Jimmie D wrote:
Thanks Cecil This was my first plan but I dont have room to run the stub
straight out so I kind of tabled the idea for a while. Now that I have
thought about it there is no reason I couldnt wrap it around the antenna.

There's no reason why you couldn't spiral it around
the antenna like a pancake inductor. If you kept each
spiral about a foot away from the next one, the area
occupied would be pretty small. Good luck.
--
73, Cecil http://www.w5dxp.com

On Mon, 4 Sep 2006 15:23:37 -0400, "Jimmie D"
wrote:

I heard once upon a time that the Ringo utilizes
the mast as part of the radiator.

Hi Jimmie,

What was meant was that the mast inappropriately became part of the
radiator due to the design of the Ringo (which has had a reputation
for being a dummy load). The problem with half-wave designs is they
are high Z. Being high Z they are difficult to choke. Being
difficult to choke, they appropriate masts, supports, feed lines, as
additional radiation surfaces. When you add these lengths to the
radiator (and they are co-linear) then your radiation lobes begin to
climb into the sky (no one there to hear you) and the antenna becomes
deaf and dumb.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Mon, 4 Sep 2006 15:23:37 -0400, "Jimmie D"
wrote:

I heard once upon a time that the Ringo utilizes
the mast as part of the radiator.

Hi Jimmie,

What was meant was that the mast inappropriately became part of the
radiator due to the design of the Ringo (which has had a reputation
for being a dummy load). The problem with half-wave designs is they
are high Z. Being high Z they are difficult to choke. Being
difficult to choke, they appropriate masts, supports, feed lines, as
additional radiation surfaces. When you add these lengths to the
radiator (and they are co-linear) then your radiation lobes begin to
climb into the sky (no one there to hear you) and the antenna becomes
deaf and dumb.

It's probably more critical on VHF/UHF, but on the HF bands I never
had any trouble with ringos and decoupling problems overly skewing
the pattern. I've used a few with no decoupling at all, and they
worked
fine. But I'm of the opinion that the "gamma loop" type feed helps
decouple the feedline a bit better than some other methods of feeding.
I tried adding a decoupling section to one I used on 10m a few years
ago, and it did help, but not in a huge amount. I found the antennas
pretty easy to choke by using a 1/4 WL section of coax, and then 4
radials.
Much the same as used on the "ringo ranger" antennas. Anyway, I've
never seen a case on HF where I thought a ringo acted like a dummy
load.
I imagine it's possible on VHF though, if precautions aren't taken.
I've used lots of them on 10m at various heights. Always worked pretty
well. And I never noticed an overly hot feedline.
The only times I had horrible results with a half wave was a time years
ago when
I tried to make a center fed job, using peeled back coax braid as part
of the
antenna. The decoupling from the line was horrible on that thing.
That was on VHF though where the problem shows up more.
MK

Richard Clark wrote:
On Mon, 4 Sep 2006 15:23:37 -0400, "Jimmie D"
wrote:

I heard once upon a time that the Ringo utilizes
the mast as part of the radiator.

Hi Jimmie,

What was meant was that the mast inappropriately became part of the
radiator due to the design of the Ringo (which has had a reputation
for being a dummy load). The problem with half-wave designs is they
are high Z. Being high Z they are difficult to choke. Being
difficult to choke, they appropriate masts, supports, feed lines, as
additional radiation surfaces. When you add these lengths to the
radiator (and they are co-linear) then your radiation lobes begin to
climb into the sky (no one there to hear you) and the antenna becomes
deaf and dumb.

