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J.R. Buchanan

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Midnight Science 1 tube regenerative receiver

(Peebles Original)

A few weeks ago I was browsing the web and came across this:

http://www.midnightscience.com/xs104.htm (Note from years later: Sadly long gone)

It reminded me of a regenerative radio I had built as a teeneager way too long ago. It also reminded me of Alfed Morgan's various "Boys Books of Radio and Electronics", which I loved as a kid. So I ordered a kit.

It's together now, and I'm quite happy with it. It works well, and is fun to use.

It's a basic regenerative receiver using a 1T4 remote cutoff pentode in a basic Armstrong-style (tickler coil) circuit. It uses a vari-coupler for regeneration control, and runs off of a stack of five 9V radio batteries (45V) and one D cell. Bandswitching is done with alligator clips and posts. Coverage is from about 550KHz to about 7.5 MHz.

In the day I get lots of AM broadcast stations, but not much on shortwave. At night I get even more broadcast stations, plus a fair number of shortwave stations. This is using a 70 foot antenna about 15 feet above the ground.

Here is a picture of the front panel: Picture of radio

Here is a picture of the back, with the batteries connected: Picture of radio

Posts to homebuilttuberadios Yahoo Group (mailing list)



The 1 tube regen kit that I ordered came earlier in the week. It looks pretty decent, and quite easy to build. I just dumped all of the wife's salt into a tupperware container so that I can use the salt box as the body for the vari-coupler. So far this crime has gone undetected. I got a tiny can of varnish to coat the coils with while we were out today. The first step in the instructions is to wind the coils. I think that first I will do a trial assembly of the chassis/front panel so that I can be *sure* that the hole for the vari-coupler shaft and the hole in the front panel line up. It'll have to come back apart later to put the front panel labeling on the front, and the aluminum foil shielding on the back of the front panel. Thursday night I put up a 75 foot antennae and put in a ground rod, geting ready. I won't get much construction done tonight or tomorrow, lots of honey-do stuff. I'd better do it too, 'cause the salt box crime will likely be discovered some time soon... :-) ===== -- Jim Buchanan jbuchana@b... jbuchana@y... =============== http://www.buchanan1.net/ ================== "Nothing is real but the way that I feel, and I feel like going down, down, down..." -Ronnie James Dio ========== Visit: http://www.thehungersite.com =============
Yesterday I got some time to work on the kit. I cut up the salt box (an Xacto razor saw did a very nice job) and made the holes for the shaft. The plans said to make the main section of the vari-coupler (the salt box) 4 3/4 inches long. That seemed too long, after adding up the individual dimensions, I got 3 3/4 inches, which I used. Instead of just making the hole for the shaft at the specified place, I did a trial assembly of the chassis and front panel, and made *really* sure that the holes in the salt box lined up with the hole in the front panel. The hole in the fromt panel was too small for the shaft, I opened it up a little with a tapered reamer. I marked the holes on the salt box with a hole template and then cut the holes a little undersized with a 1/8 inch wood chisel. I then opened them up a little with a tapered reamer. The shaft is nice and snug in the holes. I made the holes in the (supplied with the kit) two inch rotating section of the vari-coupler in the same way. I then wound the four 10 turn windings on both tubes. I still have to wind the tapped 35 turn coil on the salt box. After that, the windings have to be varnished, and then the rest of the assembly done. So far, it's been easy pleasant work that's gone very smoothly. ===== -- Jim Buchanan jbuchana@b... jbuchana@y... =============== http://www.buchanan1.net/ ================== "Nothing is real but the way that I feel, and I feel like going down, down, down..." -Ronnie James Dio ========== Visit: http://www.thehungersite.com =============
Yesterday I got the tapped 35 turn coil wound and varnished all the windings. Today I assembled the vari-coupler, which included gluing the shaft to the moving coil. I noticed a minor design "problem". There is no stop to the vari-coupler, it would be quite possible to rotate the knob until the wires wrap tightly around the rotating shaft and coil, damaging the assembly. I'm not going to do anything about that, I just won't do that. I also have the aluminum foil and paper glued to the back of the panel. They kept pulling away from the panel, so I laid the assembly on the bench and weighted it down with two transformers. I'm a little worried that some glue will seep out and the assembly will wind up glued down to the bench. :-) I was fairly light on the glue, so hopefully that won't happen. I tried to take some pictures to put up, but the batteries in my digital camera went dead, and are recharging now. ===== -- Jim Buchanan jbuchana@b... jbuchana@y... =============== http://www.buchanan1.net/ ================== "Nothing is real but the way that I feel, and I feel like going down, down, down..." -Ronnie James Dio ========== Visit: http://www.thehungersite.com =============
Yesterday it had been several days since I'd worked on the kit. The last thing I had done was to glue the aluminum foil to the back of the front panel, and the front panel artwork to the front of the panel. Last night I mounted the front panel and started the wiring. I connected all of the leads from the vari-coupler, and all the leads from the front panel band "switches" (actually alligator clips and bolts). I got paged from work and did not get any more done. I'd say that this is a bit more than half the wiring. Today at lunch I got five 9V batteries for the 45V B+ and some D cells for the A+. I doubt that I get much time to work on it tonight. ===== -- Jim Buchanan jbuchana@b... jbuchana@y... =============== http://www.buchanan1.net/ ================== "Nothing is real but the way that I feel, and I feel like going down, down, down..." -Ronnie James Dio ========== Visit: http://www.thehungersite.com =============
Well, last Friday I got it all wired up. It turns out that I was more than half way there, it went together pretty fast. My "good" antenna is run into my copmputer room, not my workshop. Still, since I live two miles from an AM radio station, I figured that 10 feet of wire would be enough for that station, if no others. I connected the headphones that I got from Antique Electronic Supply, clipped together 5 9V batteries, connected them up, along with a D cell for the filament. Nothing. I could hear a sighing 'pop' when I tunred up the regeneration, but no sign of a signal. I hooked my signal generator up to the antenna terminals. I could hear it... For fun, I hooked a frequency counter up to the antenna terminals and turned up the regen. The radio tunes between 550 KHz and 7.5 MHz I didn't mess with it yesterday, this morning I carried it into the computer room and hooked it to the 70 foot outside antenna. Sucess! Lots of stations, some annoyingly loud, many so soft that I could not understand what was being received. All of those were broadcast band. I could only receive one station on shortwave, too soft to make out. I'd forgotten how selecteve a regen receiver is. A vernier dial would be nice, it's hard to tune as it is. A little touch and you're too far. I might want to look into a way of lowering the regen, as the coil is barely rotated from the lowest position when the set starts oscillating. I'm not sure now whether I should first try an antenna tuner or an audio amp for those stations that are so weak? I have two more 1t4 tubes to play with, one should make a nice audio amp. I've been looking for one of those Japanese vernier dials that were so easy to find in the '70s. I got outbid on one on eBay the other night (I suspected that I'd want one). Plenty of antique and high-end verniers, but that was the only mid-quality fairly new one. An antique or high grade dial from the 50s/60s would look out of place. Plus they are kind of large for the size of the radio panel. I have two antique verniers if I do give up and go that route, ===== -- Jim Buchanan jbuchana@b... jbuchana@y... =============== http://www.buchanan1.net/ ================== "Nothing is real but the way that I feel, and I feel like going down, down, down..." -Ronnie James Dio ========== Visit: http://www.thehungersite.com =============