[MRCA] ARC-5 RCA Dayton project

[Peter Gottlieb]

The chances of today's technology working in 80 years is slim to none.  For 
basic, long term functionality that old technology is hard to beat.

Peter
kb2vtl


On 12/23/2017 10:56 AM, Ray Fantini wrote:
>
> A 20K 5 watt resistor between the plate and screen grid did the trick. 
> Increased the modulation and simplified wiring. This means that the +165 is 
> only used for the MO so I put a switch upstream that will allow the MO to be 
> powered without keying the transmitter so I can “spot” the transmitter on the 
> receiver. The idea being I can hear the other traffic on 3.885 at the event 
> and set the receiver and then set the transmitter by spotting it on the receiver.
>
> I did notice that the output loading has big effect on modulation and 
> distortion. Transmitter sounds best loaded at half power around five watts but 
> has noticeable distortion at nine watts. Best audio is with loading at 35 Ma 
> for 5.5 watts, that’s an indirect power of about 11.5 watts and getting a 
> little over 5.5 out gives me an efficiency of around 50%. Not bad for 
> something built out of seventy year old technology.
>
> The whole system consumes just under 6 Amps @ 12.0 volts so that’s about 72 
> watts to produce 5 watts of RF power or 2 watts of audio from the receiver by 
> today’s standard of Yahoos and Kenwoods that’s a tremendous waste of power but 
> there is no substitute for the joy that’s derived from a transmitter and 
> receiver that’s using twelve tubes and designs from 1938, next week that will 
> be 80 years ago!
>
> If anyone is interested I can post the updated finished schematic or 
> additional pictures and may have to do another YouTube for this also. Still 
> have to work out the T/R relay and maybe a frame or box for all this to fit 
> in. just hate to put any kind of cover over the receiver being that its layout 
> and construction is in my mind a work of art.
>
> Ray F/KA3EKH
>
>
>
>
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