Skipp, the PA modules did not work at 29 MHz, tested individually into a dummy load. I had a chance to play with them yesterday, and as it turns out, there is no need for additional transformer cable length. I got each module to put out close to 300 W while drawing just under 7A of current per transistor, without any bias. I added an inductor in parallel with a 75 pF capacitor across the drains, and increased the coupling capacitors to 1500 pF from 1000 pF and added 130 pF (25%) to the transformer input. That was it!!! Hopefully the combiner and low pass filter will work. The amplifier control board has problems that I'll have to tackle after getting the PA working on 10 Meters... Alex
--- In [email protected], "skipp025" <[EMAIL PROTECTED]> wrote: > > > Based on what I've seen for Quintron Glenayre Equipment I would > question if you really need to rewind the xmfr for that > relatively short distance from 36 MHz. > > If the manual doesn't have different part values for the low range > split I'd take a careful look at the circuits after the xmfr. A > case can be made where a non 180 degree filter after the PA would > echo larger problems back at the xmfr. > > Did you measure the pa operation before the frequency change? > > You might also consider joining the yahoo rfamplifier group where > a number of folks migh help you sort through this conversion process. > > http://groups.yahoo.com/group/rfamplifiers/ > > cheers, > s. > > > "kq2h" <kq2h@> wrote: > > > > Perhaps a little off topic subject.... Does anyone know of a source for > > 25 Ohm, 0.10" diameter flexible coax cable? I am in the process of > > converting a 500 Watt Quintron QT-7095 station to 10 Meters. The RF > > amplifier uses four 28V MOSFET's matched to 50 Ohms with a Guanella 4:1 > > transmission line transformer. Unfortunately, the amplifier is tuned to > > 36 MHz. The Guanella transformer gets very hot at 29 MHz while output > > power is low. It looks like I may have to rewind it, but am unable to > > find a source for 25 Ohm mini flexible cable. The closest thing I can > > find is semi-rigid, which is no good for this application....Alex > > >
