GM, thanks for confirming my old brain isn't completely fossilized.
I was almost positive that it was single conversion because I replaced it with a PRO-10, that was dual conversion, and the reduction of intermod and birdies was amazing. I think the PRO-9 was single conversion precisely because of that tunable VFO. I don't think they had the technology available to make a combination receiver like that in dual conversion.
The incandescent bulbs in the PRO-9 were definitely not being run under voltage. They were blindingly bright at night, so much so that I made a cardboard hood for it when it was installed in my 1970 Toyota Corolla (how's that for a trip in the wayback machine
) so I wouldn't get reflections from the indicator lights on the windshield. The replacement bulbs were 12 volts and the voltage at the terminals was also 12 volts.
I remember now that the center frequency on that thing was 157 MHz with rated sensitivity from 153 MZ to 161 MHZ. It was the only scanner out at the time that had really good sensitivity in the railroad bands and the VFO meant you could tune across the entire 148 to 174 MHz range with good sensitivity over the whole range. It was kind of the first scanner with V folders. If you were out of town, you just twirled the dial back and forth until you found something.
I don't know if replacing any of the VFO components would result in more stability. The dial wasn't very well calibrated so you always had to guess within about 1 MHz if you were close to the right frequency and then wait for transmission and tune it in. The selectivity was such that being within about 1 MHz meant you'd be able to hear the transmission. That was another downside. If you were in any RF rich areas, you heard a lot more on the VFO section than you wanted to. Still, it was an interesting idea but pretty much a failure, since RS never produced another scanner like it again.
