Re: {Collins} extention cords



Wow, I guess I had better get busy ordering some parts for a 5' extension cord, - - - Wait- - - One of my 6293's in my 32S-3A just hollered saying "We don't care bout no stinkin .17 volt on our filaments, we're tough" Enjoy your weekend guys.
73
Don WC4G
Charleston, SC

-----Original Message----- From: Colin Lamb
Sent: Friday, July 12, 2013 3:54 PM
To: wc4g@xxxxxxxxxxx
Cc: Collins@xxxxxxxxxxxxx
Subject: Re: {Collins} extention cords

An extension cable for the Collins KWM-2 is an opportunity to solve a problem created by higher line voltage.

Today's higher line voltage means the filament voltage on the tubes is higher than desired. You can solve that problem using an extension cable. Here is an example of the simple calculations:

Measure the voltage at the 6146 tube socket. Assume it reads 6.47 volts. That is .17 volts higher than desired. Also assume that you want a 5 foot cable extension. We know the KWM-2 draws 11 amps at 6.3 volts which means that we need to add .015 ohms of resistance to the filament circuit. #12 wire is 1.5 ohms per 1,000 feet, which is .015 ohms per 10 feet. So, if the cable was 5 feet long, that would use 10 feet of #12 leading to .17 volts drop of filament voltage. Perfect.

Colin  K7FM
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