Turnstile question
 

On Jun 18, 12:08 pm, "Jerry Martes" wrote:
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On Jun 17, 2:02 pm, "Jerry Martes" wrote:
wrote in message

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On Jun 17, 12:47 pm, "Jerry Martes" wrote:

I figured 1.8 inches for 1066 MHz. I wanted to build it into a pvc
pipe cap so there isn't much room to work. Also, am I correct to
assume the 1.8 is the total length, including what is stripped back
to
make the connection?
Ralph

Hi Ralph

I dont know what your needs are for this Turnstile antenna, so my
input
may be of no value. But, a Turnstile can be made to work by feeding
both
dipoles with one feed point. No phasing harness is needed. Make one
dipole a little short so it is capacitive and the other dipole a
little
long
so it is inducvtive.

Jerry

The only problem with that is the antenna will still have basically a
dipole
pattern. I assume he is wanting the usual omni pattern with circular
polarization at the higher angles..
But maybe not... You need the phase line if you want a true omni
"turnstile"
pattern.
But saying that , I have used turnstiles with no line.. But usually on
80m..
And it does change the pattern a bit from the original single dipole,
but not
quite the same as using a phase line.
MK

Hi MK

I may have screwed up, but I think that a pair of dipoles on the same
plane, configured like a pair of non-symetrical Vs could be fed with one
feed point to produce a free space cardiod pattern. That would be one
short dipole and one one longer dipole fed in parallel.

Jerry

Jerry

I'm not sure exactly what you mean.. Normally, a turnstile has both
the elements the same length. If you feed two dipoles cut for the
same band, but at different freq's, and feed with a single feedline,
all it will do is effect the SWR plot.. Will look as a "W"..
If you feed a normal turnstile with one line, but no phasing line,
it will act as a normal dipole in one of the 2 plots you could have
from the antenna. In that case, you could feed with two lines,
and switch directions. "dipole pattern each way". You could then
add 90 degrees to one line, and get an omni pattern..
That would give you three choices in plots..
But if you feed with a single line, you must use the phasing line
if you want the omni "turnstile" pattern.
This can be easily modeled using any modeling program..
You set the phasing in the "source" menu..
MK

Hi MK

The concept seemed correct in my mind. It was/is -- Feed two dipoles in
parallel, then turn one so it is at right angles to the other. Make one
dipole slightly inductive by making it longer than halfwave. Make the
other dipole capacitive by making it slightly shorter than half wave. One
dipole will radiate before the other due to their reactice impedances. It
shouldnt be too difficult to get enough phase delay to get a decent amount
of CP broadside to the plane of the dipoles.
The objective of this "no phasing line" approach was to make it physically
easier for the OP to fabricate a Turnstile. I have never tried building a
Turnstile this way, but It almost *has to work*. It sure would be easier
than making 1,000 MHz transmission line stuff.
I didnt catch the reference to "omniazimuth" but I am surprised that the
azimuth pattern is not fairly uniform when *no* phasing line is used, as
outlined above.

Jerry


I see what you are getting at now.. I tried modeling it, but it didn't
seem
to work. I took a previous model which had the elements the same
length,
and fed with one 90 out of phase with the other.. Gave a pretty much
perfect omni pattern. Then I tried shortening one element, and
lengthening
the other. One leg was 118 ft, the other 122.. I then fed both in
phase, using
no delay in the source.. Didn't seem to work so far.. Still got a
dipole pattern..
But I will mess with it some more later. I've used the exact antenna
you
describe on 80m.. But more to get more bandwidth, rather than a good
omni pattern.
MK

Turnstile question
 

wrote in message
oups.com...
On Jun 18, 12:08 pm, "Jerry Martes" wrote:
wrote in message

oups.com...



On Jun 17, 2:02 pm, "Jerry Martes" wrote:
wrote in message

groups.com...

On Jun 17, 12:47 pm, "Jerry Martes" wrote:

I figured 1.8 inches for 1066 MHz. I wanted to build it into a
pvc
pipe cap so there isn't much room to work. Also, am I correct to
assume the 1.8 is the total length, including what is stripped
back
to
make the connection?
Ralph

Hi Ralph

I dont know what your needs are for this Turnstile antenna, so my
input
may be of no value. But, a Turnstile can be made to work by
feeding
both
dipoles with one feed point. No phasing harness is needed. Make
one
dipole a little short so it is capacitive and the other dipole a
little
long
so it is inducvtive.

