No. 19 Set Linear Amplifier


Wireless Set No. 19 amplifier was developed for use with the 19 set in order to extend its range to around 35 miles. The amplifier was conceived and developed by the Development Group of Directorate of Signals Design, A.E.D.B., during the early months of 1942. In June, 1942, an order for 37 units was released through the Branch, 25 to be made at Canadian Marconi Company and 12 at Canadian Signals Experimental Establishment (CSEE).  Early production forecasts were for delivery in September, 1942.

In October, Canadian Marconi Company had not completed the order because of lack of materials. During November the company had experienced numerous difficulties in make the design operate. In January, 1943, Canadian Marconi completed delivery of their 25 units but the sets did not meet all the desired operating conditions.

In March, 1943, an additional order for 450 amplifiers was placed on Rogers Majestic Limited after Canadian Marconi had declined to accept it because of already heavy commitments.   About the same time an order for 30 more units was placed on C.S.E.E.

Alan Rosenthal, VE3DI, worked at Rogers Majestic at the time and was appointed as the project engineer on that product. He recalls the following:

"We had inherited the amplifier from Canadian Marconi with an inherent problem the amplifier amplified all the spurious output from the 19 set and caused a lot of interference on adjacent bands, as well as giving the enemy that much more chance of finding the signal for interception purposes.

We had to devise and design a tuning circuit for the input to limit the spurious signals getting to the 813. We also had to solve a problem with corrosion and power loss at the output tank roller coil bearing which had to carry the output of the 813 to the coil. We finally settled on a very special plating technique for the shaft and the bearing".

Some additional information on the No. 19 set amplifier can be found on pages 45 and 46 of the Signals Production Branch document dated October 15
 
 

no19_set_amplifier.jpg
This 19 set linear amplifier atop a 19 set is held  by the Communications and Electronics Museum in Kingston. (Photo by Jerry Proc)
SPECIFICATIONS:

Frequency Rage: 2-8 MHz , same as the 'A' section of the 19 Set.
Power output: CW - Up to 100 watts.
                        Voice: Up to 70 watts.
Amplifier tube: 813
Primary power: 12 VDC or 115 VAC depending on power supply.
Packaging: Separate amplifier and power supply.

Dimensions/Weights (of the Canadian Marconi version) :

Amplifier Unit
12.75 " L, 11" H, 17 1/2" W
Weight 47 lbs.

Power Supply Unit
17.5 " L, 8 1/2" H, 12" W
Weight 77 lbs.

Mounting frame
33" L, 25.25" H, 17.5" W
Weight-  172 lbs with amp and power supply fitted.

Note 1  - The "L" is actually the dimension across the front and the "W" is the depth.
Note 2 -  The British version of the 19 set amp has different weights, dimensions and power level.
 

MORE PHOTOS
no19_set_linear_amp2_front.jpg
Linear amp  - front view.
no19_set_linear_amp_2a.jpg
View of linear amp when detached from its power supply. 
no19_set_linear_amp3a_side.jpg
Linear amp  - side view.
no19_set_linear_amp6_bottom.jpg
Linear amp  - bottom view.
no19_set_linear_amp4_rear.jpg
Linear amp  - rear view.
no19_set_linear_amp_ps2_front.jpg
Linear amp  power supply - front view
no19_set_linear_amp_ps5_back.jpg
Linear amp  power supply - rear view.
no19_set_linear_amp_ps8_top.jpg
Linear amp  power supply - top view.
All photos in this table by Geert Hommes

Contributors and Credits:

1) #19 Set Web page. http://www.qsl.net/ve3bdb/signalshistory3.htm by Bob Cooke, VE3BDB
2) Bruce MacMillan <radio(at)telus.net>
3) Alan Rosenthal <alanrosenthal(at)sympatico.ca>
4) Linear amp photos - Geert Hommes <geert(at)tominstitute.com>
5) History - Signals Production Branch , Department of Munitions and Supply, October 15, 1943
6) Jacques Fortin <jacques.f(at)videotron.ca>]
 
 

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Dec 3/12