Jeff Liebermann wrote:
On Sat, 11 Oct 2014 18:04:07 -0000, wrote:

Jeff Liebermann wrote:

snip

Speaking of dipole antennas, I did this study a while back:
http://802.11junk.com/jeffl/antennas/vertical-dipole/index.html
Animated version:
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/animated-v-dipole.html
It's a 1/2 wave dipole at various heights above a real ground. Any
semblance to textbook dipole pattern is long gone.

Yep, ground has a huge effect on some types of antennas.

An instructive slide show would be the vertical pattern of a horizontal
1/2 dipole at .1, .2, ... .5 wavelengths over ground.

Another one would be a 3 element beam at those heights.

I can do both of these, but I'm busy/lazy this weekend. I also can't
find the program I used to create the annimated GIF file. Argh. It
would also be helpful if someone would specify the frequency range of
interest.

It doesn't matter if everything is done in wavelengths.

I guess there are some who would want to see that a 160 meter dipole
at say .2 wavelengths high has the same pattern as a 2 meter dipole
at .2 wavelengths if for no other reason than to be assured the effects
are frequency independant.



--
Jim Pennino

On 10/12/2014 12:41 AM, wrote:
Jeff Liebermann wrote:
On Sat, 11 Oct 2014 18:04:07 -0000, wrote:

Jeff Liebermann wrote:

snip

Speaking of dipole antennas, I did this study a while back:
http://802.11junk.com/jeffl/antennas/vertical-dipole/index.html
Animated version:
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/animated-v-dipole.html
It's a 1/2 wave dipole at various heights above a real ground. Any
semblance to textbook dipole pattern is long gone.

Yep, ground has a huge effect on some types of antennas.

An instructive slide show would be the vertical pattern of a horizontal
1/2 dipole at .1, .2, ... .5 wavelengths over ground.

Another one would be a 3 element beam at those heights.

I can do both of these, but I'm busy/lazy this weekend. I also can't
find the program I used to create the annimated GIF file. Argh. It
would also be helpful if someone would specify the frequency range of
interest.

It doesn't matter if everything is done in wavelengths.

I guess there are some who would want to see that a 160 meter dipole
at say .2 wavelengths high has the same pattern as a 2 meter dipole
at .2 wavelengths if for no other reason than to be assured the effects
are frequency independant.

Something else might be interesting; include the effects of sag
(centenary) in a wire antenna. Has anyone done that? I mean, using EZNEC
or NEC modeling.

On 10/12/2014 10:20 AM, John S wrote:
On 10/12/2014 12:41 AM, wrote:
Jeff Liebermann wrote:
On Sat, 11 Oct 2014 18:04:07 -0000, wrote:

Jeff Liebermann wrote:

snip

Speaking of dipole antennas, I did this study a while back:
http://802.11junk.com/jeffl/antennas/vertical-dipole/index.html
Animated version:
http://802.11junk.com/jeffl/antennas/vertical-dipole/slides/animated-v-dipole.html

It's a 1/2 wave dipole at various heights above a real ground. Any
semblance to textbook dipole pattern is long gone.

Yep, ground has a huge effect on some types of antennas.

An instructive slide show would be the vertical pattern of a horizontal
1/2 dipole at .1, .2, ... .5 wavelengths over ground.

Another one would be a 3 element beam at those heights.

I can do both of these, but I'm busy/lazy this weekend. I also can't
find the program I used to create the annimated GIF file. Argh. It
would also be helpful if someone would specify the frequency range of
interest.

It doesn't matter if everything is done in wavelengths.

I guess there are some who would want to see that a 160 meter dipole
at say .2 wavelengths high has the same pattern as a 2 meter dipole
at .2 wavelengths if for no other reason than to be assured the effects
are frequency independant.

Something else might be interesting; include the effects of sag
(centenary) in a wire antenna. Has anyone done that? I mean, using EZNEC
or NEC modeling.


Arrgh! Catenary instead of what I posted. Damn spell checker is dumb on
a lot of math and engineering terms. Sorry

John S wrote in :

Catenary instead of what I posted.

Yes. I should have read your second post before my first reply..

On 10/12/2014 11:19 AM, Lostgallifreyan wrote:
John S wrote in :

Catenary instead of what I posted.

Yes. I should have read your second post before my first reply..

No problem. Your reply was completely appropriate. We might be just a
bit out of sink (he, he) sync. Let's not get too serious.

John S wrote in :

On 10/12/2014 11:19 AM, Lostgallifreyan wrote:
John S wrote in :

Catenary instead of what I posted.

Yes. I should have read your second post before my first reply..

No problem. Your reply was completely appropriate. We might be just a
bit out of sink (he, he) sync. Let's not get too serious.



I try not to. It's one reason I had a bit of off-topic fun with Douglas Adams
last night when the opportunity arose.

On 10/12/2014 12:13 PM, Lostgallifreyan wrote:
John S wrote in :

On 10/12/2014 11:19 AM, Lostgallifreyan wrote:
John S wrote in :

Catenary instead of what I posted.

Yes. I should have read your second post before my first reply..

No problem. Your reply was completely appropriate. We might be just a
bit out of sink (he, he) sync. Let's not get too serious.



I try not to. It's one reason I had a bit of off-topic fun with Douglas Adams
last night when the opportunity arose.


I'm sorry, I don't know that person. Should I?

John S wrote in :

Something else might be interesting; include the effects of sag
(centenary) in a wire antenna.

Agreed. I was thinking about that possibility last night. Meaning 'catenary',
perhaps? As in 'hanging chain'? I doubt any longwire would lack this, so
modelling it would be useful.

On 10/12/2014 11:18 AM, Lostgallifreyan wrote:
John S wrote in :

Something else might be interesting; include the effects of sag
(centenary) in a wire antenna.

Agreed. I was thinking about that possibility last night. Meaning 'catenary',
perhaps? As in 'hanging chain'? I doubt any longwire would lack this, so
modelling it would be useful.


This is an interesting modeling situation. After you get acquainted with
your modeling software of choice, let's work on it to see what
differences there are. We can compare notes, if you like. Sound like
fun? If so, let's start another thread, yes?

John S wrote in :

On 10/12/2014 11:18 AM, Lostgallifreyan wrote:
John S wrote in :

Something else might be interesting; include the effects of sag
(centenary) in a wire antenna.

Agreed. I was thinking about that possibility last night. Meaning
'catenary', perhaps? As in 'hanging chain'? I doubt any longwire would
lack this, so modelling it would be useful.


This is an interesting modeling situation. After you get acquainted with
your modeling software of choice, let's work on it to see what
differences there are. We can compare notes, if you like. Sound like
fun? If so, let's start another thread, yes?


I won't be up to speed that fast, but once I have something that doesn't look
like it will waste people's time I'll have a go. I did look up catenary
curves some time back for some forgotten purpose (actually, I think is was
to do with loads on lengthy beams in a PV installation) so I have some idea
where to start looking, maybe. I'm assuming that the pysical properties would
relate to the electrical ones in some way, but it's not something I've
thought through.