100-Watt Incandescent Light Bulb Dummy Load

[cadillaccharlie]

Hi All!

I understand the concept of 50-ohm impedance & SWRs on plate output of a radio transmitter. Back in my earlier years I had a Johnson Viking that I loved to experiment with. The owner's manual suggested the use of a 100-watt light bulb as a dummy load to dip the plate and tune the PA with. I even used the light bulb as an antenna to transmit and check my modulation which worked very well. I now have a Siltronix 1011D that I want to tune up off the air, but I don't want to spend more than what I paid for it in a 100-watt dummy load. Would a 100-watt light bulb be okay to tune the PA Sweep Tube 8950 if I tuned to maximum brightness of the light bulb in a quick but efficient manner. Thanks for any advice or other cost saving methods that anyone might suggest.

CC

[2600]

The biggest problem with an incandescent bulb as a dummy load is the impedance. Tungsten has a really extreme temperature coefficient of resistance. A cold tungsten filament has a much lower resistance than a hot filament. As the RF power level rises and falls while tuning up, the load impedance rises and falls with it.

A bulb was a handy low/no-cost tool 60 years ago, but I don't recommend it now. Small dummy loads for barefoot radios are cheaper than the kilowatt types. The final tube in the 1011 probably costs more than a 200-Watt rated dummy. Sounds like cheap insurance to me.

73

[cadillaccharlie]

Thanks for your input.

CC