20 meters. By varying the length the
coil, the coil wire may be varies from 1mm to 12mm.

Richard Clark wrote:
On Sat, 18 Feb 2006 08:20:38 -0800, dansawyeror
wrote:


The devil is in the details. Modeling shows large coils with 1 mm wire have a Q
in the range of a few hundred. On the other hand a coil with 12 mm tubing has a
Q of about 2000. The R of the 1 mm coil is about 6 Ohms while the 12 mm coil is
on the order of 1 Ohm.

Given these model results it says there is a significant difference between 1 mm
and 12 mm coils.


Hi Dan,

In the details, indeed.

What is the LENGTH of wire in this 6 Ohm resistor? What is the LENGTH
of wire in this 1 Ohm resistor? How many turns are in these "large
coils?" What is their diameter? What is their solenoid length?

Without these details, there is nothing said that is significant.

73's
Richard Clark, KB7QHC

Q meters, above the range of 150, fall into the same category as so
called SWR meters above the range of 1.5

Neither are of much use. Just an opinion!
----
Reg.

May I suggest the use of PVC pipe as a form for winding the
coax? Tape it in place while you're "monkeying" and then fiberglass it
when
you like what you have. (Auto supply stores sell the fiberglass for doing
auto body work -- it's durable & light-weight.)

KD6VKW
ET USN (ret)


That sounds like a good idea - and I have used pvc forms myself.
I wonder if ecasing the coil in that 'Great Stuff' spray foam would be ample
protection ?

my 2¢
W4PMJ

These results were from Reg's c_poise program. The band is 75 meters and the
coils were about 70 uH. The coils were a relatively large diameter, on the order
of a meter. The wire lengths were about 20 meters. By varying the length the
coil, the coil wire may be varies from 1mm to 12mm.

I haven't tried that program, so don't know what it's for...
But... 70 uh is not far off from the usual inductance
needed to match a 80m mobile antenna. When using
Reg's "vertload" program, which I use for designing mobiles,
I don't see near the spread of coil loss that you see in that
program.
In vertload, to make that large a coil using 12 mm wire,
the coil diameter has to be fairly large just to be able to
fit enough turns in the appx 12 inch height I allowed for
the coil. But when comparing a like coil using 1 mm wire,
and the same coil using 12 mm wire, I only saw about
1 ohm difference, not 5. I'm not sure which is the most
accurate, but so far my real world results in mobile
whips seems to jive pretty well with vertload. I've made
a few coils with pretty thin wire, and had good results
as long as the turn ratio was ok. Ditto for fatter wire coils.
I made one that was 12 gauge and could see only a small
difference from one made with 16 gauge wire. Seemed to
shrink my bandwidth very slightly.
So...Dunno..Would have to do some tests to get the real
lowdown on the differences in loss I guess. But with the
mobiles, I came to the conclusion that real thick wire was not
really needed for a good coil, as long as the winding ratio
was right.
MK

Frank,

Good morning. Let me start at the beginning. I have a loaded vertical on 75
meters. The combination of the antenna and ground measure about 40 Ohms at the
antenna. The models all show such an antenna over a perfect ground should have a
radiation resistance of between 3 and 4 Ohms. That says the antenna system is
less the 10% efficient.

This then is a journey to reduce ground resistance. Attempts to add radials and
wire mesh to the ground have had very little if no effect. This leads to Reg's
c_poise model. It predicts a coil in the range of 60 uH to 90 uH tuned to a 2
meter by 18 mm 'wire' will have a total resistance in the 2 to 4 Ohms range.

Together this should result is a 8 Ohm system. The ratio can be directly
inferred as an performance improvement of 5 to 1 or 7 db. This is worth some
effort.

To answer your question the first step will be one coil and one radial. The
objective is the get the antenna system close to 10 Ohms. From there I will
experiment with adding radials and coils. I am not sure what to expect.

Thanks - Dan





Frank wrote:
Not sure I understand what is going on Dan. Are you planning on loading
each radial element?

Frank


"dansawyeror" wrote in message
...

These results were from Reg's c_poise program. The band is 75 meters and
the coils were about 70 uH. The coils were a relatively large diameter, on
the order of a meter. The wire lengths were about 20 meters. By varying
the length the coil, the coil wire may be varies from 1mm to 12mm.

Richard Clark wrote:

On Sat, 18 Feb 2006 08:20:38 -0800, dansawyeror
wrote:



The devil is in the details. Modeling shows large coils with 1 mm wire
have a Q in the range of a few hundred. On the other hand a coil with 12
mm tubing has a Q of about 2000. The R of the 1 mm coil is about 6 Ohms
while the 12 mm coil is on the order of 1 Ohm.

