I don’t know the Kolster circuit but I can tell you, RCA never made any direction finding receiver that used a regenerative detector.
I have a pretty good stock of reference material on RCA communications products if you want to contest that.
The problem I see with the regenerative detector for direction finding is that its use requires much more attention to task, more skill.
The regeneration level between low signal strength and maximum signal strength may need readjusting, or else there is a kind of limiting
action, that is, nonlinear gain with signal strength, which may be a problem. This ( I think, anyway ) is a confusing factor, like using AGC
when trying to DF. It CAN be done, but more time consuming and more likely to contain inaccuracy. It occurs to me at this moment that
the gridleak detector, with a larger signal, will have more negative bias on the control grid, hence a kind of control against gain. Perhaps
this is why the advice on using regen receivers for CW, when the regen is advanced just beyond the most sensitive point of operation, there
will be a “leveling” effect on all signals.
I am thinking now of a German WW2 era receiver used for both communications and airfield DF use. I think this is the EP-2 / HE-1 receiver
with a tuning range of something like 75 – 3700 kHz. ( I still have one to sell, which I need to pull out of storage. ) It does use a regenerative
detector at 50 kHz IF. But as a superhet with an RF and IF stage, the detector regeneration effect can be turned way down and the receiver
still function as a nonregenerative circuit. The regenerative detector in the superhet receiver was something only the Germans and Japanese
used, and even there it was not usual.
Some of you readers may have tried the regenerative IF stage trick, like on the “Command Sets” receivers. I think most people who tried this
found it very unsatisfactory. Having one control that affects both selectivity and gain at the same time is an annoying experience. The separate
Q-multiplier as I recall, has mostly eliminated this complication.
-Hue Miller