Forgot to add....I never persued the SWR power reducing beyond the simple divider. Our converstion won't drop power all the way to zero when there's an SWR problem..yet. Once, the controller got confused and keyed the repeater over night at about 60 watts out without a problem. I think it's bullet proof in that respect.
de WD7F John in Tucson ----- Original Message ----- From: WD7F - John in Tucson To: Repeater-Builder@yahoogroups.com Sent: Wednesday, September 03, 2008 8:46 AM Subject: Re: [building-repeaters] Re: [Repeater-Builder] Re: Micor to 222 MHz PA Conversion If you want to see how many hoops we jumped through to convert a high-band VHF Micor to 220 go here: There's a PA link near the top. http://home.comcast.net/~micorrepeater/ de WD7F John in Tucson ----- Original Message ----- From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] ; Repeater-Builder@yahoogroups.com ; [EMAIL PROTECTED] Cc: Kevin Custer Sent: Wednesday, September 03, 2008 7:29 AM Subject: Re: [building-repeaters] Re: [Repeater-Builder] Re: Micor to 222 MHz PA Conversion Kevin, I've been meaning to postabout a similar project, and this prompts me to ask - have you done this to "rebuild" a UHF amp? I have several dead TLD-1713 UHF 75w PAs, and need a good PA or two at the moment. Rather than messing with trying to find Moto transistors, caps, and Z-matches, I was thinking of stripping the heatsink down, buying two Mxxxxx UHF 40-50w modules, and trying to combine them. I was curious as to how they would hold up under continuously linked repeater duty.... Can you provide some more details on the 'Wilkinson" power dividers? I have experience with HF torroid combiners/splitters, but UHF is another animal altogether. Do you sell them with the boards? Is it as simple as mounting the two modules (and the supporting RB circuit boards), the combiner/splitters, and wiring it all up? I'd like to get a UHF one together asap. Thanks Eric KE2D -------------- Original message -------------- From: Kevin Custer <[EMAIL PROTECTED]> Joe Burkleo wrote: Kevin Thanks for the information. I figured that if anyone had tried it you would be aware. I was just looking for more than 30 Watts out. Scott and I have been successful in building small IPA's (intermediate power amplifiers) that take the power from the exciter and make 3/4 to 1 watt with a single transistor. This stage then feeds a Wilkinson power divider and it feeds two of these brick devices. Another WPD is used to combine the power. About 75 to 80 watts is possible. We have a prototype that has one brick module (as the IPA) feeding four more, and over 150 watts is possible. We never fully developed the 150 watt high-power version because the single brick PA we build will easily deliver enough drive for any good external 220 PA, however we do have several of the 75 watt versions in service. Can these modules be considered continuous duty if they are properly mounted on a Micor station PA chassis. Absolutely - especially if running one or two modules. In addition, we actually use the MICOR power set control to retain all of its features (SWR protection, power leveling, etc.) The AMP BD that Scott builds has the pass transistor built on it and it is run from the power set control lead that originally went to the MICOR PA. Scott also builds a custom heat spreader that is used to mate the module to the MICOR heatsink. This eliminates the need to machine a flat spot on the heatsink that big enough for the surface of the module. While Scott doesn't advertise these, I feel sure he would sell them individually; they are used in our custom 220 MICOR conversions. The heat spreader is not necessary in a MASTR II conversion, as there are no protruding 'bosses' for the original mounting of the RF power output transistors. The pictures in this document shows the mounting arrangement he has developed: http://www.repeater-builder.com/products/ampbddocs.pdf Good luck and let us know how you make out... Kevin Custer Repeater Builder
