I have always been a stickler for creating neat, orderly
arrangements when building any type of circuit assembly. Many moons ago when starting out as an electrician, I made a point of installing straight
runs of Romex type cable with no twists, evenly spaced staples, and keeping the identification marking to the outside. Conduit was precisely bent
and installed, again with organized parallel runs and even spacing where possible (all while conforming to the
NEC). Circuit breaker panel wiring looked like something
seen in an Apollo space capsule (ok, I exaggerated a bit here). Electrical inspectors often complimented my work. Moving on to an electronics
career, the habits carried over when prototyping and even when directing layout for production PCBs or chassis assemblies, including cabling. The greatest
enjoyment I had was when laying out runs of waveguide. Standardized manufactured straight and corner bends, along with integral components like
switches, couplers, circulators, etc., to some extent guaranteed a nice-looking configuration, but a thoughtful planning guaranteed an impressive
result. Rectangular waveguide always looks more high-tech IMHO since circular waveguide can look like coaxial cable (if you overlook the bolted
flanges). This advertisement by Bell Telephone Labs highlights waveguide circuits used in their relatively new (in 1948) microwave long distance
relay distribution system. For a company that really had no domestic competition at the time, Bell Labs put a lot of effort into promoting their
Bell Telephone Laboratories Ad: Pipe Circuits
radio broadcast waves, microwaves are too short to be handled effectively in wire circuits. So, for carrying microwaves to and from antennas,
Bell Laboratories scientists have developed circuits in "pipes," or waveguides.
Although the waves travel in the space within the waveguides, still they are influenced by those characteristics which are common to wire
circuits, such as capacitance and inductance. A screw through the guide wall acts like a capacitor; a rod across the inside, like an inductance
coil. Thus transformers, wave filters, resonant circuits - all have their counterpart in waveguide fittings. Such fittings, together with the
connection sections of waveguide, constitute a waveguide circuit.
From Bell Laboratories research came the waveguide circuits which carry radio waves between apparatus and antennas of the New York-Boston
radio relay system. As in long distance wire communication, the aim is to transmit wide frequency bands with high efficiency - band widths which
some day can be expanded to carry thousands of telephone conversations and many television pictures.
Practical aspects of waveguides were demonstrated by Bell Telephone Laboratories back in 1932. Steady exploration in new fields, years ahead
of commercial use, continues to keep your telephone system the most advanced in the world.
1 - Base of a waveguide circuit in a repeater station of the New York-Boston radio relay system.
2 - The waveguide continues upward through the roof of the station toward the antennas.
3 - The waveguide connects with antennas, which are oriented in azimuth with antennas at next station. At right is complete
Bell Telephone Laboratories
Exploring and Inventing, Devising and Perfecting for Continued Improvements and Economies in Telephone Service
Posted December 10, 2015