OK, let's discuss dipoles vs length
 

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?

OK, let's discuss dipoles vs length
 

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. :)

OK, let's discuss dipoles vs length
 

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, let's discuss dipoles vs length
 

On 10/12/2014 12:09 PM, Lostgallifreyan wrote:
John S wrote in :

Excellent! I like to explore and I encourage everyone to do so whether
it be with math tools or getting your hands dirty. Keep it up.


Indeed. :) That synth I mentioned, it took me a good chunk of lifetime
waiting for someone to make so I could pay for it. I gave up waiting. :)

Jeff just posted about the perils of antenna towers and hillsides vs NEC2's
flat earth, and many earlier things (liek modellign with Sketchup prior to
engineering in metals and plastics, have taught me caution. measure thrice,
cut once. THis is how and why I want to use NEC, to save me from falling into
expensive and time consuming traps, which I think it will do very well.


Jeff seems to be a very experience man with RF. I don't doubt his
comments about what is possible with a practical situation. I, however,
am playing with some fundamentals (free space, antenna characteristics,
etc) so that I understand how to catch up to the gurus here. My toy is
the modeling program. I do like to compare theory to practical
situations, however.

OK, let's discuss dipoles vs length
 

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?

OK, let's discuss dipoles vs length
 

John S wrote in :

Jeff seems to be a very experience man with RF. I don't doubt his
comments about what is possible with a practical situation. I, however,
am playing with some fundamentals (free space, antenna characteristics,
etc) so that I understand how to catch up to the gurus here. My toy is
the modeling program. I do like to compare theory to practical
situations, however.


Yep, while nowt is perfect, there is always worth in something as a guide. I
got spoiled by op-amps, it's a different thing imagine stuff with actual
transistors. Just one example of how tough it can be without the guides.

OK, let's discuss dipoles vs length
 

John S wrote in :

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?


Writer of The Hitch-Hiker's Guide To The Galaxy, and others. He's fairly
popular in technical and scientific circles so he gets mentioned at
surprising and sometimes very funny moments. Aquired taste actually, but I
was lucky enough to aquire it early.

OK, let's discuss dipoles vs length
 

On 10/12/2014 12:26 PM, Lostgallifreyan wrote:
John S wrote in :

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?


Writer of The Hitch-Hiker's Guide To The Galaxy, and others. He's fairly
popular in technical and scientific circles so he gets mentioned at
surprising and sometimes very funny moments. Aquired taste actually, but I
was lucky enough to aquire it early.


I know of Hitch-Hiker's Guide To The Galaxy, but I have never watched.
Probably my loss. In any case, let's do the antenna thing. Yes?

OK, let's discuss dipoles vs length
 

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?

OK, let's discuss dipoles vs length
 

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