My son’s Cub Scout pack is selling Christmas wreaths as a fundraiser. This year, we can deliver anywhere in the continental United States. For more information, please visit my wreath page.
Civil Defense Emergency Antenna Instructions, 1973
In 1973, the Defense Civil Preparedness Agency was grappling with the issue of how to keep broadcast stations on the air after a disaster, presumably up to and including nuclear war. It was recognized that a station’s weakest link was its antenna. While most antennas are designed to survive normal environmental disturbances, they are the most exposed element of a station and could be destroyed by extreme disturbances. Therefore, the agency commissioned a study on the subject, the final report of which is available online.
In the report, the engineers propose that expedient antenna kits be supplied to stations, and proposed instructions are included. The report proposed kits for both AM and FM stations, along with instructions for station personnel to deploy them. The cost of the expedient AM antenna kit, a quarter-wave horizontal wire, would be $425.37. The expedient FM antenna kit would be about $1000. Both antennas would require installation at the station, prior to the disaster, the necessary utility poles that would support the antennas.
Recognizing, however, that the government might not want to bear this expense, the report also includes instructions for station personnel to construct an AM antenna using available materials. Once again, the recommended antenna is a horizontal wire, either the length of the destroyed tower or a quarter wavelength. The diagram of the recommended antenna is shown above.
Ideally, the feed point of the emergency antenna would be at the base of the fallen tower, but other options are discussed. A last resort, if the feed line were destroyed, would be to put the feed point of the antenna directly at the transmitter. The instructions caution that “it is possible to construct a transmission line, but don’t try. The performance of an antenna fed at a transmitter without a good ground will probably be better than the performance with a good ground and an improvised transmission line.”
These instructions also presuppose that the utility poles were never installed prior to the disaster. Instead, it advises to use “any existing structures available such as trees, buildings, and utility poles. A step ladder or even an automobile can be used if nothing else is available.”
Improvised antenna insulators.
Since antenna insulators probably aren’t on hand, the instructions suggest some possibilities, shown here, using things that might be found around the radio station, such as the soft drink bottle.
The main idea was to get back on the air as soon as possible. “Time is more important than radiated power, so an inefficient operation in 15 minutes is better than full power in two hours.”
A 1950-Era One Tube Radio
Photo, WS1K
Jon, WS1K, sent me these pictures of a very nice find: A regenerative receiver that he found under a dealer’s table at an antique show in Brimfield, MA. He originally thought it was the receiver from the 1950 ARRL handbook, but after finding this site, he realized that it was closer to the Boys’ Life set that I wrote about earlier.
Photo, WS1K.
Pictures of his receiver are shown here. In addition to the receiver, he got the AC power supply to replace the A and B batteries. It also came with a schematic diagram, which is shown here:
From the way this schematic is drawn, it looks like whoever drew it copied it from the actual constructed radio, rather than vice versa. This circuit is very similar to the 1950 Boys’ Life set, but there are a few variations. For example, the component layout is different (it’s basically a mirror image of the BL set). It also has plug-in coils rather than the fixed coil in the BL set. (Jon believes the coils are for the broadcast band and about 5-6 MHz.)
Unlike the Handbook version, this set uses a transformer to couple the two stages, just like the BL version. It does have a few minor differences, however. For example, the BL version uses only two of the terminals on the regeneration control. Jon’s version uses all three. Both circuits have the cathodes of the tube hooked to one filament pin. However, the BL version calls for the connection to be made to pin 8, whereas Jon’s version calls for the connection to be made to pin 7. There’s no electrical difference, but the use of the different pin indicates that the builder probably wasn’t using the BL schematic. Jon’s version also has another variable capacitor, presumably for fine tuning.
As you can see in the schematic, the hand-drawn diagram of Jon’s set is entitled, “Dan Drummond’s Set.” Despite a little bit of sleuthing, neither of us was able to figure out who Dan Drummond was.
The 1939 Information Age
Seventy five years ago, the March 1939 issue of Popular Mechanics shows the latest in mobile navigation technology.
The robotic “Infomat” provided information on the location of prominent places in a city. The user merely lifted the receiver and raised one of up to 500 levers with the name of the place. The user would then listen to the voice of the machine provide the information.
1934 Scout’s One Tube Radio
Shown here in the September 1934 issue of Radio News is Scout Robert Crockett of Troop 3 of the BSA Siwanoy Council, Pelham, New York. He is shown operating the receiver that he designed and built, based upon a design in an earlier issue of the magazine. His circuit uses a single type 30 tube and a handful of other components, all of which can be obtained fairly easily today. For ideas on sourcing the components, you can visit my page describing another 1930’s era receiver or my crystal set parts page. Full construction details are included in the 1934 article.
The author of the article was Robert’s “Scout Radio Examiner,” which presumably means Radio Merit Badge Counselor. According to this 1935 newspaper, Robert did go on to complete the Radio Merit Badge. The magazine article concludes by pointing out that as his daily Good Turn, the Scout would be glad to help anyone building the set with their problems, and that such letters can be sent in care of the magazine. The article notes that he had logged over 300 shortwave stations with the set.
According to the National Eagle Scout Association database, Mr. Crockett became an Eagle Scout on February 24, 1937. And according to this newspaper and this one, he was serving in the military in 1943 and 1944. According to his sister’s 1943 obituary, his service was as an Ensign in the U.S. Naval Reserve.
