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Buyer's Guide to Shortwave Receivers
February 1965 Popular Mechanics

February 1965 Popular Mechanics
February 1965 Popular Mechanics - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early mechanics and electronics. See articles from Popular Mechanics, published continuously since 1902. All copyrights hereby acknowledged.

In 1965 when this "Buyer's Guide to Shortwave Receivers" article appeared in Popular Mechanics magazine, radio was a big deal. Transmitting required a license of some sort, but anyone could buy a receiver and listen. It was decades before the Internet and cellphones (which are radios) would make anytime, anywhere communications possible. News services still reported breaking stories via "wire" or "wireless." Only big media organizations and local newspaper offices had access to worldwide happenings. Many people used shortwave radio broadcasts to listen in on news from across the state, country, and world. Of course a lot of it was in a foreign language, but many countries also broadcast in English. Three-letter government agencies also listened in to receive reports from inside Communist countries where some oppressed citizens managed to operate bootleg transmitters. Listening for coded messages from secret agents was good sport; there were groups who traded information on them - much to the consternation of the government. Believe it or not, there is still today a cadre of shortwave listeners who maintain websites for assisting and trading info with the brethren. To wit: SWLing, ShortwaveDB, DXing

Buyer's Guide to Shortwave Receivers

Buyer's Guide to Shortwave Receivers, February 1965 Popular Mechanics - RF CafeAmateur or all-wave? $39 or $150? And how much of that alphabet soup of extras do you need? Try these shopping tips.

By Larry Steckler

To tap that world of airwave adventure surrounding you - police calls, marine communications, satellite signals, radio amateurs, aircraft or foreign broadcast stations - you may think that you need only to switch on any shortwave radio receiver.

But step into a radio showroom, or leaf through the radio receiver pages of an electronics catalog, and you enter a world of confusion.

Suddenly, you're surrounded by amateur and "all-wave receivers" ranging from $39.95 to over $500 in price - not to mention a veritable alphabet soup of mysterious abbreviations (BFO, ANL, AVC, Q multipliers, to name a few) which may or may not be important to the type of shortwave listening you have in mind. We'll try and sort out the significance of these alphabet extras for you in this article.

Before you walk into the showroom you should decide what type of listening you intend to do - amateur radio or general-purpose "all-wave" shortwave listening. The amateur receiver concentrates on the amateur radio bands at 3.5-, 7-, 14-, 21- and 28-megacycles. The bandspread dial on these sets is calibrated for these bands.

What the Shortwave Dollar Will Buy

PRICE: Under $75             FEATURES

4 bands
No r.f. stage
540-kc to 30-mc
May not have S-meter
Fixed frequency BFO
May not have headphone jack

PRICE: Under $100

4 bands
May not have r.f. stage
540-kc to 34-mc
S-meter, but may not be calibrated
Fixed frequency BFO
Headphone jack
May have basic Q multiplier
May have basic noise limiter

PRICE: Under $150

4 bands R.F. stage
540-kc to 34-mc
25:1 tuning ratio
S-meter
Automatic noise limiter
BFO, may be fixed frequency circuit Antenna trimmer
Headphone jack

PRICE: Under $200

5 bands
R.F. stage 540-kc to 34-mc
30:1 tuning ratio
Calibrated S-meter
BFO with pitch control
Automatic noise limiter
Basic Q multiplier
Dual conversion
Antenna trimmer
Headphone jack

PRICE: Under $300

5 bands
R.F. stage 540-kc to 34-mc
60:1 tuning ratio
Calibrated S-meter
Variable i.f. selectivity
Noise limiter automatic Automatic volume control
Single-sideband reception
Dual conversion
Antenna trimmer
Headphone jack

PRICE: Under $450

6 bands
2 r.f. stages
540-kc to 109-mc
AM and FM (27-MC to 109-MC)
60:1 tuning ratio
Single sideband reception
Automatic volume control
Automatic noise limiter, adjustable
Triple conversion
Adjustable i.f. selectivity, notch filter
Plug-in crystal tuning
Push-pull 10-watt audio output
Clock timer
Antenna trimmer
Headphone jack

S-meters - RF Cafe

S-Meters measure signal strength. Standard types (top) are easiest to read and large scale makes them most accurate. Current trend is to smaller vertical dial. Avoid the uncalibrated ones. (center)

The general-purpose set, on the other hand, carries labels at around 1.6-mc. (1600 kc) for police radio, 2.5-mc. for ship-to-shore phones, as well as amateur frequencies and the most commonly used foreign-broadcast frequencies.