Given these model results it says there is a significant difference
between 1 mm and 12 mm coils.


Hi Dan,

In the details, indeed. What is the LENGTH of wire in this 6 Ohm
resistor? What is the LENGTH
of wire in this 1 Ohm resistor? How many turns are in these "large
coils?" What is their diameter? What is their solenoid length?

Without these details, there is nothing said that is significant.

73's
Richard Clark, KB7QHC

Frank,

Thanks for the model. I did not expect you to model this or I would have been
more specific. The antenna is about 14 feet. The coil is about 4 feet from the
base.

Now the radials: Did you base the radial from Reg's model? Try 3.97 MHz, 1 meter
above ground, 3 meter radials, and a 60mm long by 300 mm dia 66.7 uH loading
coil. These grounds have to be tuned as well.

I am using 4nec2 and am getting errors from the GM card. Wasn't there an issue
with these being a decimal instead of an integer?

BTW - The simulation on my laptop takes over 5 minutes to run.

Dan

Frank's Basement 2 wrote:
Hi Dan, thanks for the interesting info. You did not specify dimensions,
but from your comments it appears you are using a vertical about 23 ft high.
Such a monopole would have a 3.5 ohm input impedance when placed above a
perfectly conducting ground, and gain about +4.5 dBi. Adding a center
loading coil raises the input impedance to 11.5 ohms, and gain +2.6 dBi.
Base loading provides an input impedance of 5.5 ohms with almost the same
gain as center loading (Q = 400). Adding ten, 6ft radials, at 3" above an
average ground, the input impedance increases to 40 ohms, and gain -6.3 dBi.

Adding lumped element loading coils, (75 uH, Q = 400) in each radial
(antenna base end) drops the input impedance to 37 ohms, and gain -6.4 dBi.
Don't know why this does not agree with Reg's program. Probably I made some
fundamental error with the NEC model. Included the code below, so you may
see an error I missed.

73,

Frank

CM 75 m Vertical 23 ft high
CE
GW 1 64 0 0 23 0 0 0.25 0.0026706
GW 2 12 0 0 0.25 6 0 0.25 0.0026706
GM 1 9 0 0 36 0 0 0 002.002
GS 0 0 .3048
GE 1
GN 2 0 0 0 13.0000 0.0050
EX 0 1 64 0 1.00000 0.00000
LD 5 1 1 184 5.8001E7
LD 4 1 33 33 4 1600
LD 4 2 1 1 4 1750
LD 4 3 1 1 4 1750
LD 4 4 1 1 4 1750
LD 4 5 1 1 4 1750
LD 4 6 1 1 4 1750
LD 4 7 1 1 4 1750
LD 4 8 1 1 4 1750
LD 4 9 1 1 4 1750
LD 4 10 1 1 4 1750
LD 4 11 1 1 4 1750
FR 0 11 0 0 3.5 0.05
RP 0 181 1 1000 -90 0 1.00000 1.00000
EN





Frank,

Good morning. Let me start at the beginning. I have a loaded vertical on

75

meters. The combination of the antenna and ground measure about 40 Ohms at

the

antenna. The models all show such an antenna over a perfect ground should

have a

radiation resistance of between 3 and 4 Ohms. That says the antenna system

is

less the 10% efficient.

This then is a journey to reduce ground resistance. Attempts to add

radials and

wire mesh to the ground have had very little if no effect. This leads to

Reg's

c_poise model. It predicts a coil in the range of 60 uH to 90 uH tuned to

a 2

meter by 18 mm 'wire' will have a total resistance in the 2 to 4 Ohms

range.

Together this should result is a 8 Ohm system. The ratio can be directly
inferred as an performance improvement of 5 to 1 or 7 db. This is worth

some

effort.

To answer your question the first step will be one coil and one radial.

The

objective is the get the antenna system close to 10 Ohms. From there I

will

experiment with adding radials and coils. I am not sure what to expect.

Thanks - Dan





Frank wrote:

Not sure I understand what is going on Dan. Are you planning on loading
each radial element?

Frank


"dansawyeror" wrote in message
...


These results were from Reg's c_poise program. The band is 75 meters and
the coils were about 70 uH. The coils were a relatively large diameter,

on

the order of a meter. The wire lengths were about 20 meters. By varying
the length the coil, the coil wire may be varies from 1mm to 12mm.

Richard Clark wrote:


On Sat, 18 Feb 2006 08:20:38 -0800, dansawyeror
wrote:




The devil is in the details. Modeling shows large coils with 1 mm wire
have a Q in the range of a few hundred. On the other hand a coil with

12

mm tubing has a Q of about 2000. The R of the 1 mm coil is about 6

Ohms

while the 12 mm coil is on the order of 1 Ohm.

