Category Archives: Radio

1941 ARRL Battery-Powered Equipment Test

1941SeptQSTToday marks the 80th anniversary of an ARRL contest that, as far as I can tell, happened only one time, the 1941 ARRL Battery-Powered Equipment Test. The announcement shown here appeared in the September 1941 issue of QST, and the full rules appeared in the October issue.

While June Field Day was, and is, dominated by gasoline powered generators, this event was “aimed at individual-class lighter weight equipment.” To stress this, the official contest exchange included the transmitter weight. Participants could work non-contest stations for one point, with an extra point for sending and getting acknowledgment of the transmitter weight. If the other station was battery powered, there was an additional point for copying their transmitter weight.

WFD1In my opinion, the small advantage gained by an electric generator is more than offset by the convenience of operating with batteries.  For example, as I previously reported, I worked the 2021 Winter Field Day contest with my trusty fish finder battery.  Especially if you’re thinking in terms of emergency preparedness, it’s an easy matter to keep fully charged batteries on hand, whereas a generator usually requires a certain amount of maintenance, as well as keeping fuel on hand.

The maximum power level for the 1941 contest was set at 30 watts, although it would have been a stretch to get more from battery-powered equipment. Operation from the field was encouraged, with a multiplier of of 2 for all contacts. However, stations could also be operated from home, as long as batteries provided all power for transmitter and receiver. The contest rules reminded hams that portable operation required 48 hours advance notice to the FCC.

There were categories for both HF and VHF (called in those days “low frequency” and UHF). Interestingly, HF operation was confined to the daylight hours, but UHF could continue all night. The UHF category allowed 5 meters and up, but all of the entries in that category used exclusively the 2-1/2 meter band.

The results weren’t published until after Pearl Harbor, in the March 1942 issue of QST.  They are shown below, with W8RMH, Edgar Cantelon of Detroit, later W8CV, taking the honors for high score with 82 contacts from a portable location. Among the calls is one familiar one, that of Don Wallace, W6AM, whom we have previously profiled.

In the “UHF” category, W2NPN took top honors, with an impressive 72 contacts from a portable location, all on 112 MHz.

The “transmitter weight” is an interesting piece of data to exchange. Even though this contest is no more, transmitter weight is still a factor in at least one contest. While it’s not sent on the air, transmitter weight is an important factor in scoring for the Adventure Radio Society Spartan Sprint contest.  In the most recent running, K4PQC managed 11 contacts with a station (transmitter, receiver, headphones, and battery) weighing in at 0.1268 pounds (2 ounces). He reported that his station consisted of a 40 meter ATS-3b.  The rig is designed to fit inside an Altoid’s tin, but he ran it without the case to shave a whopping 1.2 ounces off the station weight.

I suspect W8RMH’s rig weighed a bit more in 1941, but he probably used a lot of other gear, both larger and smaller, over the years. According to his 2016 obituary, he had just started working at WJBK radio (now WLQV) shortly after this contest, and he was in the transmitter room when the station reported that Pearl Harbor had been attacked. He then secured a new job in a defense plant, later becoming a radio operator for bomber test flights. He later served in the Merchant Marine as a radio operator, and then the army. He later went back to WJBK and served as an engineer for their TV station.

BatteryPowerContestScores1941



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Field Day 1946

WFD1This weekend is ARRL Field Day, an amateur radio operating event in which hams set up their stations in remote locations and attempt to make as many contacts as possible.  It’s a hotly debated question of whether it’s an emergency preparedness exercise, a contest, or just a fun weekend.  The truth is that it’s all three.

Even if all infrastructure were to be destroyed immediately, it would still be quite possible for hams to communicate worldwide using simple equipment, relying on nothing other than the laws of physics.  Short of a zombie apocalypse, the need for such ability might be rare, but it’s a point of pride with hams what they can do.

1946 Field Day. QST for Feb. 1947.

1946 Field Day. QST for Feb. 1947.

Amateur radio was off the air for the duration of World War II, so Field Day 1946, 75 years ago, was the first postwar opportunity for hams to show that they could still communicate off-grid.

