> Can somebody please explain how the insertion loss of a duplexer is
properly measured using a HP 8920A (with specan).
1. Connect duplexer Tx port to duplex port on 8920.
2. Connect antenna port on duplexer to antenna port on 8920.
3. Go to spectrum analyzer screen.
4. Set center frequency = repeater tx frequency
5. Set generate mode to TRACKing
6. Set input to ANTENNA
7. Set generate port to DUPLEX
8. Set generate level to 0 dBm
9. Set the sweep span to something reasonable, like 500 kHz.
10. By default, the marker should be at the center graticule, which should
be the Tx frequency you entered in #4 above (if not, go into the marker
menu, and set the marker to 5.00, which is the center of the display). The
difference between the marker level and the generated level is the loss,
minus your cable losses.
For example, if you're generating 0 dBm, and the amplitude at the marker is
-2.10 dBm, and you have 0.5 dB of patch cable loss, the insertion loss
through that leg of the duplexer is 1.6 dB.
Repeat the same test for the Rx leg of the duplexer by moving the cable from
the Tx port to the Rx port, and changing the center frequency to the Rx
frequency.
> P.S.: Is it correct that a duplexer that has 40 dB isolation
> in each leg does have 80 dB overall isolation?
No.
--- Jeff WN3A
