Z-Dyne Shortwave tube radio


My goal was to make a shortwave radio that have a tuning indicator included in the design. The radio also had to be a super-heterodyne style radio. I wasn't familiair with none of the technologies but i didn't expect much trouble building one. I was proven wrong dearly.
Not only had i a hard time with the IF filters, i also struggled for weeks with the oscillator and RF circuits. I didn't have any tools other then a DMV to start with. This meant that i had to build some additional tools too. Much did i learn, many mistakes did i make but in the end all is well and many lessons learned.

First the specs:
Four tubes, PCF80, EBF89, PCL86 and VT138 as a tuning indicator.

3 Bands covering 40m, 41m, 49m, 30m and 31m
These bands cover broadcast and amateur frequencies.
   Band 1 : 6200 - 6550 Khz
   Band 2 : 7000 - 7700 Khz
   Band 3 : 9400 - 10200 Khz

I included some additional functionality such as:
   Tone controle
   Headphone output
   Audio Input/Output
   A beat frequency oscillator (BFO)

The Audio I/O can be used to output audio such as morse code to a computer for decoding. Or if you want to use the amplifier stage of the radio then this is the place to where you connect your audio source. The BFO is added as a loosly coupled seperate circuit to make it possible to listen to SSB signals and to enhance morse code reception.

Work in progress Work in progress. Here you can see the dail plate clearly. I've used a piece of laser engraved plexiglass and did illuminate this on the top and bottom side.
The tuning wiring is two folded. I made two different sized disks on the variable capacitor. One to give the tuning knob more reduction for a better tuning experience. The other disk controls the wiring for the dial needle. This disk is made exactly the right size so that the needle will go from bottom to the top of the scale over the same path lenght that the variable capacitor takes to go from fully meshed to completly open. The wiring had to be redirected over several supporting disks to get the dail needle move horizontal up and down.

The result of the lit dail plate is shown here with the radio in a dark room. The dailplate is well readable and the glowing tuning eye next to it gives it a nice additional glow.

The exterior of the radio was also a very time consuming piece. I wanted a radio that looked like it was art deco or something around that era. So for me this means exposed wood, shinny laquer and a curved design. None of the things that i feel comfortable with making so. This was another challenge for me to do.
Lastly there is a schema to discuss about.
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