When the results were published, it was pointed out that comparisons with earlier Field Days were not appropriate.  Hams had only recently come back on the air, and they were not yet allowed on all bands.  In particular, they did not yet have privileges on the 160, 40, and 20 meter bands, all workhorses of earlier Field Days.  Instead, their HF was limited to 80, 11 and 10 meters.  The top portion of the 80 meter band had just been re-opened, and here were the allocations, as shown in the June 1946 issue of QST:

1946JunQST

The top score in the 1946 event was W2FC/2, the Jersey Shore Amateur Radio Association, which netted 9621 points from a total of 809 contacts.  The 27 participants had eight transmitters on the air simultaneously.

Shown above is my most recent field operation.  It wasn’t ARRL Field Day, but instead Winter Field Day 2021.

 

 



Winter Field Day 2021

WFD1This previous weekend was Winter Field Day.  While this event is billed as an emergency preparedness exercise, it’s also simply a fun opportunity to get on the air from a portable location, and make the most of limited resources.

As happened with ARRL Field Day this past June, the event was affected by COVID-19.  Since the pandemic generally prevents operation as a group, many who would have otherwise participated stayed home.  But in my opinion, being part of a group is not what defines this event.  The event is not called “Group Day,” it is called “Field Day.”  The focus is operating from out in the field somewhere.  And while groups of people can be dangerous because of COVID, there is absolutely nothing that is unsafe about a field.  I was completely socially distanced during the entire event.  I saw a few other campers and said hello to some of them from 50 feet away.  As I’ve previously written, camping is an excellent safe way to travel during the pandemic.

As an emergency preparedness exercise, it seems to me that it was best to adapt to the actual emergency conditions.  Because of COVID, it wasn’t possible to do it as a group.  But in many emergency situations, a group of helpers might not be available to set up a station and get it on the air.  It seems to me that the ability to get a station on the air, even a minimalist station, without outside assistance, is a valuable skill in an emergency.

FD1For summer Field Day, my wife and I operated for an hour or two from a city park, shown here.  If it weren’t for all of the naysayers lamenting that they had to stay home for Winter Field Day, I probably would have done something similar and just operated for a while from the back yard, or maybe again from a city park.  But since so many people were lamenting that it was impossible to truly go out and operate away from home, I decided to do a winter camping trip in our popup camper.

I made reservations for William O’Brien State Park, which is only a 45 minute drive from home.  The temperature never got below 20 degrees, and it was actually a very nice weekend for camping.  There were several other campers in the campground.  I spotted three RV’s, as well as three family groups camping in tents.  Also, I believe at least one of the park’s cabins was occupied.  So at least a few non-hams were undaunted by being in the field in the middle of winter, in the middle of a pandemic.

Even though it’s not insulated, the popup camper stays quite warm inside with electric heaters and/or the furnace running.  Since I was paying for the electricity anyway, I used two electric space heaters.  One was plugged into the outlet in the camper, which was hooked up to the campground’s 30 amp circuit.  The other heater was plugged into a separate extension cord going to the campground’s 20 amp circuit.  Therefore, if needed, I could run both heaters full blast.  When I needed the electricity for cooking, I temporarily unplugged one of the heaters.  There was a light dusting of snow Sunday morning, but the camper’s canvas was bone dry by the time I folded it up.

WFD2I didn’t set out to make hundreds of contacts.  In fact, after making the first one, which happened to be with Rhode Island, I felt like I had proved the concept.  But I was on the air for a total of about three hours out of the 24 hours of the contest, and made 27 contacts with 14 states.

