W8CDX 1930s FD Setup at NO3M

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I had been tossing around the idea of doing an antique FD (Field Day) setup this year after having a lot of fun running my 1920s replica transmitters during several of the recent 160M Stew Perry (TBDC) events.  Once I committed to the idea by inviting several friends out for Saturday afternoon, I knew it was time to get busy, as I did not even have a transmitter built for 40M yet and it was about a week and a half before the FD weekend! Continue reading W8CDX 1930s FD Setup at NO3M

Electrolytic Rectifiers

Before tube rectifiers were readily available, electrolytic rectifier banks (Slop Jar rectifiers) were common.

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There is numerous literature in old QSTs on the construction, use and care of these type of rectifiers:

“A Symposium on Aluminum Electrolytic Rectifier Operation”, June 1922 QST

“Operating Notes on Electrolytic Rectifiers”, Sept 1921 QST

“An Electrolytic Rectifier for C.W.”, Feb 1921 QST

I chose to use a solution of distilled water and Sodium Bi-carbonate (Baking Soda), which works just as well as the more popularly referenced Sodium Borate (Borax).  A 385-0-385 volt Thordarson power transformer was used during initial testing, each side of the high voltage winding connects to a bank of eight (8) jars, C.T. (center tap) “grounded”.  No smoothing filter has been setup yet, but the output of the rectifier bank shows 400VDC on the voltmeter.  Once a suitable permanent setup is built for the transformer and filtering components (Stancor swinging choke and 20uF oil capacitors), this rectifier will be part of a B+ supply for several of my 1920s reproduction rigs.

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