Antenna
Newsletter of the Mercurians

Today, for better or worse, we commonly see someone driving and talking on a cell phone at the same time. The technological marriage of the cell phone and automobile, however, is only the latest stage in the long evolution of two-way wireless mobile communication. Its ancestor, the automobile radiotelephone, has been around for decades, as has the citizens band radio. Another long-standing user community of automotive wireless communications is the amateur radio operator. Their small, solid-state, high-frequency transceivers fit unobtrusively under the dash of an automobile and connect easily to the 12-volt electrical system. “Ham” radiotelephony became widespread in the 1950s. Their creation of a new form of mobile communication is an interesting story and shows the difficulty of joining one technology with another, despite the relative maturity of both.

By the 1920s, hams were experimenting with vacuum-tube transmitters and radiotelephony, and by the 1930s, radio sub-bands existed for amateur voice communications. However, only a relatively small number (perhaps 25 percent) of hams were using voice communications, probably because the equipment was physically large and costly, and in the midst of the Great Depression very few hams could afford them. Then, during World War II, amateur radio communications ceased until the conflict ended.

The 1950s saw the return of prosperity for many Americans, and gradually more and more hams could afford to dabble in radiotelephony, or phone communications as it had come to be known. The creation of the Novice class license brought in a whole new generation of hams. Many wanted to use their Ham equipment in their automobiles. Police departments and other users of commercial two-way mobile radio equipment often installed an alternator and a second battery to power the equipment. Unfortunately, this rather expensive arrangement was well beyond the reach of the average ham. Then, too, there was the daunting technological problem of adapting the technology to the automobile.

The difference between the automobile electric generator of the 1950s and today’s alternator is the difference between night and day. While today’s alternator provides a constant amount of current regardless of the automobile’s speed. A 1950s-era generator increased or decreased its current output in proportion to the speed of the automobile. As a result, when one sat in traffic with the lights on, the generator would fail to keep up with the drain on the battery. Worse yet, even when driving at highway speed, a generator could not produce enough current to keep up with the drain of the vacuum-tube transmitter.

In addition, the automobile was an electrically noisy environment. One needed noise suppressers for the spark plugs and distributor, bypass capacitors for the instrument panel gauges, and even wheel noise suppressers that fit between the front wheel bearings and the hubcaps. Despite these technological realities, if a ham still wanted to go mobile, they might start with just a receiver, then add the ability to transmit later.

One option was to convert an existing car radio into one capable of receiving amateur frequencies. This was done by connecting a small, tunable shortwave converter to it. The operator would set the auto radio to a specific frequency, and the shortwave tuner would use the auto radio as an intermediate frequency and audio amplifier. Another option was to use a crystal-controlled, fixed-tuner converter, which required tuning the auto radio to select a receiving frequency. These approaches worked, both because the 1950s was still the era of amplitude modulation (AM) radio, and because the power requirements were low.

Adding a mobile transmitting capability was much more challenging. One could buy a commercial ham transmitter or build one based on schematic diagrams, parts lists, and photos in ham radio magazines. Mobile kits, such as those sold by Heathkit, just were not available. The next step was to try to find the parts. This could be a very time consuming process. While some large cities had retail and surplus parts stores, mail order suppliers usually were the best source for new and military surplus parts. Next, the amateur drilled holes in a metal chassis for the vacuum tubes and individual components, and started wiring and soldering everything together. The availability of printed circuits and transistors was still years into the future. The final step was to install it under the dash of the automobile and to mount the antenna.

Clearly, after all this hard work, the first mobile contact had to be a thrill. The ham could now hold a conversation with another amateur radio operator, transmitting from either a fixed or mobile base, while driving down the highway. Of course, the mobile ham operator’s automobile might be mistaken for an undercover police vehicle, because both hams and police vehicles used the same type of whip antennas.

After the 1950s, mobile ham radio technology continued to evolve in step with changes in stationary sets. By the 1960s, the popularity of AM phone operations operations on the high-frequency (HF) bands had created a real interference problem, so gradually phone operations on those bands switched from AM to single side band (SSB). Although SSB theory was understood as early as the 1930s, the technology did not become available to amateur radio operators until the 1960s. The Heath Company played a significant role in the transition to SSB, with the introduction of the inexpensive (under $300) HW-100 transceiver, which, when installed in an automobile, made mobile operations more of a practical reality.

Another key change was use of repeaters on the VHF bands, because they prompted the move from amplitude modulation (AM) to frequency modulation (FM). The VHF bands now came to life, and the 1970s saw the introduction of small hand-held rigs that made VHF FM operations even more popular. These small rigs made mobile operation a practical reality for every ham. Even diehard HF operators eventually ended up owning a VHF/FM set. The 1980s and 1990s saw a further increase in the transition to phone operations, which today is simply taken for granted. However, while enjoying the fun of phone operations, it is worth remembering that it took a lot of hard work to make phone operations widely available to every ham.