Only eight of those contacts were with other portable stations.  Six were outdoors, and two were indoors but at temporary locations.  I’m grateful for the other 19, who were operating at their home stations, since they gave me someone to make contacts with.  But I feel a little sorry for them that they didn’t figure out some way to operate in an actual field for Field Day, even though they couldn’t do it as part of a group.  Also, I was a little bit mystified to hear home stations working other home stations, while calling it Field Day.  For previous Field Days when I’ve stayed home, I’ve often made some contacts, but since it’s Field Day, I’ve made a point to seek out stations who were actually in a field.  There are contests almost every weekend that are geared up for home stations to work other home stations.  I guess I don’t see the point of ignoring those opportunities, and then getting on only for a weekend called Field Day.  Again, I was grateful that I had stations to work, but I really didn’t get the point of home stations spending the whole weekend working other home stations.

My original plan was to use dipoles for 20 and 40 meters, along with a quarter wave wire for 80 meters.  The 80 meter wire was a bust, and didn’t really get out, due undoubtedly to its very low height and lack of much of a ground system.  But the dipole for 20 meters did a great job, and I made all of my contacts on that band.  You can see (just barely) that antenna at left.  It’s held up at the center, inverted-vee style, with my telescoping golf ball retriever, and the ends are tied loosely to some bushes that happened to be at about the right spot.  I was running low on wire before the contest, so I ordered a roll of speaker wire that did the job.  I cut it to the proper length of about 16-1/2 feet, and then unzipped it when it was in place.  I thought I had forgotten to bring a tape measure (it turns out there was one in the toolbox), but I used a six-inch ruler to measure the table, and then used the table to measure the wire.

My original plan was to put up a 40 meter antenna as well, but when 20 meters closed in the early evening, I decided to simply call it a night, and made a few more contacts Sunday morning.  As with most of my NPOTA activations, I operated mostly CW, but also made a few SSB contacts.  I also made one PSK-31 contact using my tablet computer and the DroidPSK app.

My station consisted of my Yaesu FT-817 powered by a fish-finder battery, which still had plenty of charge left at the end of the contest.  The one digital contact was made possible with the Signalink USB interface, which performed flawlessly with the inexpensive RCA tablet computer.  For some reason, the tablet’s keyboard didn’t work very well with the DroidPSK software, so I had to use the touchscreen, which seemed like a rather laborious process to me.  I probably could have made the process much easier by setting up some macros in advance.  But for the first time using it, I was glad that I was able to make my first ever portable digital contact.

As you can see in the picture above, I needed something to prop up the radio on the table, and a box of matches did a perfect job with this important task.

Am I going to save any lives with my ability to operate a portable station?  Almost certainly not.  On the other hand, if there is ever an emergency, large or small, that makes other forms of communication impossible, I know that I am able to send messages to friends and relatives in other states.  I can do it formally by checking in to a National Traffic System net, or I can do it informally simply by working someone and asking them to make a phone call or send an e-mail for me.  I can also do that for neighbors who want to let their friends in other states know that they’re safe.  I’m also well equipped to receive information from the outside world simply by knowing that I can power up a broadcast receiver to listen to either local or distant stations.  It’s unlikely that I’ll ever have a need, but it’s good to know that I have the ability.

The point of exercises like Field Day is to show that hams can adapt to emergency situations and still be able to communicate.  COVID has shown us that there are some emergencies where you are cut off from the group that normally helps you establish communications.  Can you adapt and still communicate if you are cut off from both this group and your normal station setup?  Field Day and Winter Field Day during COVID gave me the opportunity to show that I can.

Here’s a short video tour of my setup:

 

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1940 RCA Ad

Life1940Oct21This ad showing RCA’s product lineup for 1941 appeared 80 years ago today, in the October 21, 1940, issue of Life magazine.

For those on a budget, the model 45X-1 for $9.95.  The ad bills that set as having one police band, but in reality, it covers the broadcast band but with a bit of extended coverage to pull in police calls in many areas.

The most expensive of the table radios shown is the 18T for $49.95.  That 8-tube set featured six pushbuttons and two shortwave bands for pulling in the war news from Europe.  At the top of the line of the tabletop radio-phonos was the V-102, a 7 tube set which appears to be broadcast only, for $59.95.

