[Milsurplus] RBM - MF question(RU-19 selectivity)

[Hubert Miller]

Pat Hawker G3VA's book "Ham Radio Techniques" shows such a Q multiplier which requires no additional tuned circuits. 
Uses a single dualtriode like 12AT7. The control pot is at DC only. This would be connected to the first IF tuned circuit in a
superhet receiver. This is the idea I was thinking of, except implement it with FETs. Yes, not as elegant as an RU standalone,
but with the figures Jack supplied, it looks like only at 200 kHz is the RU selectivity satisfactory. I suppose you could use a 
tunable converter, something like a Gonset idea, to convert 80M down to the RU set at 200 kHz, but it's more realistic fun
to tune via the RU.
-H