[ARC5] RU/GF sets

[Roy Morgan]

On Aug 22, 2010, at 5:13 PM, Henry Mei'l's wrote:

> ... The Germans made extensive use of regeneration in their TRF  
> receivers to
> improve selectivty (and sensitivity).
> Isn't regeneration also used in the RAL? (Or is it the RAK or maybe  
> both - I
> could check it out.)

Henry,

Ken Gordon may have more info, and certainly more experience using the  
RAL, but here is what I understand:

Both the RAL (HF) and RAK (VLF to 600 kc) have two stages of tuned RF  
amplification (6D6's) followed by a regenerative detector (also a 6D6)  
controlled by a rheostat in the screen supply.  They have a  
regeneration test button that shuts off the regeneration when pressed  
to let the operator know the state of the detector.

The detector is followed by a most amazing audio filter (though the  
filters differ a little bit in the two radios), a noise limiter, audio  
preamp stage (6D6) and an audio output stage (type 41 tube).  The  
audio output is meant for one or two headphones at 600 ohms (and is  
center tap grounded.)

That may not sound all that amazing, but the astounding  
characteristics of the RAL and RAK are the mechanical build quality,  
the stability and clarity of the signals you hear, and the bless-my- 
soul smoothness of the regeneration control.

A drawback compared to the later octal-tubed RBL is no direct  
frequency readout.  If I understand the typical operation of the day,  
however, especially on 500 KC and related frequencies, moving between  
frequencies was not done too often, and the number of frequencies was  
small.  Each of the radios has a place on the front to log dial  
settings for a set of often used QRG;'s

By the way, Bob Keys, son of a maritime radio operator, and long time  
user of a marine transmitter and an RAL, has for years run his RAL on  
batteries.  He reports a sense of clarity and transparency and lack of  
extra noise in the signals compared with the use of line power supplies.

Richard Brunner, AA1P, has developed a half dozen or more changes to  
the RAL that he believes solve problems he found in them.  I have not  
yet done these to an RAL, but I certainly do intend to try them out as  
soon as I can.

Roy

Roy Morgan
k1lky at earthlink.net
K1LKY Since 1958 - Keep 'em Glowing!