I wonder how much difference it would make if I were to
build a loading coil on a piece of 3''x3" wood? It would be
very easy and I could suspend the winding above the wood
form with plastic dowel glued on each corner of the wood.

I could also make a similar coil using PVC pipe. Even in that
case the winding would have a somewhat rectangular form
factor.

It wouldn't be air core considering that it would be over
wood (dry and waterproofed) or PVC pipe.

I do require the structure be relatively strong or I
would wind the coil, put epoxy glue strips along it
to make it like AirDux and the like.

Any comments or suggestions??

Irv VE6BP

On Friday, October 4, 2013 10:48:30 PM UTC-5, Irv Finkleman wrote:
Any comments or suggestions??

http://www.g3ynh.info/zdocs/comps/part_6.html

On Fri, 4 Oct 2013 21:48:30 -0600, "Irv Finkleman"
wrote:

I wonder how much difference it would make if I were to
build a loading coil on a piece of 3''x3" wood?

Difference from what? What are you comparing the wood coil with?

It would be
very easy and I could suspend the winding above the wood
form with plastic dowel glued on each corner of the wood.
I could also make a similar coil using PVC pipe. Even in that
case the winding would have a somewhat rectangular form
factor.

Yep. Both PCV and wood are lossy. Put a piece in your microwave oven
and watch them both get warm. Actually, if the wood has a high
moisture content, it will get quite hot. If exposed, both materials
also have problems with UV resistance. If you must use plastic
tubing, you can possibly find something in polysulfone, polystyrene,
polypropylene, or polycarbonate (in order of preference). If you
can't find these, white ABS schedule 40 sorta works at low power
levels.

High power or low power? If low power, you could probably wind the
loading coal on kiln dried and sealed wood or PVC and it will work. On
the other foot, high power will heat anything that's lossy, including
the coil form.

High Q or low Q? If you need a really high Q loading coil, the
material losses might be a problem.

Hints:
http://www.w8ji.com/loading_inductors.htm
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HiQCoil.htm
Notice the preferred loading coil construction.

This might give you some ideas (good and bad):
https://www.google.com/search?tbm=isch&q=antenna+loading+coil

It wouldn't be air core considering that it would be over
wood (dry and waterproofed) or PVC pipe.

I do require the structure be relatively strong or I
would wind the coil, put epoxy glue strips along it
to make it like AirDux and the like.

Strong, relative to what? Are you supporting a tower on the coil, or
a length of wire? Some clues as to the weight load, and other
stresses (torque, shear, vibration, etc) would be helpful.

Any comments or suggestions??

Nope. You haven't stated what you're trying to accomplish or what you
have to work with.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Hi Jeff, and thanks for your reply.

To begin with I run QRP (5W on a Yaesu ft-817ND).
I have limited workshop space (my desk in a senior's villa), but
lots of my old tools.

I ran into problems in the last senior's residence I lived in and have just
now moved into a new one. All my previous preparations to set up an
antenna have been foiled -- one old busybody saw us stringing a line
out of my window to a nearby tree. Before anything could be done she
had a whole bunch crying to the General Manager that we were (a) killing
trees (b) setting up satellite antennas on the roof (c) going to interfere
with
radios, TVs, heating pads and such. So much attention was drawn to
a simple twenty foot piece of small nearly invisible wire that I decided it
would be easier to move than fight a battle that I had little chance of
winning.

The unit I am in now has a balcony, and I have moved in with the
understanding that I will not have any wires hanging off the balcony
to nearby trees etc., and that anything I do set up will remain within
the confines of the small balcony (roughly 6ft x 10ft. They do not
mind if I have a collapsible whip or somnething similar which could
be taken in (or out ofsight) when I'm not operating -- they don't
want it left sticking out.

