Thanks Dave.
My old 40 meter elements all have big fiberglass rod insulators, so that
is what will insulate the stinger. We're on the right track.
I appreciate all the detail in your email. K6STI allows me to place a
simple source at the bottom and leave it there. I need to review how to
add a lump capacitance at the base, since the resonant frequency will be
little lower than the operating frequency. I figure I can dial in the
resonant frequency with a variable capacitor but the model will get me
in the ballpark as far as the range of the capacitor I will be looking
for in the junk box.
The guy wires will all be insulated less than a foot out. I'm ignoring
them in the model.
On the right track here. I might be on for the stew tonight after all :-)
73 - Mark N5OT
On 10/23/2021 8:16 AM, Haring family wrote:
I haven't used that program in a long time, but here are some comments
which might be helpful:
1. 8-1/2" effective dia works fine.
2. Use full dia or 2" only. On top, use 2/3 of taper length at full
diameter, and add the rest of the taper length to the 2" stinger. I
believe for singers and cap loading you are supposed to use pretty big
segments compared to the rest of the antenna.
3. Full dia for the base.
4. Build your model from ground - not from insulator/feed point.No
taper or taper adjustment.
5. Are you cap loading with a beam or wires?
6. Presuming 80 meter band, are your 2 or 3 sets of guys Philly or
steel? Insulated? I've included brackets and starts of guys before,
when steel and connected to the tower.
7. In EZNEC, source placement can be annoying. Build the vert as 1
element and you have to watch the segmentation carefully to know where
your source is. If you want to be sure, in EZ I'd make the model with
a bottom stub of length to the insulator, and build the top part
electrically connecting from there. You would feed at that junction as
a split source (SI); I don't remember that sti didthat though. The
only down-side: segmentation on both sides of the SI need to be the
same length.
8. EZ 6.0 must use Mininec for that type of antenna, and I believe STI
also uses MiniNec. You need to estimate reasonably accurately your
effective ground loss for your radial field. Much less accurate than
the rest of the model.
I responded to your other email first... definitely use fiberglass,
not pvc or Teflon, for insulator up top.
regards, Dave N3AC
On Sat, Oct 23, 2021, 07:48 Mark - N5OT <r-emails@n5ot.com> 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?
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
|