Sometimes same amplifier used for VHF High-Band and UHF can be modified up/down to the 224 MHz band... but the conversion project is not for the faint of heart.
In the case of the Micor PA... they are not an easy mod by any means and I was never able to get more than about 45% of the original rated power from some versions. The first problem is the frequency limit of the transistors, then modifying the substrate traces. One can retrofit replacement boards for the ceramic substrates (circuit boards used in the Micor and MSR-2000 RF Amplifiers) with the proper parts, but you're really building a new amplifier in place of the old. So why not start from scratch if it's a ground up project. I was able to get the UHF GE MVP amp to work quite well on 224 MHz, haven't yet had my hands in the Master Series Power Amplifier. That's a winter project... For the 224 MHz band... I've been building PA's from scratch and modified commercial gear. Lately it's been hard trying to find cheap enough power devices (transistors and fets) in any type of quantity. But I sometimes get luck on Ebay. What you end up with is mostly determined by the available drive level from your exciter (transmitter). cheers, s. --- In Repeater-Builder@yahoogroups.com, "K5IN" <k...@...> wrote: > > Kevin, > > > Any suggestions for a decent quality 220mhz amp for repeater duty? > > Micor 20-25 watts drive or pull the PA and exciter in and 50-60 watts > output? > > > Thanks > > -----Original Message----- > From: Repeater-Builder@yahoogroups.com > [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin Custer > Sent: Wednesday, October 14, 2009 5:57 PM > To: Repeater-Builder@yahoogroups.com > Subject: Re: [Repeater-Builder] Radio conversion to 225MHZ > > > > J wrote: > > Has anyone converted any of the commercial (GE/Motorola) radios to the 220 > band? If so what works and what doesnt. I need several 225 radios and > thought this might be a route to go. > > I have converted MASTR II Mobiles, both multiplier and PLL exciter, with > standard receivers to 220 MHz. - they work fine, the PLL is easier. > There are preferred instructions on the MASTR II conversion site: > http://www.repeater-builder.com/rbtip/geindex.html#220 > <http://www.repeater-builder.com/rbtip/geindex.html#220> > > For the M2 with a PLL exciter, Scott sells a complete conversion kit: > http://www.repeater-builder.com/products/MIIconversionkit.html > <http://www.repeater-builder.com/products/MIIconversionkit.html> > > The PA's won't convert, but there is an easy fix: > http://www.repeater-builder.com/products/ampbd.html > <http://www.repeater-builder.com/products/ampbd.html> > > I have converted MICOR Mobiles and Stations to 220 MHz. - they also work > fine. There are preferred instructions on the MICOR conversion site: > http://www.repeater-builder.com/rbtip/micor-index.html#220 > <http://www.repeater-builder.com/rbtip/micor-index.html#220> > Helical Resonators modified for 220 operation are available here: > http://www.repeater-builder.com/products/ > <http://www.repeater-builder.com/products/> > > The PA's won't convert, but again - never fear, the amp board is the > solution: > http://www.repeater-builder.com/products/ampbd.html > <http://www.repeater-builder.com/products/ampbd.html> > > Any of the above radios can be converted to 220 MHz and achieve book > specification sensitivity on the new band. My favorite is the MICOR. > > Hope this helps... > Kevin Custer >