I'm considering a homebrew loaded whip, as it would be quick and simple.
Later on I hope to build a magnetic loop. I only run QRP on a Yaesu
FT-817ND. I also have at my disposal an artificial ground tuner, an
MFJ-949E Antenna Tuner, an MFJ-259B Analyzer, a MFJ-1625
Window/Balcony Mount Antenna system, and a MFJ-931 Artificial
Ground. The Windowsill/Balcony tuner also has an Artificial Ground
Tuner in it too.

The loading coil with the MFJ-1625 is pretty flimsy and I might just
consider rewinding the coil with heavier copper (the orginal coil had
a broken turn). All of the aforementioned
equipment I picked up used or broken and fixed
up (a little extra solder in the right places never
hurt MFJ stuff), the 931 had a blown meter, the
FT-817ND had a burned foil on the board due to faulty hookup or
something, and the 949 needed a switch replaced. The 259B I bought new
in the box!


I was comparing a wood coil with an air wound coil.
I should have said ABS rather than PVC, and I am
well aware of dielectric losses although I don't worry
about them too much as even 5W minus the losses will
keep me on the air. I'm not overly concerned about
Q as long as I can get a signal out!

My main concern was with winding a loading coil on
a square form, and I was just wondering how much
effect that would have.

Coincidentally, today was our local Ham Flea Market,
but I am somewhat handicapped and was not up to
going -- normally I would crawl across broken glass
to attend. I might have found something there. I've
undergone three major surgeries since late 2009 and
had to sell my house. I gave all my ham stuff to the
local radio club thinking then that I'd never be able to
ham again -- now I'm starting again! I've had my
ticket for 55 years and it's not easy to stop!!!

After this discussion I think I'll go ABS, and with
the aid of some epoxy may even slip it off the
pipe and go air core supporting the coil off to the
side of the whip mounting. Remember the old
'Gotham Vertical' antennas (1956 Handbook ads)?

All of this is planning ahead -- I'll try the MFJ-1625
setup first, just to get going.

In any event, what do you think of the homebrew
equivalent of AirDux, but square instead of round?

Irv VE6BP




"Jeff Liebermann" wrote in message
...
On Fri, 4 Oct 2013 21:48:30 -0600, "Irv Finkleman"
wrote:

I wonder how much difference it would make if I were to
build a loading coil on a piece of 3''x3" wood?

Difference from what? What are you comparing the wood coil with?

It would be
very easy and I could suspend the winding above the wood
form with plastic dowel glued on each corner of the wood.
I could also make a similar coil using PVC pipe. Even in that
case the winding would have a somewhat rectangular form
factor.

Yep. Both PCV and wood are lossy. Put a piece in your microwave oven
and watch them both get warm. Actually, if the wood has a high
moisture content, it will get quite hot. If exposed, both materials
also have problems with UV resistance. If you must use plastic
tubing, you can possibly find something in polysulfone, polystyrene,
polypropylene, or polycarbonate (in order of preference). If you
can't find these, white ABS schedule 40 sorta works at low power
levels.

High power or low power? If low power, you could probably wind the
loading coal on kiln dried and sealed wood or PVC and it will work. On
the other foot, high power will heat anything that's lossy, including
the coil form.

High Q or low Q? If you need a really high Q loading coil, the
material losses might be a problem.

Hints:
http://www.w8ji.com/loading_inductors.htm
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HiQCoil.htm
Notice the preferred loading coil construction.

This might give you some ideas (good and bad):
https://www.google.com/search?tbm=isch&q=antenna+loading+coil

It wouldn't be air core considering that it would be over
wood (dry and waterproofed) or PVC pipe.

I do require the structure be relatively strong or I
would wind the coil, put epoxy glue strips along it
to make it like AirDux and the like.

Strong, relative to what? Are you supporting a tower on the coil, or
a length of wire? Some clues as to the weight load, and other
stresses (torque, shear, vibration, etc) would be helpful.

Any comments or suggestions??

Nope. You haven't stated what you're trying to accomplish or what you
have to work with.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

While it migh be out of your price range, look into the screwdrver
antennas. Usually for mobile,but I don't see why you could not get it to
work for you .

