Mike,
For being a mostly Motorola man I don't see how you missed that in the
1970's & 1980's Motorola manufactured a 450-470 MHz Motrac series T54-64-74
MST, 50 - 75 - & 90 W RF power output mobiles which had an 75 MHz xctr output,
a power tripler to 225 Mhz followed by a BPF feeding a 450 doubler/amp
transistor followed by a BPF to the PA tube..
In the 1990's when these mobiles became available on the used equipment
market I acquired two units upon which I separated the transmitters from the
26v power supply, removed the 450 MHz power doubler, the 450 MHz BPF and the
final 450 power amp tube an 8072, then added a three transistor power amp I
designed using the transistors removed from the existing circuitry, a M9584, a
M9585, and a M9586 for an RF output of 25 W.
Retune of the 225-235 MHz BPF to my repeater frequency of 224.5 MHZ
completed the conversion operating now for more than 10 years, never having had
to use the spare 2nd xmtr.
An external 28vdc ps completed the transmiter construction.
A 150 MHz Motrac rcvr converted in the 1970's, a Motorola remote control
chassis, and a Celwave duplexer makes up the remainder of the repeater.
No other changes were needed as the xtal in the channel element still
operates at 18 MHz. Only the deviation pot needed adjustment to get +/-5 KHz.
Cost of the conversion was only my time and effort, a new xtal and a surplus
p.s.
73 Allan Crites WA9ZZU
Mike Morris WA6ILQ <[EMAIL PROTECTED]> wrote:
At 08:55 AM 02/20/08, you wrote:
>Hey Scott, Kevin and all you GE Guys...
>
>Looking through the Repeater-Builder Web Page "GE Section" I
>see a lot of GE Radio Information (thank you). In specific a nice
>selection of 224 MHz Band conversion information. However, most
>all of the conversion information involves High Band (150 MHz)
>Radios.
>
>Looking through a UHF 450MHz Band GE MVP Service Manual I see
>the frequency is multiplied right up through the 220 MHz band
>before the last doubler and final amplifier.
>
>Has anyone tried to reconfigure the last doubler stage as a
>buffer? Has anyone followed through to try and make the trailing
>PA section operate "down" on the 224 MHz Amateur Band?
>
>Converting the 5 watt GE MVP PA down to 224MHz might not be
>such an unwieldy project.
>
>Without first looking at the GE Master II Service Manuals I
>might suspect a similar UHF 450MHz to 224MHz conversion is
>possible?
>
>Just thinking out loud questions...
>
>cheers,
>skipp
I'm not a "GE guy" even though I put together that collection
(1,632 files at about 1.8gb).
There was a conversion of the old GE Prog receiver and
transmitter back in the 1970s for 220 that did the exact
same thing - converted a 440 radio to 220.
The transmitter used 1/2 wave tuned lines so it was relatively
easy to relocate the doubler-driver plate and both the final grid
and the plate tuning capacitors from one end to the other,
changing the doubler-driver into a driver, and leaving the
final straight-through.
The only think I forgot (and had to go back and do) was to turn
up the dev when I was done (the missing doubler cut the total
dev in half).
Mike WA6ILQ