It's probably more critical on VHF/UHF, but on the HF bands I never
had any trouble with ringos and decoupling problems overly skewing
the pattern. I've used a few with no decoupling at all, and they
worked
fine. But I'm of the opinion that the "gamma loop" type feed helps
decouple the feedline a bit better than some other methods of feeding.
I tried adding a decoupling section to one I used on 10m a few years
ago, and it did help, but not in a huge amount. I found the antennas
pretty easy to choke by using a 1/4 WL section of coax, and then 4
radials.
Much the same as used on the "ringo ranger" antennas. Anyway, I've
never seen a case on HF where I thought a ringo acted like a dummy
load.
I imagine it's possible on VHF though, if precautions aren't taken.
I've used lots of them on 10m at various heights. Always worked pretty
well. And I never noticed an overly hot feedline.
The only times I had horrible results with a half wave was a time years
ago when
I tried to make a center fed job, using peeled back coax braid as part
of the
antenna. The decoupling from the line was horrible on that thing.
That was on VHF though where the problem shows up more.
MK

..
The only times I had horrible results with a half wave was a time years
ago when
I tried to make a center fed job, using peeled back coax braid as part
of the
antenna. The decoupling from the line was horrible on that thing.
That was on VHF though where the problem shows up more.
MK


Ive had trouble with this type of antenna too. Turning the shield inside out
over the feedline is not a good idea. The outer viynl jacket has some very
poor RF characteristics not to mention it is a bear to do. Stangely enough
plans for this antenna abound. Shakespeare used to build a CB antenna lie
this called the big stick They latter change it to four wires inside a
fibergas tube with th wires imbedded in the fiberglass connected to the
shield of the feedline. Then the feedline is centered in the tube using
styrofoam. I built something similar using a metal tube connecting to the
shield with the coax down the middle of the tube also using little pieces of
styrofam to center the cable in the tube. This seemed to work pretty good.

"Cecil Moore" wrote in message
om...
Jimmie D wrote:
Thanks Cecil This was my first plan but I dont have room to run the stub
straight out so I kind of tabled the idea for a while. Now that I have
thought about it there is no reason I couldnt wrap it around the antenna.

There's no reason why you couldn't spiral it around
the antenna like a pancake inductor. If you kept each
spiral about a foot away from the next one, the area
occupied would be pretty small. Good luck.
--
73, Cecil http://www.w5dxp.com

Cecil, I got the antenna up Sunday, for now the stub is straight out from
the antenna. Is it normal for the 50 ohm point to be a little hard to find?
About the best VSWR I can get now is 1.7:1 This is pretty close to the point
where my radio starts limiting power. I m thinking either the stub or the
antenna may be a little long is there an easy way to tell or is easier just
to try something and see what happens? Checking the VSWR at differerent
freqs doesnt help much. Maybe a slight indication that it is too long.

Jimmie

Jimmie D wrote:
Cecil, I got the antenna up Sunday, for now the stub is straight out from
the antenna. Is it normal for the 50 ohm point to be a little hard to find?
About the best VSWR I can get now is 1.7:1 This is pretty close to the point
where my radio starts limiting power. I m thinking either the stub or the
antenna may be a little long is there an easy way to tell or is easier just
to try something and see what happens? Checking the VSWR at differerent
freqs doesnt help much. Maybe a slight indication that it is too long.

You've discovered the problem with SWR meters. They
don't read phase. If you were using an antenna analyzer,
the solution would probably be obvious. With only an
SWR meter, your tuning algorithm either converges or
diverges but you may not know which. The easy way to
tune the antenna is to use an antenna analyzer to
determine where the impedance is purely resistive and
then adjust the stub tap point to 50 ohms. An antenna
analyzer is a good investment.
--
73, Cecil http://www.w5dxp.com

"Cecil Moore" wrote in message
...
Jimmie D wrote:
Cecil, I got the antenna up Sunday, for now the stub is straight out from
the antenna. Is it normal for the 50 ohm point to be a little hard to
find? About the best VSWR I can get now is 1.7:1 This is pretty close to
the point where my radio starts limiting power. I m thinking either the
stub or the antenna may be a little long is there an easy way to tell or
is easier just to try something and see what happens? Checking the VSWR
at differerent freqs doesnt help much. Maybe a slight indication that it
is too long.