You do not need a tuner with it as it does its own tuning by a motor. I
have worked lots of mobiles that had them and they seem to put out a good
signal.

"Irv Finkleman" wrote in message
...
Hi Jeff, and thanks for your reply.

To begin with I run QRP (5W on a Yaesu ft-817ND).
I have limited workshop space (my desk in a senior's villa), but
lots of my old tools.

I ran into problems in the last senior's residence I lived in and have
just
now moved into a new one. All my previous preparations to set up an
antenna have been foiled -- one old busybody saw us stringing a line
out of my window to a nearby tree. Before anything could be done she
had a whole bunch crying to the General Manager that we were (a) killing
trees (b) setting up satellite antennas on the roof (c) going to
interfere with
radios, TVs, heating pads and such. So much attention was drawn to
a simple twenty foot piece of small nearly invisible wire that I decided
it
would be easier to move than fight a battle that I had little chance of
winning.

The unit I am in now has a balcony, and I have moved in with the
understanding that I will not have any wires hanging off the balcony
to nearby trees etc., and that anything I do set up will remain within
the confines of the small balcony (roughly 6ft x 10ft. They do not
mind if I have a collapsible whip or somnething similar which could
be taken in (or out ofsight) when I'm not operating -- they don't
want it left sticking out.

Thanks Ealph,

I'd consider a screwdriver but it's not in my blood to buy
something unless (1) I really need it fast, or (2) I can get
a used or broken one cheap and fix it up. Most of the
gear I have I got under those conditions and they have
served me well.

I nust admit that I have looked at them and they are
getting pretty good reviews. If my lottery comes
through I'll reconsider! :-)

"Ralph Mowery" wrote in message
...
While it migh be out of your price range, look into the screwdrver
antennas. Usually for mobile,but I don't see why you could not get it to
work for you .

You do not need a tuner with it as it does its own tuning by a motor. I
have worked lots of mobiles that had them and they seem to put out a good
signal.

"Irv Finkleman" wrote in message
...
Hi Jeff, and thanks for your reply.

To begin with I run QRP (5W on a Yaesu ft-817ND).
I have limited workshop space (my desk in a senior's villa), but
lots of my old tools.

I ran into problems in the last senior's residence I lived in and have
just
now moved into a new one. All my previous preparations to set up an
antenna have been foiled -- one old busybody saw us stringing a line
out of my window to a nearby tree. Before anything could be done she
had a whole bunch crying to the General Manager that we were (a) killing
trees (b) setting up satellite antennas on the roof (c) going to
interfere with
radios, TVs, heating pads and such. So much attention was drawn to
a simple twenty foot piece of small nearly invisible wire that I decided
it
would be easier to move than fight a battle that I had little chance of
winning.

The unit I am in now has a balcony, and I have moved in with the
understanding that I will not have any wires hanging off the balcony
to nearby trees etc., and that anything I do set up will remain within
the confines of the small balcony (roughly 6ft x 10ft. They do not
mind if I have a collapsible whip or somnething similar which could
be taken in (or out ofsight) when I'm not operating -- they don't
want it left sticking out.

"Irv Finkleman" wrote in message
...
Hi Jeff, and thanks for your reply.

To begin with I run QRP (5W on a Yaesu ft-817ND).
I have limited workshop space (my desk in a senior's villa), but
lots of my old tools.

I was comparing a wood coil with an air wound coil.
I should have said ABS rather than PVC, and I am
well aware of dielectric losses although I don't worry
about them too much as even 5W minus the losses will
keep me on the air. I'm not overly concerned about
Q as long as I can get a signal out!

My main concern was with winding a loading coil on
a square form, and I was just wondering how much
effect that would have.


After this discussion I think I'll go ABS, and with
the aid of some epoxy may even slip it off the
pipe and go air core supporting the coil off to the
side of the whip mounting. Remember the old
'Gotham Vertical' antennas (1956 Handbook ads)?

Lots of sutff cut out..

