[robsradioactive]

Thanks again you guys! I swapped the 6A7 for a tested and, apparently, N.O.S. tube. That made a huge improvement.
I then tested the original 6A7 on my (calibrated) Hickok 600A and it showed [?] on the pentode section.

Turned the english to 73 and that made the meter read Gm of about 600/1000 (average new tube).
The oscillator section was fine at nearly 500/300(" ").

Emission tests good, so I must have originally just done an emission test (or maybe enhanced emission test depending on who you believe) on my Jackson 648. I don't know how else I could have missed that marginal tube.

Also, I may try that tunable loop antenna!

Rob