Re: gain in a monopole wire antenna

Very likely your example antenna doesn't use a perfect conducting infinite ground, and then you don't have the +3 db gain increase.

Other thing, they state the gain for one value of elevation (or theta angle), maybe the gain is higher at somewhat higher elevation (lower theta). This happens frequently with small ground planes.

Best you can do is to get more details about the radiation pattern you provided (that is actual antenna geometry with ground plane and dielectrics if present, and check their definition of gain as you know that there can be some confusion).

thank you Wim.
yes,you right.
1. ground plane is not perfect.
2. this is in theta=90 and phi=0.
my problem was solved.

"? Please read a few books antennas!"
Sorry I`m not reader I`m writer.
Simply simulate with antenna CAD s.

Bob60!
please don't answer in my topics!
I have read antenna books as much hair on your head!
you are a Newbie level4 only!ok?
so,don't reply in my topics.
thanks.



I mean that why gain in a large bandwidth is smooth,while in practice,a monopole antenna has small bandwidth.
Anyway,my problem was solved.Bob60!please don't reply at all!

wow you know my head? you are welcome, plus read as much as you have on your head.

Here we are.
I spend one day of my very expensive time for the yours monopol simulations. May be you know that for monopol ( against to dipol who don`t needs the ground ) necessary ground plane as much as possible. Here are result of retaliated Gain versus ground dimensions from 0.25 up to 4 lambda and gain varied from 1.5dB to 5dB, that is for impedance Z =36 and PEC (perfectly conductive ) surfaces. For dipol was very fast and easy directivity and gain ~ 2.05 dB.
it depend... against to you I`m professional (with antennas I earn money) and at your show concerning "our earth ? is it cylinder or non?" I`ll try not disturb. So body, sorry for possible inconvenient, my first language is not English, I`m really not responsible for all texts bellow.

Well, here is one, not bad sample of the dipol, for 2.4GHz .Same are from 400MHz up to 5GHz.
Ground not necessary, return loses -25dB .

@Bob60: My First impression, based on the image, is folded dipole. If so there should be some impedance transform and balun function. As I can't guess the actual length in combination with the thick patches at left and right side,, is this antenna really operating in a half wave resonant mode?

Regarding the ground plane: I think Ghasem interest was in why actual gain for a ground plane / monopole combination is below the values stated in many references (where infinite PEC ground plane is assumed).

Yes of course here is transformer I`d never show. Finally it is normal practice never show key details and directed to the wrong way ( like in Czech republic or Korea ( there are cretinism) or smart books like Eric Tart Red Arbeitsbuch fur den HF- Techniker moust of the sheema was wrong)

@Bob60: In this forum it is NOT normal practice to NEVER show details or to guide people to the wrong direction. There are many professionals posting in this forum and it is clear that it is not always possible to provide details as this may violate non-disclosure agreements (NDA).

So if you can't provide information because of restrictions, or other reason: just don't respond and don't provide misleading or irrelevant information.

All my info here is correct and quite actual and based on own simulation and prototyping as well.
Texts above only like illustration, what was happens with me or my friends.
As for foiled dipol it is very useful and like a part of the mirrored dish antenna with gain up to 22dBi @ 2.5GHz like excitatory
simply the best.

I think that real obstacles are far from infinite PEC ground plane. Especially some physically short variants: helical, some F or inverted F or multi bands solutions for mobiles and so on. It depends from height of feeding, lambda and so on ( for 300MHz 1m lambda ). And big gain for OMNI directional antenna inst very nice and Chines products are significantly complicate understanding with these staff.
Сertainly ideally D should be: dipol directivity + 3dB, because vertical pattern is half, more narrow ( but it dependents from the ground dimensions, and conductivity ). For instance ground plane impedance is closer to 50 ohm.

Ground Plane is antenna. Something mix between monopole and dipole or non symmetrical dipole.