Let's design a short antenna just for fun
 

"John S" wrote in message
...

Please, Mark. Try.

I am pleased that my exhortations that you should improve your
previous behaviour have taken effect.

Well done!

Keep up the good work!

Let's design a short antenna just for fun
 

On 11/5/2014 2:42 PM, wrote:
On Wednesday, November 5, 2014 2:35:40 PM UTC-6, John S wrote:
On 11/5/2014 1:02 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..
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.

Grabbing an unused call sign. Don't know exactly why. My initials are
JLS and I thought N1 would be Number 1! So that would make me Number 1
John L Smith. How vain is that?

No more than mine, which the M and the K are my initials.
I really wanted W5MK, and I was going to grab it as the guy
lived here locally, and I knew he went SK. But I had to wait
2 years, and when it come up for grabs, I had forgot about it,
and someone else hopped on it. But I much prefer what I have now,
vs my old call. Many used to confuse the L for an O on phone,
and the new call is lickity split fast on CW vs the old call.

Your sign is to be envied. Good for you!

Let's design a short antenna just for fun
 

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

Let's design a short antenna just for fun
 

On 11/5/2014 3:21 PM, John S wrote:
On 11/5/2014 1:32 PM, 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? ;-)


Rickman, please. Is that the tact a Gentleman would use? It seems that
your comment may be designed to invoke an ungentlemanly response. This
is exactly the sort of response I was hoping to avoid. I beg you to be a
bit more tactful.

Chill dude. Did you see the smiley? It was meant to be humorous.


For example "Well, of course, but what do you, personally, consider is a
short antenna?"

Hey! Who are you calling short?

--

Rick

Let's design a short antenna just for fun
 

On 11/5/2014 5:41 PM, rickman wrote:
On 11/5/2014 3:21 PM, John S wrote:
On 11/5/2014 1:32 PM, 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? ;-)


Rickman, please. Is that the tact a Gentleman would use? It seems that
your comment may be designed to invoke an ungentlemanly response. This
is exactly the sort of response I was hoping to avoid. I beg you to be a
bit more tactful.

Chill dude. Did you see the smiley? It was meant to be humorous.


For example "Well, of course, but what do you, personally, consider is a
short antenna?"

Hey! Who are you calling short?

;-)

--

Rick

Let's design a short antenna just for fun
 

On 11/5/2014 1:08 PM, wrote:
On Wednesday, November 5, 2014 1:01:02 PM UTC-6,
I would think a dipole would be a bad candidate for a "short" antenna
as you need to get the matching stuff close to the antenna to avoid
I^2R losses.

I'd probably use small matching coils at the feed point, about the
same as a mobile antenna.
In the real world, I try to avoid short antennas.. :)
It's only a last resort due to lack of room. I rarely actually use one.


OK, nuff jabbering.
I'll set the rules 15ft tall, designed for 80 meters.
16 radials, base mounted inductor and whatever tophat you desire.
Do the theoretical design find the feed impedance with some efficiency
numbers.
Then compare data to a dipole at 1/4 wave height.

Ready Set GO!

Wait, do you have a better idea than a base mounted inductor?
How long are the radials?
Do you want to compare 8 to 16 radials.
The tophat needs to survive 80 mile an hr wind.
I'm sure there's more.

Mikek

Let's design a short antenna just for fun
 

On 11/5/2014 4:41 PM, rickman wrote:
On 11/5/2014 3:21 PM, John S wrote:
On 11/5/2014 1:32 PM, 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? ;-)


Rickman, please. Is that the tact a Gentleman would use? It seems that
your comment may be designed to invoke an ungentlemanly response. This
is exactly the sort of response I was hoping to avoid. I beg you to be a
bit more tactful.

Chill dude. Did you see the smiley? It was meant to be humorous.

Sorry. I miss noticing those frequently.


For example "Well, of course, but what do you, personally, consider is a
short antenna?"

Hey! Who are you calling short?

