Hans,
As you note, the specifics of the pattern count a lot. Side and back
lobes, & high angle lobes all add QRN and QRM you don't want to hear.
So often it is better to sacrifice a bit of gain to have a very clean
pattern. Stacks add gain and also change the elevation angle of lobes
as yagis are placed higher above ground, and both are reasons to have a
stack. Much of the "big gun" advantage of mono-banders is the superior
pattern as well as the slightly higher gain over similarly sized
multi-band yagis. So in the right situation, good F/B may be better
than a few more db's of gain.
I can A/B a 5L x 2 monobander stack against a very good 4L multiband
yagi, noise and QRM go down and signals come up on the stack. It can be
less than one to about 2 S units both ways, depending on arrival angles,
etc. Of course, that is an totally unfair comparison $ for $ of cost.
RE the other post, it is not surprising that a "super shorty" multi-band
beam at it worst design point (2L on a 6' boom for 20m!) has a negative
advantage over a dipole at one half wavelength up. Resonant dipoles at
1/2 wl and higher are very good antennas. Fan dipoles in my experience
beat other "all band" horizontal single wire antennas.
One "golden rule" oft quoted is a db costs about $1500. Against a
dipole at 3/4 wl high that is a low estimate for tower + rotator + yagi
+ install. One GR that I subscribe to for yagis is boom length is what
counts. Five elements on a 70% wavelength boom works great. Three
elements on a 25% wavelength boom might be a waste of money.
Grant KZ1W
On 1/12/2016 9:54 AM, Hans Hammarquist via TowerTalk wrote:
I wonder, I believe there are many other solutions to give "maximum gain" and "louder signals" than
yagi antennae if it is only the gain that counts. I was,early in my time at this hobby that the more gain you got the
better. I built more than one type of "high gain" antenna configurations without getting even close to the
"big guys". Isn't it just as important that you can hear the other guys out there through all the QRM and QRN
that is out there. I have found that a lousy yagi or quad with a reasonable F/B ratio is better than a better gain
antenna.
Correct me if I'm wrong.
Hans -N2JFS
-----Original Message-----
From: dw <bw_dw@fastmail.fm>
To: towertalk <towertalk@contesting.com>
Sent: Sun, Jan 10, 2016 9:53 am
Subject: [TowerTalk] Return on investment (golden rules) for antenna
installations
I read an interesting article in eham where EZNEC was used to compare a
specific commercial beam to a dipole.
I guess I was a little surprised at the results.
The article is here.
http://www.eham.net/articles/35421
It goes to the question of whether or not a given antenna solution
represents an improvement significant enough to warrant investment.
I wonder how others formulate return on investment considerations.
Perhaps years of experience, and some "been-there-done-that", have
allowed you to develop some golden-rules about antennas?
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