A hundred years ago today, this Montana newspaper explains how mariners are now able to receive weather reports from the towers of the powerful radio station NAA in Virginia.

Like many aspiring young hams, I got my start in two-way radio with a set of walkie-talkies not unlike this set shown on page 561 of the 1969 Sears Christmas Catalog.

My set was a different brand, but quite similar to this set and millions of others like it. They all consisted of a crystal-controlled transmitter, usually on CB channel 14, along with a superregenerative receiver. The receivers on these sets were so wide that they could hear all 23 channels simultaneously, which meant that I could hear local CB’ers, as well as communicate with these and other toy walkie-talkies. And the superregenerative receiver meant that when a signal was not being received, the radio put out a constant rushing sound, undoubtedly to the great annoyance of millions of parents.

Despite hearing CB’ers, and despite valiant efforts on my part involving various attempts at external antennas, I never managed to make contact with any owner of a “real CB.” The antenna on mine was affixed to the case with a screw at the bottom, and to allow easy connection to an external antenna, I even put a Fahnestock clip on the outside of the case, attached to this screw. I could no longer set the radio down on its base, but it made for easy connection to various external antenna attempts.

There were two reasons for my lack of communication with the elusive “real CB’ers.” First of all, I was probably hearing all 23 channels at once, so even if the other station was quite close, he probably wouldn’t have been tuned to channel 14 to hear me. And even if he happened to be on channel 14, I would have been able to hear his 5 watt signal much further than he would be able to hear my 100 (if I was lucky) milliwatts.

One neighborhood kid claimed that he had made contact with a “real” CB’er with his toy walkie-talkie. I, of course, was extremely jealous of this accomplishment, although I didn’t let on. I had to content myself with contacting the other radio I owned, or those of other kids with whom I was playing, assuming we had enough pocket change to buy the requisite nine-volt batteries (or perhaps “borrow” them from other devices around the house). At this time, most of these radios came crystalled for channel 14, but since most had the wide receiver, it really didn’t matter which channel we were on. The typical range was from one side of the house to the other.

Interestingly, one friend’s walkie-talkie had a crystal for channel 9, which didn’t become the emergency channel until about 1970, as discussed in this February 1970 Popular Electronics article.

On those occasions when I didn’t have anyone to talk to, I sometimes used a rubber band to hold down the push-to-talk button and placed one near the TV. I could then listen in another room. Of course, I put an end to this practice when someone pointed out to me that I was at one point rebroadcasting a baseball game, without the express written consent of the Minnesota Twins, and suggested that doing this might land me in jail.

The era of these 27 MHz toy walkie-talkies came to an end with a change to the FCC rules in 1977, which is explained in detail in the August 1977 issue of Popular Electronics (page 46).

Until that time, these unlicensed radios were allowed on 27 MHz, as long as the input power was less than 100 mW. While many of these radios were equipped with a crystal for channel 14, there was no requirement that the radio opearate on any particular frequency. They were allowed anywhere in the range 26.97 to 27.27 MHz. Under the rules currently in effect (which I believe were the same as adopted in 1977), the limit for an “intentional radiator” of this type is now measured in terms of field strength, and the limit is 10,000 microvolts/meter at 3 meters. 47 C.F.R. §15.227. Since a 100 mW transmitter would exceed this limit by a very considerable amount, this regulation meant the end of toy walkie-talkies on 27 MHz.

Instead, the new 1977 rules called for the move of these toy walkie-talkies to five specific frequencies in the 49 MHz band, 49.830, 49.845, 49.860, 49.875, and 49.890. Under the new rules, the toy 27 MHz walkie-talkies could not be sold after March 1978.

We can see the transition from the Radio Shack catalogs for 1978 and 1979. The 1978 issue showed these toy walkie-talkies for 27 Mhz:

The 1979 issue showed similar models, but for 49 MHz:

One bit of confusion is added by the fact that 100 mW walkie-talkies for 27 MHz remained on the market. For example, if we turn in the 1978 catalog to the “toy” section to the “CB” section, we see a number of CB walkie talkies, some of which are 100 mW.

