WD0GOF
06-08-2012, 02:36 PM
What is a good 80 40 20 meter beam?
73, Walt
73, Walt
View Full Version : Who makes a good 80, 40, 20 meter beam
AD7N
06-08-2012, 03:23 PM
The OptiBeam OB804020 is an excellent choice:
http://www.optibeam.info/index.php?article_id=83&clang=1
http://www.optibeam.info/index.php?article_id=83&clang=1
WD0GOF
06-08-2012, 03:33 PM
The OptiBeam OB804020 is an excellent choice:
http://www.optibeam.info/index.php?article_id=83&clang=1
Very good choice, however too large for my application.
http://www.optibeam.info/index.php?article_id=83&clang=1
Very good choice, however too large for my application.
WB2WIK
06-08-2012, 04:54 PM
Very good choice, however too large for my application.
There can't be a "small" beam that covers 80 meters. A 1/2-wavelength driven element alone is 120 feet long. With linear loading could be compressed to about half that (60 feet long) with a small loss in operating bandwidth.
With "loading" to make it smaller, operating bandwidth becomes so narrow it doesn't work like a beam anymore.
There can't be a "small" beam that covers 80 meters. A 1/2-wavelength driven element alone is 120 feet long. With linear loading could be compressed to about half that (60 feet long) with a small loss in operating bandwidth.
With "loading" to make it smaller, operating bandwidth becomes so narrow it doesn't work like a beam anymore.
K4SAV
06-08-2012, 05:25 PM
Here is a homebrew 3 element 80m / 5 element 40m quad. Weighs 3 metric tons.
http://www.pbase.com/df3kv/image/46485719
Think about how you would get this onto the tower.
Jerry, K4SAV
http://www.pbase.com/df3kv/image/46485719
Think about how you would get this onto the tower.
Jerry, K4SAV
N7WR
06-08-2012, 05:29 PM
Optibeam and Step IR are your choices and neither are small.
AC0H
06-08-2012, 06:28 PM
There can't be a "small" beam that covers 80 meters. A 1/2-wavelength driven element alone is 120 feet long. With linear loading could be compressed to about half that (60 feet long) with a small loss in operating bandwidth.
With "loading" to make it smaller, operating bandwidth becomes so narrow it doesn't work like a beam anymore.
And most folks don't have towers high enough to take advantage of an 80m Yagi's attributes.
You need to have it 1/2 wavelength off the ground for it to perfom and it better be a stout tower.
If you can't do that you'd be better served by a 1/4 wavelength vertical with copious radials, if chasing DX.
Or, a 1/2 wavelength NVIS dipole if medium to short range 75m ragchewing is your thing.
With "loading" to make it smaller, operating bandwidth becomes so narrow it doesn't work like a beam anymore.
And most folks don't have towers high enough to take advantage of an 80m Yagi's attributes.
You need to have it 1/2 wavelength off the ground for it to perfom and it better be a stout tower.
If you can't do that you'd be better served by a 1/4 wavelength vertical with copious radials, if chasing DX.
Or, a 1/2 wavelength NVIS dipole if medium to short range 75m ragchewing is your thing.
KO6WB
06-08-2012, 08:22 PM
For 80/75 perhaps a four square would do well and you could make one for 40 meters as well. You could then put up a mono-band beam for 20 on a tower. Most folks opt for a tri-band beam for more versatility. There are other directive arrangements for 40 meters using multiple dipoles to produce a 360 degree selectable arrangement.
There are published dimensions in the ARRL Antenna Book. There are certain things that cannot be shorten on a beam and that is the spacing between elements. These will be quite large at 80/75 meters. There is not a good market for a beam on the lower bands and as such very few manufacturers will produce that type of antenna.
I have heard of and seen some operators using two element quads with a rotatable tower as the support on 80/75.
Most installations are homebrewed.
If you don't currently have an antenna book there is one that you can down load here; http://www.eagle3.net/n4ywn/docs/PracticalAntennaHandbook-vol4.pdf.
Hope this helps
73
Gary
There are published dimensions in the ARRL Antenna Book. There are certain things that cannot be shorten on a beam and that is the spacing between elements. These will be quite large at 80/75 meters. There is not a good market for a beam on the lower bands and as such very few manufacturers will produce that type of antenna.
I have heard of and seen some operators using two element quads with a rotatable tower as the support on 80/75.
Most installations are homebrewed.
If you don't currently have an antenna book there is one that you can down load here; http://www.eagle3.net/n4ywn/docs/PracticalAntennaHandbook-vol4.pdf.
Hope this helps
73
Gary
