As it turns out, I have a questionable test cable. Either that or I have an attenuator turned on in my test set that I'm not aware of. I'm still learning how to use this HP8920. I removed the cables from the cavity and connected them together and my measured input was 1.75-2.0 db lower than the set output. In other words, the output is set at -15.0 dbm. The unit displays the received level at -17.0 dbm.
Someone else mentioned adjusting the coupling loops. On this particular cavity, they don't appear to be adjustable. Both connectors are mounted on the same plate. There are no screws to loosen to allow the conector/loop assembly to rotate. Jamey Wright KD4SIY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] Behalf Of Eric Lemmon Sent: Friday, March 10, 2006 11:40 PM To: [email protected] Subject: RE: [Repeater-Builder] Bandpass Cavity Insertion Loss Jamey, If your measurement is accurate, 3.2 dB insertion loss is excessive. A single bandpass cavity performs best when its insertion loss is between 0.5 and 1.0 dB. How are you measuring this? If you are using a spectrum analyzer with an accurate frequency reference, the preferred method is to put a "barrel" (double female) adapter between the two test cables and set the reference cursor to zero dB. Then remove the barrel and connect the test cables to the cavity. You can then read the insertion loss directly. If you're using the bandpass filter on the receive side, no more than 1.0 dB IL should be used. If you're using the filter on the transmit side to eliminate spurs or harmonics, 0.5 dB IL will usually be fine. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Jamey Wright Sent: Friday, March 10, 2006 8:12 PM To: [email protected] Subject: [Repeater-Builder] Bandpass Cavity Insertion Loss I just got through tuning up a Phelps Dodge VHF bandpass cavity. The measured loss through this thing is 3.2 dB. I am generating at -10 dBm. The level measured on the output is -13.2 dBm. It is a Phelps Dodge VHF bandpass cavity but I can't find a model number on it. Is this amount of loss normal? Thanks in advance. Jamey Wright KD4SIY Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