Given these model results it says there is a significant difference
between 1 mm and 12 mm coils.


Hi Dan,

In the details, indeed. What is the LENGTH of wire in this 6 Ohm
resistor? What is the LENGTH
of wire in this 1 Ohm resistor? How many turns are in these "large
coils?" What is their diameter? What is their solenoid length?

Without these details, there is nothing said that is significant.

73's
Richard Clark, KB7QHC

Follow up:

One of the not so apparent results of Reg's program is the relationship of
radial length to height. I chose 2 meters because they were only .7 meters high.

I raised your model to 2 meters, that reduced the R to about 20 Ohms. Raising it
to 3 meters lowers it to 18 Ohms.

How did you calculate the H of the loading coils? Is that easy to edit? It would
seem that these values are closer.

Dan

Frank's Basement 2 wrote:
Hi Dan, thanks for the interesting info. You did not specify dimensions,
but from your comments it appears you are using a vertical about 23 ft high.
Such a monopole would have a 3.5 ohm input impedance when placed above a
perfectly conducting ground, and gain about +4.5 dBi. Adding a center
loading coil raises the input impedance to 11.5 ohms, and gain +2.6 dBi.
Base loading provides an input impedance of 5.5 ohms with almost the same
gain as center loading (Q = 400). Adding ten, 6ft radials, at 3" above an
average ground, the input impedance increases to 40 ohms, and gain -6.3 dBi.

Adding lumped element loading coils, (75 uH, Q = 400) in each radial
(antenna base end) drops the input impedance to 37 ohms, and gain -6.4 dBi.
Don't know why this does not agree with Reg's program. Probably I made some
fundamental error with the NEC model. Included the code below, so you may
see an error I missed.

73,

Frank

CM 75 m Vertical 23 ft high
CE
GW 1 64 0 0 23 0 0 0.25 0.0026706
GW 2 12 0 0 0.25 6 0 0.25 0.0026706
GM 1 9 0 0 36 0 0 0 002.002
GS 0 0 .3048
GE 1
GN 2 0 0 0 13.0000 0.0050
EX 0 1 64 0 1.00000 0.00000
LD 5 1 1 184 5.8001E7
LD 4 1 33 33 4 1600
LD 4 2 1 1 4 1750
LD 4 3 1 1 4 1750
LD 4 4 1 1 4 1750
LD 4 5 1 1 4 1750
LD 4 6 1 1 4 1750
LD 4 7 1 1 4 1750
LD 4 8 1 1 4 1750
LD 4 9 1 1 4 1750
LD 4 10 1 1 4 1750
LD 4 11 1 1 4 1750
FR 0 11 0 0 3.5 0.05
RP 0 181 1 1000 -90 0 1.00000 1.00000
EN





Frank,

Good morning. Let me start at the beginning. I have a loaded vertical on

75

meters. The combination of the antenna and ground measure about 40 Ohms at

the

antenna. The models all show such an antenna over a perfect ground should

have a

radiation resistance of between 3 and 4 Ohms. That says the antenna system

is

less the 10% efficient.

This then is a journey to reduce ground resistance. Attempts to add

radials and

wire mesh to the ground have had very little if no effect. This leads to

Reg's

c_poise model. It predicts a coil in the range of 60 uH to 90 uH tuned to

a 2

meter by 18 mm 'wire' will have a total resistance in the 2 to 4 Ohms

range.

Together this should result is a 8 Ohm system. The ratio can be directly
inferred as an performance improvement of 5 to 1 or 7 db. This is worth

some

effort.

To answer your question the first step will be one coil and one radial.

The

objective is the get the antenna system close to 10 Ohms. From there I

will

experiment with adding radials and coils. I am not sure what to expect.

Thanks - Dan





Frank wrote:

Not sure I understand what is going on Dan. Are you planning on loading
each radial element?

Frank


"dansawyeror" wrote in message
...


These results were from Reg's c_poise program. The band is 75 meters and
the coils were about 70 uH. The coils were a relatively large diameter,

on

the order of a meter. The wire lengths were about 20 meters. By varying
the length the coil, the coil wire may be varies from 1mm to 12mm.

Richard Clark wrote:


On Sat, 18 Feb 2006 08:20:38 -0800, dansawyeror
wrote:




The devil is in the details. Modeling shows large coils with 1 mm wire
have a Q in the range of a few hundred. On the other hand a coil with

12

mm tubing has a Q of about 2000. The R of the 1 mm coil is about 6

Ohms

while the 12 mm coil is on the order of 1 Ohm.

Given these model results it says there is a significant difference
between 1 mm and 12 mm coils.


