[AMRadio] Early version Johnson Ranger I


Donald Chester k4kyv at hotmail.com
Sat Jan 1 09:46:27 EST 2005



>
>I am in the process of restoring a Johnson Ranger I.  I obtained part of 
>the
>manual and a schematic.  That's when I noticed that two of the tubes were
>"missing."  The tubes are the 6AL5 bias tube and the 12AU7 keyer tube.
>
>A second question is whether I should refit this old Ranger to bring it up
>to the later version standard.  Makes sense from an operational standpoint,
>but what's the feeling about keeping this Ranger preserved as the early
>version.

The early version used cathode bias for the modulator.  The  later one used 
fixed bias with an external bias rectifier.  You can get a little more 
positive modulation peaks by changing to fixed bias.  On mine, I used a tiny 
6-volt transformer (think I bought it at Radio Shack, but any small 
transformer will do - you might scavage one from an old wall wart).  I 
connected the 6-volt winding across the filament line, and used a solid 
state rectifier to rectify the voltage that appeared across the 110 volt 
winding, an electrolytic cap, and a small pot to complete the bias supply.  
Once I set the resting plate current for the modulators, it stayed put and I 
never had to reset it again.

I was able to mount all the components into existing space and use existing 
screw holes to avoid drilling any new holes.

I would say adding the keying mods would depend on your preferences for cw.  
My rigs all use cathode keying, and I use a TV sweep transistor similar to a 
circuit in the 1980-era ARRL handbook, as a solid-state keying relay, so I 
wouldn't need to modify the rig to get direct keying voltage off the key.

Don k4kyv





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