It is interesting to note that the 1.5 to 4-mc. area is generally good for reception up to 300 miles and nighttime listening. From 4 to 8-mc., expect 300 miles daytime and up to 1500 miles at night. From 8 to 14-mc., look for under 2000-mile range during the day and over 2000 miles at night. For 14-mc. to 34-mc., expect 1500 miles or more with best results in the early morning or evening.

Q-Multipliers narrow bandpass of the i.f. amplifiers resulting in greater selectivity in the receiver. Means more stations and less jumble to you

Quarter Turn of high-ratio dial at left covers less tuning distance (colored band) than same turn of low-ratio dial at right. Simplifies tuning.

Portable all-wave sets are usually transistorized and come with a built-in pole-type antenna. In general, they will not perform as well as a nonportable receiver selling for the same price. The built-in antenna can only deliver a small fraction (as little as one tenth or less) the signal picked up by a long 150-foot single-wire antenna. Also the portable's transistor circuitry is inherently noisier. When you are listening to a strong station, this noise cannot even be heard. However, tune in a weak distant signal and you may find yourself getting more noise than signal. For best performance for the price, then, stick to a nonportable vacuum-tube type receiver.

Speaking of price, a key difference between rock-bottom $39 sets and more expensive ones is that cheaper sets usually have fewer tubes.

When comparing receiver performance in the store and trying some of the tests mentioned in this article, ask the salesman to be sure that the sets you try are all connected to the same antenna. Most stores have a setup for switching any radio on display to a particular antenna. But if you really want to play it safe, don't rely on the switching. Try one set plugged into one particular antenna jack, then unplug it and hook up the next one. A good set hooked to a poor antenna will not perform as well as a poor set connected to a good antenna.

Three main factors determine quality.

They are stability, sensitivity and selectivity.

Stability refers to the set's ability to stay tuned to a station and not drift off frequency. Check by tuning in a weak station for 10 minutes or so. The station may fade in and out (volume level may change) but you should not have to touch the tuning control again.

Sensitivity is the ability of a radio to receive a weak station. Check by tuning in the same weak distant station on several sets. If one delivers a stronger, clearer signal than the rest, it's the most sensitive set.

Selectivity is the receiver's ability to pick out one station from a group of stations crammed tightly together. Tune a receiver to a crowded portion of any band. Then, using the bandspread control, see how many stations you can sort out of the jumble. Test several sets this way. The one that most easily tunes in the largest number of stations is best.

The Alphabet Soup

Almost all short-wave radios include a headphone jack and an S-meter. The jack should be mounted on the front panel for easy access. Headphones are a must for good listening to weak or distant stations, and adding a jack to a set that doesn't have one can sometimes be difficult.

If you start collecting QSLs (confirmation cards from the stations you listen to), you want the S-meter to give you a signal-strength reading to relay to the station when asking for a card. But the S-meter should be calibrated and have a large easily read dial. If you have a real basic set that does not include an S-meter, there's an accessory meter you can add.

Q-multiplier circuits - RF Cafe

Until Recently Q-multiplier circuits were only available as accessories (right). Now they are being incorporated into design of newer sets (left). They help separate shortwave stations that are crowded together and overlapping.

Preselector cluster of controls - RF Cafe

Preselector (left)can really bring in long-range broadcasts. This extra tuned r.f. stage is found in only the very best and most costly shortwave receivers.

Cluster of Controls  (right)looks impressive; and noise-limiter knobs are switches, do not adjust. Rf. gain and selectivity controls are not calibrated.

