The instrument you have goes with a GR1710 vector network analyzer
system, rated 400kHz-500MHz.
It is likely 50 ohms as the 75 ohm versions were clearly marked "75
ohms" all over the place.
RF IN is from the VNA sweeper,
REFLECT OUT is the reflected signal from the device under test,
REFERENCE OUT is the reference signal from the VNA
UNKNOWN is the DUT port.
Just a directional bridge arrangement, but set up for coherent
(vector, phase-referenced) measurements.



On Mon, 4 Aug 2003 17:00:48 -0500, "Henry Kolesnik"
wrote:

I just got a General Radio 1710-P2 Transmission/Reflection Bridge with 4
ports. On the front, RF IN, REFLECTION OUT, REFERENCE OUT (-12dB), and on
the left side, UNKNOWN B. I can't find any docs on google so can anyone
please tell me the frequency range, impedance and how the 4th port is used,
or perhaps where to find more info.
tnx
hank wd5jfr