At 7/29/2008 20:37, you wrote: >Rber s, I posted a note very early this week about my looking for a >someplace to get a 220 duplexer tuned in the TAMPA area. Having not much >luck I contacted a local MOTOROLA shop and paid $95 for the service. The >receipt returned with the cans indicates that the specifications published >by WACOM are very close. Having tuned these merely to incoming signals >before, peaking them while the repeater is still in a testing mode, seemed >to return decent results but the tune-up was thought to be a better >idea. Not so&. Today s tune-up hardly was worth the wait or the price >based on the results. While a 5 watt HT 10 miles away could work the >repeater, now 25 watts from a roof top antenna is now just about full >quieting. Fifteen watts does not make the repeater through the same roof >top ground plane. Does logic dictate that we go back to seat of the pants >tuning and cast fate to the wind? - Mike
Trying not to open the Pandora's Box of the "should the duplexer be 'touched up' after installation" debate, I will say that I normally never have to readjust the duplexer tuning after tuning on "proper" test equipment (in my case a spectrum analyzer with tracking generator & 10 dB pads on the generator output & analyzer input). However, if you have very little reserve isolation in your duplexer or your TX, RX and/or antenna impedances are very far from 50 ohms it may be necessary. What kind of repeater are you using? You may have an unstable RFPA that doesn't "like" the new off-channel reactance being presented to it by the duplexer. Bob NO6B