Slide switches - RF Cafe

Slide Switches always look neat but frequently lead to trouble. They are more likely to break down and require replacement or service than standard toggle switches.

Noise Limiters are electronic circuits intended to protect your ears against sudden loud bursts of static. Almost all receivers above the economy class include such a circuit. Automatic noise limiters (ANL) are handy, but should have a sensitivity control so you can select the point at which they go into operation; an On-Off switch is not enough.

To compare such circuits, tune to a noisy spot on the dial, then flip in the circuit and judge how effectively the noise level is cut back, without eliminating the station signal you are trying to receive.

Know Your Receiver Features

R.F. Stage

Radio frequency amplifier located ahead of other receiver stages. If you want really long-range reception make sure your receiver includes this circuit. Best sets have 2·stage circuit (preselector)

S-Meter

Signal-strength meter. Look for large calibrated dials and a long scale. Vital if you intend to obtain QSL cards. Large dial eases tuning and taking accurate signal-strength readings for QSL's

Tuning Ratio

Ratio of distance tuning control knob turns to distance station selector dial actually moves. Larger the ratio, the more selective your tuning. See the diagram on page 118 for greater detail

BFO (Beat Frequency Oscillator)

Absolute must if you intend to listen to Morse code broadcasts. Keeps tone of signal constant making code reading easier. Look for a variable pitch control so you can select the tone you want

Variable Selectivity

Electronic circuit that adjusts bandwidth of i.f. stages enabling reception of weaker more distant stations. Look for range of adjustment and crystal filters. See diagram on page 118

ANL (Automatic Noise Limiter)

Circuit designed to reduce background noises of all types. A real help if you live in an area where a lot of electronic static is present. Look for a sensitivity control if circuit is not automatic

Antenna Trimmer

Matches receiver input to antenna for best performance. Look for front panel control. It often helps to readjust trimmer after tuning station. Brings the desired station up out of the clutter

Headphone Jack

A must for listening to distant stations. Phones eliminate otherwise distracting local noises. Look for front panel jack. Other locations are not as convenient. Found on almost all receivers

Beat-frequency oscillator (BFO)

Most shortwave radios have this oscillator which is triggered by code signals you may want to tune in. The BFO keeps the pitch of code signals you receive constant. But receivers that have a BFO should include a variable pitch control so you can select both the most pleasing tone and one which can be most readily distinguished from background noise.

Know Your Receiver Features - RF CafePreselector

Only better receivers include this extra tunable r.f. amplifier in front of the other receiver circuits. It helps bring in weak, hard-to-hear stations. To check its effectiveness, tune to a weak station on a set without a preselector and compare reception of the same station on a set with a preselector.

Variable selectivity of the i.f. (intermediate frequency) circuits is quite popular. One version of this circuit, called a Q-multiplier, lets you narrow the range of frequencies your receiver is amplifying. This helps separate crowded stations. Test by tuning to a crowded portion of some shortwave band, and seeing how many different stations you can get both using the Q-multiplier and with it off. Some Q-multipliers are more effective than others.

On some of the most expensive sets variable selectivity circuits include crystal filters to give really sharp narrow bandwidth.

Calibrator (CAL).

On some receivers this circuit is built-in. It produces audible tones at precise frequencies, so you can zero the set's dial tuning indicator to conform exactly to the specific frequency it indicates. Make sure the dial itself can be easily adjusted. If you want even more tuning precision, your set should have a crystal type calibration circuit, which cannot drift off frequency. The crystal calibrator is also available as an accessory you can add later.

Band spread.

The ratio of how far you have to turn the tuning knob to how far the dial moves determines how finely you can tune to a station. Generally speaking, the more expensive the set, the higher the tuning ratio. But make sure the tuning control moves smoothly and easily.

How many bands?

Most all-wave sets cover all frequencies between 55G-kc. and about 34-mc. (Some special sets cover other frequencies.) But within the normal frequency limits, a set divides its range into a number of bands, usually four, five, or six. The more bands there are. the finer the tuning and the easier it will be to select stations.

 

 

Posted December 11, 2023

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