hello;

until now I have used 4nec2 to model cubical quad type antennas. Now,
I have been asked to design an end-fire helical antenna with a
groundplane. I've figured out how to model a ground plane using 'fast
ground' and radials and stuff, but I'm having trouble with the
excitation. I guess I don't really know the particulars of it. When
I was designing cubical quads, I'd just slap it on the loop and be
done with it; I assumed that nec was sort of making an open circuit in
the loop and connecting a transmission line to it--that type of
thing. How do I tell nec that I want one end of the conductors
connected to the ground plane, and the other to the helix? Does it
know somehow?

Any more tips on modeling helical antennas with ground planes in
4nec2?

Thanks alot for your help;
Sean.

wrote in message
oups.com...
hello;

until now I have used 4nec2 to model cubical quad type antennas. Now,
I have been asked to design an end-fire helical antenna with a
groundplane. I've figured out how to model a ground plane using 'fast
ground' and radials and stuff, but I'm having trouble with the
excitation. I guess I don't really know the particulars of it. When
I was designing cubical quads, I'd just slap it on the loop and be
done with it; I assumed that nec was sort of making an open circuit in
the loop and connecting a transmission line to it--that type of
thing. How do I tell nec that I want one end of the conductors
connected to the ground plane, and the other to the helix? Does it
know somehow?

Any more tips on modeling helical antennas with ground planes in
4nec2?

Thanks alot for your help;
Sean.

Hi Sean

If you are willing to let me learn along with you, I'd like to try modeling
your helix using EZNEC. I think I can model a helix over an infinite
ground plane using EZNEC.
I am interested in learning to use 4nec2but am a real poor learner,
especially when I dont bother to read the instructions.

Jerry KD6JDJ

On Nov 10, 11:16 pm, "Jerry Martes" wrote:
wrote in message

oups.com...



hello;

until now I have used 4nec2 to model cubical quad type antennas. Now,
I have been asked to design an end-fire helical antenna with a
groundplane. I've figured out how to model a ground plane using 'fast
ground' and radials and stuff, but I'm having trouble with the
excitation. I guess I don't really know the particulars of it. When
I was designing cubical quads, I'd just slap it on the loop and be
done with it; I assumed that nec was sort of making an open circuit in
the loop and connecting a transmission line to it--that type of
thing. How do I tell nec that I want one end of the conductors
connected to the ground plane, and the other to the helix? Does it
know somehow?

Any more tips on modeling helical antennas with ground planes in
4nec2?

Thanks alot for your help;
Sean.

Hi Sean

If you are willing to let me learn along with you, I'd like to try modeling
your helix using EZNEC. I think I can model a helix over an infinite
ground plane using EZNEC.
I am interested in learning to use 4nec2but am a real poor learner,
especially when I dont bother to read the instructions.

Jerry KD6JDJ

this sounds good.

you said you can model a helix over an infinite ground plane in
eznec? What are you powering it with? a coax? if so, you have one
conductor connected to the helix, and the other is where? this is the
source of my confusion, i guess.

sean.

wrote in message
oups.com...
On Nov 10, 11:16 pm, "Jerry Martes" wrote:
wrote in message

oups.com...



hello;

until now I have used 4nec2 to model cubical quad type antennas. Now,
I have been asked to design an end-fire helical antenna with a
groundplane. I've figured out how to model a ground plane using 'fast
ground' and radials and stuff, but I'm having trouble with the
excitation. I guess I don't really know the particulars of it. When
I was designing cubical quads, I'd just slap it on the loop and be
done with it; I assumed that nec was sort of making an open circuit in
the loop and connecting a transmission line to it--that type of
thing. How do I tell nec that I want one end of the conductors
connected to the ground plane, and the other to the helix? Does it
know somehow?

Any more tips on modeling helical antennas with ground planes in
4nec2?

Thanks alot for your help;
Sean.

Hi Sean

If you are willing to let me learn along with you, I'd like to try
modeling
your helix using EZNEC. I think I can model a helix over an infinite
ground plane using EZNEC.
I am interested in learning to use 4nec2but am a real poor learner,
especially when I dont bother to read the instructions.

Jerry KD6JDJ

this sounds good.

you said you can model a helix over an infinite ground plane in
eznec? What are you powering it with? a coax? if so, you have one
conductor connected to the helix, and the other is where? this is the
source of my confusion, i guess.

sean.


Hi Sean

I can make a helix with EZNEC very easily. I located the ground end of
the helix slightly away from ground. A short wire from the ground end of
the helix to ground becomes the feed.
Contact me at my E-mail and we can try your dimensions.
I'd sure like to learn to maneuver in 4nec2. This may be a motivator so
I can get more familiar with 4nec2

Jerry Martes wrote:
wrote in message
oups.com...

On Nov 10, 11:16 pm, "Jerry Martes" wrote:

wrote in message

egroups.com...




hello;

until now I have used 4nec2 to model cubical quad type antennas. Now,


I can make a helix with EZNEC very easily. I located the ground end of
the helix slightly away from ground. A short wire from the ground end of
the helix to ground becomes the feed.
Contact me at my E-mail and we can try your dimensions.
I'd sure like to learn to maneuver in 4nec2. This may be a motivator so
I can get more familiar with 4nec2

Exactly right. Either end the helix on the ground plane and put the
excitation on the first segment of the helix, or create a short segment
that connects the helix to the ground plane, and put the excitation there.

The trick in modeling a helix isn't the helical part, it's the ground
plane. Radial wires with circles, a rectangular grid of wires, etc.
For simple hacking, just point the helix straight up and use a perfectly
conductive ground.

Jim

wow thanks alot. i can't believe i didn't think of that! well not
really.

only thing is, i need some backlobes in my pattern, so i think ill
have to figure out the radials