[Milsurplus] Bendix TA-12G, antenna selections

[Dennis DuVall]

Ralph,

Looking at my Northern Electric manual for the TA-12C the three HF channels used pi-network output filters with variable inductors and fixed and variable capacitors in various combinations.  The variable capacitor (365 pf to ground) for each channel was always connected to the input (PA plate circuit) end of the variable inductor.  Each HF channel also had a fixed capacitor (300 pf to ground) which could be switched to the input or the output end of the variable inductor or out of the circuit entirely.  Each channel also included a series capacitor (100 pf paralleled by a static drain resistor) connected between the output end of the inductor to the antenna terminal.  This capacitor could be shorted out by means of another leaf spring switch thus connecting the input end of the inductor directly to the antenna terminal.

The capacitor values listed above were he same for all three HF channels.  The variable inductors had different total numbers of turns, more for the lower frequency ranges and fewer for the higher frequency channels

Hope this is helpful.

Dennis D.  W7QHO
Glendale, CA

*************

> On May 14, 2015, at 8:44 AM, Ralph Cameron <ramcam at magma.ca> wrote:
> 
> The Bendix series of transmitters had a metal shield over the antenna network selection leaf spring selectors for changing values and placement of capacitors and inductor to match antenna impedance. Can anyone send my a photo of what those networks were. They were imprinted on the top of the metal shield and it appears they are very pertinent to home brew amateur transmitters of today. I had a TA-12G at one time and found the networks worked amazinglywell and there was usually only one network that produced maximum antenna current.
> Thanks
> 
> Ralph
> VE3BBM
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