[ARC5] RAK-5 and RAL-5 Receivers

[CARL HUETHER]

Since both of mine are -7 models I "assume" it is safe to believe they have the improved circuit?


I use them fairly often and have not noticed sensitivity issues which would be more noticeable on the RAL which I havent used beyond 14mc on CW for regular ham use.  While testing at 23mc it is noticeably less sensitive which I credit to the tubes used in the front end. Even my 1935 HRO is kinda deaf up there.


Carl


> On April 28, 2019 at 12:20 PM Robert Eleazer <releazer at earthlink.net> wrote:
> 
>     From the US Navy's Electron Magazine of July 1945
> 
>     It has been found that the carbon resistors used in the bleeder and screen-dropping circuits of the RAK-5 and the RAL-5 receivers are notorious for changing
> 
>     value. This is apparently due to the fact that they are incapable of withstanding the excessive amount of heat that is generated in these units. If this drift is to a
> 
>     lower value of screen-dropping resistor, pla.te potential of the receiver may be caused to drop as much as 30 volts, resulting in decreased performance.
> 
>     This condition is eliminated by changing the 20,000-ohm bleeder resistor R-202 from a 2 waft carbon to a 5 or 10 watt wirewound, and the two parallel-connected
> 
>     6200-ohm screen-dropping resistors R-203 and R-204 to a single 10 watt 3100-ohm wi·rewound resistor. There is adequate space for the larger resistors above the bakelite
> 
>     mounting strip from which the original carbon resistors were removed. ;
> 
>     Also it has a noise suppressor mod for the RBH-1 receiver, if anyone is interested.
> 
>     Wayne  WB5WSV 
> 
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