The Tube Transmitter Contest
(Held in 2001)

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.

Some of the members listening to the rules.
Yes, they are all awake!

The Rules, by Mike Moraghan

Transmitter Building Contest
 Louisville Electronic Homebrewers Club

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                                     

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

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,
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
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!

The Entries
(Click on image for larger size picture)
Jack Bell's entry, a one tube set with a nice front panel look.  Operates on
40 and 80 meters with interchangeable coils.
Top view of Jack's rig.
Mike Moraghan's one tuber.
Top view.  Mike is good at making something out of nothing.  He wins the
"Best use of scrounged parts" award.
Jay Fox's miniature one tuber.  Has built-in power supply. Notice the vintage
Bliley Crystal on top.
Another view.  Jay is our RF expert.
Darrell Darby's machine, another one tuber.  Looks like 1920's.
Top View.  Nice tuning mechanism.
Mike Starcher's five tube set with two 6146's.
Bottom view.  Lotta parts here!  Are they all necessary?
View inside shielded section.

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© 2006 ~ Michael R. Starcher ~ All Rights Reserved