OK…
So I have a Cushcraft A3S up at about 60′ and I’ve always thought it plays pretty well. Before the A3S I operated a Force 12 C3 on the same tower but from a different QTH. The problem I’m having is some friends of mine (“seasoned” Hams mind you) are always giving me crap about my “rotatable dipole” and “lame tribander” when compared to their 20 Meter 204BA Monoband antennas.
So I figured I’d do a little homework, ask a few questions from knowledgable Hams and then try to figure out just what the real differences are between my Tribander and their Monobander(s). Here’s a little bit of what I’ve found and also a couple observations…
One “S” unit equals 6 db of gain (http://www.ve3fyn.ca/nvis/Decibel.htm)
Doubling power equals 3db of gain (http://www.phys.unsw.edu.au/jw/dB.html)
The typical loss in a 100′ run of Belden 9913 (RG8) coax on 14 MHZ at 1,000 watts is .46 db (899 watts Effective Radiated Power) – (http://www.ocarc.ca/coax.htm)
The typical loss in a 100′ run of Belden 9258 (RG8X) coax on 14 MHZ at 1,000 watts is 1.087 db (779 watts Effective Radiated Power) – (http://www.ocarc.ca/coax.htm)
A Hy-Gain 4 Element MONOBAND Yagi model 204BA has 8.2 dbi (6.0dbd) of gain. (http://hy-gain.com/man/pdf/LJ-204BA.pdf)
And from the same manufacturer (with what I suspect are the same measuring techniques and formulas) the 3 Element TRIBAND Yagi (TH3MK4) has 8.0 dbi (5.8dbd) of gain. (http://hy-gain.com/man/pdf/TH-3MK4.pdf)
Very similar specs for the Cushcraft A3S vs. a Hy-gain TH3MK4 – (http://www.texastowers.com/cushcraft_a3s.htm)
Hmmmmm…
Maybe I should just switch my coax (from RG8X to 9913), pick up .63 db along the way and still have a solid db of gain more than a 20 meter 204BA Monobander fed with RG8X?
In the next few days/weeks I’ll gather information on a couple of other tribanders (namely the M2 KT34XA and Force 12 C3) and then I’ll compare those to their 204BA’s, but for now and until somebody can come along and prove me wrong, it seems to me that for a measly .2 db of gain and a little more directionality, I can’t justify erecting 3 towers, swinging 3 heavier, clumsier, larger and single band use antennas when you can have similar results on 3 bands and only one tower.
It’s a no-brainer in my opinion. Maybe someone can enlighten me as to what I’m missing? Bring your best shot, but make sure you back it up with some kind of fact(s) or it’s just another worthless opinion.
73,
NØUN
Agree with you on that Wayne. There is no magic wand
I like your way of thinking. Yes its always nice to improve your set up but somtimes i think too many people just like talking about how big there antenna is (you know what they say about people with big antennas). Cheers Ross 2M0XAT. P.S. i really enjoyed the QSO the other day.
Wayne you’re so right. I just went through the same exercise and came to exactly the same conclusion. Why spend 9dB more dollars for a gigantic antenna, beefy rotator and heavy duty tower just to get an imperceptible 1dB of gain (or less!) over the little tribander?
It would be interesting to do side by side comparison or measurement of the antennas to see if those numbers really hold up but I will suggest that instead of looking at the forward gain of the antennas you look at the F/B ratios of the antennas. This HF radio game is all about hearing and to hear well you need to manage the noise. At HF the pattern is more important than the forward gain. It is all about noise management. You will never hear 1 or 2 or even 3 or more of forward gain in an antenna but 5 or 10 or more of Noise rejection is very important. As an example a beverage receiving antenna has negative gain over a dipole but can have a great pattern and that makes a world of difference.