On Wednesday, November 5, 2014 10:56:53 AM UTC-6, John S wrote:
Hi, Gentlemen -

What if we (just for fun and knowledge) design a short dipole antenna
together here in the group? How short should we go as a practical matter?

* What would be the worst input impedance we would would wish to deal
with? That will actually determine the shortness of the dipole, yes?

* There will be losses. How much are we willing to accept? This is
another determining factor to the shortness, yes?

* What might be the best feed arrangement for our short antenna? There
are lots of ways.

I don't know much about small loop antennas, but I can fade into the
shadows and try to learn from you.

Any other suggestions to this endeavor is also fine. Let's just discuss
what we enjoy doing. If you have other topics of small antennas, let's
put them on the table.

Gentlemanly arguments are welcome concerning the technical aspects of
our discussion. I have never had a problem with anyone who says "I
believe you are wrong in this assumption and here is why."

Thanks, Gentlemen.

Cheers,
John KD5YI

In very general terms, I would design a small dipole the same as
I would design a mobile whip. Except I would have two of them
back to back. The design would include all the usual considerations
about loading coil location, top/end capacity hats, etc.
What is good for the car, is good for the house.

I have plenty of old software, much from Reg EdwardsSK, that can be
used to design the antenna, determine appx losses, determine the
number of turns for the loading coils, etc, etc.

And then use EZNEC or whatever modeler to test the final design
before going out to the garage to whip up the actual antenna.

On 11/5/2014 11:58 AM, wrote:
On Wednesday, November 5, 2014 10:56:53 AM UTC-6, John S wrote:
Hi, Gentlemen -

What if we (just for fun and knowledge) design a short dipole antenna
together here in the group? How short should we go as a practical matter?

* What would be the worst input impedance we would would wish to deal
with? That will actually determine the shortness of the dipole, yes?

* There will be losses. How much are we willing to accept? This is
another determining factor to the shortness, yes?

* What might be the best feed arrangement for our short antenna? There
are lots of ways.

I don't know much about small loop antennas, but I can fade into the
shadows and try to learn from you.

Any other suggestions to this endeavor is also fine. Let's just discuss
what we enjoy doing. If you have other topics of small antennas, let's
put them on the table.

Gentlemanly arguments are welcome concerning the technical aspects of
our discussion. I have never had a problem with anyone who says "I
believe you are wrong in this assumption and here is why."

Thanks, Gentlemen.

Cheers,
John KD5YI

In very general terms, I would design a small dipole the same as
I would design a mobile whip. Except I would have two of them
back to back. The design would include all the usual considerations
about loading coil location, top/end capacity hats, etc.
What is good for the car, is good for the house.

I have plenty of old software, much from Reg EdwardsSK, that can be
used to design the antenna, determine appx losses, determine the
number of turns for the loading coils, etc, etc.

And then use EZNEC or whatever modeler to test the final design
before going out to the garage to whip up the actual antenna.

That sounds great, Mark.

Can you tell us how big would it be? And what about the coil dimensions,
losses? Can you do an EZNEC model so those of us who have the simulator
can look at all the parameters/arguments?

Many thanks for your input.

John (who was KD5YI but will be N1JLS in a few weeks due to vanity)

On Wednesday, November 5, 2014 12:33:48 PM UTC-6, John S wrote:


Can you tell us how big would it be? And what about the coil dimensions,
losses? Can you do an EZNEC model so those of us who have the simulator
can look at all the parameters/arguments?

It can be any size one wants. The bigger the better of course..
And all the other parameters can be adjusted also.. You use what
you can get away with to fit the room you have.
I don't recall having any mobile whips modeled, but it's hard to
say as all the older designs I did are on older unused hard drives
and I don't have ready access to them. I had to re-download quite
a few programs due to that reason.. I change drives quite often.
I just added two more 2 TB drives about a month ago.. I have several
TB these days.

