[Boatanchors] Plug in coils

[Jbrannig at verizon.net]

The additional inductance and capacitance introduced by long wires to 
switches raised havoc with early radios.
So it was more efficient and cheaper to use plug in coils.

Pill bottles, toilet paper rolls and Quaker Oats boxes, just about anything 
round was used for coil forms.

My first 811 amplifier was TPTG and used B&W plug-in coils in the grid and 
plate circuits (almost forgot to shut off the B+... ONCE! )

The QST archives has a LOT of articles on the winding, use and whys of 
plug-in coils.

Jim

Hello Preston,

I believe plug-in coils came about in the mid-1920's with the move to
shortwaves (HF).  The earliest example I can cite is the RCA AR-1496
TRF-autodyne receiver which covered 4 shortwave bands from about 3.5 to
24 MHz.  The coils are mounted horizontally on rectangles of Bakelite
that hold pin jacks to engage pin plugs in the radio.

There's a long homebrew tradition of gluing cylindrical things to
discarded tube bases, or using just a tall tube base for higher frequencies.

Oops.  Found one a year earlier.  Grebe CR-18.  See:
http://www.stonevintageradio.com/description.php?II=61&UID=20130719091421

Al

On 7/19/2013 10:22 AM, Preston Clark wrote:
> Hello group I am reading surviving technology  and I have seen on eBay the 
> coils of certain bands that plug into the radio. I am curious when did 
> these start and how hard are they to make from scratch  73 Preston kf5evv
> Sent from my iPhone
> ______________________________________________________________
>

-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

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