WHAT’S THE FREQUENCY?
Last month we had some questions about the “VHF” radio we featured in the opener of Cecilia Kiely’s article, “Titans of Technology.” We photographed the radio while aboard the lightship Swiftsure, so we felt fairly confident that it was used for ship-to-ship or ship-to-shore
communications. But once we had seeded doubt in our original thought (translation: once Cecilia asked if we were sure the photo was of a VHF), we knew we needed to sort out the origins of this relic. We reached out to Northwest Seaport, the historical society overseeing the lightship’s restoration and they, in turn, found Philip Cole, a local maritime archaeologist, (next life career goals) who sent us the following summary on what he found out about the radio:
This radio was made in Seattle by the Northern Radio Company. HF bands were in common use during the 20’s through the 40’s. They were popular due to the long range that you could realize (well past the horizon, at least at night), but they suffered from atmospheric interference (including lightning strikes, sunspots, etc.), low quality audio, and had diminished range during the daylight hours.
In 1947, the Atlantic City Radio Conference proposed 156.80MHz as the universal hailing frequency, and that was the beginning of the standardization of the marine VHF band plan. In 1948, the USCG traded some spectrum in order to acquire what would become Ch 2124 and 81-84. By 1959, the marine VHF band plan we recognize today was adopted, stretching from 156.05 MHz to 162.00 MHz, inclusive.
The vintage of this radio appears to be mid to late 1950’s. It has 5 channels which you would set through the use of the yellow, red, orange, blue and green controls to the left and right of the center selector knob. That center knob would select the channel you had dialed in. One set of adjustments would be course, the other fine tuning.
So, looking at the photos you sent over, it looks like this radio ran from around 550 kHz up to 45 mHz. This puts its range solidly in the HF band, and up to the bottom of the VHF band. The frequency card shows that it was probably used around the 20-30 mHz frequency range, which is around 10-11 meter wavelength. Coincidentally, CB radio is in the 11 meter band. So, while this radio appears to be able to operate up in the very bottom of the VHF band, it was likely operated in the HF bands. So, while this radio appears to be able to operate up in the very bottom of the VHF band, it was likely operated in the HF bands.
Radio frequencies are clumped into bands that are referred to in three ways. The “common name”, the Frequency range, or the wavelength. Also of note, until the 1950’s, radio frequencies were listed
in cycles, megacycles and kilocycles, rather than Hertz. Functionally, they are identical, it’s just different nomenclature.
At the bottom is ULF, with frequencies of between 300 Hz and 3 kHz. These frequencies are too low for us to make use of, but the earth transmits them as a result of magnetosphere fluctuations.
Moving up, you get VLF, with frequencies between 3 and 300 kHz. These have a wavelength of between 10 to 100 kilometers. This long wavelength allows them to pass through water, and is the only way to communicate with submerged submarines. The very low bandwidth limits transmissions to small code or text strings only, as there is not enough bandwidth available to transmit voice carriers.
Moving up again, you get LF, or Low Frequency. These frequencies are between 30 and 300 khz, and wavelengths of between 10 to 1 kilometer. These frequencies can propagate very far, and can carry very low quality audio. They require vertical antenna at least 1/8 the wavelength to operate properly, or a phased-array system to create a “virtual” antenna.
Next step up is MF, or Medium frequency. These bands fall between 300kHz and 3 mHz, with wavelengths between 100 to 1000 meters. This is the band at which commercial AM radio broadcasts take place, as well as long-distance marine ship-to-shore radio communications.
Next up is HF, or High Frequency. This is the most common civilian long-range band, covering wavelengths from 3 to 30 mHz, with wavelengths between 10 and 100 meters. This is the most common region for amateur radio operators to work, due to the good balance between antenna size requirements, long propagation distances, and reasonable bandwidth for audio.
Next is VHF, or Very High Frequency. This is also a very common civilian band which includes marine VHF, 2-meter ham radio bands, FM radio broadcasts, television broadcasting, police / aid / fire radios, etc. This band has relatively low range; line of sight only, but carries crisp, clear audio, and does not require a large antenna.
Now we come to UHF, or Ultra High Frequency. This is the next higher band, and is home to another ham band, FRS and GMRS radios, more emergency services, wifi, bluetooth, and other similar short-range devices.
As we move up the bands, the range continues to decrease, while the amount of data that can be transmitted continues to go up, until we end up in the microwave, and finally xray regions of the EM spectrum.
Unfortunately, little information remains available about the products that Northern Radio Company made, and their radio sets
are very rare. At some point, I would like to send this radio, and our spare tube assortment, up to our friends with the Snohomish Ham radio club; they have expressed an interest in the past about refurbishing it and getting it back on the air.
ONE SMALL STEP
Dear Sue, A very important safety article (“One Small Step” September 2018) and an interesting read. The one thing I never saw mentioned in the article was a life vest. My husband and I never get on the swim platform or into our dingy or kayak without one. And we always wear them when we dock, myself who is getting on to the dock and my husband, even though he is at the helm. Never know if he may need to save me. We do the same while anchoring, with me at the helm and he on the bow. We have had so many boats blasting pass us when we are getting into our dingy and while anchoring. We boat in the San Juan Islands and it can get crazy with boaters and we are in cold water year-around. Thanks for the great articles. Nora Elliott
Dear Sue, Very much enjoyed the article, “One Small Step.” Thanks for sharing it. And as a (what I thought), was a “seasoned mariner” myself, I can also add that there is a “compounding” or “stacking” of seemingly benign decisions that can roll up quickly and cause significant safety issues, injury, or worse. Something as simple as looking back and saying “Mmm, those kids stacked all their dive gear on the scuppers, well we don’t have far to go … and it’s pretty calm….” Then compound that with being a little overweight; low in the water, and a “where did that 4 foot chop come from?” add a little “wow, the bilge is running nonstop” and all of sudden you’ve got some serious safety issues onboard. And as you’re shouting directions, turning down sea, trying to mitigate the emergency, there’s a flash of “how did you allow this to happen”?.
So I’ve learned over the years and looking back on all of my own bad experiences, there was always that little voice of reason and common sense. That day it was shut out of the decision making process. And in all cases, excitement, maybe a little laziness, pressure from the Wife or Kids or Clients made me deaf to that little voice. In over 30 years of Florida and Bahamas fishing and cruising (with a 100 Ton Masters) there are too many “man that could of been bad” stories to tell here. But in analyzing all of those, the one constant was that little voice calling for prudence. He just got shouted down that day and at that moment. Thanks again for sharing.
Brad E. Shaffer Top Shelf Marine Products
A breakdown of U.S. amateur radio bands.