W8BAC   Mike in Shelby Township Michigan




This is a new addition to the shack. It is a modified Gates Vanguard 1, 1000 watt AM broadcast transmitter. The original station/owner is unknown. I purchased it on eBay and it was in rough shape. Extra holes drilled through the cabinet, dents and scrapes, burned components and so on.

Gates originally designed this transmitter using a small transistorized 100 watt exciter. The exciter was housed under a panel near the mid section where you now see the band and multi meter switch knobs. Today the exciter is a Flex Radio SDR 1000 software defined radio. The Vanguard 1 transmitter now functions as a class AB1 amplifier

 On the left is the original tuning network. Above is the new tuning network featuring band switching 160 through 10 meters and a PI/L network. Two vacuum variable capacitors handle the tune and load functions.


Below is the tube compartment as found and reworked for 160 meters through 10 meters.

     

The power supply compartment has been changed a bit from the original. The Gates plate transformer was very noisy. It was replaced with an RCA with a bit more potential and very quiet. The bias supply was modified so the amp can be used in all modes. A step start circuit was added to cushion the push to talk jolt and two other small power supplies added for control circuits. A lot of attention was paid to paint and detail work inside and out.