Also the series inductor should have a very high Q for 160 m. A Q of 1000
will loose about 30% of your power.

That's all well and good, but he wants to work over a wide frequency range.
Any L network will be a compromise. The Q as well as many other parameters
will have to be considered.

73 Gary N4AST

boy....from what I have been reading it looks like I would be miles ahead
using my twin lead fed 80 meter doublet...either as a very short dipole or
top loaded vertical on 160
"Frank" wrote in message
news:w7n1d.147$t61.135@clgrps13...
"Art Unwin KB9MZ" wrote in message
m...
I doubt that the coil will have a Q of more than 300 if that !
Art





"Frank" wrote in message
news:JCe1d.97059$jZ5.12695@clgrps13...
"denton" wrote in message
...
Hi all...
I am starting to work on something to use on 160 thru 20 meters.
I currently have an aluminum mast that is 32 ft long with a small cap
hat
on
top.
the antenna will sit in the center of an area approx 50 z 50'
(backyard).
I
plan to put down 40 plus radials, the majority which will be situated
to
radiate out from the base of the vertical.
some will meander along the house foundation and property line..
I plan on also tying in the galvanized (not chain link) fence around
the
back yard to the radial system, as well as the house plumbing.
40 meters should be direct feed.
I will homebrew a matching L network for use on 160 thru 60 meters.
I will also try a 20 meter tuning stubb.
Does anyone know what the size of the loading coil that MFJ uses in
their
80
& 40 meter vertical?
I have read of just about everything I can find online of this sort
of
project and have played with Eznec demo a bit and think this will be
a
doable project.

Also the series inductor should have a very high Q for 160 m. A Q of
1000
will loose about 30% of your power.

Frank

Based on Terman's "Radio Engineers Handbook" dated 1943, pp 31 - 53. I
have
written a program In MathCAD Pro, which indicates a coil made from 1/4"
copper pipe, 12" long, and 3 inches diameter has an inductance of 39 uH
and
a Q of 1132 at 1.8 MHz. (6" in diameter and 24" long shows a nominal Q of
1600). To be honest I have never built such a coil, and it would probably
be very difficult to measure. I agree that typical "Airdux" coils have a
Q
in the range of 300 or so.(Silver plating, or gold, would also be
desirable
to prevent lossy copper oxide build up). Anyway if you are interested I
can send you the MathCAD file. I would be very happy if somebody could
check
my math. It think the point I was trying to make it that electrically
short
antennas have such a low real input impedance that building an efficient
matching network is challenging to say the least. Even if such networks
are
feasible the huge voltages developed at the base could prove to be a
problem.

73,

Frank

Could be, but short dipoles can also be difficult to match, although as long
as you do not go below a quarter wave it should be reasonably ok. Even with
450 Ohm ladder line the losses can sometimes be very high, not to mention
the tuner losses, and, like the vertical, very high voltages.

The thing I like about verticals is the excellent low angle radiation. I
have been playing around with NEC models of 32 ft verticals all evening, but
not satisfied with the results yet. Roy Lewallen makes some good points, so
you may not need to build a 2 ft long gold plated coil yet! Somebody else
also pointed out that you want to use the vertical on other bands, which
will make for a complicated tuner. I have been trying to make up my mind
about 160 m antennas for about a year, still not sure what I want to do.

Frank Meredith (VE6CB)


"denton" wrote in message
...
boy....from what I have been reading it looks like I would be miles ahead
using my twin lead fed 80 meter doublet...either as a very short dipole or
top loaded vertical on 160
"Frank" wrote in message
news:w7n1d.147$t61.135@clgrps13...
"Art Unwin KB9MZ" wrote in message
m...
I doubt that the coil will have a Q of more than 300 if that !
Art





"Frank" wrote in message
news:JCe1d.97059$jZ5.12695@clgrps13...
"denton" wrote in message
...
Hi all...
I am starting to work on something to use on 160 thru 20 meters.
I currently have an aluminum mast that is 32 ft long with a small
cap
hat
on
top.
the antenna will sit in the center of an area approx 50 z 50'
(backyard).
I
plan to put down 40 plus radials, the majority which will be
situated
to
radiate out from the base of the vertical.
some will meander along the house foundation and property line..
I plan on also tying in the galvanized (not chain link) fence
around
the
back yard to the radial system, as well as the house plumbing.
40 meters should be direct feed.
I will homebrew a matching L network for use on 160 thru 60 meters.
I will also try a 20 meter tuning stubb.
Does anyone know what the size of the loading coil that MFJ uses in
their
80
& 40 meter vertical?
I have read of just about everything I can find online of this sort
of
project and have played with Eznec demo a bit and think this will
be
a
doable project.

Also the series inductor should have a very high Q for 160 m. A Q of
1000
will loose about 30% of your power.