Under the old rules, these 100 MW units had a dual status. They could be used under Part 15 without a license, since they fully complied with the 100 mW limitation. However, these radios were also “type accepted” under Part 95 of the rules, meaning that they could be legally used by licensed CB’ers.  (These “real” CB walkie-talkies also typically had a superheterodyne receiver, meaning that they didn’t make the annoying “rushing” sound when no signal was present.)  The CB rules at the time allowed CB’ers to communicate only with other CB stations. Therefore, it was technically illegal to communicate between a “real” CB and a toy 27 MHz walkie-talkie. (Unlike the prohibition on retransmitting baseball games, nobody ever told me that my attempts to do so were illegal.  However, I doubt if there were many prosecutions for this particular offense.)  In the case of a cheap toy walkie-talkie, this would have been true even if the toy was being used by a licensed CB’er, since the radio wasn’t type accepted for CB use. But because of their dual status, the three100 mW walkie-talkies shown here could have been legally used to communicate with a toy walkie-talkie (since the radio was under 100 mW) or by a licensed CB’er to communicate with another CB’er (since the radio was type accepted under Part 95).

The 100 mW walkie talkies continued to be sold by Radio Shack and other retailers. In practice, some of these were sold as high-end toy walkie-talkies for kids, since the type-accepted units were generally of much higher quality. But technically, after 1978, the use of the 100 mW 27 MHz radios required a CB license.

In 1983, the FCC ended the requirement for CB licenses, as reported in the April 28, 1983, issue of the New York Times.  (Technically, CB is now “licensed by rule,” meaning basically that a license is required, but if you follow the rules, you are automatically granted a license by 47 C.F.R. §95.404.)

Therefore, it once again became legal (as long as the user obeyed the CB rules) for an unlicensed person to use the 27 MHz radios, whether they were the 100 mW model or one of the more powerful ones.

This illustration is from the 1914 text “Wireless telegraphy: a handbook for the use of operators and students“.

It shows the somewhat cramped, but well equipped, wireless cabin of the Cunard Line’s R.M.S. Franconia. The wireless equipment was supplied by the Marconi Company, and consisted of a 1-1/2 kw spark transmitter, in addition to a totally independent 500 watt emergency transmitter. The receiver consisted of either a magnetic detector or a Fleming valve.

The first voyage of the Franconia was from Liverpool to New York in February, 1911. She served commercially until 1915, when she was called in for use as a troop transport in the Mediterrranean. She was sunk by a German U-Boat on October 4, 1916. Fortunately, she was carrying no troops at the time, but of the 314 crew, 12 were lost.  The ship, along with the equipment shown above, lies at the bottom of the Mediterranean, 195 miles east of Malta.

75 years ago, the 1939 Allied Radio catalog carried these two kits. The “One Tube Flashlight Set” sold for $4.45, and included everything (tube, batteries, and coils) with the exception of the headphones, which started in the same catalog for 66 cents. The “Hurricane Receiver” sold for $3.85, but in addition to the headphones, also required a 6J7 and a 6F6 tube, which sold for 77 cents each.

Both sets ran on 6 volts. The one-tube “flashlight” set tuned shortwave, 18 to 200 meters, with four plug-in coils.

Both of these sets are regenerative receivers, and originated as construction articles in Popular Mechanics. The “Flashlight” set originated in the April 1938 issue, where it was billed as a “one-tube DX short-wave set” that ran on flashlight batteries, hence the name.

The “hurricane set” was featured in the February 1937 issue, which stated:

The primary idea behind the design is to provide a simple, rugged portable receiver that will work from a 6-volt storage battery, or a few dry cells, when other sources of power fail. When floods, hurricanes or other natural catastrophes occur and all ordinary means of communication go out, it is satisfying, and sometimes vitally important, to be able to learn from outside radio stations just what is going on. As a portable knockabout set, it also has other useful applications in the home, boat or camp.

