Okay,
1) Measuring the impedance of the line isn't a trivial undertaking. The
conventional method (with a device such as yours) is to make two reflection
measurements, one with the line open-circuit and the other with a short-circuit.
The equations for calculating line parameters are out there, but a better way is
to use AC6LA's "Zplots" program (https://ac6la.com/zplots1.html)
As has been suggested elsewhere in this thread, you might be tempted to try
connecting the balanced line to the unbalanced test port of the analyzer, in the
belief that since it is a "floating" device it's also "balanced". This has not
worked for me. I believe the reason for this is thus: With an open, short or
other pair of highly reflective loads, the loads are not only terminations, they
are balanced sources too. The terminations for these signals propagating in the
reverse direction is the instrument, which with OSL calibration is
mathematically "perfect" except, if for no reason other than its physical size,
isn't perfectly balanced. So the line radiates; it's part transmission line and
part antenna.
(I was actually trying to quantify this on a 100' length of window line out in
the yard but when the temperature hit 100 degrees, I decided to wait until
cooler WX.) For true open wire line, I think you would do just fine using the
equations, which work well.
2) I'm not sure you mean measure the antenna impedance at its terminals or
through the line at a different feedpoint. If the latter then you don't really
have to know the line parameters anyway. You take what you get and match it,
which is pretty much why you use low-loss lines in the first place.
3) If you are going to stub match then you don't need to fuss with impedance
transforming baluns. Use a good common-choke, appropriate for the frequency and
stub-match to 50 ohm.
Wes N7WS
On 9/3/2019 5:17 AM, Neal Sulmeyer wrote:
First to measure the impedance of the home brew open wire feeder. Then measure
the antenna impedance when at its final operating position/height. Finally to
use stub matching on the open wire to match to the balun (whatever ration is
required) and then coax back to the shack.
On Tue, 09/03/2019 08:05 AM, Wes <wes_n7ws@triconet.org> wrote:
What parameter(s) are you trying to measure? Why?
Wes N7WS
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|