I've been kind of busy lately with other things, but I have managed to squeeze in a few minutes most days to work on my latest receiver project. I call it the Armand HROish receiver. Armand WA1UQO sent me the big National HRO-style dial and gear box, and he was there at the Manassas hamfest when I bought the dual variable cap that now serves in the front end pre-selector.
I went with a 455 kHz IF. The idea is to have a receiver that tunes from around 6.5 MHz to around 8 MHz so I can do some shortwave listening AND listen to 40 meters.
So far the filter consists of three IF cans (one small transistor can and two larger tube-type cans). The small transistor can was given to me by Michael Rainey AA1TJ - thanks Mike. Doug DeMaw suggested this use of IF transformers in his "Design Notebook."
At the front end I have a tunable dual tuned circuit filter followed by a 40673 amp.
The mixer is an SBL-1.
1st and 2nd IF amps are a 23 db 50 ohm termination insensitive amplifiers.
I have a second SBL-1 that will be the product detector, but I haven't built the BFO yet. So today I hooked up two 1N34A diodes in voltage double config and -- with a bit of AF amplification, got the receiver inhaling with a diode detector. I could pick up Radio Canada. Then I heard SSB sigs on 40. With no BFO, I decided to put my sig gen on 455 kHz and just wrap the lead around the IF cans. It worked -- I could listen to SSB and CW sigs. Very satisfying.
Still to do:
-- BFO and product detector.
-- Work on AF amp.
-- Get my CM-455 crystal mechanical amp in there with some relays around it so I can switch from narrow to broad via the front panel.
Lots of soul in this receiver: All parts either 1) came out of the junkbox, 2) were gifts from friends, or 3) were recent hamfest purchases. The HRO dial from Armand and the IF can from AA1TJ. The 455 kHz filter idea came from Doug DeMaw, the VFO circuit from SSDRA. The VFO base is from Whole Foods and the whole thing is built on a kitchen cutting board. It includes a 40673 and germanium diodes. The VFO amps are in Altoid tins. It will, when finished, go into a big metal box given to me by Tim KI6BGE and shipped east by Pete Juliano. And when I was working on the 1st mixer, I accidentally pricked my finger and a drop of N2CQR blood went onto the breadboard. Of course, I left it there. SOUL!
The Radio Gods are apparently pleased: In the first hour or so of listening, I was rewarded for my efforts when I managed to hear Tim WA1HLR on 40 AM describe his troubleshooting of an old piece of gear. TRGHS.