Stub J-pole for six meters
 

Can anyone direct me to the dimensions to build a six meter J-pole
that is patterned after the Arrow Antenna two meter design that had
the feed point at the bottom of one of the elements rather than at a
point part way up the height of the matching stub.

The reason that I would like to use that design is that I would like
to use Rigid Aluminum Conduit to build the antenna. There not being a
lot of simple inexpensive fittings for Conduit the way there is for
copper pipe a mechanically simpler design would be easier to build.

Replies are welcome on or off list. Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design. That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

--
Tom Horne, W3TDH

Stub J-pole for six meters
 

Tom Horne wrote in news:8b22e1d5-907a-4ee6-ab40-
:

....
Replies are welcome on or off list. Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design. That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

It is a sad statement of the state of affairs when you feel a need to
compose a help request with such conditions, 40% of your post is setting
conditions on your would be helpers responses.

This is not unusualy, the posts can often can be paraphrased as "I have
got this really good idea, and I don't want to hear from anyone that it
is less than a really good idea... over".

Your 40% conditions is by no means a record, higher percentages have
been observed on QRZ and eHam, such high percentage as to make the whole
thing look like a troll rather than a genuine request for help.

My own view is that it helps to be a little humble when seeking help.

Owen

Stub J-pole for six meters
 

On Sat, 26 Nov 2011 14:22:52 -0800 (PST), Tom Horne
wrote:

Can anyone direct me to the dimensions to build a six meter J-pole
that is patterned after the Arrow Antenna two meter design that had
the feed point at the bottom of one of the elements rather than at a
point part way up the height of the matching stub.

The 144/440 antenna can be found at:
http://www.arrowantennas.com/inst/OSJ146440.pdf
with dimensions included. You probably won't need the short element
in the middle which seems to do something for 440Mhz operation.

Two ways to do this:
1. Plug the dimensions (in wavelengths) into an EZNec or 4NEC2
antenna model, and scale it for 52MHz.
2. Scale the antenna dimensions linearly from 146 to 52MHz and
optimize with cut-n-try. The driven element is 1/4 wavelength long,
and the parasitic element is 3/4 wavelength long.

The reason that I would like to use that design is that I would like
to use Rigid Aluminum Conduit to build the antenna. There not being a
lot of simple inexpensive fittings for Conduit the way there is for
copper pipe a mechanically simpler design would be easier to build.

Maybe, but the 3/4 wavelength element is going to end up about 15ft
long, which is rather long for tubing without a top support. The
"rigid" aluminum conduit is made to be bent to shape. I suspect this
15ft long tube might deform in the wind.

Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design.

Ok. I'll just ignore my experience with J-poles and pretend that
they're suitable for your unstated purpose.

That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

Approach for what application and mounting? If you want an antenna
with a rather high takeoff angle, an end fed antenna, such as the
J-pole will send most of your RF towards the birds instead of the
horizon. If you want an antenna with a radiating coax cable (by
lacking a balun), the J-pole is quite appropriate. If you want an
antenna that produces impressive cloverleaf horizontal gain patterns
when side mounted on a tower, the J-pole is the hot ticket. The
J-pole does have one big advantage. It was originally called a Zepp
antenna, after the Zepplin airship, where the antenna was suspended
downward. Because the low voltage point is at the base of the
antenna, there would be no sparks to ignite the hydrogen gas. However,
if you don't plan on flying your j-pole on a Zepplin, this advantage
might not be very useful.
http://en.wikipedia.org/wiki/J-pole_antenna (first paragraph)

Please feel free to offer undying praise and monetary renumeration for
the advice. I'm always open to being paid. There are probably better
designs but since you've already decided on a J-pole, it's probably
futile to suggest alternatives. Besides, it might precipitate a
debate or arguement. Oddly, I learn more from such debates and
arguments, than from pontifications.

5/8 wave 6m ground plane:
http://802.11junk.com/jeffl/antennas/gnd-plane-02/index.html
5/8 + 5/8 wave 6m ground plane:
http://802.11junk.com/jeffl/antennas/gnd-plane-05/index.html

I would normally offer to build you a NEC2 model of your proposed
antenna, but since I don't know what diameter aluminum tubing you have
in mind, and since it's 1:30AM, I'll pass for tonite.


