Thanks everyone! I got a 6v rechargeable battery and now the hum is gone. My 130 foot antenna is about 20 feet above ground gets good day and night reception. The 71A tube drives the speaker loud enough for weak stations.
What I find odd is that many of late-20s AC sets had tubes (27s and 45s with direct-heated cathodes) with filaments served from a dedicated transformer winding. There are hum controls in the 27 and 45 filament circuits on the Temple 8-60 I just picked up. it appears to be a means to cancel hum on the filament by varying grounding reference of the cathode.
This was the first TRF set I ever tinkered with. What an experience!