Portable Gas Refrigerator
Portable Gas Refrigerator
On various outdoor and “prepper” forums, one common question is the availability of refrigeration in the absence of electric power. In most cases, the best option is to do as our ancestors did before the early 1900’s and simply live without this convenience. But in some cases (such as those with medicines that require refrigeration), a reliable form of refrigeration is needed.
Until recently, there were only three options, each with shortcomings. The first was to procure a generator to power a traditional home refrigerator. This is a poor solution, because the home refrigerator has an electric motor and thus requires a large generator (or very large inverter) and enough fuel to run it.
Another option is a “12 volt cooler” such as the ones shown here:
One of these can be a relatively good solution in many cases. While they don’t work as well as the big refrigerator at home, they are often adequate for the task. Compared to a home refrigerator, they require much less current. However, they draw enough current that they can’t simply be left unattended for long periods of time. The battery needs to be charged quite often, which entails having fuel to do so, or perhaps a relatively large solar charger.
The best solution has been the “3-way” Refrigerator. This type of refrigerator is commonly used in RV’s, and runs on 120 volts, 12 volts, or propane gas. They typically use about 1/2 pound of gas per day, meaning that a 20 pound tank will last about 40 days. In other words, storing fuel for long-term use is a definite possibility. Here are some examples:
The disadvantage of this type of refrigerator is that it is not portable. It is designed to be mounted permanently and, at a minimum, you would need to construct a cabinet to house it.
This objection has now been solved, however, with the following portable 3-way refrigerators:
Like the other 3-way refrigerators, these will operate on either gas, 120 volts, or 12 volts. But they are designed for portable use, and come with the hardware to hook it up to a portable LP tank, the type available everywhere. For those who absolutely need refrigeration “off the grid,” this is a very viable option.
Storm Warnings By Wireless: 1914
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.
1924: A Radio Summer
In 1924, it was going to be a radio summer. This picture, from the May 1924 issue of Radio Age, shows two motor tourists who made the radio receiver an important part of their roadside camp. The magazine points out that such portable sets are easily made or purchased.
Brothers Melvin and Peter Myhre, Casualties of WW1
Melvin and Peter Myhre
Periodically, I use this page to remember some of the forgotten young American men who gave their lives in the First World War. Private Melvin Myhre of Fosston, Minnesota, was killed in action on October 10, 1918, about a month before the armistice. He is buried in France with over 14,000 of his comarades at the at Meuse-Argonne American Cemetery. He served in the U.S. Army, 327th Infantry Regiment, 82nd Division.
The Meuse-Argonne Offensive, in which Private Myhre gave his life, was the largest battle in U.S. history, and involved 1.2 million American soldiers. Over 26,000, including Private Myhre, were killed. In addition, some 70,000 French soldiers were killed, as were between 90,000 and 120,000 Germans.
His brother, Private Peter Myhre, also died in France on November 1, 1918, only ten days before the Armistice. He is buried at the St. Mihiel American Cemetery, along with over 4000 American soldiers.
According to Polk County Minnesota in the World War, Melvin and Peter were sons of Mr. and Mrs. Mikkel Myhre. Melvin entered service on March 2, 1918. Peter entered the service on July 26 and was taken sick about October 15 behind the front near Clermont Woods. He died at the Mesves hospital.
Their pictures shown here, are from the three-volume Soldiers of the Great War (Vol. 2, p. 99).
Nurses at U.S. Army Hospital, Mesves, France. (Nat’l Institutes of Health photo).
1964: The Last of the One Tube Radios?
Fifty years ago, the vacuum tube was still king, although its days were coming to an end. The September 1964 issue of Electronics Illustrated contained several construction projects, most of which relied on tubes. The Micron Electron Tube Company advertised a few dozen common tubes for 37 cents each. Other tubes were available at reasonable prices. For example, hams looking for finals for their transmitter could find an 807 for a dollar, or a 6146 for $2.45.
Some transistor gear was starting to show up, but it was pricey. E.F. Johnson advertised two transistorized CB handheld radios. The 100 milliwatt version sold for $109.50, and the 1.5 watt version commanded $129.50.
The construction projects included a CB preamplifier and calibrator for tuning 11 meters on a shortwave receiver. This article bears the byline of prolific author Len Buckwalter
For hams, the magazine featured a transmitter for 80 and 40 meters, which the article claimed could be built for five dollars. It used a 6V6GT and a 5U4G rectifier, both of which were on the 37 cent list.
And, as fitting for this site, the magazine featured the one-tube AM radio shown above, which used a 6AL11 dual pentode. Half the tube was used as a regenerative detector, the other half being an audio amp which would deliver a full two watts to the speaker. According to the text, the circuit “has only one tube but in terms of performance it’s a mighty far cry from that one-tube job of 30 or more years ago,” with sensitivity and tone that will surprise you.
What’s intriguing about this project is that it’s probably one of the last times that an electronics magazine would feature an article on how to build a standard AM radio that appears to be designed for everyday use. The 1964 Radio Shack catalog included an “all American five” AM radio for only $7.95, so even the most frugal builder would probably save very little by building his own.
Len Buckwalter seems to still be around. He is listed as a founder of publisher avionics.com of Leesburg, Virginia. It appears that he let his ham license lapse at some point, but he appears to be currently licensed as KK4GJX, which is listed as being issued in 2012. According to a biography, he graduated from college in 1951, which would mean that he’s now about 85 years old.
If you’re interested in building this radio, most of the parts should be readily obtainable. Antique Electronics Supply is probably the best supplier for the power transformer. They don’t carry the tube, but it can be found on eBay. On another post, I have links to suppliers where you can find most of the other parts.
References
Len Buckwalter at semiconductormuseum.com