For a larger view of the ad, from most browsers, click twice on the image.



Drive-In Educational Programs and Meetings for COVID-19

DriveInCLEI’ve previously written about why I believe outdoor spaces should be utilized for learning and other group activities during the COVID-19 emergency. Since I’m in the business of providing continuing education programs for attorneys, a few weeks ago, I presented an outdoor program at a city park.

The weather for that program was excellent, and everyone enjoyed the opportunity to be outside. However, the weather can be unpredictable, and it won’t always work to be outside. For that reason, today, I presented a live drive-in program in a parking lot. The attendees watched from their car, and listened on their car radio. If there had been questions or feedback, they could have phoned me at any time.

Why a Drive-In Program?

It was a bit more work, and it would actually have been more pleasant to just get out of our cars and do it outside, as with the previous program. But a drive-in program is a very viable option for any group that needs to be meet in person, since the weather won’t always cooperate completely.

I didn’t bring it today, because the weather was nice, but if there had been a chance of rain, I would have brought a canopy such as the one shown here.  For an outdoor presentation of any kind, the speaker obviously needs to dress for the weather.  But the attendees can take advantage of their car, or even run the car for heat or air conditioning if needed.

My transmitter was the  InfOspot Talking House transmitter, which I previously reviewed.  As expected, my transmitter easily covered the parking lot.  I parked near a tree, and tied the end of the 10 foot antenna to a convenient branch.  I should have tested everything, since the audio quality wasn’t quite as good as I had expected.  In most of my tests at home, I fed the transmitter with an MP3 player, and the audio quality was absolutely astounding.  Today’s audio quality was quite good–certainly good enough for a lecture.  But if the transmitter was used for any kind of musical presentation, it wouldn’t have been quite good enough.  I’ll need to experiment with a different mike, or possibly run the existing mike through a preamp and feed the auxiliary input rather than the mike input.  (The audio quality through the line-in jack is excellent, so if you’re broadcasting from a location where another PA system is in use, that’s the best option, but you will need an inexpensive isolation transformer to prevent 60-cycle hum.)

Caveat Emptor:  The Importance of a Legal Transmitter

When buying a transmitter, it’s important to buy a transmitter that is legal.  Unfortunately, most of the transmitters in use for drive-in events these days don’t appear to be legal.  In particular, it would be very difficult to use a legal FM transmitter for an event such as this, because FCC rules (section 15.239) limit the transmitted signal to an extremely low level.  Amazon and eBay are full of FM transmitters that claim to be legal for unlicensed use, but even a cursory examination of their specifications reveal that their power level is many times what is allowed.  On the other hand, the rules governing AM transmitters (section 15.219) are much less restrictive.  The  Talking House transmitter is certified as complying with this section of the rules, and has a very good range for this type of use.  It is, therefore, the transmitter that I recommend for this application.  Chances are, nobody will complain to the FCC.  But if they do, and especially if there is interference with aircraft communications, which are near the FM band, the fines are typically in the range of $10,000.  It’s best to use a transmitter that you know is legal, and the Talking House is.

Here’s another writer who agrees with me that most FM transmitters used for this purpose are illegal.  As he puts it, they are all lying when they say on eBay or Amazon that they are legal.  And in my experience, as both a lawyer and a licensed radio engineer, he’s right.  Some of the listings claim that the transmitters are FCC certified.  In some cases, the certification appears to be for use by a licensed radio station.  In one case, the transmitter appeared to be certified for unlicensed use.   I checked the FCC website, and sure enough, there was a report from a Chinese lab certifying that the transmitter was compliant.  The report even contained test results showing compliance with some of the requirements.  But noticeably absent was any report showing that the transmitted field strength was compliant.  It couldn’t have been, because the transmitter was using hundreds or thousands more times power than allowed.  It appears than an overworked FCC simply failed to notice that this critical measurement was missing from the report.  Let the buyer beware.  Just because an eBay listing says that a product is legal doesn’t mean it’s legal.

