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.

On 10/12/2014 12:17 PM, Lostgallifreyan wrote:
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.


Ok. Putting the catenary into the simulator will take some thought from
me as well. I'll do my best, but don't wait for me. Pursue it as you
wish. (Or anybody else reading the thread)

Can somebody start another thread if you are interested?

John S wrote in :

Ok. Putting the catenary into the simulator will take some thought from
me as well. I'll do my best, but don't wait for me. Pursue it as you
wish. (Or anybody else reading the thread)

Can somebody start another thread if you are interested?


Sweconded. I'll admit at this point welcoming an easy start, and a prepared
example of this would be a hell of an incentive for me to get into exploring
NEC too.

Lostgallifreyan wrote in
:

Seconded. I'll admit at this point welcoming an easy start, and a
prepared example of this would be a hell of an incentive for me to get
into exploring NEC too.


Actually to be fair, with ,y longwire tests I'll likely be using very thin
strong stainless wire and pulling it tight enough to reduce my need to worry
about it much. STill interesting though, I've seen heavy-looking HF antennas
strung over the apex of a roof in a valley near here, and that had a
pronounced sag that may or may not have been bothersome to whoever owned it.

Lostgallifreyan wrote:
Lostgallifreyan wrote in
:

Seconded. I'll admit at this point welcoming an easy start, and a
prepared example of this would be a hell of an incentive for me to get
into exploring NEC too.


Actually to be fair, with ,y longwire tests I'll likely be using very thin
strong stainless wire and pulling it tight enough to reduce my need to worry
about it much. STill interesting though, I've seen heavy-looking HF antennas
strung over the apex of a roof in a valley near here, and that had a
pronounced sag that may or may not have been bothersome to whoever owned it.

You might want to read this before you put up stainless steel wi

http://www.mwrs.org.au/2011/06/23/an...eel-vs-copper/

There is a link to a report in there.



--
Jim Pennino

"Lostgallifreyan" wrote in message
. ..
Lostgallifreyan wrote in
:

Actually to be fair, with ,y longwire tests I'll likely be using very thin
strong stainless wire and pulling it tight enough to reduce my need to
worry
about it much. STill interesting though, I've seen heavy-looking HF
antennas
strung over the apex of a roof in a valley near here, and that had a
pronounced sag that may or may not have been bothersome to whoever owned
it.

Looking at a chart in an old ARRL antenna handbook gives a rough estiment of
a length of 500 feet and a tension of 400 pounds a wire of around 12 to 14
gauge will drop about 10 feet if Idid it right.



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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.

I doubt you will see any significant difference.

I've done a lot of modeling with V's and inverted V's. Except for a slight
diffenence due to ground effects at low heights, there is no difference
between them.

As the angle goes from 180 degrees, i.e. a dipole, the impedance goes
down and and the pattern spreads out.

As the angle gets smaller, the gain goes down, the pattern becomes almost
circular like a vertical, and the antenna starts looking like a transmission
line, which it becomes when the angle gets to 0, with some spacing between
the wires of course.

And like an ordinary dipole, height over ground has a major effect on
the pattern.

Example: At 108 degrees, the impedance is about 65 Ohms and the broadside
null of the dipole is now only about 7 dB down from the main lobe.

But as the inverted V is a popular antenna, the pattern with common
leg angles would be instrutive.



--
Jim Pennino

wrote in message
...
I've done a lot of modeling with V's and inverted V's. Except for a slight
diffenence due to ground effects at low heights, there is no difference
between them.

As the angle goes from 180 degrees, i.e. a dipole, the impedance goes
down and and the pattern spreads out.


I have not played with the programs , but often wondered what the effect is
on antennas that are suported on the ends and the middle is dropped in a U
or V shape and not the inverted V shape. Many antenna books and articals
seem to show the flat top and inverted V paterns, but I have not seen any
with the actual V type.



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