Jerry

The only problem with that is the antenna will still have basically
a
dipole
pattern. I assume he is wanting the usual omni pattern with circular
polarization at the higher angles..
But maybe not... You need the phase line if you want a true omni
"turnstile"
pattern.
But saying that , I have used turnstiles with no line.. But usually
on
80m..
And it does change the pattern a bit from the original single
dipole,
but not
quite the same as using a phase line.
MK

Hi MK

I may have screwed up, but I think that a pair of dipoles on the
same
plane, configured like a pair of non-symetrical Vs could be fed with
one
feed point to produce a free space cardiod pattern. That would be
one
short dipole and one one longer dipole fed in parallel.

Jerry

Jerry

I'm not sure exactly what you mean.. Normally, a turnstile has both
the elements the same length. If you feed two dipoles cut for the
same band, but at different freq's, and feed with a single feedline,
all it will do is effect the SWR plot.. Will look as a "W"..
If you feed a normal turnstile with one line, but no phasing line,
it will act as a normal dipole in one of the 2 plots you could have
from the antenna. In that case, you could feed with two lines,
and switch directions. "dipole pattern each way". You could then
add 90 degrees to one line, and get an omni pattern..
That would give you three choices in plots..
But if you feed with a single line, you must use the phasing line
if you want the omni "turnstile" pattern.
This can be easily modeled using any modeling program..
You set the phasing in the "source" menu..
MK

Hi MK

The concept seemed correct in my mind. It was/is -- Feed two dipoles
in
parallel, then turn one so it is at right angles to the other. Make one
dipole slightly inductive by making it longer than halfwave. Make the
other dipole capacitive by making it slightly shorter than half wave.
One
dipole will radiate before the other due to their reactice impedances.
It
shouldnt be too difficult to get enough phase delay to get a decent
amount
of CP broadside to the plane of the dipoles.
The objective of this "no phasing line" approach was to make it
physically
easier for the OP to fabricate a Turnstile. I have never tried building
a
Turnstile this way, but It almost *has to work*. It sure would be easier
than making 1,000 MHz transmission line stuff.
I didnt catch the reference to "omniazimuth" but I am surprised that
the
azimuth pattern is not fairly uniform when *no* phasing line is used, as
outlined above.

Jerry


I see what you are getting at now.. I tried modeling it, but it didn't
seem
to work. I took a previous model which had the elements the same
length,
and fed with one 90 out of phase with the other.. Gave a pretty much
perfect omni pattern. Then I tried shortening one element, and
lengthening
the other. One leg was 118 ft, the other 122.. I then fed both in
phase, using
no delay in the source.. Didn't seem to work so far.. Still got a
dipole pattern..
But I will mess with it some more later. I've used the exact antenna
you
describe on 80m.. But more to get more bandwidth, rather than a good
omni pattern.
MK


Hi MK

Can we change the antenna lengths more than ? We will probably need a
bigger change in dipole length to get the antenna terminal impedance to be
sufficiently reactive.
I know the "+jx with -jx" concept works for some antennas. I assume it
will work with a Turnstile. I have read articles that deal with the math
and equations, but I sure done want to get involved with that.
If the OP really cared about the suggestion I made, it might be fun to do
more investigation into exactly how close to *good enough* we could get with
the single feed point Turnstile. Heck, if you want to investigate the
applicapability of this I'd sure dig into the concept further. Right now,
I am pretty sure the concept will work for Turnstiles. I just dont know how
good the antenna needs to be.

Jerry

Turnstile question
 

On Jun 18, 5:33 pm, "Jerry Martes" wrote:
wrote in message

oups.com...



On Jun 18, 12:08 pm, "Jerry Martes" wrote:
wrote in message

groups.com...

On Jun 17, 2:02 pm, "Jerry Martes" wrote:
wrote in message

groups.com...

