Category Archives: Radio

ARRL National Parks On The Air

The Ice Age National Scenic Trail at the St. Croix River, by MDuchek at English Wikipedia. Licensed under Public Domain via Commons.

This year marks the 100th Anniversary of the National Park Service (NPS), being established on August 25, 1916.  The national parks actually predate the establishment of the NPS.  For example, the first national park, Yellowstone, was established in 1872.  Prior to 1916, the National Parks and National Monuments were individually managed under the Department of the Interior.   Today, the NPS consists of 483 administrative units, including National Parks, National Monuments, and other historic, cultural, and recreational sites.

To celebrate the anniversary, the American Radio Relay League is sponsoring an operating event known as National Parks On The Air (NPOTA) in which individual hams or groups of hams will operate from one of these 483 locations, and other hams at home will attempt to make contact with them.  So far, the event has been a great success, with about 200 activations of individual parks, and more than 2300 hams making at least one contact with those parks.

For me, the most exciting part of this event is that it allows any ham to take part in a “Field Day” type event at any time during the year.  Field Day is an annual event where hams set up portable stations at remote locations.  These stations can be either simple or elaborate, and it is an extremely popular activity.  But it only takes place once a year.  NPOTA gives an opportunity for hams to engage in the same activity on very short notice.

Every state of the Union has at least one NPS site within its borders.  Minnesota, for example, has Grand Portage National Monument, the Mississippi National River and Recreation Areas, the North Country National Scenic Trail, Pipestone National Monument, the Saint Croix National Scenic Riverway, and Voyageurs National Park.  Two of these, along with one Wisconsin site, the Ice Age National Scenic Trail, are located conveniently to the Twin Cities, allowing an activation with little advance planning.

The two metro-area rivers, the Mississippi and St. Croix, are easy to activate because the NPOTA rules specify that the activating ham must be within 100 feet of the river.  One particularly convenient spot to do this activation (although it leaves something to be desired for radio propagation) is Raspberry Island in St. Paul.  It’s located just across (and partially underneath) the Wabasha bridge from downtown St. Paul, and most of the parking lot is within 100 feet of the river.

Last week, I did a very minimalist activation of this location, and worked 12 stations, running just 5 watts with my Yaesu FT-817into a Hamstick mobile antenna mounted with a trunk mount to the car.  Despite the minimal station, I worked stations as far away as New Hampshire and Utah in less than a half hour, and then drove home in fifteen minutes.
LOTWscreenshotWinter weather precludes many outdoor operations, but even with cold temperatures, operating mobile from a warm car is a fun way to get out and get on the air.  My next such operation will probably be from the Saint Croix Boom Site near Stillwater, where it appears that most of the parking lot is within the required 100 foot distance from the river.

When the weather gets a bit warmer, I’ll probably also do some VHF activations of the Mississippi River from one of the bridges crossing the river between Highway 169 and Hastings, all of which appear to be in the NPS unit.

One NPS unit which I wasn’t even aware existed was the Ice Age National Scenic Trail in Wisconsin.  It starts at the St. Croix River in Interstate State Park in St. Croix Falls, at the point shown above.  Since the trail begins at the river, this spot actually counts for both NPS units.  Under the NPOTA rules, activation of a scenic trail requires that the equipment be brought in by human power, so this one cannot be done mobile, and will probably wait until this summer.  But it requires little advance preparation, it’s less than an hour from home, and I can be on the air working the pileups within a half hour of arriving.

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Piezoelectrics For Your Time Travel and Post-Apocalyptic Needs

Completed piezoelectric speaker from 1968 article.

Completed piezoelectric speaker from 1968 article.

A few weeks ago, I wrote about some plans for homemade microphones from 1945. One was very crude but easy to duplicate. But one was quite sophisticated, and could be made at home by growing a piezoelectric crystal from a saturated solution of Rochelle Salt.

