Department and University.
See my other radios too! (Here is the next one.)
A radio of my own design and construction.
|Type||Tuned Radio Frequent Radio (`Rechtuit' in Dutch)|
|Band||Medium Wave, circa 600-1400 kHz.|
|Cabinet||Wood, size 36.5x28x17 cm|
(former loudspeaker box).
|Tubes||6x EF80 (1st and 2nd RF,|
det., 1st AF, 2x out), AZ1 (Rect.).
|Controls||Volume/off, tone, tune, attenuator.|
|Produced||1996, The Netherlands.|
Besides the tube line-up, I aimed for two more design criteria. Second, I wanted to do myself as much as possible: so I chose for handwound coils. Third, I wanted to use recycled parts as much as possible to allow many scrapped apparatus to donate some organs to the project. This explains for the cabinet (scrapped loudspeaker box) and the power cord (three-prone from refridgerator).
It was a real headache to design the thing (Henk Tattje was a great help in reviewing the schematic), but designing and constructing your own radio is a lot of fun. This thrill when it plays for the first time!
The audio-frequent pre-amplifier is an EF80, and the output stage is planned for two EF80's connected in parallel to increase output power. The power supply is fairly standard but noteworthily it uses 50 year old electrolytics from a Philips radio, that still had their original capacity and almost no leakage.
It was very difficult to keep the radio from oscillating; I had to bend a few wires in the HF section, and the LF part always oscillates if I place EF80's in both output tube sockets. So I use the set with only one output tube.
The radio plays and receives about 20-30 stations in the evening. Selectivity is rather poor, especially on the lower part of the MW band. This performance results from the handwound coils; their Q is lower than that of factory coils, and it is difficult to match their inductance precisely so that the synchrony between the three tuned circuits is difficult to achieve.
After all, the performance is hardly better than what can be achieved with a single tube, but to build this thing was a lot of fun.
Gerard Tel, firstname.lastname@example.org