Frank

Based on Terman's "Radio Engineers Handbook" dated 1943, pp 31 - 53. I
have
written a program In MathCAD Pro, which indicates a coil made from 1/4"
copper pipe, 12" long, and 3 inches diameter has an inductance of 39 uH
and
a Q of 1132 at 1.8 MHz. (6" in diameter and 24" long shows a nominal Q
of
1600). To be honest I have never built such a coil, and it would
probably
be very difficult to measure. I agree that typical "Airdux" coils have
a
Q
in the range of 300 or so.(Silver plating, or gold, would also be
desirable
to prevent lossy copper oxide build up). Anyway if you are interested
I
can send you the MathCAD file. I would be very happy if somebody could
check
my math. It think the point I was trying to make it that electrically
short
antennas have such a low real input impedance that building an efficient
matching network is challenging to say the least. Even if such networks
are
feasible the huge voltages developed at the base could prove to be a
problem.

73,

Frank

Tom W8JI talks about coils on his page and
if my memory is correct he has never measured a Q beyond 300
I use the 200/300 figure for my modelling and use as much as 800/1000
for capacitors. I am not competant enough to do any checking
of your particular program but I suspect your answers are in error
and await guru comments with interest
Art








"Frank" wrote in message news:w7n1d.147$t61.135@clgrps13...
"Art Unwin KB9MZ" wrote in message
m...
I doubt that the coil will have a Q of more than 300 if that !
Art





"Frank" wrote in message
news:JCe1d.97059$jZ5.12695@clgrps13...
"denton" wrote in message
...
Hi all...
I am starting to work on something to use on 160 thru 20 meters.
I currently have an aluminum mast that is 32 ft long with a small cap
hat
on
top.
the antenna will sit in the center of an area approx 50 z 50'
(backyard).
I
plan to put down 40 plus radials, the majority which will be situated
to
radiate out from the base of the vertical.
some will meander along the house foundation and property line..
I plan on also tying in the galvanized (not chain link) fence around
the
back yard to the radial system, as well as the house plumbing.
40 meters should be direct feed.
I will homebrew a matching L network for use on 160 thru 60 meters.
I will also try a 20 meter tuning stubb.
Does anyone know what the size of the loading coil that MFJ uses in
their
80
& 40 meter vertical?
I have read of just about everything I can find online of this sort of
project and have played with Eznec demo a bit and think this will be a
doable project.

Also the series inductor should have a very high Q for 160 m. A Q of
1000
will loose about 30% of your power.

Frank

Based on Terman's "Radio Engineers Handbook" dated 1943, pp 31 - 53. I have
written a program In MathCAD Pro, which indicates a coil made from 1/4"
copper pipe, 12" long, and 3 inches diameter has an inductance of 39 uH and
a Q of 1132 at 1.8 MHz. (6" in diameter and 24" long shows a nominal Q of
1600). To be honest I have never built such a coil, and it would probably
be very difficult to measure. I agree that typical "Airdux" coils have a Q
in the range of 300 or so.(Silver plating, or gold, would also be desirable
to prevent lossy copper oxide build up). Anyway if you are interested I
can send you the MathCAD file. I would be very happy if somebody could check
my math. It think the point I was trying to make it that electrically short
antennas have such a low real input impedance that building an efficient
matching network is challenging to say the least. Even if such networks are
feasible the huge voltages developed at the base could prove to be a
problem.

73,

Frank

On Mon, 13 Sep 2004 20:09:00 GMT, "Frank" wrote:

Silver plating, or gold, would also be desirable
to prevent lossy copper oxide build up

Hi Frank,

Not to raise your hopes on hi Q, but step back and consider: Why would
current want to push its way through copper oxide when there is so
much conductive copper a micro-inch beneath it? This is like saying
insulated wire is non conductive because the plastic layer has so much
high resistance that current can't flow.

Copper oxide is only an issue if you are trying to penetrate it for a
contact (like in a switch, or a poor connection - tighten the screw).

73's
Richard Clark, KB7QHC

Another ham in Calgary (VE6WZ, Don't know him) has done some work on high Q
coils (http://www.qsl.net/ve6wz/coil.), and provides a link (now dead) to
W8JI. My calculations seem to show reasonable agreement with the program he
used from K6STI, which does not seem to be available. I would certainly
like to see some independent verification of the results. I am tempted to
build a coil and measure its Q.

Frank


"Art Unwin KB9MZ" wrote in message
m...
Tom W8JI talks about coils on his page and
if my memory is correct he has never measured a Q beyond 300
I use the 200/300 figure for my modelling and use as much as 800/1000
for capacitors. I am not competant enough to do any checking
of your particular program but I suspect your answers are in error
and await guru comments with interest
Art








"Frank" wrote in message
news:w7n1d.147$t61.135@clgrps13...
"Art Unwin KB9MZ" wrote in message
m...
I doubt that the coil will have a Q of more than 300 if that !
Art