On Jun 17, 12:47 pm, "Jerry Martes" wrote:

I figured 1.8 inches for 1066 MHz. I wanted to build it into a
pvc
pipe cap so there isn't much room to work. Also, am I correct to
assume the 1.8 is the total length, including what is stripped
back
to
make the connection?
Ralph

Hi Ralph

I dont know what your needs are for this Turnstile antenna, so my
input
may be of no value. But, a Turnstile can be made to work by
feeding
both
dipoles with one feed point. No phasing harness is needed. Make
one
dipole a little short so it is capacitive and the other dipole a
little
long
so it is inducvtive.

Jerry

The only problem with that is the antenna will still have basically
a
dipole
pattern. I assume he is wanting the usual omni pattern with circular
polarization at the higher angles..
But maybe not... You need the phase line if you want a true omni
"turnstile"
pattern.
But saying that , I have used turnstiles with no line.. But usually
on
80m..
And it does change the pattern a bit from the original single
dipole,
but not
quite the same as using a phase line.
MK

Hi MK

I may have screwed up, but I think that a pair of dipoles on the
same
plane, configured like a pair of non-symetrical Vs could be fed with
one
feed point to produce a free space cardiod pattern. That would be
one
short dipole and one one longer dipole fed in parallel.

Jerry

Jerry

I'm not sure exactly what you mean.. Normally, a turnstile has both
the elements the same length. If you feed two dipoles cut for the
same band, but at different freq's, and feed with a single feedline,
all it will do is effect the SWR plot.. Will look as a "W"..
If you feed a normal turnstile with one line, but no phasing line,
it will act as a normal dipole in one of the 2 plots you could have
from the antenna. In that case, you could feed with two lines,
and switch directions. "dipole pattern each way". You could then
add 90 degrees to one line, and get an omni pattern..
That would give you three choices in plots..
But if you feed with a single line, you must use the phasing line
if you want the omni "turnstile" pattern.
This can be easily modeled using any modeling program..
You set the phasing in the "source" menu..
MK

Hi MK

The concept seemed correct in my mind. It was/is -- Feed two dipoles
in
parallel, then turn one so it is at right angles to the other. Make one
dipole slightly inductive by making it longer than halfwave. Make the
other dipole capacitive by making it slightly shorter than half wave.
One
dipole will radiate before the other due to their reactice impedances.
It
shouldnt be too difficult to get enough phase delay to get a decent
amount
of CP broadside to the plane of the dipoles.
The objective of this "no phasing line" approach was to make it
physically
easier for the OP to fabricate a Turnstile. I have never tried building
a
Turnstile this way, but It almost *has to work*. It sure would be easier
than making 1,000 MHz transmission line stuff.
I didnt catch the reference to "omniazimuth" but I am surprised that
the
azimuth pattern is not fairly uniform when *no* phasing line is used, as
outlined above.

Jerry

I see what you are getting at now.. I tried modeling it, but it didn't
seem
to work. I took a previous model which had the elements the same
length,
and fed with one 90 out of phase with the other.. Gave a pretty much
perfect omni pattern. Then I tried shortening one element, and
lengthening
the other. One leg was 118 ft, the other 122.. I then fed both in
phase, using
no delay in the source.. Didn't seem to work so far.. Still got a
dipole pattern..
But I will mess with it some more later. I've used the exact antenna
you
describe on 80m.. But more to get more bandwidth, rather than a good
omni pattern.
MK

Hi MK

Can we change the antenna lengths more than ? We will probably need a
bigger change in dipole length to get the antenna terminal impedance to be
sufficiently reactive.
I know the "+jx with -jx" concept works for some antennas. I assume it
will work with a Turnstile. I have read articles that deal with the math
and equations, but I sure done want to get involved with that.
If the OP really cared about the suggestion I made, it might be fun to do
more investigation into exactly how close to *good enough* we could get with
the single feed point Turnstile. Heck, if you want to investigate the
applicapability of this I'd sure dig into the concept further. Right now,
I am pretty sure the concept will work for Turnstiles. I just dont know how
good the antenna needs to be.

Jerry


I can try it, but I think he would be better off using the actual
coax line if he can rig it up.
MK