[ARC5] ARC-5 receivers - running from a 60V B+ supply.

[Leslie Smith]

Hello list-members,
Recently the topic of power supply voltage was discussed, both for the
transmitters and receivers.  

I experimented with running the receivers on 60 and 90V B+ supplies. 
The result of my observations are available at "yahoo" groups, in the
group ARC-5radio, including the circuit I used to generate the 60V B+
supply from 24V AC (used as the filament supply).  The address is
"www.groups.yahoo.com"  There is no space between ARC-5 and radio in the
group name.  

When I first used the ARC-5 receivers I knew nothing about their
history, or that a full tech manual was available.  I quickly found a
circuit diagram, and that was my basic starting point.  Had I known more
I might have taken a different approach to generating the B+ supply -
for example I may have favoured running the filaments from a DC supply
rather than the 24V AC system I chose.  Still 24V 1 amp transformers are
common enough.

Briefly I found that a nav. band receiver (R-23 or BC-453) behind a 3
transistor xtal controlled converter was comparable in performance to a
modern commercial receiver on 80 meters, with a 60V B+ supply.  The only
mod I made to the ARC-5 receiver was in the HF and CW oscillator plate
circuits.  I soldered a 33k resistor across the plate dropping resistor.
  More detail is available in the yahoo group files area, including a
photograph of the prototype power supply.  The key point, so far as the
mod is concerned is to know that the HF oscillator dropping resistor is
inside the oscillator coil can.

  
If anyone has difficulty getting access to the yahoo group I can send a
copy of the circuit diagram via an email.  Just let me know.

73s,
 
  Leslie Smith
  vk2bcu at operamail.com

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