The piezoelectric microphone is particularly intriguing because it should function equally well as a piezoelectric speaker.  For this reason, it has an interesting application, albeit perhaps not one that is immediately practical.

Being Prepared for Inadvertent Time Travel

The knowledge of how to build such a speaker could come in handy in a couple of situations, at least one of which is probably unlikely.  The first situation would be that of inadvertent time travel.  If you get caught in a time warp and sent to the past, it would be wise if you could make the best of a bad situation and be able to “invent” some technological devices.  (And as I’ve previously written, having a WikiReader in your pocket would make the situation much more bearable.)  And as a loyal reader of this blog, it stands to reason that one of the technologies that you could “invent” would be radio.


While there are no documented cases of this ever happening, the science fiction literature is full of examples.  Probably the oldest example is Mark Twain‘s A Connecticut Yankee in King Arthur’s Court.  Other examples include 1632 by Eric Flint and the Island in the Sea of Time series by S.M. Stirling.

Cobbling together a transmitter would be relatively easy, as long as the time period into which you were deposited had some rudimentary industries.  You’ll need some wire for winding coils and putting up an antenna, some metal for building capacitors and a spark gap, some acid for making batteries, and a few other bits and pieces that should be readily available in the Middle Ages.  With a bit of ingenuity, you should be able to come up with a transmitter with a range of hundreds of miles.

And with the exception of one component, a suitable receiver would be relatively easy to make.  Once again, you’ll need some wire for the coil and antenna, a few pieces of metal for fabricating other parts, and something to serve as a detector.  The detector would be quite simple.  The most common material, which would give good results, would be a chunk of Galena (lead ore).  If you find yourself in an area where this mineral is unavailable, there are many substitutes, as discussed in my earlier posts (this one and this one) about “foxhole radios” or my earlier post about emergency wartime crystal sets.

The one part, however, that will be difficult to procure is a suitable earphone.  If you’re lucky enough to be transported back in time after the invention of the telephone, then your problem is partially solved.  A telephone receiver will have an impedance that is too low for your receiver, but by rewinding the coil, you should be able to come up with a suitable headphone.  If the telephone hasn’t been invented yet, you can of course take the honors and invent it.  But if you want to jump ahead to radio technology, you’ll need to fabricate a suitable headphone to hook up to your radio.

This brings us back to the piezoelectric microphone we discussed earlier.   This type of microphone works equally well in either direction:  It can change electrical impulses to sound, as well as working the other way around and changing sound into electrical impulses.  Therefore, if you build a piezoelectric microphone, you can hook it up to your crystal set and listen to that transmitter you put on the air.

As discussed in my earlier post, the piezoelectric microphone/headphone should be relatively straightforward.  All you need, in addition to the scraps of metal you already procured, is a piezoelectric crystal.  And the article linked there gives you the basics of growing one.  In addition to water, all you will need is Rochelle Salt, also known as potassium sodium tartrate tetrahydrate.  This compound was first prepared in 1675 by Pierre Seignette. So if your time travel lands you after that date, you should be able to procure it. Of if it’s about 1675 and you’re anywhere near La Rochelle, France, you would be advised to look up Monsieur Seignette and collaborate with him on the project.

If you arrive before 1675, all hope is not lost. According to this site, you can whip up a batch using the ingredients cream of tartar and washing soda.  Cream of tartar is a byproduct of the wine making process, so it should be available at any time after the invention of wine, which dates back to antiquity.  So as long as those ingredients are available, you should be able to recreate radio.

An alternative method of building the headphone is described in the book The Voice of the Crystal by H. Peter Friedrichs.  This is a magnetic headphone which would require a very fine gauge of insulated wire, but a good jeweler of almost any era should be able to help you procure the components.

