[CW] SAQ Xmas transmission

[Ken Brown]

k3miy at csonline.net wrote:
> Hi Ken
>
> The reason I ask is that some of the alternators used a tap on the
> coil of the tuned circuit (see the book W6AM by N6AW)to shift the
> frequency slightly so the RX op could get the keying. Wasn't sure
> how the Alexanderson units did it. Thanks and season's greetings.
>
> Ron
> K3MIY
>   
Hi Ron,

I was fortunate to have a very personalized tour of SAQ. Mary K6FK and I 
were in Sweden in 1998, We visited the radio museum in Motala, and we 
went to Grimeton. Bengt Dagas (I think was his last name, Bengt his 
first name for sure) had worked at SAQ since the war. He picked us up 
from the hotel in Warberg and took us out to SAQ. He showed us the 
Alexanderson alternator.

They have some other gears which can be put in the gear box to set the 
system to a different frequency. Originally they had two Alexanderson 
alternators there, and I would guess they had them set up for different 
frequencies. The extra set of gears may have come from the other 
alternator set. The speed of the motor which drives the alternator is 
controlled by a liquid rheostat. It is a big vat with two electrodes in 
it. By changing the level of the water using pumps, the resistance is 
varied. There is some sort of control loop using that liquid rheostat to 
maintain constant RPM.

The system is huge and all electromechanical. There are knife switches, 
contactors and motors all over the place. The keying relays have blowers 
to blow out the arc in the keying contacts. I would guess the  blower 
motors are about 1 or 2 horsepower motors. The liquid rheostat pump 
motors are similarly sized.

The keying is performed on the output of the alternator using satureable 
(sp?) reactors. DC current is switched through control windings to 
saturate the core and change the coupling between the primary and 
secondary that the 250 kW of 17.2 kHz tx power passes through.

Overall an incredible setup. Too bad none of the Alexandersons in the 
USA were preserved. As far as I know SAQ is the only one left. Same 
thing goes for the huge arc rigs. You can find a picture of the magnet 
used in an old arc rig if you do some searching for the cyclotron at 
Berkeley. Wireless technology adapted for subatomic physics research.

Ken
N6KB