Let's design a short antenna just for fun
 

On 11/6/2014 7:16 AM, amdx wrote:
On 11/5/2014 1:08 PM, wrote:
On Wednesday, November 5, 2014 1:01:02 PM UTC-6,

I would think a dipole would be a bad candidate for a "short" antenna
as you need to get the matching stuff close to the antenna to avoid
I^2R losses.

I'd probably use small matching coils at the feed point, about the
same as a mobile antenna.
In the real world, I try to avoid short antennas.. :)
It's only a last resort due to lack of room. I rarely actually use one.


OK, nuff jabbering.
I'll set the rules 15ft tall, designed for 80 meters.
16 radials, base mounted inductor and whatever tophat you desire.
Do the theoretical design find the feed impedance with some efficiency
numbers.
Then compare data to a dipole at 1/4 wave height.

Ready Set GO!

Wait, do you have a better idea than a base mounted inductor?
How long are the radials?
Do you want to compare 8 to 16 radials.
The tophat needs to survive 80 mile an hr wind.
I'm sure there's more.

Mikek

What wire material/size? Some stainless steel rods might have a
permeability that will reduce the efficiency. It will certainly have a
higher resistance than copper. Also note that copper-clad steel must
have a cladding several times the skin depth for high efficiency.

John

Let's design a short antenna just for fun
 

On 11/6/2014 7:16 AM, amdx wrote:
On 11/5/2014 1:08 PM, wrote:
On Wednesday, November 5, 2014 1:01:02 PM UTC-6,

I would think a dipole would be a bad candidate for a "short" antenna
as you need to get the matching stuff close to the antenna to avoid
I^2R losses.

I'd probably use small matching coils at the feed point, about the
same as a mobile antenna.
In the real world, I try to avoid short antennas.. :)
It's only a last resort due to lack of room. I rarely actually use one.


OK, nuff jabbering.
I'll set the rules 15ft tall, designed for 80 meters.
16 radials, base mounted inductor and whatever tophat you desire.
Do the theoretical design find the feed impedance with some efficiency
numbers.
Then compare data to a dipole at 1/4 wave height.

Ready Set GO!

Wait, do you have a better idea than a base mounted inductor?

As Mark said, maybe 50-75% along the antenna.

How long are the radials?

How much space can you give us?

Do you want to compare 8 to 16 radials.

We can do that. (Or you can do it yourself with EZNEC)

The tophat needs to survive 80 mile an hr wind.

I don't know how to do that.

I'm sure there's more.

Yes, always.

Mikek


John

Let's design a short antenna just for fun
 

On Thursday, November 6, 2014 7:16:32 AM UTC-6, amdx wrote:

OK, nuff jabbering.
I'll set the rules 15ft tall, designed for 80 meters.
16 radials, base mounted inductor and whatever tophat you desire.
Do the theoretical design find the feed impedance with some efficiency
numbers.
Then compare data to a dipole at 1/4 wave height.

Ready Set GO!

I'll let you all do the actual design and calculating. All of
the software needed can be had free on the web.


Wait, do you have a better idea than a base mounted inductor?

If you use a large enough hat, it really doesn't matter where
the coil is as far as improving current distribution.

How long are the radials?

I dunno.. how much wire is available? How much room?
In general for a limited amount of wire, many short radials
are better than just a few long ones.

Do you want to compare 8 to 16 radials.

Neither one is really enough for top performance over avg ground
with a short vertical.

The tophat needs to survive 80 mile an hr wind.

Use guyed off wire spokes I suppose..

It depends on the path/distance, etc but in general a 1/2 wl dipole
at 1/4 wave is going to smoke most any short vertical of that appx
design. NVIS, HUGELY so.. far DX, might be a toss if the vertical
is performing well. But to really perform well, I'd want at least
60 radials, not 8-16.. In the real world, I generally wouldn't use
such an antenna unless it was all I could get away with.

With ground mount verticals, the shorter the antenna, the more
critical the ground radial system becomes.

On 80m, 99 percent of my jibber jabber is NVIS, and I'd be the laughing
stock of the frequency with such an antenna.
My signal would be quite puny, compared to my normal dipoles and such.
I'd be heckled and tormented endlessly to build a "real" antenna.
I ain't joking either. They can be a tough crowd out there. lol