I ran a quick and dirty check for you. I took about 8 turns of about #22
wire and a 100 pf capacitor. Wound the wire around a piece of 1/2 inch PVC
pipe that is about 7/8 inch outside diameter. I made a parallel circuit of
the two. Put it on a HP 8924c set as a spectrum generator and tracking
generator.

It resonated about 13.08 mhz and had a relative loss of -46.46 db. Took it
off the form and resonated about 13.14 with a loss of -47.0 db back on the
pvc and it went back to the first number.
I did not have a piece of wood that would exectally fit it,but one that was
close. Resonated at 13.05 mhz and loss of -46.94.

All in all, I doubt there would be enough loss or change to make any
differance. The small loss and frequency change could just be the spreading
of the coil slightly and the loss could be how close the leads are to each
other.

For running the 5 watts like you are, I don't see any problems with
changing the forms on the low bands. I doubt that even at 100 watts it
would have any noticable effect.

On 10/5/2013 4:14 PM, Ralph Mowery wrote:
"Irv Finkleman" wrote in message
...
Hi Jeff, and thanks for your reply.

To begin with I run QRP (5W on a Yaesu ft-817ND).
I have limited workshop space (my desk in a senior's villa), but
lots of my old tools.

I was comparing a wood coil with an air wound coil.
I should have said ABS rather than PVC, and I am
well aware of dielectric losses although I don't worry
about them too much as even 5W minus the losses will
keep me on the air. I'm not overly concerned about
Q as long as I can get a signal out!

My main concern was with winding a loading coil on
a square form, and I was just wondering how much
effect that would have.


After this discussion I think I'll go ABS, and with
the aid of some epoxy may even slip it off the
pipe and go air core supporting the coil off to the
side of the whip mounting. Remember the old
'Gotham Vertical' antennas (1956 Handbook ads)?

Lots of sutff cut out..

I ran a quick and dirty check for you. I took about 8 turns of about #22
wire and a 100 pf capacitor. Wound the wire around a piece of 1/2 inch PVC
pipe that is about 7/8 inch outside diameter. I made a parallel circuit of
the two. Put it on a HP 8924c set as a spectrum generator and tracking
generator.

It resonated about 13.08 mhz and had a relative loss of -46.46 db. Took it
off the form and resonated about 13.14 with a loss of -47.0 db back on the
pvc and it went back to the first number.
I did not have a piece of wood that would exectally fit it,but one that was
close. Resonated at 13.05 mhz and loss of -46.94.

All in all, I doubt there would be enough loss or change to make any
differance. The small loss and frequency change could just be the spreading
of the coil slightly and the loss could be how close the leads are to each
other.

For running the 5 watts like you are, I don't see any problems with
changing the forms on the low bands. I doubt that even at 100 watts it
would have any noticable effect.

Excellent work, Ralph. This is very useful information. Many thanks!

73,
John

On Sat, 5 Oct 2013 13:27:43 -0600, "Irv Finkleman"
wrote:

To begin with I run QRP (5W on a Yaesu ft-817ND).

In that case, almost any coil form will work. There's little danger
from losses causing the plastic to melt. However, I'm not so thrilled
with the idea of using wood. The wood is not the problem. It's the
water in the wood. You can seal it with the traditional bees wax, but
that tends to become a sticky mess.

I'm considering a homebrew loaded whip, as it would be quick and simple.

Nothing is both quick and simple. The simple things take forever to
get right and the quick things that are thrown together never seem to
work.

Later on I hope to build a magnetic loop.

That's the best idea yet. They're very narrow band, kinda
temperamental, require plenty of expensive copper, good soldering,
giant air dielectric or vacuum capacitors, but work better than
anything their size.

However, if you must waste your time with a base loaded whip, your
first problem will be finding a suitable ground. That's a problem you
don't have with a dipole or loop. I guess some welded wire mesh on
the balcony will barely suffice. Next, you need a base insulator. I
recommend an empty thick glass wine bottle. Wrap some stiff insulated
wire around the bottle as a loading coil. Use your MFJ259 to tune to
the right band. Make an assortment of wine bottle loading coils, one
for each band.

