I built a so called "Super J-pole" which is really two stacked
collinear half
wave antennas with a quarter wave phasing stub between them. The
design is by
N7QVC and it can be seen at http://www.n7qvc.com/amateur_radio/
copper.html. I
also placed a photograph of a representative build in the photo
section of this
reflector at
http://groups.yahoo.com/group/amateu...um/1449680574/
pic/3362107\
0/view?picmode=&mode=tn&order=ordinal&start=1&count= 20&dir=asc.

I have had good results with this antenna but I wanted to make it into
a dual
band antenna that would work on seventy centimeters as well as on two
meters. I
was wondering if I could use a technique developed by Edison Fong,
WB6IQN on
this antenna in the same way he used it on an ordinary single half
wave J-pole.
What he did is to place an open quarter wave stub at the top of the
two half
wave lengths for seventy centimeters. That stub limits the UHF signal
to the
two half waves length at UHF of the antenna. It seems like it would
work from
having read his paper on the combination two meter and seventy
centimeter J-pole
antenna. That would give the antenna the same gain on seventy
centimeters as a
J-pole that is just for that band. For reference I have placed WB6IQNs
paper in
the files section of the newsgroup at
http://f1.grp.yahoofs.com/v1/
kL6QTZLk1DQjM_Cn3vuvnsLUIuEsvRHSqUZyX2mw294a7mYKkc \
FBIXXlRY_6QxreqNWVpn0b7Dogiw9LafU63W429yoO/DBJ2_port_art.pdf.

My first question is does anyone see any reason why this would not
work?

My second question is how would I construct the stub into a copper J-
pole.
Since WB6IQNs J-pole is a wire antenna, with or without a plastic
radome, he
used a piece of Coaxial cable as part of his two meter wire with the
shield at
the end of the seventy centimeter portion of the antenna shorted to
the two
meter radiator and the bottom of the shield, which is a quarter wave
at UHF
below the top of the UHF segment, open relative to the two meter
radiator.
Could I just use a full quarter wave stub made from a copper T, a
street L, and
a short length of copper pipe turned back down along the two meter
radiator? (A
street L is a ninety degree bend formed to allow it to be close
coupled to an
adjacent fitting without a pipe nipple in between.)

My third question is if instead of shortening the lower VHF half wave
electrically to a UHF length I found a way to short out the quarter
wave phasing
stub between the two VHF half wave radiators to UHF signals thus
giving UHF
signals three full wave lengths of radiator to use would the gain be
worth the
effort. To provide the shunting of the VHF quarter wave phasing stub I
was
GUESSING that a half wave UHF coupling stub might work.

I freely admit to being out of my depth; or as a mariner might say off
my
soundings; here. So I'm fully prepared to hear that the UHF half wave
coupling
stub would not work as a shunt for the UHF signals to get past the VHF
quarter
wave phasing stub. I have no pretense to any expertise. I'm trying to
learn.
Laugh all you want but if it won't work please tell me in neophyte
decipherable
language why not. If you have any guidance to offer it would be most
welcome
but please keep the fog index down to the degree you are able. Thank
you in
advance.

--
Tom Horne, W3TDH

On Mon, 28 Mar 2011 11:29:25 -0700 (PDT), Tom Horne
wrote:

please keep the fog index down to the degree you are able

Hi Tom,

After looking at the mile long URL to one of your offerings - I would
like to see the fog lift too.

Why don't you simply tell us what performance you want to achieve from
an antenna?

A simple quarterwave antenna built on a SO-239 connector with four
drooping radials is squat simple, cheap, and can be built and trimmed
to near perfect match in half an hour or less. You want multiband?
Make two vertical, slightly skewed elements (each cut for the suited
band) joined at the feedpoint. You want more gain? How much more?
Build two or (n-times) more and spend your effort in learning to
construct feedline systems to additively join them.

73's
Richard Clark, KB7QHC

On Mar 30, 2:09*am, Richard Clark wrote:
On Mon, 28 Mar 2011 11:29:25 -0700 (PDT), Tom Horne

wrote:
please keep the fog index down to the degree you are able

Hi Tom,

After looking at the mile long URL to one of your offerings - I would
like to see the fog lift too.

Why don't you simply tell us what performance you want to achieve from
an antenna?

A simple quarterwave antenna built on a SO-239 connector with four
drooping radials is squat simple, cheap, and can be built and trimmed
to near perfect match in half an hour or less. *You want multiband?
Make two vertical, slightly skewed elements (each cut for the suited
band) joined at the feedpoint. *You want more gain? *How much more?
Build two or (n-times) more and spend your effort in learning to
construct feedline systems to additively join them.