The article promises that with six volts, the hurricane set with a 25-foot antenna should be sufficient for satisfactory reception of medium or high-power stations within a range of about 500 miles.

Parts List for “Flashlight Set”

If you are interested in building a one-tube radio, the “flashlight set” would be a good starter, and you can use the Popular Mechanics article for all of the construction details. Some of the parts might be difficult to find. But all of them are available online. Some of the links below are rather expensive, so it’s best to find most of the parts locally. But if you’re missing one or two items, you can find them at the links below.

Some of the values shown here are not identical to those shown in the article, but all of them are close enough. The only effect of substituting parts is that the tuning range of the radio will vary, depending on the exact dimensions of the coil, and the value of the tuning capacitor. Therefore, you’ll have to experiment a bit to figure out the exact tuning range of the radio once it’s done.

• Plug-in coil form
  • Plug-in Coil Forms at National RF
  • Plug-in coil forms at eBay
  • How to make plug-in coil forms
• Coil socket
  • 4-pin sockets at Antique Electronic Supply
• 30 ga. enameled wire
  • 30 ga. enamel wire at Amazon
  • 32-ga wire at Antique Electronic Supply
• 26 ga. enameled wire
  • 26 ga enamel wire at Amazon
  • 24-ga wire at Antique Electronic Supply
• 0-30 pF trimmer capacitor
  • 6pF – 80pF Trimmer Capacitor at Amazon
  • 34 pF trimmer capacitor at Jameco
    
  • 100 pF capacitor at Antique Electronic Supply
• .00014 uF (140 pF) variable capacitor
  • 365 pF capacitor at Antique Electronic Supply
  • 365 pF variable capacitor at Amazon
• 2 megohm resistor
  • 2 megohm resistor at Amazon
  • 1 Megohm Resistor at Jameco (use two in series)
    
    
• .0001 uF (10 pF) capacitor
  • 10 pF capacitor at Amazon
  • 10 pF capacitor at Jameco
    
    
• .0005 uF (50 pF) capacitor
  • 47 pF capacitor at Amazon
  • 47 pF capacitor at Jameco
    
    
• 200 kilohm variable resistor with switch
  • 500 kilohm variable resistor with switch at Jameco
    
  • 200K variable resistor at Amazon (without switch)
• RF Choke
  • RF choke at Amazon
  • RF choke at Jameco
    
    
• Type 49 tube
  • Type 49 Tube at Antique Electronic Supply
  • Type 49 Tube at eBay
• Tube socket
  • 5- pin Tube socket at Antique Electronic Supply
• Battery holder for one AA-cell battery
  • AA battery holder at Amazon
  • 1 AA cell holder at Jameco
    
    
• Battery holder for four AA-cell batteries
  • 4 AA battery holder at Amazon
  • 4 AA cell holder at Jameco
    
    
• Knobs
  • Knobs at Amazon
  • Knob at Jameco
    
    

Some of my earlier articles have shown crystal radios from the early days of radio. For example, I have an article with the history of the “foxhole radio” popularized by soldiers in World War 2.  I also have a link to a 1922 newspaper article with details for building one.   I also have links to this and this radio, both from 1914.

I received an e-mail from someone who wanted to build a crystal set with his grandson, who requested construction details and parts lists. There are many sites with such information, the best of which is The Xtal Set Society.  You’ll also find some simple plans at this link. The first radio I made as a youth was basically identical to the fourth one shown on the bottom of the page. It requires only a board, a toilet paper tube, some enameled wire, a piece of metal to use as the slider, a diode, and the earphone.

It’s an interesting project, and as long as you have at least one fairly strong AM radio station nearby, almost any design you put together will work. If you have an antenna, ground, detector, and headphones, you’ll hear one or more stations as soon as you connect them together, in almost any configuration. Therefore, I can’t add much as far as construction details. Any of the sets you find on the internet should work just fine. It’s best to start with a simple set of plans and work your way up.

If you can’t find all of the parts locally, here are some tips on finding them.

