Updated 5-17-2010

July 2010 Column


Early Factory-Built Transmitters

This is the Lafayette model 5B40P, a 3-unit, 40-watt, 5 band Phone and CW transmitter. The complete transmitter with cabinet and one coil set, but less tubes, was $142.50. A tube kit consisting of a 6C5, 6L6, 2-6L6-G's, 2-6N7's, 6J7, 2-83's and the Raytheon RK37, less the 913 tube was an additional $16.71. And the RCA 913 tube was an additional $5.00. Additional coil sets were $3.95 for each band.

The shipping weight was 125 pounds to give you an idea how big it is. The catalog didn't say the dimensions of the cabinet, but it appears to be 19-inches wide, by about 27-inches tall, and 13-inches deep.

Because each unit, the transmitter ($71.50), modulator ($40.95), and antenna coupling panel ($27.75) were available separately, the amateur could buy them one at a time and assemble the pieces as his money became available. A single panel sized cabinet was also available for $5.17, if only one unit was wanted. Two-panel and three-panel sized cabinets were also available.

Lafayette specs states that it covers the 10, 20, 40, 80 and 160 meter bands. Tubes used in the transmitter portion which incorporates the "Les-Tet" harmonic oscillator using a 6C5 and 6L6, and drives an RK-37 final amplifier. The modulator uses a 6J7 driving 2-6N7's to 2-6L6's.

The modulator also utilized the newly designed 913 oscillograph tube, as a built-in oscilloscope for monitoring the modulated RF. (See my column in the August 2009 QST for more on this tube.)

Lafayette advertised that it is built on the "Add-A-Unit" principal. The amateur can start with the RF unit only. Then later the modulator can be added to make the rig suitable for both CW and phone. Each unit contained its own power supply, keeping it simple. The antenna panel could be added at any time. All the panels and cabinet were painted in a grey wrinkle finish making it a nice looking unit.

K2TQN's Speaking Tour for this Year

I will be making a few presentations about the 1923 Bowdoin expedition, titled the “Wireless North Pole and the Adventures of Don Mix” with lots of the original photos. I regret not being able to go everywhere I have been invited.

If you are in the area, I hope you will attend.

August 2010 at the AWA meet in Rochester, NY (Tenative, check back for date and time.)

John Dilks, K2TQN    125 Warf Road, Egg Harbor Township, NJ 08234-8501   e-mail: K2TQN@arrl.net