"Wes" wrote in message
ups.com...
This will be the last word I have on this topic.
As: This is the last word from the higher authority, like, no more
arguments, I am right, case closed? Just in case you might be wrong, here
we go:-)
I have placed two files he
www.k6mhe.com/n7ws/N7WS_Yagi_Resonant.EZ
and he
www.k6mhe.com/n7ws/N7WS_Yagi_Shortened.EZ
The files are models of my 20-meter three-element Yagi that are as
nearly representative of the physical antenna and its location as I
can make them. The only difference between them is the half-length of
the DE. The actual antenna uses the shortened version with a stub
(Beta) matching/balun arrangement.
What you mean half length of DE?
Resonant DE is 410.68" long
Shortened DE is 399.64" long - that is 11.04" difference
Resonant frequency on resonant model is 14.18 and shortened is 14.48
Instead of the integral stub, which Yuri believes is part of the
antenna that is "folded back" along the boom, I will move the matching
system away from this location using an ideal ½ wavelength (34.7 foot)
transmission line with an ideal current balun at the antenna end. I
don't believe anyone would argue that the feedpoint impedance is not
replicated exactly at the input end of this line.
Yuri believes? Is anyone there who does not believe that hairpin loading
stub or beta match stub inserted in the middle of driven element is not the
part of the element, aka, standing wave resonant circuit? Like there is no
RF current flowing into the hairpin? Like element does not have to be
shortened to compensate for the insertion of the stub? Doesn't Yagi antenna
work with half wave (+-) resonant elements? If you loaded, inserted stubs in
the parasitic elements, you would not have to shorten them?
"Calculations" proving ??? snipped
The network loss remains 0.02 dB. So much for this less than
ideal stub vs. Yuri's preferred discrete inductor.
There you have it. The stub matching method is equal to a discrete L-
network in efficiency, it does not detract from the antenna efficiency
one bit, it can incorporate the balun function without additional
components, it grounds the feedpoint, with a little sealant on the
cable, it is weatherproof and unlike Gammas and Tee-matches, it will
handle full power without being prone to capacitor breakdown. It is
not part of the radiator; it is part of the matching network. Period.
Claiming that beta match or hairpin loading inductance is not the part of
the radiator is news to me.
Claiming that driven element was shortened to half, when in fact just by 11"
and resonant frequency moved from abt 14.18 to 14.48 MHz, and modeling the
antenna without the beta match hair pin, and then "calculating" 0.02 dB
difference in gain, sure "proves" the point.
Here I described the real life situation and modeling by using simple case
of 40m dipole, resonant and resonant shortened with "beta match" hairpin. I
maintain the resonant frequency and compensate for the effects of inserting
the hairpin. The gain on the dipole drops by 0.15 dB when fed at the 75 ohm
point and by 0.2 dB when fed close to 50 ohm point. You can read the rest at
my web site:
http://www.k3bu.us/beta_match.htm
Again, it has ben proven by modeling and in practice that loading solenoid
coils are better performers as loading element than hairpins, especially
when better symetry along the element is important for bettern pattern and
F/B. But I guess, that's another story to argue.
Not the last word from me, if I am wrong and made error in modeling, I would
like to be corrected. (I tried to post the EZNEC files, but having problem
downloading them. Will try to rectify.)
73 Yuri, K3BU.us