On 11/26/14, 11:39 AM, Ken wrote:
On Nov 26, 2014, at 12:48 PM, Wilson <infomet@embarqmail.com> wrote:
My own take is that after hearing a lot of talk, much of it BS, and being exposed to a lot of
colorful ads, we have developed a “need” that far overshadows reality.
Wilson, I tend to support your view. “Back in the days”, there was little or no use
of baluns. Look back at my 1960’s handbooks and antenna books and the mention was rare and
certainly not a mainstream requirement.
On the other hand, back in the 50s and 60s, many rigs had tube finals
with an output matching network, and there was substantial use of
open-wire line. These things have a pretty wide range of Z that they can
match to, and nobody gives a second thought to the narrow band-ness:
you'd retune when switching bands or even within a band.
So, weird impedances resulting from unbalance, parasitic coupling
between antenna and feedline and such probably weren't as big an issue.
The solid state rigs were MUCH more picky about load impedance. If your
Yagi design happened to have a 22 ohm feedpoint impedance, and you fed
it with 50 ohm coax, and it transformed into anywhere from 22 to 120
ohms, your tube rig probably didn't care much, so the antenna mfrs
didn't see the need to put a matching transformer in the design. But
your brand new solid state rig certainly did.
That might have been the start of the whole thing.
The other thing is that the RFI and RFI tolerance environment were
somewhat different back then. There wasn't the plethora of sensitive
low power receivers floating around: phones were analog, twisted pair
(which is pretty good for EMI rejection). TVs,AM/FM radios, and Hi-Fi
stereo gear had their issues. But that was about it.
So having weird pattern lobes (from coupling to the feedline) that
radiate or receive in unintended directions may not have been as
noticeable. Or it might have been written off to something else
(probably grounding, even if that had nothing to do with it. I can hear
Jim's teeth gnashing from 300 miles away as I write this)
Think about all the "magic" attributed to the use of a balun that is
incorrect: it's probably all based on somebody trying it, it happening
to work better, and it going from there.
In the 50s and 60s, doing a detailed analysis of it, to understand the
physics at a root level, would have been very challenging using only
analytical means, without numerical codes like NEC to try it "in silico"
as the current phrase has it. And the sheer physical labor needed to do
a good field experiment is daunting.
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