You didn't mention the specific frequency, and that can make a big
difference. I would expect wire to give you roughly four nanohenries
per centimeter, and if you add 12cm*4nH/cm=48nH in series with 50
ohms, you get to a 2:1 SWR at about 120MHz. That doesn't account for
the shunt capacitance the wires also introduce, which would reduce the
SWR somewhat, or increase the frequency at which you see 2:1. In
general, you should connect the load either immediately at the balun
or unun output, or through transmission line with impedance equal to
the load (or at least the same as the impedance of the transmission
line you plan to connect).

I'm assuming your meter doesn't respond to external fields, and only
to forward and reflected on the line, but if it does respond to
external fields, that's also an issue.

Cheers,
Tom


Wolfgang K. Meister wrote in message . ..
Hi all,

I was experimenting over the weekend to design a 1:1 Balun and a 1:9
Unun. Unfortunately I have been not very happy with my results.

Finally I realized that my Vectronics SWR showed a frequency depending
SWR of up to 1:2 at higher frequncies, if I used simple 1,5 inch wire
clips with a 50 Ohm resistor connected to the PL plug.

My setup was: the Vectronics, the Balun or Unun and a termination
resistor, either 50 Ohms or 450 Ohms, very tiny carbon resistors. The
wires of the Balun and Unun have been just an inch or so on each side.

By connecting the resistors as short as possible to the PL plug of the
Vectronics, I did see a 1:1, so it's the setup that makes a mess.

How can I measure a Balun or Unun, what setup do I need?

Thanks for your replies in advance,
73s de Wolfgang
OE1MWW