WHAT’S THE FREQUENCY?

Passage Maker - - Crosstalk -

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.

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