Rebuilding Civilization After a Collapse

The other time one would need to recreate radio technology would be after a collapse of society.  There are billions of radios in existence, any many more component parts, so it is very unlikely that you would need to start from scratch.  Even after hundreds of years of dark ages, many relics of our current technological society would still be available to provide usable parts.  This scenario is discussed in detail in the book The Knowledge: How to Rebuild Civilization in the Aftermath of a Cataclysm by Lewis Dartnell, which I previously reviewed.

The most abundant source of headphones for your post-apocalyptic crystal set would probably be the microphones from the billions of cell phones currently in existence.  In most cases, these are probably piezoelectric, and would work well for a crystal set headphone.  (The billions of stereo headphones and earbuds probably wouldn’t be of much use, since they are too low an impedance to work properly with a crystal set.)

Science Fair Project

Even if you don’t anticipate time travel or TEOTWAWKI (The End Of the World As We Know It), a homemade speaker or microphone could be part of a most impressive science fair project.  Even very young students could fabricate the simple three-nail microphone shown in my earlier post.  And more advanced students will be capable of making speakers or microphones that rival commercially available ones.

A More Refined Version of the Piezoelectric Speaker

Near perfect crystals from 1968 article.

Near perfect crystals from 1968 article.

The 1945 piezoelectric microphone linked in my original post is probably suitable for all of your time travel or post-apocalyptic needs.  However, a more refined version, shown at the top of this page, is from the May-June 1968 issue of Elementary Electronics.  While the 1945 article probably gives enough detail for the experimenter to grow a crystal and put it to work, the 1968 article goes into much greater detail.  It gives detailed instructions on growing the crystal, and the completed crystals, shown here, turn out nearly perfect.  In particular, the 1968 article gives detailed instructions on starting with a seed crystal and maintaining the temperature of the saturated solution as the crystals form.  While the 1945 article would probably result in a usable crystal looking like a piece of rock candy, the details in the later article result in a crystal that can be further ground to dimensions that would make it quite sensitive.

Construction details of 1968 piezoelectric speaker.

Construction details of 1968 piezoelectric speaker.

The construction details of the final speaker are shown above.  The crystal is ground and polished to about 1/16 inch in thickness, and then sandwiched between two pieces of aluminum foil.  (If your time travels take you to a time when aluminum was still considered a precious metal, substitution of other metal shouldn’t present a problem.)  A current applied to the two pieces of foil causes the crystal to vibrate.  The author of the 1968 article used the cone of a defunct 12 inch radio speaker, which could be replaced by some other type of cone.  For use with a crystal set, the large cone might prove a detriment, since the crystal set might not be putting out enough audio to set it into vibration.  Constructing some sort of headphone would probably be more suitable for a crystal set.

The photo above shows a matching transformer, but this would not be necessary for use with a crystal set.  The example shown in the 1968 article was designed to replace a standard low-impedance permanent magnet speaker.  The high impedance of the piezoelectric speaker would be perfectly suited to the output of a crystal set.

For even more details on growing crystals, the author of the 1968 article recommends the book Crystals and Crystal Growing by by Alan Holden and Phylis Morrison, which is still available and in print.  And if you’re just looking to make a crystal set and want to buy a piezoelectric earphone (or other needed parts), you can find them on my crystal set parts page.

 

 

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Jamboree On The Air 2015

This weekend is Jamboree On The Air (JOTA) and on Saturday, I’ll be with K0BSA at the North Star Museum of Boy Scouting and Girl Scouting in North Saint Paul, Minnesota.  K0BSA is sponsored by the Minnesota Youth Amateur Radio Council (MNYARC), and photos of previous JOTA operations are available on their website.

JOTA is an international scouting event which allows Scouts around the world to communicate via amateur radio with other scouts and other amateur radio operators.  Our event at the North Star Museum is open to all Scouts, and to the public.  It’s free of charge (although we encourage you to also visit the rest of the museum while you’re there, which does have an admission charge.)

This is the 58th annual JOTA, the first one being run in 1958.  The illustration above is from the announcement for the 1959 version, which at the time was called Radio-Jambo.  The call signs in the illustration were Scout headquarters stations around the world that were on the air that year.