"Frank" wrote in message
news:JCe1d.97059$jZ5.12695@clgrps13...
"denton" wrote in message
...
Hi all...
I am starting to work on something to use on 160 thru 20 meters.
I currently have an aluminum mast that is 32 ft long with a small
cap
hat
on
top.
the antenna will sit in the center of an area approx 50 z 50'
(backyard).
I
plan to put down 40 plus radials, the majority which will be
situated
to
radiate out from the base of the vertical.
some will meander along the house foundation and property line..
I plan on also tying in the galvanized (not chain link) fence
around
the
back yard to the radial system, as well as the house plumbing.
40 meters should be direct feed.
I will homebrew a matching L network for use on 160 thru 60
meters.
I will also try a 20 meter tuning stubb.
Does anyone know what the size of the loading coil that MFJ uses
in
their
80
& 40 meter vertical?
I have read of just about everything I can find online of this
sort of
project and have played with Eznec demo a bit and think this will
be a
doable project.

Also the series inductor should have a very high Q for 160 m. A Q
of
1000
will loose about 30% of your power.

Frank

Based on Terman's "Radio Engineers Handbook" dated 1943, pp 31 - 53. I
have
written a program In MathCAD Pro, which indicates a coil made from 1/4"
copper pipe, 12" long, and 3 inches diameter has an inductance of 39 uH
and
a Q of 1132 at 1.8 MHz. (6" in diameter and 24" long shows a nominal Q
of
1600). To be honest I have never built such a coil, and it would
probably
be very difficult to measure. I agree that typical "Airdux" coils have
a Q
in the range of 300 or so.(Silver plating, or gold, would also be
desirable
to prevent lossy copper oxide build up). Anyway if you are interested
I
can send you the MathCAD file. I would be very happy if somebody could
check
my math. It think the point I was trying to make it that electrically
short
antennas have such a low real input impedance that building an efficient
matching network is challenging to say the least. Even if such networks
are
feasible the huge voltages developed at the base could prove to be a
problem.

73,

Frank

This link http://www.w8ji.com/loading_inductors.htm also seems to confirm my
results with estimates for copper tube inductors.

Frank


"Frank" wrote in message
news:_HD1d.25581$XP3.18559@edtnps84...
Another ham in Calgary (VE6WZ, Don't know him) has done some work on high
Q
coils (http://www.qsl.net/ve6wz/coil.), and provides a link (now dead) to
W8JI. My calculations seem to show reasonable agreement with the program
he
used from K6STI, which does not seem to be available. I would certainly
like to see some independent verification of the results. I am tempted to
build a coil and measure its Q.

Frank


"Art Unwin KB9MZ" wrote in message
m...
Tom W8JI talks about coils on his page and
if my memory is correct he has never measured a Q beyond 300
I use the 200/300 figure for my modelling and use as much as 800/1000
for capacitors. I am not competant enough to do any checking
of your particular program but I suspect your answers are in error
and await guru comments with interest
Art








"Frank" wrote in message
news:w7n1d.147$t61.135@clgrps13...
"Art Unwin KB9MZ" wrote in message
m...
I doubt that the coil will have a Q of more than 300 if that !
Art





"Frank" wrote in message
news:JCe1d.97059$jZ5.12695@clgrps13...
"denton" wrote in message
...
Hi all...
I am starting to work on something to use on 160 thru 20 meters.
I currently have an aluminum mast that is 32 ft long with a
small
cap
hat
on
top.
the antenna will sit in the center of an area approx 50 z 50'
(backyard).
I
plan to put down 40 plus radials, the majority which will be
situated
to
radiate out from the base of the vertical.
some will meander along the house foundation and property line..
I plan on also tying in the galvanized (not chain link) fence
around
the
back yard to the radial system, as well as the house plumbing.
40 meters should be direct feed.
I will homebrew a matching L network for use on 160 thru 60
meters.
I will also try a 20 meter tuning stubb.
Does anyone know what the size of the loading coil that MFJ uses
in
their
80
& 40 meter vertical?
I have read of just about everything I can find online of this
sort of
project and have played with Eznec demo a bit and think this
will
be a
doable project.

Also the series inductor should have a very high Q for 160 m. A Q
of
1000
will loose about 30% of your power.

Frank

Based on Terman's "Radio Engineers Handbook" dated 1943, pp 31 - 53.
I
have
written a program In MathCAD Pro, which indicates a coil made from
1/4"
copper pipe, 12" long, and 3 inches diameter has an inductance of 39
uH
and
a Q of 1132 at 1.8 MHz. (6" in diameter and 24" long shows a nominal Q
of
1600). To be honest I have never built such a coil, and it would
probably
be very difficult to measure. I agree that typical "Airdux" coils
have
a Q
in the range of 300 or so.(Silver plating, or gold, would also be
desirable
to prevent lossy copper oxide build up). Anyway if you are
interested
I
can send you the MathCAD file. I would be very happy if somebody could
check
my math. It think the point I was trying to make it that electrically
short
antennas have such a low real input impedance that building an
efficient
matching network is challenging to say the least. Even if such
networks
are
feasible the huge voltages developed at the base could prove to be a
problem.

73,

Frank