[Milsurplus] RAK AND RAL

[Kenneth G. Gordon]

On 22 Jul 2016 at 5:30, Richard wrote:

> The RBL is an excellent receiver, as good as the RAK,

Well, having used both over an extended period, I have to disagree with you, Richard. The 
RBL has many advantages over the RAK, but stability is NOT one of those.

The RAK (and the RAL) have a voltage-regulated detector stage, while the RBL has no 
voltage regulation anywhere. 

When using the RBL to monitor the Navy VLF stations back in the 1970s, it became very 
apparent that even slight line-voltage changes caused very obvious frequency changes with 
the RBL, while the RAK never moved.

The stability of the RAK/RAL is outstanding.

In fact, some time ago, I designed a special circuit to enable voltage regulation of the 
detector stage of the RBL which would, in my opinion, make a significant improvement in that 
receiver's stability. So far, other projects have precluded my installing this in my almost-new 
RBL here, though. 

> The RAK/RAL power supply has a design defect in that some voltage
> dropping resistors are nestled underneath a fiber board with no air
> circulation, and are always shot.  Also they put too much current
> through the 884 regulator as it's only regulating a half-mill load. 
> It's easy to make a power supply - I've gone both ways, and it may
> have been less work to make a new one. 

Agreed. In fact, my RAL and RAK operate from a far smaller and lighter power supply (not 
designed by me, BTW) which maintains the RAK/RAL's good stability, yet draws far less 
power and puts out far less heat, while weighing only a few pounds.

BTW, the supply voltage input circuitry of the RAK/RAL is pretty interesting. It is designed so 
that one can operate the receiver from a 6 volt battery for filaments and a 90 V "B" battery, 
the internal connections providing the necsssary voltage to the detector stage while 
automatically bypassing any need for regulated detector B+. Very neat.

Ken W7EKB