Some things are interesting, even if totally useless nowadays.   Such is the case with the Philco 426-3034 Crossover Kit for UHF TV.   What the heck is that?

Well, back in the late 50s,  UHF television stations operating on channels 14-83 started to appear in many areas of the US where viewers had a VHF-only TV antenna, and in many cases an externa UHF converter was required.  Tese barriers meant UHF viewership remained low.   To speed the growth of UHF broadcasting, in 1962 Congress passed the All Channel Receiver Act, which provided "that the Federal Communications Commission shall "have authority to require that apparatus designed to receive television pictures broadcast simultaneously with sound be capable of adequately receiving all frequencies allocated by the Commission to television broadcasting".     This put UHF stations on par with the established VHF stations.

To receive UHF signals, set owners needed to put up a UHF antenna, or to replace their existing antenna with one capable of receiving both VHF and UHF signals.   If the took the latter approach, which was promoted by TV dealers because there was more money in it - a new problem arose:  how to attach a single new twinlead feedline to the TV receiver that had separate antenna terminals for VHF and UHF?

Philco's answer was the 426-3034 Crossover Kit.   In ham terms, it was what we'd call a duplexer - a device that could allow a single antenna to be used on two different frequency bands without interference.     What is interesting is HOW Philco designed it.   As the photos show, the crossover kit was built almost entirely on a printed circuit board, which was still fairly new technology at the time. 

The circuit includes inductors and capacitors, both fabricated by traces on the PC board.   Zig-zag lines are inductors, and those with interleaved fingers are capacitors,  forming tuned circuts that would separate the two signal bands, along with a pair of carbon comp resistors.   There were no CAD systems in those day,   no modelling software to simulate the performance.   Each element was created by hand calculations from first principles, such as the dielectric characteristics of the material and area of conductors.  At most the engineer who designed this device might have had the use of a Monroe calculator for some of his calculations, but changes are good that most of the work was done with slide-rule, pencil and paper.    Prototype boards would have been etched and the result tested in the lab, using vacuum-tube based test equipment. 

Today, many hobbyists could duplicate this task using tools like ELSIE to design the network and LTSpice to simulate how it worked,  then lay out the board with KiCad.   All these are very powerful Computer Aided Design software tools that are completely free!

Things have chaged a lot to be sure, but looking at how things were done in the past can be educational.  And the truth is,  the same need would probably be addressed in a very similar way today.