| The
Tube Transmitter Contest came about because we had built receivers with
tubes in
previous contests but not a transmitter.
To keep it
simple, The rules specified that it must be crystal controlled, (no VFO's.) This sounds easy, but it
turned
out to be very difficult since we
decided to judge partly on
stability of the keyed waveform. The junk box crystals we had,
were not the most stable,
since some of them
dated back to WWII and were in FT-243
holders. Regardless, there were five entries, as shown below, that represented various methods of construction and individual style. They all worked and for the most part, had very acceptable looking waveforms. The power out varied from a few watts on one to over 100 watts on another rig. This contest was hard to judge because where one was lacking something, it made up for it in another area. I believe it came down to a tie in the end. We didn't really care because they were all winners to us. We just had a good time. |

| Scenario: Your company has
transferred you to Inner Slobovia (as opposed to Outer Slobovia), a technically starved country with restrictive import policies. They refuse to allow transistors into the country as it interferes with the basic tenants of their state religion of Bassackwardism. They have, however, embraced the use of tube type equipment, since the vacuum inside is considered to be an ideal state of affairs. As a result, there are all kinds of old TV sets and “all American 5’s” laying around. After you have arrived, the local amateur radio wannabes contact you to help them get on the air and set up their stations. Since the country is not flush with Slobbos (the local currency, 30 Slobbos =$2.264825) they need to adopt something that can be produced from the “junque” lying around. Your basic limitations are: 1. Must be a tube rig, any kind you care to use! (Diodes in the power supply are OK) 2. Must be crystal controlled. 3. You can use any circuit you want, although simpler is better. 4. Any power source can be used, you do have access to 120VAC and can use any power supply you want, even a yak on a treadmill! 5. Safety concerns require that high voltage circuits be shielded from accidental contact by both the operator and visitors in the shack. 6. Any type of construction can be used, chassis, breadboard, ugly, handsome, etc. 7. No limits on the number of tubes, (refer to #2). 8. Keying waveform will be examined and rated. 9. Consideration will be given to the ingenious use of scrounged parts in the construction. 10. Neatness, while not critical, is encouraged. 11. Efficiency will be defined as power out divided by power in times 100. This will be calculated from measurements at the meeting. Have fun and be creative! |