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 a section of an off center fed dipole as measured by my HP 87510A
VNA. If you take the absolute value of the phase data (ie, have it
bounce off zero as it would with a meter that can't determine phase
sign), then you will see the problem. If you look at the phase in this
plot, starting at the left edge, and remembering that all the negative
values have to be reversed to look like a meter without sign detection,
by your definition, the reactance makes the following changes from left
to right edge...
C, L, C, L, C, L, C, L
In reality, as the VNA shows, there are fewer changes. The sequence is...
C, L, C, L, C
Without the visual aid, it can be confusing, to say the least.
In my Plot software, I take into account a number of factors, based on
the slopes of the magnitude and phase of impedance. If you don't do
this, you could easily be exactly wrong ;-)
73,
Larry N8LP
Stuart Rohre wrote:
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
reactance, (-).
Once you get used to that, and make a little reminder note to paste on the
analyzer case, you can do the check easily and remember which type of
reactance change you are seeing re frequency.
Stuart
K5KVH
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
