All 220 Linear amps should work great on 220 FM without any mods except maybe the addition of a small fan but even the fan isn't really required.
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?I had several Morrow electronics/UPS Aviation Technology/Garmin Aviation Technology 50 watt 220 MHz Linear amps from the days when they stole the lower half of the 220 ham band and they all work just fine on 220 FM for my remote base and as mobile amps without any mods at all.
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I added a small fan but even without the fan I haven't killed any yet but for me it was a psychological thing just knowing that the transistor junction temp was always going to be below the data book max.? even if stuck in tx for an hour.
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My amps are all around 50 watts out each and with a home brew wilkinson? combiner I have? around 90 watts going to the antenna.
