HOLY CRAP!!!! I've been wondering that for some time. Guess the "manual" isn't always right. and maybe that's why the GE Z-match is there for the recruiting of true GE tuners.. Never-mind keeping your PA happy at 100% DC. I always wanted to ask but never did (for thought of flames from the GE manual) because I thought I heard somewhere that tuning procedure wasn't ideal for most cavity/duplexer applications (on this list in a unrelated post) so investigated. Now I always settled for the best low ratio of the two. PA current/TP1 from z-match. You'll see that the relationship of the two is not even close to linear. What I've found is you basically want to try to be on the edge of both curves knee's.. I think I have the right idea, for a 50mV gain from the TP1 z-match null I could drop PA current by 2500mA. And this was until now (a month ago) that I finally have a good HP8924 SM to help take the guess work out. Plus your PA and TX cavity temps go way down. Just glad to hear I was probably doing the right thing. Also I always did the final 1st 2nd pass cavity tuning this way. Retuning cavities for highest output power with least current vs. low TP1 on z-match. One tuning session on a friends machine with this method dropped TX cavity temps by more then 10deg to almost ambient temp while dropping PA temp, and current by 2 amps with no drop in output power or RX sense. This probably means the match in the cavity coupling or cabling was off but hey that PA will live longer. If I'm wrong or missing something here, let me know. 73's groupies Ross www.kc7rjk.net <http://www.kc7rjk.net/> -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of larynl2 Sent: Saturday, August 14, 2010 8:17 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Coax length, etc. GE Z-Matcher
--- In Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> , "Jeff DePolo" <j...@...> wrote: > > c) Although not explictly described in GE's tuning procedures, significant > improvement in efficiency can be obtained with proper tuning of the > Z-matcher. Tuning for 50+j0 at the input to the Z-matcher is NOT > necessarily the RIGHT match! Right, GE's instructions on tuning the Z-Matcher in their base stations are not correct. Instructions should instead describe a procedure that reduces current draw of the amplifier while simultaneously maintaining or increasing the output power. > > d) To charge more. I'm half-joking on this; I can't say I've statistically > seen more or less failures on M2 PA's with or without the Z-matcher, so I'll > give this answer half a smiley: .-, If the failures you've seen are in amps with Z-Matchers that were tuned following GE's Z-Matcher instructions, that *could* explain why you've given half a smiley... :-) Laryn K8TVZ