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

Stub J-pole for six meters
 

"Tom Horne" wrote in message
...
Can anyone direct me to the dimensions to build a six meter J-pole
that is patterned after the Arrow Antenna two meter design that had
the feed point at the bottom of one of the elements rather than at a
point part way up the height of the matching stub.

The reason that I would like to use that design is that I would like
to use Rigid Aluminum Conduit to build the antenna. There not being a
lot of simple inexpensive fittings for Conduit the way there is for
copper pipe a mechanically simpler design would be easier to build.

Replies are welcome on or off list. Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design. That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

--
Tom Horne, W3TDH

Certainly not a rant but a question about the question:

Is your reason for this approach mainly your access to beaucoup aluminum
conduit? I ask because I'm a j-pole fan and I've built dozens of them,
including three for 6m using copper pipe and one 6m from window line. The
feed is less than 7 inches from the bottom of the active portion of the 6m
version.

Using your conduit, you might employ the "standard" j-pole design and bolt
the segments together, placing wooden dowels inside your conduit ends to
resist crushing forces. Am I striking a chord, yet?

A brace near the top of the stub section would likely be required to prevent
rotation where the bottom of the "j" attaches to the main section. You
might be well-served to wrap the bottom of the "j" with a tight spiral of
mesh sleeve (like the braid-only of some unneeded coax) and clamp the ends.
This would help mitigate the electrical consequences of a bad joint or two.
Alternatively, bridge (jumper) the individual joints.

But see http://www.wagnercompanies.com/cast_aluminum.aspx , where a single
3/4 - inch tee or elbow is about $7.00. Do-able?

Note, my 6m copper j-poles are all 3/4 - inch material except the top three
feet of of the long section. I tried using all 1/2 - inch copper once but
that build was so wobbly that I immediately took it apart. (It's about 13
feet tall.)

Some of my j-poles have benefitted from having a capacitor from the feed
connector center pin over to the the long side, in lieu of a straight piece
of wire. I use one whenever the VSWR is mid-band but above 1:1. No science
to it; I just tried a few around 100pF and SHAZAM! I was inspired by the
capacitive feed in a gamma match.

Happy brewing.

"Sal"
(KD6VKW)

Stub J-pole for six meters
 

On Sat, 26 Nov 2011 14:22:52 -0800 (PST), Tom Horne wrote:

Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design. That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

Are you so clueless that you don't see the above as throwing down the gauntlet
to every prospective troll within 50 groups of here?

Good luck.

Stub J-pole for six meters
 

On Nov 27, 7:07*pm, Andiour wrote:
On Sat, 26 Nov 2011 14:22:52 -0800 (PST), Tom Horne wrote:
Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design. *That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

Are you so clueless that you don't see the above as throwing down the gauntlet
to every prospective troll within 50 groups of here?

Good luck.

OK I'm clueless because I asked to be spared tirades and rants. Than
I guess I'm clueless but not so rude as you.
--
Tom Horne, W3TDH

Stub J-pole for six meters
 

On Nov 27, 2:53*am, Owen Duffy wrote:
Tom Horne wrote in news:8b22e1d5-907a-4ee6-ab40-
:

...

Replies are welcome on or off list. *Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design. *That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

It is a sad statement of the state of affairs when you feel a need to
compose a help request with such conditions, 40% of your post is setting
conditions on your would be helpers responses.

This is not unusualy, the posts can often can be paraphrased as "I have
got this really good idea, and I don't want to hear from anyone that it
is less than a really good idea... over".

Your 40% conditions is by no means a record, higher percentages have
been observed on QRZ and eHam, such high percentage as to make the whole
thing look like a troll rather than a genuine request for help.

My own view is that it helps to be a little humble when seeking help.

Owen

Owen

I apologize for coming across as arrogant. I didn't mean to.

