explaining antenna specs

[gouzou]

Hi to everyone.
This is my first post in the forum and i would like your help.
I have an antenna (of 300mhz operating frequency range) with the following specifications. Can anyone explain me what each specification represent in practice, cause i am a little bit comfused.

3db beamwidth:
- E-plane: 18deg to 32deg
- H plane: 18deg to 28deg

Sidelobe suppression:
- up to +/-70deg from maximum ( >xdb)
- from +/-70deg from maximum ( >ydb)

Front-to-back ratio from +/-90deg: ( >zdb)


p.s.I undestand that the 3db beamwidth is the half-power beamwidth for E(vertical)plane and H(Horizontal)plane. But why is there a range (e.g. 18-32)?
Also, i understand that the sidelobe suppression is how much lower are the sidelobes compared to the main lobe. But what do the 2 specs represent exactly?

 

[ve9jmc]

the 3DB is the Gain on that antenna.

the 18-32deg is the actual beam width. the smaller beam antenna's have a wider beam width as you have there. now if you were to have a 7 or 13 element beam the beam width could be as low as 5 to 10 degrees wide.

the front to back ratio means that all of the signals should be received from the front of the antenna, but if there is a signal from the back, then the reflector of the beam antenna should block that signal from the back.

as far as side lobe suppression. in a beam antenna you do not want many if any side lobed while you are transmitting. you want all of that signal to be shooting out the front of the antenna. so the better the side lobe suppression the more signal going where it should be.

hope it help you out.

 

[rfradioconsult]

the 3DB is the Gain on that antenna.

the 18-32deg is the actual beam width. the smaller beam antenna's have a wider beam width as you have there. now if you were to have a 7 or 13 element beam the beam width could be as low as 5 to 10 degrees wide.

the front to back ratio means that all of the signals should be received from the front of the antenna, but if there is a signal from the back, then the reflector of the beam antenna should block that signal from the back.

as far as side lobe suppression. in a beam antenna you do not want many if any side lobed while you are transmitting. you want all of that signal to be shooting out the front of the antenna. so the better the side lobe suppression the more signal going where it should be.

hope it help you out.

Unfortunally your answer(s) completly miss the mark; you have posted answers that are not at all related to the question. I would hazard that the OP is looking for the answer to a college assignment and is not related to actual practices.

 

[gouzou]

Unfortunally your answer(s) completly miss the mark; you have posted answers that are not at all related to the question. I would hazard that the OP is looking for the answer to a college assignment and is not related to actual practices.

I think I would agree.
Can anyone please explain me what the characteristics mean in practice?

 

[Token]

Hi to everyone.
This is my first post in the forum and i would like your help.
I have an antenna (of 300mhz operating frequency range) with the following specifications. Can anyone explain me what each specification represent in practice, cause i am a little bit comfused.

3db beamwidth:
- E-plane: 18deg to 32deg
- H plane: 18deg to 28deg

p.s.I undestand that the 3db beamwidth is the half-power beamwidth for E(vertical)plane and H(Horizontal)plane. But why is there a range (e.g. 18-32)?

Without knowing the specific antenna in question my guess on the range of beamwidths is that the beamwidth, and gain, varies accross the frequency range. Most likely the 18 deg applies at the upper end of the frequency range and 28 and 32 deg at the lower end.

What antenna you are talking about might help explain some of it.

T!

 

[gouzou]

The antenna is used for comms covering long distances.
So, i see. As far as i understand, the upper frequency makes the antenna more directive, so that's why the beamwidth is narrower.
What about the sidelobe specifications?
The "from +/-70deg from maximum ( >ydb)" means that the suppression of the lobe is greater than ydb at +/-70deg from the maximum, where maximum is the maximum power output, meaning the φ=0?

 

[gouzou]

What i want to do, is to draw the radation pattern of the antenna

 

[jim202]

What i want to do, is to draw the radation pattern of the antenna

If your looking for the radiation pattern of the antenna, why not just go to the web site of the company that
makes the antenna and get it direct from the horses mouth. To my best recollection, they all publish
that as part of their standard specs. Why re invent the wheel when it's there for the taking.

 

[gouzou]

because neither do i know the manufacturer company nor i can find any information on the internet

 

[Token]

The data you have provided is not enough, by a long shot, to draw a radiation pattern.

T!

 

[gouzou]

I'll tell you what i think and mark me if i'm wrong.

About the sidelobe suppression:
the suppression increases (meaning the power signal is being diminished) as we move from the maximum (meaning the maximum power output which occurs at φ=0). The maximum suppression stated by the data is at point +/-70deg from the max, where the suppression has reached ydb.

About the front to back ratio:
the received signal from the main lobe (in the front of the antenna) is by zdb greater than the secondary lobe located at the back of the antenna.

 

[nanZor]

What i want to do, is to draw the radation pattern of the antenna

EZNEC might do what you want:
EZNEC Antenna Software by W7EL

 

[majoco]

Go to another company's website, find an antenna that looks like yours, and copy their radiation pattern. They'll all be about the same - it ain't rocket science.

The old ARRL handbook has heaps of yagi designs and their patterns. Mostly theoretical, as the antenna in free space doesn't perform the same as soon as you put it on a pole above the ground or a roof.

Cheers - Martin ZL2MC

 

[steve300]

AN-SOF antenna software

You could also try AN-SOF