A Good Way to Conduct In Person Meetings

As with my previous program, we could have just as easily done it over the phone, or via Zoom.  But some activities are best done in person, and after a long quarantine where everything has been done remotely, it’s refreshing to interact with others in person, even if they are six feet away and/or on the other side of a windshield.  Creatively making use of outdoor locations, whether it’s for business, education, or worship will serve an important role until things get back to normal.  And history tells us that yes, eventually, things will get back to normal.



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1970 Multiband Mobile Antenna

1970AugustPE

1970AugustPE2This month marks the 50th birthday of a pretty good idea, as evidenced by the cover story in the August 1970 issue of Popular Electronics. The article was penned by Russ Alexander, W6IEL, who was likely the originator. The article specifically addresses how to use a compact antenna from an apartment, and it makes use of Hustler mobile antennas.

The Hustler antenna is still available today, in more or less identical form. It amounts to a center loaded vertical antenna. The bottom half is a mast that attaches to the car. On top of that is a loading coil, and on top of that is a whip antenna. The loading coil and whip are tuned to a specific band. And because you need different coils and whips for different bands, the coil and whip are sold as a one-piece resonator.

So it’s fairly easy to change bands: You stop the car, get out, and swap out the resonator. But that doesn’t work very well if the antenna is mounted on the roof of your apartment building. And it doesn’t work very well if you want to change bands without getting out of the car.

1970AugustPE3So the author went to his metal shop, and made a piece which allowed him to mount up to four resonators on the same mast. For bands that are not being used, the coil acts as a trap, so the unused resonators have little impact on the transmitted signal.

The idea caught on. I first remember seeing one of these as a young ham in the 1970s in the parking lot at a hamfest on the car of prominent Minnesota ham Tod Olson, K0TO (then W0IYP). I remember thinking that it was a pretty good idea. Chances are, it originated with the magazine article shown here.

W6LENShown in these pictures W6LEN2is the mobile antenna of W6LEN, an avid WWFF activator of Southern California parks and beaches. He uses the Hustler mobile antenna on a magnetic mount on top of his minivan. While the magnetic mount is probably too small to use in motion, he has had good success with this antenna, and it takes only a few minutes to deploy when he arrives at his destination.  As with the 1970 article, he uses a homemade bracket to mount the four resonators.

Hustler eventually realized that using multiple resonators was a good idea, and they now sell the part, shown at right, so you don’t have to have your own metalworking tools. The author of the 1970 article recommended having the part plated with copper and then cadmium, after which “the finished bracket will look like a commercially marketed item.”  The 1970 Popular Electronics version had room for four resonators, whereas the commercial product has only three wings.  However, a fourth resonator can be added in the middle.



Field Day 1940: Lessons for 2020

1940June15BCField Day 1940 should give some inspiration to those who are operating Field Day 2020.

Eighty years ago, the U.S. was still 18 months away from being drawn into the war, but the subject was on the mind of the FCC. Amateur radio operators were not silenced until Pearl Harbor, but there were already restrictions in place, as described in the June 15, 1940, issue of Broadcasting magazine.

The magazine noted that non-essential services, such as amateur, experimental, and special private radio might be curtailed or shut down due to wartime conditions. On June 5, 1940, the FCC banned all amateur communications with hams in foreign countries.

On June 7, the FCC banned portable and mobile operations with a couple of exceptions. First of all, such operations were allowed above 56 MHz, the thinking being that there was little threat from these line-of-sight signals.

Operators at ____ getting ready to launch a balloon-supported antenna, Field Day 1940. Photo, QST for December 1940.

Operators at W8QLU/8 getting ready to launch a balloon-supported antenna, Field Day 1940. Photo, QST for December 1940.

In addition, there was a blanket exception allowed for stations participating in the 1940 ARRL Field Day, which the magazine described as “tests of portable transmitters designed for special use in time of emergency.”

