hansen64
Electrical
- Oct 29, 2004
- 6
Hi,
I am using an Anritsu/Wiltron 54111A with the accessory SWR autotester to test SWR in the AMPS-CELL band, the GPS band and the PCS band.
This is a production test arrangement, and I want to test an antenna that I know is of about VSWR = 1.6 or so. The problem is the antenna is at the end of a long cable (about 16 feet, but low loss -- about 2 db or less loss). I also have a microwave Teledyne relay (rated at VSWR < 1.2) in the line near the antenna. I also have a bias tee in the line to power the active GPS antenna. I am cal-ing through all of this stuff, the bias tee, the cable, and the relay.
This Scaler NA uses only a short-open cal arrangement. I try to cal with my standards at the end of this 16' cable, and accurate measurements seem to be hit or miss. Often the measured VSWR is way worse than what I know the antenna to be. Yes, when I look at the display of freq vs VSWR, I do see "waves" corresponding to some phase effect --- I know this means something, but I forget exactly what.
Here's the odd thing.... I also have an HP Vector Network Analyzer, and when I cal through all this stuff (cable, bias tee, relay) I get perfect measurements every time.
What's the difference here? Why is the Scaler analyzer not giving good measurements?
What is the HP doing for me that the Anritsu is not??
Thanks very much.