No sir, we could most certainly *not* debate the definition of
resonance. As I said before, it's long-settled and accepted science.
To get back to the original topic, the answer is it depends on what
you're doing. Knowing hams as I do, my suggestion remains to throw up
whatever sort of antenna appeals to you and find out what works and
doesn't through experimentation. Pick any antenna design out of any
book, build it, and see if you can load it. Lather, rinse, repeat.
One can get much more out of this than arguing theory one has never
studied.
The deeper concepts might as well be black magic for the majority of
licensed Amateurs and it's probably best to leave it at that. The
vast majority of us lack the proper background in theory to discuss
the underlying concepts and that's why you see so much tail-chasing on
these mailing lists. Somebody who's "been a Ham for fifty years" will
say something utterly retarded and someone with an engineering degree
will call him on it, and around we go.
One of the FCC's reasons for allocating the spectrum to us is for
experimentation. That is for all of us, engineers and non-engineers
alike. Amateur radio was never meant to devolve into a bunch of
Talmudic debate. Therefore, I say throw some wire in the air and see
what happens!
I've heard it said that the Internet is the death of Ham Radio. It
may be, but not because of the communication afforded by the Internet.
It'll be because we'll stop building antennas and towers and
amplifiers and instead just argue over stuff most of us don't and
can't understand until we all get mad and leave.
Jeff/KD4RBG
Society of Broadcast Engineers #25244
---- Original message ----
>Date: Fri, 7 Aug 2009 22:37:57 -0700
>From: "Clay W7CE" <w7ce@curtiss.net>
>Subject: Re: [TowerTalk] Resonance is over rated
>To: <towertalk@contesting.com>
>
>It sounds like we could debate the definition of resonance for days without
>reaching a consensus. So let's get back to the original topic: is resonance
>an important attribute of a good antenna? For example, consider a 40M
>double-extended zepp antenna. At the feed point the impedance varies from
>243-j1150 at 7.0 MHz to 165-j870 at 7.3 MHz. The reactance is not zero
>anywhere in the 40M band. Yet this antenna exhibits approximately 3 dB gain
>over a "resonant" dipole, and as one would expect a narrower 3dB beamwidth.
>One could argue that a double-extended zepp is actually two end-fed
>collinear resonant dipoles whose ends are separated by 1/4 wavelengh. But
>at the feed-point, which is the only point of visibilty that we have, there
>is reactance and the circuit does not appear resonant and requires some form
>of tuning network to make the transmitter happy. It does have zero
>reactance and is resonant around 8.64 MHz, but the pattern no longer has two
>broadside lobes, but rather 4 lobes that are approximately 45 degrees from
>broadside and the maximum gain is now only 1.2 dB better than the dipole.
>In this case resonance may actually be hurting us.
>
>The bottom line is that you have to look at a much bigger picture than just
>the feedpoint to understand whether an antenna is effective or not.
>Measuring feedpoint impedance and declaring victory when the reactance is
>zero or when the SWR is below a certain point is just plain ignorant, unless
>your only goal is good SWR and antenna performance is not important. If the
>antenna is not resonant, you can always add a matching network to make it
>appear electrically resonant to the transmission line and/or transmitter.
>
>73,
>Clay W7CE
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