[ARC5] SG Keying of ARC-5 TX

[J Mcvey]

I used a mosfet for cathode keying in a hacked up unit and it worked just fine.I would suspect that an appropriate one with sufficient Vds would be Ok for SG as well. 
Are you keeping the oscillator on while idling? Is the shielding adequate to avoid RX interference?
 

    On Friday, November 18, 2016 9:32 PM, Tom Bridgers <tarheel6 at msn.com> wrote:
 

 Recently found out that you could key an ARC-5 by using an appropriate sized SPDT 28 VDC relay that toggles between a cutoff voltage and normal SG voltage.

In transmit mode, after applying B+ and VFO voltage, on key up a large negative voltage (about -200 volts)  is applied to the screen grids.  On key down the relay applies the normal +275 volts to the SG.

This circuit eliminates back wave, and was recommended in GE Ham Tips in the early 1950's. Though not specifically to the ARC-5, but for use generally to transmitters.  This method was implemented successfully by Ron Baggs , which is where I found out about it.

Instead of using a mechanical relay, it would be really cool to figure out how a MOSFET could be used instead to implement this circuit.
Tom KE4RHH


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