All of Reg's old software can still be downloaded.
http://zerobeat.net/G4FGQ/page3.html#S301%22
Vertload was one I used a lot for playing "what if" when designing
mobile whips and other short verticals, and the info can easily
be used for small dipoles. There are others programs that can be
handy also.

It's been a long time since I used it, but I believe vertload
can be used to locate the best location on the whip to place
the loading coil. In general, you want it as far out to the ends
as possible for the best current distribution, but there is a
point where coil losses start to outweigh the improved current
distribution. So in the real world, the best location is usually
appx 3/4 the way out from the feedpoint, plus or minus.

And the use of capacity hats further improve current distribution,
and slightly reduce the number of turns needed for the loading
coil. A short dipole is never going to be quite as good as a full
size version, but with proper design you can come up with quite a
respectable antenna given the dinky size.



John (who was KD5YI but will be N1JLS in a few weeks due to vanity)

Hummm.. You now in 1 land, or you just grabbing an old call?
My current call is a vanity call, which I think I've had since '96.
I was WD5CJL in a past life.. I got that call in 77 when I was 20.

I actually got into ham radio when I was in the eighth grade, learned
the code, and even built a 6v6 transmitter from junk parts.
But then I got lazy and kind of got out of it a while, and didn't
actually get a ticket. Later on I got back into it, and got a ticket about
six years later. I used my first 6v6 transmitter when I was a novice in 77.
I was a SWL for a good while before I got into ham radio.
I worked a lot of CW back in the old days. I got up to nearly 60 wpm
at one point. But due to lack of activity the past several years, I can't
do near that now.

On 11/5/2014 2:02 PM, wrote:
On Wednesday, November 5, 2014 12:33:48 PM UTC-6, John S wrote:


Can you tell us how big would it be? And what about the coil dimensions,
losses? Can you do an EZNEC model so those of us who have the simulator
can look at all the parameters/arguments?

It can be any size one wants. The bigger the better of course..

What? Maybe you don't fully grasp the idea of a "short" antenna? ;-)

--

Rick

On Wednesday, November 5, 2014 1:33:06 PM UTC-6, rickman wrote:
On 11/5/2014 2:02 PM, wrote:
On Wednesday, November 5, 2014 12:33:48 PM UTC-6, John S wrote:


Can you tell us how big would it be? And what about the coil dimensions,
losses? Can you do an EZNEC model so those of us who have the simulator
can look at all the parameters/arguments?

It can be any size one wants. The bigger the better of course..

What? Maybe you don't fully grasp the idea of a "short" antenna? ;-)

--

Rick

I grasp that the shorter the antenna, the worse it generally performs.
But if I use an 18 ft long dipole for 80 or 40 meters, I consider
that a short dipole. Others may disagree, but I don't care.
They can knock themselves out with shorter versions.
I try to avoid using short dipoles. My previously mentioned methods
can be used with any length dipole. The smaller, the smaller the
performance.
Of course, the reasons for the smaller performance are not
what he who is silly thinks are the reasons. :|

wrote:
On Wednesday, November 5, 2014 1:33:06 PM UTC-6, rickman wrote:
On 11/5/2014 2:02 PM, wrote:
On Wednesday, November 5, 2014 12:33:48 PM UTC-6, John S wrote:


Can you tell us how big would it be? And what about the coil dimensions,
losses? Can you do an EZNEC model so those of us who have the simulator
can look at all the parameters/arguments?

It can be any size one wants. The bigger the better of course..

What? Maybe you don't fully grasp the idea of a "short" antenna? ;-)

--

Rick

I grasp that the shorter the antenna, the worse it generally performs.
But if I use an 18 ft long dipole for 80 or 40 meters, I consider
that a short dipole. Others may disagree, but I don't care.
They can knock themselves out with shorter versions.
I try to avoid using short dipoles. My previously mentioned methods
can be used with any length dipole. The smaller, the smaller the
performance.
Of course, the reasons for the smaller performance are not
what he who is silly thinks are the reasons. :|

Well...

