A Schnell Receiver
A
popular circuit from the 20s.
Browsing old QSL cards it dawned on me that the Schnell
tuner/receiver
was a very popular one in its day. Searching around Google didn't
really help in determining what made a Schnell any different than other
rigs of the era but I finally found an old QST
article from February
1924 comparing it to
the 1BGF, Reinartz, etc tuners that were commonly used back then.
The distinguishing feature of the Schnell is that it used variable link
coupling on both the input and for regeneration. Thats always a
good idea. The original Schnell circuit was back in the 200 meter
days but it stuck around and many guys used it as high as 20
meters. The version I built uses a medium-wave coil that is to be
jumpered out for higher freq operation. Nice idea but
"one-size-fits-all" has its problems. In this case its the
tickler coil. There doesn't seem to be a common ground for a
tickler that works from BCB thru 40 meters even with the variable
coupling. I rigged up an interchangeable tickler coil so that it
will regenerate properly at both ends of its range. As shown the
radio tunes from about 900 to 1900 and 2900 to 7300 kc/s.
The old article indicated dial string verniers on the coils so I
fabricated them. Nice touch. It adds greatly to the 'feel'
of the receiver in actual operation. There's also a National
Velvet Vernier assembly hiding on the front panel for the main tuning
cap. Also, I added an onboard audio stage so that it is a
complete receiver.
Its a very likeable and simple circuit and performs well for its
genre. Ahhh...the good old days. Its hard to imagine the
early hams using a little guy like this and working the world.
But they did.
...
22 May 2007