You've discovered the problem with SWR meters. They
don't read phase. If you were using an antenna analyzer,
the solution would probably be obvious. With only an
SWR meter, your tuning algorithm either converges or
diverges but you may not know which. The easy way to
tune the antenna is to use an antenna analyzer to
determine where the impedance is purely resistive and
then adjust the stub tap point to 50 ohms. An antenna
analyzer is a good investment.
--
73, Cecil http://www.w5dxp.com

I think before I start cutting I will try adding a little series capacitance
or inductance to the antenna and see how it reacts to that. My work week
just started so it may be a week or so before I get back at it again.

In order to guarantee the ability to obtain a 1:1 SWR, you need to be
able to adjust at least two independent or partially independent things.
This can be two variable lumped components; any two of the following:
stub length, position, and Z0(*); and so forth. Adjusting, say, a stub
length and the value of a capacitor across the input end of the stub
won't do it because they're basically adjusting the same thing and
therefore aren't independent. If you've only been varying one item,
you'll get a perfect match only if lucky.

If you're as close as 1.7:1, it's likely as easy or easier to find the
solution by trial and error rather than calculation.

The reason that two adjustments are required is that 1:1 SWR requires a
particular value of R and a zero value of X. If you vary only one item,
it'll change only R, or only X, or, more likely, both R and X but in
some fixed relationship.

(*) Because you can practically adjust Z0 over only a relatively narrow
range, this is a good method only for fine tuning or as a way to set the
range of other adjustments.

Roy Lewallen, W7EL

Jimmie D wrote:
"Cecil Moore" wrote in message
...
Jimmie D wrote:
Cecil, I got the antenna up Sunday, for now the stub is straight out from
the antenna. Is it normal for the 50 ohm point to be a little hard to
find? About the best VSWR I can get now is 1.7:1 This is pretty close to
the point where my radio starts limiting power. I m thinking either the
stub or the antenna may be a little long is there an easy way to tell or
is easier just to try something and see what happens? Checking the VSWR
at differerent freqs doesnt help much. Maybe a slight indication that it
is too long.
You've discovered the problem with SWR meters. They
don't read phase. If you were using an antenna analyzer,
the solution would probably be obvious. With only an
SWR meter, your tuning algorithm either converges or
diverges but you may not know which. The easy way to
tune the antenna is to use an antenna analyzer to
determine where the impedance is purely resistive and
then adjust the stub tap point to 50 ohms. An antenna
analyzer is a good investment.
--
73, Cecil http://www.w5dxp.com

I think before I start cutting I will try adding a little series capacitance
or inductance to the antenna and see how it reacts to that. My work week
just started so it may be a week or so before I get back at it again.

On Tue, 12 Sep 2006 18:20:02 -0400, "Jimmie D"
wrote:


"Cecil Moore" wrote in message
t...
Jimmie D wrote:
Cecil, I got the antenna up Sunday, for now the stub is straight out from
the antenna. Is it normal for the 50 ohm point to be a little hard to
find? About the best VSWR I can get now is 1.7:1 This is pretty close to
....
I think before I start cutting I will try adding a little series capacitance
or inductance to the antenna and see how it reacts to that. My work week
just started so it may be a week or so before I get back at it again.

Roy has given you some good advice.

Some further thoughts.

I assume that the coax is not decoupled, that will complicate
achieving your outcome.

Before cutting things, an observation of whether VSWR is better at a
higher or lower frequency will help guide you in the reactance
dimension of the problem.

Find the tap point for lowest VSWR, change frequency and do it again.
This will hint to you whether the antenna / stub combination is short
or long.

Keep in mind that there is not a correct length of the radiator
independently of the stub, small reactance due to the radiator being
off resonance can be compensated by suitable stub dimensions. That
says cut / lengthen the elements that are most convenient.

Temporary increase in length by clamping an additional conductor to
top of the radiator might less final that cutting bits off. Again, the
shift in point of lowest VSWR is a hint.

With knowledge, you should be able do this easy enough without an
antenna analyser.

Owen
--