The AM Forum

With the winter season fast approaching here in the northeast, a ham's thoughts to projects indoors, building, restoring, and general on-air fun.

For those thinking of venturing into the wonderful world of transmitters built on a wooden board, I've posted a treatise by my friend John Rollins W1FPZ SK on my website, see --->> www.w1ujr.net/tptg_tx.htm

John takes you from the theory behind such rigs, to the actual construction and operation.
Measurements for coils and winding are included, as well as an easy to understand schematic.
In short, all you need to build yourself a 1920s transmitter.
You can view the information online, print it out, or download in a PDF format.

My thanks to Tim W1GIG for his efforts in searching through John's archives and forwarding aforementioned information.

Enjoy, and I hope to hear you on the air!


Cordially,
Bruce W1UJR
www.w1ujr.net

(http://www.antiquewireless.org/images/ham2002.jpg)

Bruce,

One of Johns transmitters inspired me to build one 5 years ago and I use it in the AWA contest and even fire it up on some military nets now and then. It is crafted to be a AERO copy with an upper deck (the TPTG transmitter with a type 45) and a lower deck (Power Supply with a type 80 rectifier).

I am always looking for parts to make it more authentic and have been tinkering with it for a while. Learning to tune up one of these is a trip and it acts completely stable  or completely nasty depending on if the grid is tuned above or below the plate. It oscillates on both sides, but only one side provides the stable note!

I have not added the Hiesing modulator yet and I should be using a Type 10 tube but those are big bucks now, so I will stick with the 45.

Mike WU2D

So where do you find cheap 45s, Mike?

Scott Todd

Scott, those aren't 45's that appear in Bruce's picture. They look like 203A's to me, which is what I used in my second tx in 1933.

I can't imagine why only 50 ma at 200 v was used with that sized tube. If I remember correctly from 75 years ago, the 203A was rated at 50 watts dissipation. My first tx used a single '10 osc, rated at 7.5 watts which I ran at 100 ma with 750 v, but my next rig was a single 203A driven by the '10, with 900 v at 200 ma. or more. I built both of my rigs on breadboards, along with my 2-tube regenerative receiver using 201A's. (The first receiver I built in 1925 used a single UV-200.) I didn't get into fone until 1936, using a double-button carbon mic.

Oh well,

Walt, W2DU

I use the 45's that the audio guys discard as Bad. The low emission tubes work pretty good in RF service. This makes the difference between a 75 dollar tube and a 5 dollar tube!