Software for calculating feed impedance
Software for calculating feed impedance
Does anyone know if there is software available that can calculate the feedpoint impedance (and reactances) of a ground mounted vertical of fixed height at various frequencies?
Cheers
Nev
Cheers
Nev
Re: Software for calculating feed impedance
Hi Nev,
Try the following:
http://www.arrl.org/files/file/Antenna% ... 0W8WWV.pdf
It may point you in the right direction.
73
Andrew
Try the following:
http://www.arrl.org/files/file/Antenna% ... 0W8WWV.pdf
It may point you in the right direction.
73
Andrew
Re: Software for calculating feed impedance
If using a std design then the impedence will be easily available , simply measuring it when built will aid in matching but what objectives ?
Re: Software for calculating feed impedance
If I understand your question correctly, MMANA-GAL will do it. Dunno about a graph plot - maybe it does, but I have not found it yet, being a "baby steps" user of the software still.
Cheers
John VK4TJ
Cheers
John VK4TJ
Re: Software for calculating feed impedance
Thanks all for your suggestions.
I am on holidays at the moment on VK4 time, hence the sluggishness of my reply
Perhaps I should explain my query.
If a 40m ground mounted vertical is used on other bands, there is a wide variation in feed impedance; high on 80 and 20, low on 40 and 15 etc. This can make life difficult for a 4:1 voltage balun at the feed point. Losses etc.(The antenna is to be fed with an auto matcher at the base)
The idea occurred to me that if the vertical was cut for say 8.5mHz then the variation in feed imp. on the bands would be less, the antenna being "in between ", neither high nor low Z.
That is why I asked about any relevant software.
Or am I nuts?
Cheers
Nev
I am on holidays at the moment on VK4 time, hence the sluggishness of my reply
Perhaps I should explain my query.
If a 40m ground mounted vertical is used on other bands, there is a wide variation in feed impedance; high on 80 and 20, low on 40 and 15 etc. This can make life difficult for a 4:1 voltage balun at the feed point. Losses etc.(The antenna is to be fed with an auto matcher at the base)
The idea occurred to me that if the vertical was cut for say 8.5mHz then the variation in feed imp. on the bands would be less, the antenna being "in between ", neither high nor low Z.
That is why I asked about any relevant software.
Or am I nuts?
Cheers
Nev
Re: Software for calculating feed impedance
Have a read about the 43ft vertical . mine performs very well and cost not much
http://www.ad5x.com/images/Presentation ... 43RevA.pdf
of course grounding systems help but need not be complicated or costly
http://www.ad5x.com/images/Presentation ... 43RevA.pdf
of course grounding systems help but need not be complicated or costly
Re: Software for calculating feed impedance
Thanks,
I had a look at EZNEC a few months ago and found it rather complicated to say the least. It will need a lot of reading and fiddling I suspect.
When I am back home I will have a try at MMANA-GAL.
I hope it is more user friendly.
Of course I could buy an antenna analyser and have a play with some aluminium tubing
Cheers
Nev
I had a look at EZNEC a few months ago and found it rather complicated to say the least. It will need a lot of reading and fiddling I suspect.
When I am back home I will have a try at MMANA-GAL.
I hope it is more user friendly.
Of course I could buy an antenna analyser and have a play with some aluminium tubing
Cheers
Nev
Re: Software for calculating feed impedance
MMANA-GAL will probably get you up and going faster. The key is to find a .maa file from somebody else
Quite a few ship with the base install, but there are even more in the files section of the Yahoo group.
Even if you have to alter the dimensions, height above ground etc. to suit your particular requirements, having somebody else do the hard work saves having to get your head around X,Y & Z coordinates.
Cheers
John VK4TJ
Quite a few ship with the base install, but there are even more in the files section of the Yahoo group.
Even if you have to alter the dimensions, height above ground etc. to suit your particular requirements, having somebody else do the hard work saves having to get your head around X,Y & Z coordinates.
Cheers
John VK4TJ
Re: Software for calculating feed impedance
EZNEC is easy. You just need to put in the x,y and z coordinates of each element. If you give me the dimensions of everything I will do it for you. Imclide all the ground wires too. Send to my email address VK3auu@dcsi.net.au
David
David
Re: Software for calculating feed impedance
Thanks John and David,
I read the article by AD5X and it has me interested. I was thinking of something shorter than 42 feet but it would have higher angles of radiation I would imagine.
I would like to mount it on the metal roof of a shed of 6X14 metres but the Leader of the Opposition might have a say about that.
When I get home I will spend some time on it, but at the moment it holiday time!!
Cheers
Nev
I read the article by AD5X and it has me interested. I was thinking of something shorter than 42 feet but it would have higher angles of radiation I would imagine.
I would like to mount it on the metal roof of a shed of 6X14 metres but the Leader of the Opposition might have a say about that.
When I get home I will spend some time on it, but at the moment it holiday time!!
Cheers
Nev
Re: Software for calculating feed impedance
you could use a 32'6"vertical but it is not as versatile however it does offer a good signal on 40 m , 15 with some tricks and perhaps another smaller vertical for 10 and 20m as well ? , or if you have some trees then a 43ft sloper perhaps
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Re: Software for calculating feed impedance
Hi Nev... hope you are enjoying your holiday up north.