73's
Richard Clark, KB7QHC

Richard
I wanted to explore whether it is practical to have my collinear dual
half wave J-pole serve as a dual band antenna. If it were practical I
would want the same gain on seventy centimeters that I have been
getting out of the dual stacked half wave on two meters. The
available testing that I was able to find says that it is 6 DB over a
quarter wave vertical. What I would happily settle for would be for
it to have the same gain on seventy centimeters as the dual band
simple J-pole I am using now. After talking to Rol Anders, K3RA; who
was the instructor for my Extra theory class and is the present
chairman of the Question Pool Committee of the National Council of
Volunteer Examiner Coordinators (NCVEC); last night I am taking that
later approach. That is the approach that I outlined in the first
paragraph of just putting an open blocking stub for UHF at thirty five
centimeters ~ up the lower two meter half wave and therefore below the
two meter phasing stub between the two meter half wave segments. That
has the virtue of being simple and still giving me a dual band antenna
that has better gain on UHF then the unmodified two meter antenna
would.

I wanted a dual band antenna because I only have three suitable
mounting points on my home and I already have plans for a six meter J-
pole and an anemometer / sensor array assembly on the other two. I
have an Arrow dual band J-pole up on that mounting point right now but
I wanted to return to the higher gain of the collinear dual half wave
J-pole that gave me so much better real world performance on two
meters. It is my hope that just adding the seventy centimeter band
blocking stub to the collinear antenna's lower two meter half wave
segment will do the trick.

--
Tom Horne, W3TDH

On Wed, 30 Mar 2011 10:23:51 -0700 (PDT), Tom Horne
wrote:

Richard
I wanted to explore whether it is practical to have my collinear dual
half wave J-pole serve as a dual band antenna. If it were practical I
would want the same gain on seventy centimeters that I have been
getting out of the dual stacked half wave on two meters.

Which would be quite horrible.

The
available testing that I was able to find says that it is 6 DB over a
quarter wave vertical. What I would happily settle for would be for
it to have the same gain on seventy centimeters as the dual band
simple J-pole I am using now.

Hi Tom,

It is extremely hard to accept claims for J-Poles when nothing is said
about the care in choking the feed point, and further choking the
section of line a quarter wave away from the feed point.

Typically this discussion is arrived at with some surprise on the part
of the J-Pole user who posts here (I know you have participated here
before, and are thus not a newbie). Some (which means too many)
respond that choking is unnecessary. They are satisfied with its
performance (never daring to examine that it could be vastly
improved).

We also have writers here who condemn the J-Pole vehemently in equal
measure. They, too, have not examined the necessity of choking and
they suffer from the knowledge that things could be vastly improved.

This is the pitiable lament of feeding halfwave elements in any form.

Let's examine what you call "available testing." I presume this means
in software, and not in the lab (never mind alternatives such as out
in a field). I could be wrong and you may correct this on your
response.

However, moving on with whatever presumption, the reason why choking
is important is that with High Z antennas, they tend to drive the
transmission line into radiation. This extends the length of the
radiator, and too often this raises the lobe of maximum radiation up
into the sky (you are very near that with the half wave where 5/8ths
is considered the limit of physical height before this trips over).

These are all issues related to a vertical, and its elevation goes
into the mix too to further confuse comparisons.

Now, basically you are asking the same antenna to operate at roughly
triple the frequency. This also means either element of the native
radiator will stand like something under 3/2 wavelengths tall - truly
a cloud burner (not good).

You speak of stubs to fix this. You would have to start with two 3/2
halfwave radiators, one over the other. Fixing the phase for both 2M
and 440 would be a miracle in achievement. I presume you would also
trap the individual 3/2 wave length sections into two 5/8ths (but the
ratios don't quite work out that way); or three half waves; or six
quarter waves - and then do it again for the section above. Whew!

This is a monumental task - but you have simpler goals as the
following would suggest:

just putting an open blocking stub for UHF at thirty five
centimeters ~ up the lower two meter half wave and therefore below the
two meter phasing stub between the two meter half wave segments. That
has the virtue of being simple and still giving me a dual band antenna
that has better gain on UHF then the unmodified two meter antenna
would.

The blocking stub I presume you to mean a trap for 440. It is going
to upset the matching stub between the two halfwave 2M elements. Here
you will have to juggle between tuning them both on each band.

It is less than monumental, but still quite a job, and one that
demands that you cut and try and fully erecting your last attempt to
see how it works (doing this on the ground is going to lead to grief -
especially if you ignore proper choking).

