Actually I have had excellent luck with just making sure there is no leakage from the signal generator or cable to the duplexer when using a talkie as the receiver for tuning a duplexer. After carefully tuning the pass adjustments, leave them alone when you have minimum loss and best SWR. The talkie receiver usually has enough sensitivity to dig the signal out of the noise for adjusting the notch. Tune for maximum noise while bringing the signal level up each time you make an adjustment to keep it noisy.
My service monitor has too much signal leakage from the front panel and case to accurately tune the notch. I use an old analog Motorola signal generator which has a minimum of signal leakage as the signal source. Accuracy is preserved since I tune the generator to the talkie frequency. Just remember that any signal that leaks from the signal source will probably be picked up by the unshielded talkie and will add to the signal through the duplexer, and will yield the wrong settings for the notch. So carefully shielding the signal source and using good double shielded cable from the generator to the duplexer lets you get away with using a talkie with no shielding. I do use a 6 dB pad connected to the duplexer input and output with a 50 Ohm load on the unused port. If you can put a 50 Ohm load on the output of your signal source and not pick it up with the antenna on your talkie while the generator is set to maximum output, you have a good signal source for tuning a duplexer. 73 - Jim W5ZIT --- On Thu, 12/24/09, [email protected] <[email protected]> wrote: From: [email protected] <[email protected]> Subject: Re: [Repeater-Builder] Re: Can we tuning duplexer with this equipment? To: [email protected] Date: Thursday, December 24, 2009, 11:15 AM At 12/24/2009 07:42, you wrote: >RG214 is good for this and you can still find short pieces on e-bay. It is >double shielded silver plated braid. Bill N4XIR. Yes, but if the receiver/transmitte r used isn't well shielded, the double-shielded coax does no good. This is a big problem with using HTs for tuning duplexers, as most are poorly shielded. Bob NO6B
