I usually roll out of bed anywhere between 6 and 7:30 in the morning, prompted by cats who want to be fed. The last couple of mornings, after feeding them, I have gone back to bed and napped for a few more hours. This is not normal for me, but probably has a lot to do with the very warm weather we’ve been having recently. So it was this morning, and was the reason that by the time I got a message on Facebook from my old neighbor Sue that the California Historical Radio Society was holding an auction and fleamarket in the city of Alameda today, the event was already underway. I rushed in the shower and hoofed it to the bus stop as soon as I could. I didn’t even have time to stop off at the ATM so when I got there, I only had $22 in my pocket. $5 paid my admission, leaving me with just $17 to score a cool deal. There were some lovely old vintage pieces in the auction but like all good cheapskates, the piles of “junk” in the fleamarket at the back were what drew me in. This is what I found -
What attracted me was the National ACN dial, fitted with a “Velver Vernier” drive. They were in good shape and the reduction drive operated smoothly. The drive and dial alone were well worth the $10. The dial is marked “Frequency cut-off in KC” and calibrated from 1.8 to 25. On the back, there are 2 1/4″ jacks, marked “In” and “Out”. The rectifier tube is a 6X5GT and the other one is a dual-triode 12AU7. This looks to be a tunable audio low-pass filter. I was hoping that the wiring on this homebrew project would be done poorly, so I could easily justify cannibalizing it for parts. Sadly, this was not the case. This is what it looks like without the bottom cover -
I already have a National ACN Dial like this one, and several National “Velvet Vernier” reduction drives, but this one has the smoothest action of them all. If I wanted to restore this audio filter, I’d need to at least recap it but as nice as it is, I’m thinking that the same function can now be attained more easily with solid state devices (so why would I want this one?) The front panel is thick, and the chassis stout and solid. If I were to cut out the top of the chassis and replace it with a new aluminum plate, there are any number of projects that could be built around the dial, vernier and that 3 gang variable capacitor. The variable capacitor wouldn’t be ideal for a high stability VFO, but it might work well for a preselector for MF thru’ HF, for example -
Sitting on the bus on the way back home, as I clutched this on my lap, the guy sitting next to me asked, “Is that a flux capacitor?”
So what would you do this with this if it was sitting in your shack?