Despite the restrictions, hundreds of ham stations took part in Field Day. One of the high scores was from the St. Paul (MN) Radio Club, W9KYC/9, which made 505 contacts on all bands from 160 to 10 meters. 228 of those contacts were with other Field Day stations, the rest presumably being with home stations.

This year again, Field Day is subject to emergency restrictions, and many of the large multi-transmitter operations will be off the air. Despite initially saying that they weren’t going to do so, the ARRL finally relented and will allow points for contacts between home stations operating with commercial power.

While this rule change is understandable, it would seem odd to stay home and get on the air, while pretending to be in a Field somewhere. While many hams won’t be able to do Field Day this year in the normal fashion, they can operate in an honest-to-goodness Field if they use a bit of creativity.

In 1940, despite a war looming and government restrictions, at least 228 groups of hams were able to lug their bulky transmitters, receivers, and generators to remote locations and get on the air.

One of the purposes of Field Day, then and now, is “tests of portable transmitters designed for special use in time of emergency.” This year, there’s an actual emergency going on. But despite that actual emergency, there’s nothing stopping hams from taking their equipment–which is much smaller and more portable than it was 80 years ago–into an honest-to-goodness Field to put it on the air.

CookieCrumbleThis year, my wife and I will be operating from a city park near our home. The tentative plan is to be in the two-transmitter class, probably covering 20, 6, and 2 meters. Power will be supplied with the trusty fish-finder battery, and the antenna will be supported by the trusty golf ball retriever. As a trial run this weekend, I set up in our own backyard for the annual Cookie Crumble QRP Contest. Despite poor conditions, I made contacts with Pennsylvania, New Hampshire, New York, and Texas. On Field Day, I’ll repeat the operation. Even though I’m physically distancing myself from others, there’s no reason for me to sequester myself in the basement. I can just as easily operate from a bona fide Field for Field Day.

The ARRL made another temporary rule change this year, and will publish a cumulative score for clubs. I think the idea was that, even with club members operating from their home stations, they can still be part of a club effort. I guess they can pretend they’re all in the same virtual field. And by operating from the comfort of their own home, they can get an even larger score than when they set up multiple transmitters in a real field.

But that rule change applies to all classes of entries–even those who are operating a traditional Field Day from the field. Therefore, I have taken the liberty of forming a new club for the hundreds of hams who figure out a way to operate Field Day as it was meant to be–in the Field.

The new club is named “The Outstanding In Their Field Amateur Radio Field Day Club.” It is open to any and all hams, worldwide, who plan to operate Field Day as a Class A or Class B station, namely, from a remote location with emergency power and temporary antennas. Your setup might be elaborate, or it might be as simple as a $30 Baofeng. If you believe that one contact in such conditions is better than filling up an entire logbook from your air conditioned home station, then this club is for you.

Membership in the Outstanding In Their Field Club is simple. There are no dues or long-term commitment. You can join in one of  three ways. If you are gung-ho, then you can sign the club’s articles of association, which you can view at this link. If you’re on board, but not quite to that extent, you can just send me an e-mail to w0is@arrl.net. Or if you’re not sure and want to wait until the last minute, you can join simply by naming the club in your Field Day entry.

Despite war looming, at least 228 hams hit the Field for Field Day 1940. There’s no reason why we can’t do the same. If you also think so, please consider joining The Outstanding In Their Field Amateur Radio Field Day Club.



Amateur Radio Audio Course

If you, or someone you know, is interested in getting their amateur radio license, I am the author of a study guide for starting class of license, the Technician license. The test requires some study, but not much, since it consists of 35 multiple-choice questions. The passing score is 26.

My study guide is available at Amazon, either as a paperback or as a Kindle eBook. Most people will be able to pass the test by reading the book one time. Since different people learn different ways, I’ve decided to supplement the book with a series of audio lessons. I recommend reading the book, but many will be able to pass the test simply by listening to the lessons. They are available for free download at the following links:

I also have study guides for other amateur and commercial licenses at my website.



