A corner of National's Engineering laboratory in the early 20's. [The receiver
on the bench in the lower right and being tested by the engineer in the middle left appears to be a National MB-29. This receiver was advertised in the November, 1929 issue of QST..]
One of the TRF SW series receivers in a appropriate period setting--circa
1923. [Pictured is the SW-4. This receiver is advertised in the Jan, 1929 issue of QST.]
The earliest attempt at band switching a communications receiver -- perhaps the
reason why plug-in coils stayed popular for so many years!
The "innards" of the famous SW-5 Thrillbox -- which covered 9 to 2000
meters using two type 235, one 27, and two 45 tubes in a TRF --
regenerative detector -- push-pull audio set-up. [Pictured is either a SW-58 or SW-34. Both of these had the same basic circuit as the SW-5 but with a slightly updated/improved 1932 tube lineup. The earlier version of the SW-5 had a
drum dial and two 27s in the final audio stage.]