I am big fan of old radios, and I am fascinating how precision were the radios making. 4 months ago, I was just looking for some interesting schematcs, and I found one! It's about 50 years old, but works perfectly, without any power supply. With the reciever you can listen to your favourite radio on middle waves. You just need some electronic components, long antenna, good ground and HI-Z earphones (or amplifier). To make it you don't need any money! All components I used were recycled! Please, respect the nature!!
Let's make it! :))
Step 1: Components
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What you need: Epoxy board, or any non-conducting board (for motherboard) Metal board (for frontboard, I chose dural) Old ugly log (for case)
Resistors: R1 - 100 kOhms R2 - 1 MOhms potentiometer
Capacitators: C1 - Tuning capacitator 2 * 500 pF (from an old AM radio) C2 - 100 nF C3 - 200 pF C4 - 50 nF Cc1 - 15 pF Cc2 - 10 pF
Coils: L1 - 250 uH L2&L4 - 330 uH (100 turns with 0,21 mm wire on 7 mm in diameter and 29 mm lenght ferrite stick) L3 - 20 - 30 double turns on 8 mm in diameter 40 mm lenght wooden dowel, then solder left end of A turning and right end of B turning together L5 - 2,5 mH
One germanium diode
Note: Be precision while you are winding the coils. After winding is good to measure the inductive of coils. The inductive has to be the same. It is important for future quality receive.
Other: Some wires Some banana jacks (for antenna, groung, earphones..) Long (best 20 meters) antenna Good ground (metal heating is fine) High Z earphones (best about 1-2 kOhm or more) A lot of chocolate (for patience :))
Step 2: Motherboard
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To make a motherboard for the reciever you need comprextit board (or any thin non-conducting board, wooden, platic...). Dimensions of the motherboard are 144 mm * 72 mm. Line the cuprextit board. Print the layout from original manual on paper. Stick the printed layout on the coprextit board. Mark the soldering holes with center punch. Drill all holes you need, Make holder for the ferrite core coils (L2, L4). Rivet the soldering holes with hollow brass (or any solderable metal) rivets. Make BIG hole for the tuning cap! Be happy of the result, you made the motherboard!! :))
Step 3: Frontboard
To make the frontboard I choosed dural board. It is not necessary, I just had what I had. Frontboard dimensions are 170 mm * 90 mm. Cut it! Mark it in the center and drill hole. Making some interesting things for good working cap (ellipse, holes..). Make hole for potentiometer (by your motherboard). More holes for future case. By the Motherboard make into Frontboard 4 holes for some screwsBe proud od yourself! :))
Step 4: The Case
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The original case is made from bakelite. I can't make it, so I decided to make it from the best material on the world, from the wood! Find log (I found old, ugly log, to prove, that the ugly, old log with mushrooms init doesn't worth nothing, I didn't wanna to kill tree :((..please, respect the nature:)) BTW. I thing the tree is Populus alba. Saw this log on right lenght. Side boards are 104 * 78 * 14 (lenght * width * thickness) in mm. Bottom and upper boards are 174 * 78 * 14 mm (first piece of log is shorter (104 mm), second one is longer (174mm)). (P.S. Be sure, this is aesthetics matters) Saw it on Boards. Line the log with right dimensions from the middle of log. Once you have it, next step is comming! Cut it on the one side, then in the middle, and on the end on the other side. Now you have 2 wooden boards. Repeat it with the second log. Smooth it to soft and clean surface. (don't do it with sandpaper, it's not nice. I did it with drawknife (or jack-plane), and result was perfect) Cut it on the right dimensions (lenght, width). Sketch and saw dovetail joints (25 and 12,5 mm). Be precise, I choosed 2 dovetail joints on one side. Assembly the BOX! Time to puttying. The putty consist saw dust and glue for wood or paper (everybody knows that white liquid). The putty is for the holes in the case. After puttying, let it dray about 4-7 days, for sure, than sand it with sandpaper, but carefully. :) So, we've got a case. Let's lacquer. I choosed "Boad lacquer", it has nice a bit orange color, for this old, ugly, white wood is good. Inside took only one layer. Outside took 4-6 layer of lacquer. Let it dry, and be happy! :))
Step 5: Electronic part
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Once you've got motherboard, frontboard and case for radio done, it's time on electronic part! First, collect your electronic parts from step 1 Build your alfa version of crystal tuner (this step is not important, you can skip it!) From original instruction lists you can find where every component has be placed. By numbers on schematics (this numbers are also on motherboard layout on original instructions), you will find every single soldering point on motherboard, so, just go on! :) Now, you can solder and solder! First is good to solder wire interconnections. Then you can solder other components. Another step is about coils holders. I didn't know how to solve this problem. In original, they use special rubber holders. I didn't have them. I used rubber holder from old pen, it works fine. Just look at pictures, it will say everything. :) Finish funcional/electronic part, add some ground wires (on tuning cap for example in my case) Done!..?
Step 6: Assembling
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We have already finish, just assemly all parts into the case! I chose solution with screwed mothorboard with frontboard, then frontboard is screwed with case. It's becaouse it is the siplest way for repearing/assembling/disassembling and also, I had not a good tuning cap for this case. Pictures will say the same. :3
Step 7: Final touches!
This is the last step. You can add some buttons on potentiometer, or tuning cap, add some bannana jacks for antenna, ground and headphones and so on. That's only on you!
This is the end! Thanks for your time!
If you like my project, you can support me on facebook https://www.facebook.com/pages/D-Fox/236623253020... , or on instagram http://instagram.com/ondrej_fidra .
Respect the nature!