Chapter 19A from "Reflections III" - Step 10 response
- From: Richard Clark <kb7qhc@xxxxxxxxxxx>
- Date: Sat, 21 Jun 2008 14:52:06 -0700
Step 10.
With the 17.98 + j8.77-ohm load still connected, the pi-network
loading and tuning are now re-adjusted to again deliver all available
power with drive level setting still left undisturbed. The
readjustment of the plate tuning capacitor has increased the
capacitive reactance in the pi-network by ?8.77 ohms, canceling the
+8.77 ohms of inductive reactance in the load, returning the system to
resonance. The readjustment of the loading control capacitor has
decreased the output capacitive reactance, thus reducing the output
resistance from 50 to 17.98 ohms. Thus the network readjustments have
decreased the output impedance from 50 +j0 to 17.98 ? j 8.77 ohms, the
conjugate of the load impedance, 17.98 + j8.77 ohms. The readjustments
have also returned the network input impedance ZL to 1400 + j0 ohms
(again equal to RLP), have returned the original area of the RF window
at the network input, and have returned the slope of the loadline to
its original value. For verification of the 1400-ohm network input
resistance after the readjustment, ZL was again measured using the
method described in Step 2, and found it to have returned to 1400 + j0
ohms.
Points in response:
This step is fraught with leaps of faith substituting for sound,
practical evidence.
1.This step consists of several steps. Rhetorically, what is the
meaning of steps, to so much shift stylistically? This is not an
isolated instance, so writing structure needs to be re-examined.
2.All Available Power, (a rhetorical shift from maximum) has not been
established, much less shown. It is not denied that a greater power
can be applied to the new load; but the actual amount of power is not
reported (a reporting shift from earlier protocol).
3.The declaration of attaining a reactance of -j8.77 Ohms is
unsubstantiated in reported measurements. This gives rise to the
appearance of speculation serving the argument.
4.Likewise, the declaration of lowering the output (terminal) Z to
17.98 Ohms is a remarkably precise value without any measurement
evidenced.
5.The verification measurement, a step of considerable substance, is
rendered here as an footnote, clouding the earlier responses, 2 & 3
above, jarring against the lack of the actual measurements of -j8.77
Ohms and 17.98 Ohms. In a nutshell, the verification is shortchanged
against the completeness of earlier measurements.
6.The adjustment of the plate load does not reveal a conjugation.
73's
Richard Clark, KB7QHC
.
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