Perhaps it would help to know that I was looking at the J-pole as a
transportable antenna that would be used when the operating position
is down in between buildings, ridges, mountains, etc. I did look at
the online patterns for a J-pole. When I used a diamond ground plane
under those conditions the results were less than satisfactory. The
intent is to get the signals up out of the hole. The aluminum conduit
was because it is much lighter than copper pipe and far less expensive
at present pricing. I may want to replicate the antenna several times
if it happens to overcome the problem for the purpose of reliable
communications outside of simplex two meter range without limiting the
operator pool to general and above licensees. Also there are several
places were we could use six meter APRS to collect data from, for just
example, a temporary stream gauge by installing the gauge in the time
between a flash flood watch and any subsequent flash flood warning.
Obviously the temporary gauging point may well contribute to the
decision as to whether and when to issue the warning. I was thinking
to use rigid aluminum conduit because of the availability of both
compression and threaded couplings. I intended to test which coupling
technique would stand the most bending force on the upper portion of
the antenna. I already guessed that the antenna might need to be
guyed but I wanted to try whether using a one inch or even one and a
quarter inch nominal size would avoid the need for that. Since the
Arrow Antenna design is fed at the bottom of the shorter matching stub
I thought it might be easier to transport and deploy without damaging
it. As for keeping the stub in line with the radiator I had
envisioned a short piece of 5/8" fiberglass U channel with two
stainless steel pipe clamps as being robust enough to withstand
repeated handling. The three quarter wavelength portion of the
antenna would be fashioned into three nearly equal sized sections for
ease of transport.

I have constructed a dual half wave collinear J-pole using copper
pipe. It had given me much better empirical performance than the
borrowed ground plane that I had used before it. If I could get the
needed range out of the simple J-pole I was next going to work on the
physical challenge of building another collinear dual half wave for
six meters were the second have wave could be added readily for use
when the antenna would not be located below local horizon.
--
Tom Horne, W3TDH

Stub J-pole for six meters
 

"Tom Horne" wrote in message
...
Can anyone direct me to the dimensions to build a six meter J-pole
that is patterned after the Arrow Antenna two meter design that had
the feed point at the bottom of one of the elements rather than at a
point part way up the height of the matching stub.

The reason that I would like to use that design is that I would like
to use Rigid Aluminum Conduit to build the antenna. There not being a
lot of simple inexpensive fittings for Conduit the way there is for
copper pipe a mechanically simpler design would be easier to build.

Replies are welcome on or off list. Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design. That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

--
Tom Horne, W3TDH

If you have not found anything by now, you may go here for a 2 meter
version. Then divide the 150 mhz frequency by the 50 mhz frequency and get
a number near 3. Then multiply ALL the dimensions by that number. That is
the lengths, diameter of the elements and spacing.
http://www.w4cll.com/ijpole.html

Stub J-pole for six meters
 

On Nov 27, 4:44*am, Jeff Liebermann wrote:
On Sat, 26 Nov 2011 14:22:52 -0800 (PST), Tom Horne

wrote:
Can anyone direct me to the dimensions to build a six meter J-pole
that is patterned after the Arrow Antenna two meter design that had
the feed point at the bottom of one of the elements rather than at a
point part way up the height of the matching stub.

The 144/440 antenna can be found at:
http://www.arrowantennas.com/inst/OSJ146440.pdf
with dimensions included. *You probably won't need the short element
in the middle which seems to do something for 440Mhz operation.

Two ways to do this:
1. *Plug the dimensions (in wavelengths) into an EZNec or 4NEC2
antenna model, and scale it for 52MHz.
2. *Scale the antenna dimensions linearly from 146 to 52MHz and
optimize with cut-n-try. *The driven element is 1/4 wavelength long,
and the parasitic element is 3/4 wavelength long.

The reason that I would like to use that design is that I would like
to use Rigid Aluminum Conduit to build the antenna. *There not being a
lot of simple inexpensive fittings for Conduit the way there is for
copper pipe a mechanically simpler design would be easier to build.

Maybe, but the 3/4 wavelength element is going to end up about 15ft
long, which is rather long for tubing without a top support. *The
"rigid" aluminum conduit is made to be bent to shape. *I suspect this
15ft long tube might deform in the wind.

Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design.

Ok. *I'll just ignore my experience with J-poles and pretend that
they're suitable for your unstated purpose.

That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

Approach for what application and mounting? *If you want an antenna
with a rather high takeoff angle, an end fed antenna, such as the
J-pole will send most of your RF towards the birds instead of the
horizon. *If you want an antenna with a radiating coax cable (by
lacking a balun), the J-pole is quite appropriate. *If you want an
antenna that produces impressive cloverleaf horizontal gain patterns
when side mounted on a tower, the J-pole is the hot ticket. *The
J-pole does have one big advantage. *It was originally called a Zepp
antenna, after the Zepplin airship, where the antenna was suspended
downward. *Because the low voltage point is at the base of the
antenna, there would be no sparks to ignite the hydrogen gas. However,
if you don't plan on flying your j-pole on a Zepplin, this advantage
might not be very useful.
http://en.wikipedia.org/wiki/J-pole_antenna (first paragraph)

Please feel free to offer undying praise and monetary renumeration for
the advice. *I'm always open to being paid. *There are probably better
designs but since you've already decided on a J-pole, it's probably
futile to suggest alternatives. *Besides, it might precipitate a
debate or arguement. *Oddly, I learn more from such debates and
arguments, than from pontifications.