The K0BSA call sign has been connected with the Northern Star Council of the BSA for many years, and I never realized that it had an earlier use.  The 1960 National Scout Jamboree was held in Colorado Springs, Colorado, the only time the event has been held in “Zero Land.”  There has been Radio Scouting at most, if not all, Scout Jamborees, and in 1960, the official station of the Jamboree was assigned the K0BSA call sign.  While the quality of this scan is poor, he Scout shown at the controls of K0BSA in this photo is Steve Wood, K4FJO, of High Point, N.C., who was one of many guest operators of the station.  On his QRZ.com profile, K5KG reports that he was on staff at the Jamboree trading post, and spent all of his off hours at the station.

The June 1960 issue of Boys’ Life reported that K0BSA would be operating on all bands from reveille to taps on both phone and CW, with Pedro clomping at the key or braying into the mike.

If you’re in the Twin Cities and have an interest in radio and/or scouting, please stop by and visit.  The event is open to Cub Scouts, Boy Scouts, Girl Scouts, and Non-Scouts, which should cover just about everyone.  If you’re elsewhere, you can check with your local Scout council.  And, of course, if you’re a Ham, please listen for stations calling CQ JOTA and help introduce a Scout to Amateur Radio.

I will also be counseling the Radio Merit Badge.  Last year, about 20 Scouts earned the merit badge.  “Back in the day” when I was a Scout, the merit badge required a knowledge of Morse Code, meaning that the Scouts who earned it usually did so after getting their amateur license.  However, that has changed in recent years, and the merit badge is now more of an introduction to radio.  My goal is to get Scouts interested in Amateur Radio, and a few of them have followed up by getting their license.  I hope I once again have the opportunity to help Scouts who want to follow up and get their “ticket.”



K2BSA in 1975

K2BSA1975Shown here is the flagship Amateur Radio station of the Boy Scouts of America, K2BSA, as it appeared 40 years ago this month, in the August 1975 issue of Boys’ Life.

As reported in the magazine, the station was then located at the Johnston Historical Museum, on the grounds of the BSA’s then national headquarters in North Brunswick, New Jersey. K2BSA is still active, although it no longer has a fixed location from which it operates. It is on the air on multiple bands and modes at BSA Jamborees. At the most recent one in 2013, I was on staff, and thousands of contacts were made around the world. In addition, the station call sign and even portable equipment are available for loan by licensed hams who are scouts and scouters for use at scouting events. In this way, the call sign is frequently heard during Camporees and other events at which scouts get a chance to experience amateur radio.

The article notes that in 1975, the station was put on the air on weekends on a monthly basis to allow visitors to speak to other Scouts around the country.

A larger reincarnation of the museum is open to the public at the National Scouting Museum near the organization’s present headquarters in Irving, Texas.

(Scouts who are working on the Scouting Heritage or Radio merit badges will find helpful information for both at my website.)

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1945 Kids Radio-Phono Combo

1945PMradiophonoThe young man shown here is presumably the son of Popular Mechanics author Arthur I. Rattray, and is shown next to the radio-phonograph assembled by his father, as described in the July 1945 issue of the magazine.

In the article, he notes that perhaps readers might have a small boy or girl who would like to play records and listen to the radio with a phono-radio combination of their very own. He notes that such units would undoubtedly be plentiful after the war, “but that does not solve the immediate problem.” Therefore, he decided to put one together himself. He did so by combining an old midget radio (probably similar to the $7.95 set featured in an earlier post) with an old table phonograph. He housed them in the legs and braces from a discarded radio console.

He ran the phono cartridge directly to the radio’s audio output tube. He noted that this hookup “does not permit full volume, which is an assset rather than a liability,” but that the volume was sufficient for both radio and phono.

