Circuit of my modified BFO unit at =
http://homepage.ntlworld.com/p.denby...a17proddet.JPG
Serious stuff , complete dismantle and fit B9A socket.
I used a scrap small relay for thin coil wire.
The low pass on the detector o/p cuts at 3 kc/s , so 0.047 cathode bypass restores.
The 560 pf at the o/p anode bypasses some rough harmonics which couple in the valve.
The CT on the BFO winding is earthed , as lots of 100Kc/s present.
Test the input transformer has enough inductance to work at 100kc/s
Voltages marked on cct.
I had to put an additional 56 pf on the bfo tuning for correct freq.