The 150 Series Amateur Transmitters
The 150W and 150BW transmitters were introduced to the amateur market in the May 1932 issue of QST. The first Collins QST ad to contain a photograph, the 150W used the 10A exciter (remember the kit?) as one of its building block components, which indicates that the design had been completed for sometime prior to this date.
The 150W/BW used a 10A exciter (common to all the early Collins transmitters), followed by a 3A Power Amplifier using a UX-203A output. Mounted in a six-foot rack with a protective back cover, the transmitter contained the 1200A power Supply, 30B Modulator, and a choice of several meter panels. An antenna coupler of the Pi design was not yet available.
Later in 1932 the 150W/BW underwent a minor redesign. "The 150A/150B now replace the 150W/150BW" read Collins Bulletin 100. "The basic transmitter remains the same, but the 1200A, now designated 1200B, has improved regulation for the class B modulator." The meter panels were also slightly changed.
The 150A was priced at $290.00, while the 150B was 350.00. One set of coils was included in the price. The 150B used the same components as the 150A but added the 30B Modulator. This was a class B modulator rated at 100-200 watts of audio output. It used two 245's or 250's driving a push-pull pair of 503's. Two modulation transformers were available with different impedances for use with single-ended or push-pull class C RF amplifiers.
By 1935 the 150C and later models were a completely different design. The RF deck and power supply was similar to that used in the 30FX transmitter. Control circuits featured push buttons and the design included an antenna coupler, all contained in a beautiful self enclosed rack.
One Good Thing Leads to Another
While the 150A/B were complete transmitters, they also made excellent drivers for the new 20B one-kilowatt amplifier and modulator. The first installation of the 150B and 20B combination (the "last word in appearance and performance") was described in the February 1933 Collins Signal (the first issue). The installation was made at W9BHT, world famous station of W.P. Ingersoll located Canton, Illinois. Mr. Ingersoll, "owner of a starch factory", as Art once said, was the first to purchase and receive a number of the later Collins designs.
The combination of the 150B and 20B proved to be a winner. With the addition of another pi section to the 1200B (now designated 1200C) power supply, the hum level was reduced to broadcast quality. The headline of the January 1934 Collins Signal gives the complete story:
"The BYRD Antarctic Expedition Sails with A Complete Collins Shortwave Broadcasting Station Aboard!
On Byrd's and McMillen's previous trips to the North and South Poles, amateurs handled the numerous personal messages and news releases by telegraphy. However, because of the advances made in the art of shortwave telephony, Rear Admiral Byrdís Antarctic Expedition II decided to transmit word-by-word broadcasts so that the vast radio broadcast audience of the nation-wide CBS network could hear the daily undertakings.
"A Collins type 20B Transmitter, operating at 1000 Watts output, is the basic unit used aboard the 'Jacob Ruppert' for these broadcasts. In addition two Collins 150 transmitters are being used for communication between the different camps of the expedition", the Collins Signal reported.
The publicity of these events gained Collins Radio worldwide recognition and a reputation that helped establish them as a world-class communications equipment vendor. It is also not surprising that the 20B provided Collins an entry into the booming AM broadcast market Ė with a little help from the 150B.
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