I have not tried any of these non resonant verticals myself but have done a bit of reading about them. It seems that the length needs to be something that will not produce a very high impedance on any band you want to use it on.
Some common lengths that come up regularly are:
43 feet - used from 80m to 6m
31 feet - used from 40m to 6m
24 feet - used from 20m to 6m
Hope that helps.
Catch you on 80 meters when you get back.
I have not tried any of these non resonant verticals myself but have done a bit of reading about them. It seems that the length needs to be something that will not produce a very high impedance on any band you want to use it on.
Some common lengths that come up regularly are:
43 feet - used from 80m to 6m
31 feet - used from 40m to 6m
24 feet - used from 20m to 6m
Hope that helps.
Catch you on 80 meters when you get back.
73 Mike
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Re: Software for calculating feed impedance
found this quote in reply to someones question fr non resonant verticals
And the answer is: In 2 years, 37,000+ QSO's, 223 countries, 5 Band DXCC. All with a 31' , S9 Vertical, using the metal roof as the radials, with a Balun Design 4:1 Unun, and an AT-AUTO Tuner. which tunes it better then 1.2:1 on all bands 10-80m.
I think you said you have an AH4 tuner and want to use the shed roof as the groundplane now you just have to get the 31 foot vertical past the minister for war..... good luck
And the answer is: In 2 years, 37,000+ QSO's, 223 countries, 5 Band DXCC. All with a 31' , S9 Vertical, using the metal roof as the radials, with a Balun Design 4:1 Unun, and an AT-AUTO Tuner. which tunes it better then 1.2:1 on all bands 10-80m.
I think you said you have an AH4 tuner and want to use the shed roof as the groundplane now you just have to get the 31 foot vertical past the minister for war..... good luck
73 Mike
Re: Software for calculating feed impedance
Hi Mike,
Thanks for the info. Interestingly the 24ft vertical is almost a quarter wave on 10mHz.
It makes me think about the trapped vert I made for 30/20. It's physical length is 21ft 6in.
I wonder what the radiation angles are for the 31 and 24 ft verts? The 31 ft seems to work according to the quote you posted.
I suspect the shorter verts have higher angles...perhaps.
Anyway, I'm on holidays. I will think of you when it's beer o'clock.
Cheers
Nev
Thanks for the info. Interestingly the 24ft vertical is almost a quarter wave on 10mHz.
It makes me think about the trapped vert I made for 30/20. It's physical length is 21ft 6in.
I wonder what the radiation angles are for the 31 and 24 ft verts? The 31 ft seems to work according to the quote you posted.
I suspect the shorter verts have higher angles...perhaps.
Anyway, I'm on holidays. I will think of you when it's beer o'clock.
Cheers
Nev
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Re: Software for calculating feed impedance
sun is up isn't it? ....
damb I need to add more charecters... that should do it
damb I need to add more charecters... that should do it
73 Mike
Re: Software for calculating feed impedance
EZNEC simulation seems to indicate that the angle of radiation is not changed much.VK3LU wrote:I wonder what the radiation angles are for the 31 and 24 ft verts?
I suspect the shorter verts have higher angles...perhaps.
See pic comparing a 10m tall vertical (full size @ 7MHz) with a 6m tall vertical (40% shortened). In both cases I left the ground plane as infinite real ground (a reduced ground plane will definitely change matters). Vert1 is the full size, primary is the shortened. So the shortened antenna has 1dB more gain above 45 degrees (it is getting closer to being an isotropic radiator), but below 45 degrees they are within 0.1dB.
What has changed with the short vertical is the antenna impedance is screwed up. So you will need an ATU, loading coil, or capacitive hat. Loading/matching has the potential to cause loss, so your performance decrease comes from losses not a change in radiation angle. Loading (with a coil or hat) also narrows the bandwidth.
Re: Software for calculating feed impedance
Thanks Geoff,
That chart makes trying out the 21ft6in 30/20 vertical I made worth a try. I don't know why I have never used it
I still think the 43 ft vert is the best choice from what I have read.
But I can't do a thing about it up here in VK4
Cheers
Nev
That chart makes trying out the 21ft6in 30/20 vertical I made worth a try. I don't know why I have never used it
I still think the 43 ft vert is the best choice from what I have read.
But I can't do a thing about it up here in VK4
Cheers
Nev
Re: Software for calculating feed impedance
"VK3LU"Thanks Geoff,
That chart makes trying out the 21ft6in 30/20 vertical I made worth a try. I don't know why I have never used it
I still think the 43 ft vert is the best choice from what I have read.
But I can't do a thing about it up here in VK4
Cheers
Nev "
It's quite amazing how poorly people judge the height of a thin camo painted vertical , out council claims a 10m limit and in 7 years never a problem even with huge 6m antennas covering much of the house roof
Maybe digital TV has an advantage with no tvi so no complaints ?
That chart makes trying out the 21ft6in 30/20 vertical I made worth a try. I don't know why I have never used it
I still think the 43 ft vert is the best choice from what I have read.
But I can't do a thing about it up here in VK4
Cheers
Nev "
It's quite amazing how poorly people judge the height of a thin camo painted vertical , out council claims a 10m limit and in 7 years never a problem even with huge 6m antennas covering much of the house roof
Maybe digital TV has an advantage with no tvi so no complaints ?