Incidentally, the 160m "T" I discussed below was deliberately resonated to
1.4 MHz -- not to 1.8 MHz. At 1.4 MHz, Z was 85+j0. At 1.8 MHz, Z was
50+j200. A low-pass L network then transformed that value into 50+j0.
----- Original Message -----
From: "Paul Christensen" <email@example.com>
Sent: Friday, December 23, 2011 10:36 PM
Subject: Re: [TowerTalk] Elevated vertical
>> "Would you consider my 130' center fed dipole "resonant" on 60 or 30 m
>> because the antenna tuner inside the rig can tune the
>> antenna/twin-lead/balun/coax to a 1:1 SWR inside the rig? Sorry to say
>> but that one hurts my head to think of as "resonant". Tuned? yes.
>> Matched? Yes. Resonant? No."
> How are you defining the terms "tuned," and "matched?" What is tuned and
> what is matched? How is your use of "tuned" different than "resonant?"
> Your antenna in this example is not resonant at the antenna feed point,
> resonant as a system attached to a transmission line with the help of the
> rig's tuner.
> Let's consider your example of a 130 ft center-fed dipole with some length
> of transmission line being used on 60 or 30m. If the tuner in the rig is
> performing it's job and it attains a 1:1 VSWR at the input to the tuner,
> then your 130 ft dipole and transmission line are resonated, where the
> system reactance is zero. That's a resonant antenna system - where circuit
> reactance is zero. In some circles, it's also called "tuned." See below.
> Tuned = Resonant = 0 reactance = X(0).
> That's the X value but R may be a value well above or well below 50 ohms,
> but your antenna is still resonant. However, is it also matched at the
> input (50+j0)?
> I just assisted in the design and installation of a 160m "T" radiator
> consisting of 85' ft of vertical section and a 130 ft. flat top section.
> Using 4Nec2 software, the feed-point Z was close to 50+j200. This value
> confirmed with a Vector Network Analyzer. Under this condition, tuning
> antenna to resonance and matching the antenna to 50 ohms resistive
> a low-pass L network, or simply a series capacitor to cancel inductive
> reactance by an equal but opposite amount of capacitive reactance. In
> case, one series capacitor will tune the system to resonance, while
> that the input remains matched at 50 ohms resistive (50+j0) for a 1:1
> It may have also been possible to achieve the same result by changing the
> feedline length to also tune the system into resonance. But tuning to
> resonance may not have yielded an R=50 value.
> Through the decades, this topic has been presented over and over again by
> QST's editors with re-prints of By Goodman's classic article: "My Feedline
> Tunes My Antenna." Here, Goodman used the term "tune" to denote
> Rather than using line length to resonate the system as discussed by
> Goodman, the tuner in your rig is doing it for you, and it's performing
> full tune (resonating) and match function to attain 50+j0 at the tuner
> for a 1:1 VSWR.
> Paul, W9AC
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