I doubt if anyone is going to recreate this particular project. But one warning is in order. One side of the phono cartridge (and probably the metal tone arm) is connected directly to the radio chasis. Depending on the set, there’s a 50/50 chance that this is hooked directly to the hot side of the AC line cord.

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1951 Boys’ Life One Tube Receiver

1951BLrcvrThe one-tube shortwave receiver shown here appeared in Boys’ Life magazine in October, 1951. It’s a very simple regenerative circuit using a single 3A4 tube. According to the accompanying article (which carried no byline), the circuit was designed by the ARRL. The filaments were powered by the two dry cells in series, with a 22.5 volt battery supplying the B+. The Boys’ Life editors priced the components at $17.05 in New York, and noted that most Scouts could beat that price both by shopping around and by asking a friendly local ham for components from the junk box.
1951BLrcvrSchematicThe article is a bit sketchy on details; in fact, it doesn’t mention the tuning range. But from the size of the coil and capacitor, I’m guessing that its coverage is in the vicinity of 40 meters. The Novice class license had just been created by the FCC, and the article notes that the little receiver would be good for code practice for earning that license:

For your money and time you will have a working receiver capable of picking up amateur signals, ships at sea, aircraft, and the code-practice broadcasts of the American Radio Relay League. The League broadcasts at 9:30 P.M., Monday through Friday, at Eastern Standard Time. If you’re after the Novice Class ticket, you’ll find the ARRL broadcasts tops for real practice.

The same receiver appeared in the Radio Merit Badge pamphlet, a copy of which has been scanned and placed online by AL7FS.  It appears that the receiver appeared in the merit badge book until 1962. From the text, it appears that a requirement at that time was to construct a receiver and use it to log five stations, and this one would certainly be up to the task.

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Steam Powered CW Transmitter

SteamPoweredHamTX

QRP’ers wanting to get on the air with a novel power source will appreciate the steam powered transmitter that appeared in Popular Electronics fifty years ago this month, July 1965.

The author, Hartland B. Smith, W8VVD, describes a one-transistor crystal controlled transmitter with a power output of 10-15 milliwatts, powered by a DC motor attached to a model steam engine. The motor (being used as a generator) was on a hinged mount, with a rubber grommet contacting the steam engine flywheel and with a rubber band providing the necessary tension. The rig was tested with 3 volts, but the generator was said to put out up to six volts.

The steam engine manufacturer recommended (as they still do) the use of dry fuel tablets, but the author noted that anything from a candle to a propane tank could be used. To avoid the need for frequent refueling, the author settled on a propane tank, resting between two wooden blocks.

The author notes that almost any of the model engines on the market would be up to the task, but he recommended one with a fairly large boiler to avoid delays caused by needing to refill and build up a new head of steam.

Model steam engines, practically identical to the one shown in the 1965 article, are still available, although they can be a bit pricey. My son owns a Jensen Model 75, although I don’t think we paid anywhere near its current price on Amazon. The Wilesco Model D5 appears comaprable, at a more reasonable price. Either should put out more than adequate power to run a small transmitter similar to the one shown in the article. The tank does appear somewhat smaller than the one in the article, but will give several minutes of run time, enough for a short QSO, if not a long ragchew. We power ours with the Esbit Dry Fuel Tablets, although it could easily be run with alcohol. Because of the smaller tank, it would probably be tricky to rig it up to run from the propane tank, although that could probably be managed.

