RE: [Repeater-Builder] Measuring duplexer insertion loss
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
RE: [Repeater-Builder] Measuring duplexer insertion loss
Oh, I guess I should have thrown in a couple of generally-applicable guidelines that should go without saying when using ANY sweep gear like this: - terminate the unused port on the duplexer with a high-quality 50 ohm load - it's a good idea to use 6 dB or greater pads on inputs and outputs of the test equipment - use high-quality test cables (double-shielded when you're measuring isolation) - avoid using adapters etc. etc. etc. --- Jeff WN3A -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jeff DePolo Sent: Friday, August 06, 2010 4:21 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Measuring duplexer insertion loss 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
Re: [Repeater-Builder] Measuring duplexer insertion loss
In addition to what Jeff said in his posts, I usually run a test sweep on my HP8924 connecting the two cables together with a double female of the appropriate type. The result should be a flat line sweep but will usually show some amount of loss relative to the generator level/reference level. I note the amount of loss and either increase the generator output to place the line as near as possible to 0db or just remember to subtract it from the end reading. After I do the test sweep I connect the cabling to the device to be swept and proceed with measurements and tuning. - Original Message - From: cruizzer77 atlant...@gmx.ch To: Repeater-Builder@yahoogroups.com Sent: Friday, August 06, 2010 3:35 PM Subject: [Repeater-Builder] Measuring duplexer insertion loss Can somebody please explain how the insertion loss of a duplexer is properly measured using a HP 8920A (with specan). I'm pretty new to this instrument as well as duplexer work but am eager to learn. Thanks. 73 Martin P.S.: Is it correct that a duplexer that has 40 dB isolation in each leg does have 80 dB overall isolation? Yahoo! Groups Links