Product Review: GPX Model R300S AM-FM Portable Armband Radio

I recently acquired the inexpensive radio shown here, a GPX Portable Armband Radio, model number R300S. I bought it at Walmart, and it’s also available at Amazon.  It’s a very inexpensive AM-FM radio, but of astonishingly good quality for the price. It measures about 4 by 2 by 1 inches. It has a digital tuner with LCD display, and also features an alarm clock which displays the time when the radio is turned off. The WalMart product description incorrectly states that it has an analog tuning control. Instead, it has plus and minus buttons that you use to tune the digital display up and down the dial. It comes with an armband, although this can be removed to turn it into a nice pocket-sized radio. It does not have a speaker, but has a stereo headphone jack and comes with a set of earbuds.

I didn’t use them, but the radio does have a number of preset memories. I simply used the up-and-down tuning and didn’t bother with the memories.

The Need for a Cheap Receiver

I purchased it from Walmart because I needed it quickly and didn’t have time to order online.  My pastor will be traveling to Africa to visit a remote congregation with which we partner. Our denomination also helps sponsor an FM radio station in the closest city. I do not know whether it is possible to receive the signal at “our” church in the remote village. Therefore, I wanted her to do a test to see if it’s possible. If she is able to receive even a weak signal, then it will be an easy matter to send some solar radios and perhaps an external antenna so that they can listen on a regular basis.

Therefore, I had to quickly find a suitable radio that I could send with her.  And despite all of the radios I have lying around the house, I didn’t have exactly the right thing. It needed to meet the following criteria:

  1. It had to be small. I’m sure her suitcase will be packed to the brim, not only with her personal belongings, but with other gifts to leave.
  2. It had to have digital tuning. The person doing the experiment for me is not a radio expert. To do the experiment, the radio needs to be set to the exact frequency, and then moved around to see if any signal comes up out of the noise. This wouldn’t be possible with an analog dial.
  3. It had to be relatively cheap.
  4. It had to be sensitive. I’m unsure of the exact distance, but the station we want to receive is miles away, and only puts out 1 kW. Therefore, it had to be a good tuner.  Selectivity probably isn’t important, since there will be few, if any, other FM signals.

I found the GPX R300S at WalMart for about $8. It met the first three criteria, and I hoped against hope that it would meet the fourth. It was in stock at the local WalMart store, so I ordered online and picked it up at the store about an hour later while doing some other shopping.

Surprisingly Good on Both AM and FM

I was pleasantly surprised to discover that this is an extremely good tuner on both AM and FM. I only had time to play with it for a few minutes, but it did pull in all of the local FM stations, even weak ones, with no difficulty. If any commercial receiver is going to pull in the station we want to hear, then this one probably will. If it gets absolutely nothing, then I’m satisfied that a more expensive receiver won’t, at least without a high antenna.

It wasn’t necessary for this particular experiment, but I was also astonished at how good an AM receiver this set is. Unfortunately, in most cheap radios these days, the AM receiver is tossed in as an afterthought (if it’s included at all), and is only able to pick up the strongest local stations. I did the test at night, and was astonished to see that the radio was pulling in something on almost every 10 kHz channel. I was able to positively ID WSM Nashville and KFAB Omaha from my Minnesota location. Those stations are obviously powerhouses, but in my experience, most cheap AM receivers these days are not able to pull them in. The internal AM antenna was very directional, and I was able to easily null out signals by turning the radio.

Selectivity was also remarkably good for such an inexpensive set. Local 50 kilowatt blowtorch WCCO is on 830 kHz, and on many cheap radios spills over onto the adjacent channel. But I was able to hear another station faintly on 840, with no sign of interference from WCCO.

