I did not mention that obviously, one has to watch both the impedance
variation and the reactance term to use my approximation to finding the sign
of the reactance. Larry's antenna is a good exception to the performance of
simpler antennas.
Most ham antennas have well defined harmonic related
Don Wilhelm wrote:
Folks,
There is an error in the reply I sent last night (below) that is very
important - it makes a big difference.
When increasing or decreasing the frequency to determine the sign of the
reactance:
One must observe the increasing or decreasing of the IMPEDANCE (Z) and not
Thanks for the clarification, Don. As I mentioned in my private email,
to eliminate all ambiguity, you really need to look at the slopes of
both impedance magnitude and phase (or alternatively resistance and
reactance). This will cover you for both sides of either series or
parallel resonance.
Folks,
There is an error in the reply I sent last night (below) that is very
important - it makes a big difference.
When increasing or decreasing the frequency to determine the sign of the
reactance:
One must observe the increasing or decreasing of the IMPEDANCE (Z) and not
just the reactance.
I
avoid the
extra step.
73
David
G3UNA
>
> From: J F <[EMAIL PROTECTED]>
> Date: 2007/03/16 Fri PM 12:02:58 GMT
> To: [EMAIL PROTECTED],
> Elecraft Discussion List
> Subject: [Elecraft] Antenna Analyser - Phase Angle Sensor
>
> Stuart,
>
> In the old
Stuart,
In the old Ham Radio Magazine, a 1988/89 issue there
is a very simple circuit called a PHASOMETER by the
author. It uses as zero center meter (although you
could set up LEDs to perform the same way) to
determine which side of resonance your antenna on.
The specific purpose for this unit
I was referring to a narrowband case of examining a simple antenna to see if
it is long or short. One with well defined sharp peaks and valleys of
impedance, and one principal resonance which you can estimate from the
dipole physical length. Seems to work using my Autek or MFJ 269. I was not
Thanks Don, my work around has worked for simple antennas like dipoles,
loops, verticals, etc.
His OCF antenna has an interesting sharp resonance which must be the
principle one, but also a non harmonic resonance which is interesting. I
had not looked at a horizontal OCF (off center feed) one
Larry,
I see no inconsistency with Stuart's statement in your plot. Without
looking at the specific phase angle - if the absolute magnitude of the
reactance increases with increasing frequency, then the load is inductive,
it it decreases, then the load is capacitive.
The poles of the black curve
IF it is increasing with frequency it is inductive
reactance, (+); if decreasing with frequency increase, it is capacitive
reactance, (-).
This is not quite true.
The reactance change over freq is something like a sawtooth waveform.
Assume we start at reactance=zero (resonance) and freq is
That won't work, Stuart. I wrestled with this for awhile when developing
my LP-100 Plot program. You also need to know which side of resonance
you're on, and whether it's a series or parallel resonance... at a minimum.
Take a look at the plot at www.telepostinc.com/Files/OCF_Z_PH2.jpg. This
is
It is not too simple to measure phase with a additional circuitry. However,
it is simple to move the frequency of the antenna analyzer and see the
Reactance change, IF it is increasing with frequency it is inductive
reactance, (+); if decreasing with frequency increase, it is capacitive
react
I'd be interested in the article if you have it in digital form, Mike.
I implement a sign detection algorithm in the Plot program for my LP-100
Digital Vector wattmeter. It works pretty well most of the time, but I
added editing of curve points in case it makes an obvious mistake so
that the c
Hi,
When discussing antenna analysers there's always a discussion on the issue
of measuring the sign of X. For some years now I've carted round an article
out of the Power Amplifier Handbook titled High-Speed Microprocessor
Controlled Antenna Matching Unit, in which the author implemented a phase
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