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July 14, 2024. A Vintage 1957 Solid State Transmitter.

In 1957 I had two important subjects firmly on my mind: Girls and Only 2 more years before I could escape my boring town in Western Pennsylvania -- about 30 Miles from Butler, PA which of course is in the news today.

That is my excuse for not spotting this jewel when it was first published in 1957.



Wow! A 200 milli-watt CW transmitter, all solid-state using RCA Transistors. With some attention to biasing you likely could pop in the circuit, transistors like the 2N3906, 2N2907, 2N4403 or a 2N2905. The Oscillator is a Common Base, and the Amp is a Common Emitter.

[Check Google as to why the Common Base for the Oscillator like Voltage Gain, Input Impedance, Stability, Biasing etc.]

Speaking of Biasing note the use of multiple batteries versus resistance biasing. The Oscillator is keyed, and the Oscillator/Amp is switched on during transmit using SW1. By switching on SW2 a lesser collector voltage is applied likely a spotting signal.

There are three meters in the rig and the output circuit and antenna tuner should provide for good harmonic suppression. Note also JIC (just in case), the output has a wavemeter coupled to the output to assure you are transmitting with "max smoke" on the right band. BTW 200 milliwatts of RF at 7MHz was a big deal in 1957!

I will bet the signal quality, in large, depended on the crystals being used. The plated type might yield a whoop, whoop sound as you keyed the rig. A good place for the FT-243 type.

You can find the complete article by searching for N4TRB + RCA Ham Tips ~ July 1957. This schematic has great potential for a 2024 makeover with less parts, less cost and more power output. 

Again, the fun of looking at something from 67 years ago and remaking it with modern components. There is also another incentive to not directly replicate this design -- the cost. The eBay auction site currently has an RCA 2N140 transistor for about $20 shipped.







TYGNYB.

73's
Pete N6QW

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