Has 100 kHz Tuning Steps on FM, But Only 10 kHz Steps on AM

The station we want to hear in Africa is on FM, so the AM performance wasn’t necessary for my test. But it was amazing how well it worked on that band. Unfortunately, the radio tunes only in 10 kHz steps, covering the AM band in the Americas, where all stations’ frequencies end in zero. Unfortunately, in the Eastern Hemisphere, stations are 9 kHz apart. Some frequencies are used in common, e.g., 540, 630, 720, etc. And some stations will be off by only 1 kHz, e.g., 549, 621, 639, etc. But some stations will be off by as much as 5 kHz, e.g., 585, 675, etc., and will be very difficult to tune. This is one case where an analog tuner would be better.  I suspect it’s probably possible to modify this receiver to tune in 9 kHz steps.  After all, they probably sell a similar version elsewhere in the world.  But the instruction manual didn’t hint at any method of doing this.

The station we need to tune in happens to be on a frequency that is also used in the Americas.  In other words, it’s on an “odd” frequency following the 200 kHz separation band plan, namely 96.7.  Therefore, any North American receiver would have worked.  This radio, however, does tune in 100 kHz steps and includes the “even” frequencies, such as 96.8, that are also used in the Eastern Hemisphere.  Therefore, it will be able to tune in all local stations.

Usefulness in Rural Africa

I told my pastor to leave the radio as a gift with someone in Africa, since there’s no good reason for the set to make a round trip. If it’s not useful in the village where our partner congregation is located, it will certainly be useful in the city, where there are a number of FM stations, and she’ll have an opportunity to leave it there. The AM stations are more distant, and hopefully the radio will be able to pull at least some of them in at night.   I noticed one of them in the nation’s capital was on a frequency ending in zero, so it least it will be able to pick up that one at night.  The radio also contains an alarm clock, and I set it to the Eastern Africa time zone.

Unfortunately, it won’t be of much use after the batteries run out. It uses two AAA cells. It’s unlikely that those are available in the village. They almost certainly are available in the city, but I’m not sure at what price. I included two extra sets of batteries, which I assume will allow it to work for a few months of listening an hour or two a day. A solar radio would be much more suitable, and if we send any in the future, that’s what I will use.

Bottom Line

Most of the online reviews are favorable, but a few are not. So it’s possible that quality control is not the greatest, and that some units do not perform as well as mine. But for the low price, it’s certainly worth the risk. For the price, the GPX model R300S Portable Armband Radio is a very solid performer.  If you need a cheap radio that still pulls in both AM and FM stations well, this radio is what you need.



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Radio Direction Finding

1959JuneElecWorldCoverSixty years ago this month, the June 1959 issue of Electronics World carried a good basic introduction to marine direction finding (DF).  The cover image shows a number of commercially made DF units, and the article explains how they work.

While the technology looks archaic, it actually still works quite well, and will continue to do so as long as there are AM radio stations on the air.  While commercial direction finders are no longer readily available, virtually any AM radio will work well, as long as the antenna is directional.  And if the radio has an internal loop antenna, it will be directional.

For example, the inexpensive portable shown at the right will perform very well.  (It’s available at Amazon at this link, but any other inexpensive portable will work just as well.)  You simply rotate the radio until the signal is the weakest.  At that point, the internal antenna (usually in parallel with the top of the radio) is in a straight line with a station.  You place a ruler on the map over that station’s location, and draw a line in that direction.  You repeat the process with a second station, and where the lines meet is your location.  You’ll need to orient the map, so if you don’t know what way is North, it’s a good idea to have an inexpensive compass.  And you don’t really need a ruler.  You place the map on a table oriented with the Earth–the top of the map facing North–and then use the top of the radio as your ruler.

1959JuneElecWorld

This method is surprisingly accurate.  It’s very easy to find your location within a mile, and with some practice, you’ll be able to narrow it down even more.  It’s not quite as accurate as GPS, but if GPS ever becomes unavailable for any reason, this is an excellent backup method.  The example shown at the left is typical.  By knowing the exact location of radio stations in Chicago, Milwaukee, and Benton Harbor, MI, the boat can find its location within a few hundred yards.

Radio station locations are shown on maritime and aeronautical charts.  You can also find the exact locations of AM radio stations from the FCC database.