I only run QRP on a Yaesu
FT-817ND. I also have at my disposal an artificial ground tuner, an
MFJ-949E Antenna Tuner, an MFJ-259B Analyzer, a MFJ-1625
Window/Balcony Mount Antenna system, and a MFJ-931 Artificial
Ground. The Windowsill/Balcony tuner also has an Artificial Ground
Tuner in it too.

Tuners are fun to play with but are often lossy. If you get the
loading coil close to 50 ohms at the operating frequency, you can live
without the tuner. At worst, use the tuner for minor VSWR adjustments
when you change frequency, and don't want to play with the loading
coil.

The 259B I bought new
in the box!

For when you blow it up:
http://802.11junk.com/jeffl/MFJ-269-repair/
That's for an MFJ269, which is similar.

I'm not overly concerned about
Q as long as I can get a signal out!

Besides bandwidth, Q is also way to express losses. Basically, it's a
measure of either the series resistance or parallel resistance of an
ideal inductor.

For parallel:
Rp = Xl * Q
Rp = 2 * Pi * freq * L * Q

For Series:
Rs = Xc / Q
Rs = 1 / (2 * Pi * freq * Q)
(Note that Rs is also known as the capacitor ESR).

A high Q coil has a large resistor across it with minimal effects,
while a low Q coil will have a much smaller resistor across it. Since
pure reactances do NOT dissipate any power, all the power loss in the
coil is dissipated in this equivalent resistance. There's also the DC
resistance of the coil in series but that's not part of the current
discussion.

My main concern was with winding a loading coil on
a square form, and I was just wondering how much
effect that would have.

Obviously, it produces square waves.

The shape of the form will have almost no effect on the inductance, Q,
or radiation characteristics of the antenna. If you look carefully at
the cross section of a torroid core, you'll find that it's wound in a
square pattern.

I've
undergone three major surgeries since late 2009 and
had to sell my house.

Ouch. Get better please.

I gave all my ham stuff to the
local radio club thinking then that I'd never be able to
ham again -- now I'm starting again! I've had my
ticket for 55 years and it's not easy to stop!!!

No sympathy. I've moved about 4 times. Each time, I purged my ham
radio, magazine, auto parts, and junk collections in the anticipation
of never needing them again. Each time, I quickly rebuilt the mess. I
don't plan to move, but the mess has once again reached the safe
occupancy level and needs to be purged. Sigh...

After this discussion I think I'll go ABS, and with
the aid of some epoxy may even slip it off the
pipe and go air core supporting the coil off to the
side of the whip mounting. Remember the old
'Gotham Vertical' antennas (1956 Handbook ads)?

Ok. Just use the white ABS pipe, not the black ABS irrigation pipe.

In any event, what do you think of the homebrew
equivalent of AirDux, but square instead of round?

No problem. It should work the same as the round flavor.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sat, 5 Oct 2013 13:27:43 -0600, "Irv Finkleman" wrote:

... and a MFJ-931 Artificial
Ground. The Windowsill/Balcony tuner also has an Artificial Ground
Tuner in it too.

The loading coil with the MFJ-1625 is pretty flimsy and I might just
consider rewinding the coil with heavier copper (the orginal coil had
a broken turn). All of the aforementioned
equipment I picked up used or broken and fixed
up (a little extra solder in the right places never
hurt MFJ stuff), the 931 had a blown meter, ...

Know what you mean. I bought an MFJ 931 a couple of months ago, and only
recently hooked it up to find it does nothing at all. No changes in noise level,
not a dickey birds worth of movement from the meter with the power cranked up to
100 watts - nothing. So, it looks like I am about to do what you commented on
that a little extra solder in the right places never hurt MFJ stuff!

Couldn't resist commenting after seeing your post.

73, Bob KB2ZGN