5/8 wave 6m ground plane:
http://802.11junk.com/jeffl/antennas/gnd-plane-02/index.html
5/8 + 5/8 wave 6m ground plane:
http://802.11junk.com/jeffl/antennas/gnd-plane-05/index.html

I would normally offer to build you a NEC2 model of your proposed
antenna, but since I don't know what diameter aluminum tubing you have
in mind, and since it's 1:30AM, I'll pass for tonite.

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

All hands

Let me start over. I want a transportable, six meter, vertically
polarized antenna. The parts have to be readily assembled &
disassembled. I would like it to have a somewhat higher than normally
attempted radiation pattern for use between buildings, hills,
ridges... [I had thought that a J-pole might be a good compromise
instead of antennas with a more horizontal gain pattern.] It would be
really golden if the adding of additional parts would change the
pattern back towards the horizontal to use the antenna when it is
located above local horizon. Parts should be short enough to fit in
the foot well of the back seat of an ordinary sedan. It's a stretch
but If it did not need guying that would contribute to ease of
deployment especially in an urban operating location were the
anchoring possibilities for guy lines may be limited. [I'm trying to
devise an X frame tripod. It would be made out of fiberglass
structural channel in order to lower the weight of the tripod assembly
but that is not an antenna design problem.] I may need the antenna to
be elevated when operating near pedestrian traffic to reduce the risk
of RF contact or excessive exposure. Shielding the feed point from
physical damage; such as by having it inside a piece of Box channel
would be quite desirable. I'll leave it there and see what folks can
think of that might work.

--
Tom Horne, W3TDH

Stub J-pole for six meters
 

On 11/28/2011 10:40 AM, Ralph Mowery wrote:
"Tom wrote in message
...
Can anyone direct me to the dimensions to build a six meter J-pole
that is patterned after the Arrow Antenna two meter design that had
the feed point at the bottom of one of the elements rather than at a
point part way up the height of the matching stub.

The reason that I would like to use that design is that I would like
to use Rigid Aluminum Conduit to build the antenna. There not being a
lot of simple inexpensive fittings for Conduit the way there is for
copper pipe a mechanically simpler design would be easier to build.

Replies are welcome on or off list. Let me say that I would rather
not be subjected to any tirades about the inferiority of the J-pole
approach or the superiority of some other antenna design. That does
not mean that I am not open to suggestions for a better approach as
long as it is civilly stated and I am spared the application of Rant
Mode.

--
Tom Horne, W3TDH

If you have not found anything by now, you may go here for a 2 meter
version. Then divide the 150 mhz frequency by the 50 mhz frequency and get
a number near 3. Then multiply ALL the dimensions by that number. That is
the lengths, diameter of the elements and spacing.
http://www.w4cll.com/ijpole.html


Tom,
how concerned are you about the "match"? What length of coax are you
feeding it with? Do you care if the coax radiates? What bandwidth do
you need? (fat elements have broader bandwidth, for instance). How
rugged does it need to be?

You're looking at something with an overall length around 3 meters/10 feet?


If the j-pole is being done so you have a mechanical support, there are
other ways to approach the problem. I assume you want something that is
"feedline comes out at the bottom", so why not something like a dipole
with the feedline going up inside the bottom half of the dipole? You'd
need something mechanically strong enough to hold the two pieces of
aluminum together that's an insulator. Hose clamps would work to both
make the wiring connection and hold the tubing to the insulator. (I'd
look at a piece of fiberglass or plastic rod of appropriate diameter.)
Since you want to use conduit kinds of things, what about using standard
plastic electrical things. Perhaps a plastic conduit outlet body?
(Cantex PVC conduit body, type C, 1/2" hub, Grainger part #4FYP5, about $5)

Just screw the threaded end of the conduit into the body and you're
done. (If you get the stuff with a removable coupling, especially easy..
10ft stick, saw it in half, and you're almost done)


Do you have test equipment for tuning? Or are you looking for a
cookbook design that you can just build and know it will work as long as
the dimensions match the recipe?