March 1967 Electronics World
Wax nostalgic about and learn from the history of early electronics. See articles
Electronics World, published May 1959
- December 1971. All copyrights hereby acknowledged.
Believe it or not, there are still radio operators using Citizen Band (CB) and Business Radio (BR) equipment. That's right, cellphones (which are themselves radios) have not totally supplanted traditional radio for person-to-person communications. Prior to the widespread use of cellphones beginning in the mid-1990s, CB and BR were the only radios available for use by laymen without an individual license. When I worked as an electrician between high school and entering the U.S. Air Force, my service truck was equipped with a radio dispatch transceiver in the Land Mobile Radio System (LMRS) band. I did not have an FCC license to operate the radio, but was allowed to communicate under the station license just as I was able to work as an unlicensed electrician under the purview of the company owner's Master Electrician license.
Although companies could legally use CB channels (27 MHz) and equipment at a much lower cost, LMRS permitted power levels were higher (both base and mobile) with an accompanying greater range. Unlike on the CB channels, competition for voice traffic was virtually nonexistent. The company I worked for (Simpson Electric Company, now defunct) had its base station antenna mounted on a 100-foot tower, and many times I was 40-50 miles away while still able to maintain contact. Unlike with cellphones that only need to be near one of thousands of cell towers to have messages relayed to anywhere in the world, LMRS relies on a direct over-the-air link.
Why don't all systems simply migrate to the cellular infrastructure? Simple - the need for reliability in times of emergency. Remember September 11, 2001, when Islamic terrorists attacked the Twin Towers, and cell communications on Long Island was lost for days? LMRS, CB, and Amateur Radio filled the void until cells were rebuilt. Emergency responder teams and extensive logistical networks (nets) were enabled thanks to the foresight, planning, and practice by independent operators - mostly at their own expense.
Citizens Band and Business Radio Equipment
The group of products on on cover this month are representative examples of Citizens Band and Business Radio equipment. We have included a number of transceivers, as well as some test equipment and antennas for these services. Each product has been keyed with a number to match the descriptions given in the following paragraphs.
(1) International Crystal C-12B frequency meter is a portable secondary frequency standard designed to service CB transmitters and receivers. The meter comes with 23 crystals installed covering the 23 channels. Frequency accuracy is ± 0.0015%. The beat-frequency method of frequency checking is used with the difference frequency between the unit being checked and the crystal standard being counted directly displayed on a meter. The meter also includes a modulation checker and power-output meter. (Price: $300)
(2) Polytronics "Poly-Comm B" and "Poly-Comm RC-1" are a Business Radio transmitter-receiver unit and a remote-control head for this unit. This equipment is designed to transmit and receive phase-modulated signals on one channel in the 27.29 to 35.98 MHz Business Radio band. Plate power input to the final is 18 W with at least 10 W output. The receiver has built-in squelch and a sensitivity of better than 0.25 μV for 20-dB quieting. (Price of Model B is $299.95 and the optional RC-1 is $69.50.)
(3) Seco 520-A antenna tester provides direct reading of forward or reflected power and s.w.r. It is designed for 50-ohm lines and equipment operating in the 3.5 to 160 MHz range. R.f. power is measured directly from 0.5 to 1000 watts on three scales. The unit does not require external shunts nor correction charts; it has negligible insertion loss and may be left in the line. (Price: $49.95)
(4) Pace II-S is a 5-watt all silicon transistor CB transceiver. An MOS field-effect transistor is used for precise frequency control. The double-conversion receiver has adjustable squelch, a two-step noise limiter, and a signal-strength meter. The unit can also be used as a portable p.a. system. The transceiver operates from a 12-volt d.c. source with either side grounded. ($179)
(5) Lampkin 105-B frequency meter has a fundamental frequency averaging from 2330 to 2670 kHz, a spread of 1.14 to 1. By means of harmonics and their combinations, nearby transmitters can be monitored in a continuous range from 100 kHz to 175 MHz. Radio receivers may also be aligned accurately using the meter as an unmodulated signal source. Accuracy is guaranteed to be better than 0.002% on all frequencies. ($295)
(6) Antenna Specialists "Mach III" is a base-loaded, shunt-fed, electrical quarter-wave CB whip antenna. The whip itself is 32 inches long and is made of stainless steel. A spiral printed-circuit loading coil is suspended inside the sealed base. The antenna is d.c. grounded. (From $11.20 to $25, depending on hardware.)
(7) E. F. Johnson "Messenger 350" is a solid-state single-sideband CB transceiver. Either upper or lower sideband on two channels is available for use. Diode switching is employed rather than mechanical relays. The receiver uses adjustable squelch and noise silencer. The unit can also be utilized as a public-address system, if this is desired. ($299.95)
(8) Mosley "Demon" is a short whip antenna designed for CB use. The stainless-steel whip element is about 14 inches long, over-all height is a few inches more. The element is center-loaded by means of a coil. ($13.19)
(9) Allied "Knight-kit Safari III" is a 5-watt all silicon transistor CB transceiver in kit form. Receiver has adjustable squelch, signal-strength meter, and fine-tuning adjustment for stations that are slightly off channel. A series-gate noise limiter is also incorporated. Twelve-volt d.c. operation is standard, although a separate a.c. power supply is available. ($84.50)
(10) Hallicrajters CB-11A is a pocket transportabe transceiver for CB use. It is completely self-contained, with a battery power supply (ordinary 9-V battery), built-in dynamic mike and speaker, battery-replacement indicator, and telescoping antenna. Power input is 100 milliwatts and no license is required for operation. ($74.95 per pair)
(11) Lafayette "Dyna-Com 5" is a 5-watt hand-held CB transceiver. It has three crystal-controlled transmit and receive channel positions. The superhet receiver has less than 1-μV sensitivity for 10-dB signal plus noise to noise ratio, and uses a mechanical filter for high selectivity. An automatic compressor provides high "talk power" on transmit. Battery pack consists of 12 nickel-cadmium batteries in a removable holder. ($99.95)
(12) "Heathkit" GW-14 is a solid-state 5-watt CB transceiver. The receiver has squelch, noise limiting, and a signal-strength indicator. The transmitter, along with some of the other units shown, features a twin-pi antenna matching network for high efficiency and low harmonic radiation. Unit operates from 12 V, negative ground, or from a.c. using accessory power supply. ($89.94 in kit form, $124.95 assembled)
(13) Eico 715 "Trans-Match" is a ham and CB transceiver test set. It can measure r.f. output power up to 50 watts, standing-wave ratio, modulation percentage, and field strength. The instrument has a built-in dummy load for power measurements. ($34.95 in kit form, $44.95 assembled)
(14) Amphenol 675 is a 5-watt all silicon transistor CB transceiver. The receiver is a double-conversion superhet with automatic noise limiting and squelch. Transmitter uses speech clipping for more "talk power." Like other similar units shown, this transceiver is quite compact. This unit measures only 2 1/2 inches by 6 1/2 inches by 9 inches deep. It operates from a 12-V power source. ($179.95)
Posted May 22, 2017