Thanks Jim.
I was hoping someone had done this the easy way - Dave says "8.5 inches
should work" and I'm getting predictable and usable results at the
moment using 10 inches. Mostly I'm trying to get a reality check at
this point on the lengths of the top load wires. Certainly if I can get
it to accept the 160 meter energy it will radiate it. I'm getting
wrapped around ropes and wires.
73 - Mark N5OT
On 10/23/2021 10:05 AM, Lux, Jim wrote:
On 10/23/21 4:48 AM, Mark - N5OT wrote:
Hey youall,
I want to model Rohn 25G as a transmitting antenna. Has anyone
learned how to do that fairly accurately in K6STI's AO program? In
addition to some length of regular straight sections, my tower has a
factory 8' tapered top section which I would extend with a 2" stinger
and a single-point pier base that is basically a 10 foot section with
3 feet of taper to a flange added. It appears to be "factory"
although I have never seen one in person and it could be a one-off.
1. How do I model these tapers?
2. How do I model the tower itself? Do I call it "10-inch diameter
steel?" Larger? Smaller?
For NEC (you'd have to ask Brian if AO works the same way, I think
not, though)
What you want is a "wire" that has similar electromagnetic
characteristics in terms of diameter, conductivity and permeability
per unit length. So you could put a 10" diameter wire, but you'd need
to scale the conductivity down so that it matches the tower (i.e. it's
not solid steel) - Don't forget that since it's steel, the skin depth
is quite shallow - Someone may have figured out the magic numbers to
match. You might be able to use a single smaller wire that's "close
enough". It kind of depends what you're doing with the model -
sometimes, a simple approximation works for a sensitivity analysis.
You put the wire in, get some data, take the wire out, get some data,
decide that since the data didn't change very much, you neglect the
effect of the wire. Putting the wire in and then changing the
diameter or conductivity is a similar exercise.
NEC doesn't model the currents flowing "around" the wire - Maybe you
could model three parallel wires for your corner tubes and start with
that.
Or, you just model the entire lattice (writing a short program to
grind out all the segments is how most people do this kind of thing).
Of course, you will potentially wind up with "segment very much
shorter than a wavelength" kinds of issues, but that's more a
numerical precision thing.
3. Do I have to re-learn calculus?
I would love to hear from anyone who has either done this or knows
how it is done.
Thanks in advance.
73 - Mark N5OT
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|