The Detector

The heart of the crystal set is the detector. This is what changes the radio signals into an audio signal that you can hear. You have two options. First, you can simply buy a semiconductor diode. The most commonly used diode for a crystal set is the “1N34” or “1N34A”. You can buy it on Amazon at any of the following links. As you can see, they are quite inexpensive, and you can afford to stock up in order to make multiple sets.

The other “old style” detector is the “cat’s whisker” and crystal, from which the radio gets its name. The crystal is a piece of the mineral galena, which you can find at many hobby shops. At most science museums, you’ll find for sale samples of various minerals, and you’ll be able to find your piece of galena for a low price. (If you can’t find it locally, you can buy a chunk on Amazon.)  To use it as the detector, you attach one wire to it firmly, perhaps with an alligator clip or by firmly clamping it down. The other connection is a thin wire which makes contact only at one point. This other wire is called the “cat’s whisker”. You’ll need to rig up some kind of spring to keep the wire in contact with the crystal, and you’ll also need some method to move the wire around to look for a “sweet spot” on the crystal.

And for the mad scientist who wants a very unusual type of detector, you can make a detector using an open flame.

The headphones or earphone

The headphones or earphone will be the most difficult part to find. Unfortunately, most modern headphones will not work. The crystal set requires a “high impedance” headphone. Most modern headphones are “low impedance” and simply won’t work, unless perhaps the station you are listening to is extremely strong. Typically, a “high impedance” earphone or headphone will have an impedance of about 2000 ohms. Modern “low impedance” headphones, such as for a stereo or computer, are generally about 8 ohms. I’ve found that headphones with an impedance of 600 ohms generally work OK. So if you can find some of that approximate value, they will work. Old “language laboratory” headphones generally are about this value.

The most commonly used is an earphone like this one, which is available on Amazon:

As you can see, this one comes with a 3.5 mm plug. Since you’ll need to wire the earphone directly into your circuit, you have two choices. First, you can simply cut off the wire, or perhaps make the attachment with
alligator clips
.

If you want to keep the plug intact, you can purchase the matching jack:

This jack requires soldering, but it should work adequately by simply twisting the wires firmly around the lugs. If you want to invest in a soldering iron, they’re much cheaper than you probably expected. This one, for example, comes complete with the solder, as well as some other tools that might come in handy:

Another option is to use the low-impedance headphones but with a suitable transformer, such as this one:

One side will be marked “600 ohm” and the other side will be marked “8 ohm” (or similar terminology). Ignore the center pin on either side. Hook the other two terminals of the “600 ohm” side to the radio’s output, and hook the two outer terminals of the “8 ohm” side to the headphones. This will allow the headphones (which you can get at the dollar store) to work.

Wire

The best wire for winding the coil is enameled wire of about 24 gauge.  This is also sometimes called “magnet wire”:

The enamel coating is insulation, so that the turns don’t short out. However, if you’re building a set with a slider, you’ll want to sand off the enamel at the top so that the slider can make contact with the wire.

For making connections between components, and for making the antenna, you’ll want flexible stranded wire such as this:

Capacitor

Some of the circuits will call for a capacitor, and some will show you how to make your own. (In older literature, the term “condenser” is used.)  The simplest circuits don’t have one, and the exact value is not critical, and for most circuits a capacitor of 0.1 uF will be about right:

Another good source for ordering parts such as resistors and capacitors is Jameco Electronics.  You can order online at.

Connectors and Hardware

Many of the early circuits will show “Fahnestock clips” for making connections. These certainly aren’t required, since you can simply twist the wires together. But if you want to give your crystal set a vintage look, they’re a nice touch. They’re also available at Amazon:

Most of the circuits you see are put together with wood screws, which you surely have lying around the house. If you don’t, you can go ahead and order an assortment such as this one:

If you need a piece of pine board to mount the whole thing, you can get that on Amazon as well:

Kits

If you want to bypass the whole procurement process and make a radio that works, but without the “retro” look, any of the following kits will fill the bill. They include everything you need along with directions:

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