Hi Dan,

In the details, indeed. What is the LENGTH of wire in this 6 Ohm
resistor? What is the LENGTH
of wire in this 1 Ohm resistor? How many turns are in these "large
coils?" What is their diameter? What is their solenoid length?

Without these details, there is nothing said that is significant.

73's
Richard Clark, KB7QHC

I see the length is set to 1.8 meters already. A 2 meter elevation minimum is
needed to lower ground effects.

How is the lumped inductance set of 4 Ohms and 1750 Z? What impedance does that
translate to? How did you calculate this value? Dan

Frank's Basement 2 wrote:
Hi Dan, thanks for the interesting info. You did not specify dimensions,
but from your comments it appears you are using a vertical about 23 ft high.
Such a monopole would have a 3.5 ohm input impedance when placed above a
perfectly conducting ground, and gain about +4.5 dBi. Adding a center
loading coil raises the input impedance to 11.5 ohms, and gain +2.6 dBi.
Base loading provides an input impedance of 5.5 ohms with almost the same
gain as center loading (Q = 400). Adding ten, 6ft radials, at 3" above an
average ground, the input impedance increases to 40 ohms, and gain -6.3 dBi.

Adding lumped element loading coils, (75 uH, Q = 400) in each radial
(antenna base end) drops the input impedance to 37 ohms, and gain -6.4 dBi.
Don't know why this does not agree with Reg's program. Probably I made some
fundamental error with the NEC model. Included the code below, so you may
see an error I missed.

73,

Frank

CM 75 m Vertical 23 ft high
CE
GW 1 64 0 0 23 0 0 0.25 0.0026706
GW 2 12 0 0 0.25 6 0 0.25 0.0026706
GM 1 9 0 0 36 0 0 0 002.002
GS 0 0 .3048
GE 1
GN 2 0 0 0 13.0000 0.0050
EX 0 1 64 0 1.00000 0.00000
LD 5 1 1 184 5.8001E7
LD 4 1 33 33 4 1600
LD 4 2 1 1 4 1750
LD 4 3 1 1 4 1750
LD 4 4 1 1 4 1750
LD 4 5 1 1 4 1750
LD 4 6 1 1 4 1750
LD 4 7 1 1 4 1750
LD 4 8 1 1 4 1750
LD 4 9 1 1 4 1750
LD 4 10 1 1 4 1750
LD 4 11 1 1 4 1750
FR 0 11 0 0 3.5 0.05
RP 0 181 1 1000 -90 0 1.00000 1.00000
EN





Frank,

Good morning. Let me start at the beginning. I have a loaded vertical on

75

meters. The combination of the antenna and ground measure about 40 Ohms at

the

antenna. The models all show such an antenna over a perfect ground should

have a

radiation resistance of between 3 and 4 Ohms. That says the antenna system

is

less the 10% efficient.

This then is a journey to reduce ground resistance. Attempts to add

radials and

wire mesh to the ground have had very little if no effect. This leads to

Reg's

c_poise model. It predicts a coil in the range of 60 uH to 90 uH tuned to

a 2

meter by 18 mm 'wire' will have a total resistance in the 2 to 4 Ohms

range.

Together this should result is a 8 Ohm system. The ratio can be directly
inferred as an performance improvement of 5 to 1 or 7 db. This is worth

some

effort.

To answer your question the first step will be one coil and one radial.

The

objective is the get the antenna system close to 10 Ohms. From there I

will

experiment with adding radials and coils. I am not sure what to expect.

Thanks - Dan





Frank wrote:

Not sure I understand what is going on Dan. Are you planning on loading
each radial element?

Frank


"dansawyeror" wrote in message
...


These results were from Reg's c_poise program. The band is 75 meters and
the coils were about 70 uH. The coils were a relatively large diameter,

on

the order of a meter. The wire lengths were about 20 meters. By varying
the length the coil, the coil wire may be varies from 1mm to 12mm.

Richard Clark wrote:


On Sat, 18 Feb 2006 08:20:38 -0800, dansawyeror
wrote:




The devil is in the details. Modeling shows large coils with 1 mm wire
have a Q in the range of a few hundred. On the other hand a coil with

12

mm tubing has a Q of about 2000. The R of the 1 mm coil is about 6

Ohms

while the 12 mm coil is on the order of 1 Ohm.

Given these model results it says there is a significant difference
between 1 mm and 12 mm coils.


Hi Dan,

In the details, indeed. What is the LENGTH of wire in this 6 Ohm
resistor? What is the LENGTH
of wire in this 1 Ohm resistor? How many turns are in these "large
coils?" What is their diameter? What is their solenoid length?

Without these details, there is nothing said that is significant.

73's
Richard Clark, KB7QHC