73's
Richard Clark, KB7QHC

On 3/30/2011 12:23 PM, Tom Horne wrote:

Richard
I wanted to explore whether it is practical to have my collinear dual
half wave J-pole serve as a dual band antenna. If it were practical I
would want the same gain on seventy centimeters that I have been
getting out of the dual stacked half wave on two meters. The
available testing that I was able to find says that it is 6 DB over a
quarter wave vertical. What I would happily settle for would be for
it to have the same gain on seventy centimeters as the dual band
simple J-pole I am using now. After talking to Rol Anders, K3RA; who
was the instructor for my Extra theory class and is the present
chairman of the Question Pool Committee of the National Council of
Volunteer Examiner Coordinators (NCVEC); last night I am taking that
later approach. That is the approach that I outlined in the first
paragraph of just putting an open blocking stub for UHF at thirty five
centimeters ~ up the lower two meter half wave and therefore below the
two meter phasing stub between the two meter half wave segments. That
has the virtue of being simple and still giving me a dual band antenna
that has better gain on UHF then the unmodified two meter antenna
would.

I wanted a dual band antenna because I only have three suitable
mounting points on my home and I already have plans for a six meter J-
pole and an anemometer / sensor array assembly on the other two. I
have an Arrow dual band J-pole up on that mounting point right now but
I wanted to return to the higher gain of the collinear dual half wave
J-pole that gave me so much better real world performance on two
meters. It is my hope that just adding the seventy centimeter band
blocking stub to the collinear antenna's lower two meter half wave
segment will do the trick.

--
Tom Horne, W3TDH

http://www.arrowantenna.info/osj/j-pole.html

This design works moderately well. Drive the 19.25 inch element. The
51 inch element is the radiator on 2m, the 6.xx inch element makes the
19.25 inch one radiate on 440. The thing isn't great on 440 because the
51 inch portion is there. It is rugged though.

I built a duplicate, which you can do if you look at all the parts pages
on the site. The main problem, same as all J poles, is common mode
current issues on the feedline.

tom
K0TAR

On 3/31/2011 6:43 PM, tom wrote:
On 3/30/2011 12:23 PM, Tom Horne wrote:

Richard
I wanted to explore whether it is practical to have my collinear dual
half wave J-pole serve as a dual band antenna. If it were practical I
would want the same gain on seventy centimeters that I have been
getting out of the dual stacked half wave on two meters. The
available testing that I was able to find says that it is 6 DB over a
quarter wave vertical. What I would happily settle for would be for
it to have the same gain on seventy centimeters as the dual band
simple J-pole I am using now. After talking to Rol Anders, K3RA; who
was the instructor for my Extra theory class and is the present
chairman of the Question Pool Committee of the National Council of
Volunteer Examiner Coordinators (NCVEC); last night I am taking that
later approach. That is the approach that I outlined in the first
paragraph of just putting an open blocking stub for UHF at thirty five
centimeters ~ up the lower two meter half wave and therefore below the
two meter phasing stub between the two meter half wave segments. That
has the virtue of being simple and still giving me a dual band antenna
that has better gain on UHF then the unmodified two meter antenna
would.

I wanted a dual band antenna because I only have three suitable
mounting points on my home and I already have plans for a six meter J-
pole and an anemometer / sensor array assembly on the other two. I
have an Arrow dual band J-pole up on that mounting point right now but
I wanted to return to the higher gain of the collinear dual half wave
J-pole that gave me so much better real world performance on two
meters. It is my hope that just adding the seventy centimeter band
blocking stub to the collinear antenna's lower two meter half wave
segment will do the trick.

--
Tom Horne, W3TDH

http://www.arrowantenna.info/osj/j-pole.html

This design works moderately well. Drive the 19.25 inch element. The 51
inch element is the radiator on 2m, the 6.xx inch element makes the
19.25 inch one radiate on 440. The thing isn't great on 440 because the
51 inch portion is there. It is rugged though.

I built a duplicate, which you can do if you look at all the parts pages
on the site. The main problem, same as all J poles, is common mode
current issues on the feedline.

tom
K0TAR

Sorry, missed the part where you already have this antenna. My fault
for not reading the whole post until after I responded.

tom
K0TAR

On Thu, 31 Mar 2011 18:46:22 -0500, tom wrote:

http://www.arrowantenna.info/osj/j-pole.html

This design works moderately well. Drive the 19.25 inch element. The 51
inch element is the radiator on 2m, the 6.xx inch element makes the
19.25 inch one radiate on 440. The thing isn't great on 440 because the
51 inch portion is there. It is rugged though.

I built a duplicate, which you can do if you look at all the parts pages
on the site. The main problem, same as all J poles, is common mode
current issues on the feedline.

tom
K0TAR

Sorry, missed the part where you already have this antenna. My fault
for not reading the whole post until after I responded.

Hi Tom,

Your suggestion would have been my choice too - except for Tom's first
purchase choice. The open stub has always seemed to be a more natural
feed method.

The addition of the parasitic radiator is still an option for any
design.

73's
Richard Clark, KB7QHC