RE: [Repeater-Builder] Can we tuning duplexer with this equipment?
No. It is a power meter, not a spectrum analyzer. To use such a device to tune a duplexer, you must transmit a signal through the duplexer while tuning it- not a good idea! Unfortunately, the proper equipment for tuning duplexers is seldom simple or cheap. However, for measuring the power output of a transmitter the PM-3 seems like a useful device. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Azam Sent: Wednesday, December 23, 2009 8:20 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Can we tuning duplexer with this equipment? I found this simple and cheap rf measurement kit at http://www.foxdelta.com/products/pm3.htm http://www.foxdelta.com/products/pm3.htm Can it be used to tune a duplexer? rgds azam
RE: [Repeater-Builder] Can we tuning duplexer with this equipment?
It depends on the type of duplexer. Certainly a spectrum analyser with tracking generator, or better still a network analyser, is ideal for tuning notch type duplexers, but you can get away with simpler equipment with bandpass type cavity duplexers. Indeed I have tuned several repeater duplexers with nothing more than a SWR meter, power meter, handheld TX, Attenuator, and dummy loads. A harmonic marker generator with a tunable receiver can be used as a rather crude substitute for a spec-an. I have a marker generator that produces the equivalent of a few tens of microvolts at 100kHz spacings across 2 meters. By tuning back and forth between the rx and tx frequencies of the duplexer you can get an rough idea of the notch and bandpass tuning prior to applying more power. It's not much good at measuring deep notches because you'd need a receiver with about 0.01uV sensitivity to measure a 60dB notch, but you can at least measure individual cavities. Mark Harrison VK3BYY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Azam Sent: Wednesday, December 23, 2009 8:20 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Can we tuning duplexer with this equipment? I found this simple and cheap rf measurement kit at http://www.foxdelta.com/products/pm3.htm http://www.foxdelta.com/products/pm3.htm Can it be used to tune a duplexer? rgds azam
Re: [Repeater-Builder] Can we tuning duplexer with this equipment?
You can get close with minimal equipment. Here's one I did (2 meters, 600 KHz spacing). Start by doing each cavity individually. I used my old Motorola S-1318-A signal generator to the cavity with a Tee connector, then to a UHF Tee connector with the Tee'd pin unscrewed, then to a dummy load. The missing pin connector is connected to a transceiver receiving at the desired frequency (loose coupling). Start out with lots of signal with modulation so you can get close, then reduce the generators level as you fine tune to pass the desired frequency and reject the undesired one. I didn't have a Sinadder, so I made the signal noisy and tuned by ear. After you have done each cavity, connect them together and fine tune. When your rejection is so high that the generator doesn't have enough output, use a transmitter for more power. The duplexer I did this way had no desense, and ran well for years. It was relocated to a commercial site. The Motorola tech who was doing the install put the duplexer on the bench to tune it. He said that he didn't have to touch a thing, it was perfect. We were both surprised. It takes time, but I didn't have a service monitor or better available for that install. Mike - AA8K Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: repeater-builder-dig...@yahoogroups.com repeater-builder-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: repeater-builder-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Can we tuning duplexer with this equipment?
At 12/23/2009 08:19, you wrote: found this simple and cheap rf measurement kit at http://www.foxdelta.com/products/pm3.htmhttp://www.foxdelta.com/products/pm3.htm can it be use to tune a duplexer? Hard to say, since the above doesn't really say what the instrument does. I assume from the display pictures that it's a low-level high dynamic range power meter. If so, it's well shielded, it could make a good detector for such measurements, but you still need a good shielded 50 ohm signal source. Bob NO6B