The author Hartland Smith was first licensed in 1941, and is still licensed as W8QX.  In addition to writing, he worked as a broadcast engineer, designer, and kit manufacturer.  He has a number of interesting websites which he has linked at this one.  I received a nice e-mail from him, in which he mentioned that had written a number of other articles for “PopTronics.”  I did a search and located quite a few, including the “Camper’s Special” from 1965 and the “Camper’s Cuzzin” from 1967.  Together, they formed an 80 meter QRP station suitable for camping or emergency backup.  The “Camper’s Special” was a crystal-controlled transmitter that put out 5 watts.  The author points out (as many of us later discovered with the modern rediscovery of QRP) that this is just two S-units weaker than a 100 watt signal.  The “Camper’s Cuzzin” was a companion receive converter, which allowed the builder to tune the 80 meter band on a standard broadcast receiver.  It contained three transistors, a local oscillator tuning 5.1 – 5.6 MHz, an amplifier-mixer, and a BFO set to 1.6 MHz.  By setting the converter next to a portable AM radio tuned to 1600, the result was that 80 meter CW or SSB could be heard.

He also designed two transmitters for the novice.  The “Hart-25” from 1955 put out 25 watts, and the “Hart-65” in 1967 put out 65 watts on 80 and 40.

For those looking for an even more challenging QRP transmitter, check out AA1TJ’s voice powered “CW” transmitter described at this link and seen in action on this video.  He worked a QSO of a hundred miles with no power source other than his own voice into a PM speaker.  It was probably quite a bit more than two S-units below a 100 watt signal, but by shouting loud enough, he made QSO’s without any power source, steam or otherwise.

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1940 “Mighty Midget” One Tube Shortwave Receiver

1940JulyPMrxSeventy five years ago, the father and daughter shown here were putting together a one-tube shortwave receiver according to plans in the July 1940 issue of Popular Mechanics.

The set, the “Mighty Midget” One Tuber, employed a single 1D8-GT, a dual tube, with one half being used as the regenerative detector and the other half serving as an audio amplifier.

Thanks to the efficiency of the multi-unit tube, the set was said to run rings around two-tube receivers of even a year earlier.  “Twenty-meter phone stations roll in with headphone volume at times actually uncomfortable, and there is plenty of ‘sock’ even on weak foreign stations.”

For information on sourcing parts, especially the plug-in coils, see my recent post about a similar two-tube set.

1940JulyPMpic

 

1940JulyPMschematic

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1935 Popular Science 80 Meter Portable Station

1935PS80meterstationEighty years ago, Popular Science, June 1935, carried the plans for this complete 80 meter CW station. It could be used permanently in the shack, or as a portable station. The entire station weighed in at about 35 pounds, and could be transported relatively easily. The front panel measured just 18 by 12 inches.

The top third is the transmitter, which uses a type 47 tube as crystal oscillator, and two type 46 tubes as the final amplifier, putting out about 30 watts.

1935PS80meterstationSchematicThe receiver used one type 58 tube as an untuned RF amplifier, with a type 57 tube as regenerative detector. A type 2A5 was used as an audio amplifier.

The bottom section contained the 110 volt power supply, with a transformer supplying 450 volts either side of the center tap. This was rectified by a 5Z3 tube, with several capacitors and chokes doing the filtering. The article noted that where commercial power was not available, the set could be adapted to a vibrator power supply to run off six volts.

1935PS80meterstationFrontPanel

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Foxhole Radio Update

 

Gould's rendition of the foxhole radio.

Gould’s rendition of the foxhole radio.

A few months ago, we posted about the history of the “foxhole radio,” a crystal set made with a razor blade detector,  As reported in the New York Times in June 1944 and Time Magazine in July, soldiers at the beachhead in Anzio made these receivers to pass the time. The receiver was later popularized in Jack Gould’s book All About Radio and Television.

Among those to see the plans was Radio Craft editor Hugo Gernsback.  In the September issue of Radio Craft, he pointed out that the original Razor Blade Radio Detector had actually been published by him, in the January 1909 issue of Modern Electrics. He also shows two other similar detectors published in 1906.

The 1909 razor blade detector actually differed from the “foxhole” version, however. The Modern Electrics detector uses two razor blades with a pencil lead balanced on top. The razor blade seems to be serving the function of “cat’s whisker,” as opposed to being the crystal in the foxhole version.

GernsbackRazorBlade

 

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