There is little practical reason for shortning 23 cm band antenna,
but antennas for 160M are a challenge for most people that live
in an urban area.

Where I live anything over about 30 feet tall is basically a no-go.

So in the interest of practicallity and maybe getting something usefull
out of it, how about a 160M antenna with a maximum height of 30 feet
as a goal?

That immediately eliminates dipoles as a 160M dipole at 30 feet will
radiate most of the power straight up.

--
Jim Pennino

On Wednesday, November 5, 2014 2:16:04 PM UTC-6,
There is little practical reason for shortning 23 cm band antenna,
but antennas for 160M are a challenge for most people that live
in an urban area.

Where I live anything over about 30 feet tall is basically a no-go.

So in the interest of practicallity and maybe getting something usefull
out of it, how about a 160M antenna with a maximum height of 30 feet
as a goal?

That immediately eliminates dipoles as a 160M dipole at 30 feet will
radiate most of the power straight up.

In that case, I'd use a "T" vertical, with the loading coil at the base
if the top wires are too short to tune the antenna. The main reason
for having the coil at the base is ease of changing the inductance,
and the top hat wires improve current distribution vs a whip with
no top wires. If no room for the top wires, I'd use a capacity hat if
possible.

On 11/5/2014 1:43 PM, wrote:
On Wednesday, November 5, 2014 1:33:06 PM UTC-6, rickman wrote:
On 11/5/2014 2:02 PM, wrote:
On Wednesday, November 5, 2014 12:33:48 PM UTC-6, John S wrote:


Can you tell us how big would it be? And what about the coil dimensions,
losses? Can you do an EZNEC model so those of us who have the simulator
can look at all the parameters/arguments?

It can be any size one wants. The bigger the better of course..

What? Maybe you don't fully grasp the idea of a "short" antenna? ;-)

--

Rick

I grasp that the shorter the antenna, the worse it generally performs.
But if I use an 18 ft long dipole for 80 or 40 meters, I consider
that a short dipole. Others may disagree, but I don't care.
They can knock themselves out with shorter versions.
I try to avoid using short dipoles. My previously mentioned methods
can be used with any length dipole. The smaller, the smaller the
performance.
Of course, the reasons for the smaller performance are not
what he who is silly thinks are the reasons. :|

C'mon, Mark. You didn't need to add that. I think all of your technical
responses have been excellent info. Good man.

On Wednesday, November 5, 2014 2:26:23 PM UTC-6, John S wrote:


C'mon, Mark. You didn't need to add that. I think all of your technical
responses have been excellent info. Good man.

Yea, I know, but he has a way of provoking me that is hard to resist..

On 11/5/2014 2:43 PM, wrote:
On Wednesday, November 5, 2014 1:33:06 PM UTC-6, rickman wrote:
On 11/5/2014 2:02 PM, wrote:
On Wednesday, November 5, 2014 12:33:48 PM UTC-6, John S wrote:


Can you tell us how big would it be? And what about the coil dimensions,
losses? Can you do an EZNEC model so those of us who have the simulator
can look at all the parameters/arguments?

It can be any size one wants. The bigger the better of course..

What? Maybe you don't fully grasp the idea of a "short" antenna? ;-)

--

Rick

I grasp that the shorter the antenna, the worse it generally performs.

You are starting to sound like you-know-who now!


But if I use an 18 ft long dipole for 80 or 40 meters, I consider
that a short dipole. Others may disagree, but I don't care.
They can knock themselves out with shorter versions.
I try to avoid using short dipoles. My previously mentioned methods
can be used with any length dipole. The smaller, the smaller the
performance.
Of course, the reasons for the smaller performance are not
what he who is silly thinks are the reasons. :|

Hmmm... ok. So you are happy discussing short antenna as long as they
aren't *too* short.

--

Rick