Radio Caroline went on the air forty nine years ago this weekend, broadcasting from the MV Caroline off the coast of England. Why is this important? Before off shore broadcasting was attempted, in Europe the only radio stations (and TV) were government owned. As such, they had a monopoly over the air waves and were very restrictive on which groups or types of music they allowed to be broadcast. Many of the so called “British Invasion” groups like The Beatles, Rolling Stones, The Who, The Kinks, etc got their first airplay on offshore radio stations like Radio Caroline or Radio London.
This video “Radio Caroline – A day in the life,” shows what it was like to be an offshore broadcaster:
By the haircuts and music, that appears to be sometime in the eighties.
Radio London was the one of the other well known offshore radio ships.
I am sure that there are other tribute sites with lots of technical information on how they broadcast. Much of offshore radio was outlawed in the late 1960′s by several European countries. Radio London signed off August 14, 1967. Radio Caroline continued on in various iterations until about 1991 or so.
WBCQ is airing a radio ships special on Sunday March 31, 2013, 5,110 KHz starting at 6 pm eastern daylight time (2200 UTC).
I read through this article about the ongoing restoration work of an RCA SSB T-3 transmitter and found it interesting. The RCA T-3 transmitter is a 20 KW SSB/ISB HF (2-28 MHz) unit designed for point to point telephony service. Because SSB requires class A or AB low distortion amplifiers, this is a large unit, even for its age and power levels.
From the looks of the before pictures, this transmitter was in sorry shape.
Here is a brief video of transmitter start up:
These units were designed to be switched on and run at 100% duty cycle from most of their operating lives. That is some heavy iron there. This particular unit was made in 1959. More here and video part 2:
Anyway, before geosynchronous satellites, HF point to point transmitters were used to make long distance phone call connections and send data and pictures back and forth over long distances. Out in Hicksville, Long Island, Press Wireless ran a data and fax system that used HF for long haul data transmission. Much of the WWII reporting from Europe and the Pacific Theaters was carried over this system.
Text would be printed out on a mechanical teletype machine at something like 60 words per minute, which was considered fast for the time:
Tuning across the band, one can often hear Radio Teletype (RTTY or RATT) which uses a 5 bit baudot code, 170 Hz shift with 2125 HZ representing a Mark or 1 bit and 2295 Hz representing a Space or 0 bit, which is bit different from the Bell 103 modem specifications. This is what it sounds like at 75 Baud:
So slow you can almost copy that by hand.
The RCA H (SSB T-3) unit above was independent side band (ISB), which means that either side band or both could be modulated independently of the other, thus two channels of information could be transmitted. SSB bandwidth is about 2.7 KHz, which is good for telephone grade audio or low speed data.
I sort of wish I was living in California again, I’d lend a hand.
I found this youtube video about Pittsburgh, Pennsylvania radio stations:
That’s cool and all that, but it brings up the question about the K/W calls which were misplaced during the early days of broadcasting. Originally, call letters were assigned to ships and coastal radio stations in the following way:
Three letter call signs were for coastal (land) stations. K letter calls were for shore stations in the west and W letter calls were for shore stations east. Ships were assigned four letter calls, W calls signs issued to ships homeported on the west coast and K calls for ships homeported on the east coast. There was a period of time that a few K call letters were issued to east coast broadcasting stations, no one is quite sure why. Prior to 1923, the K/W boundary was not the Mississippi River, but the eastern border of the states of Montana, Wyoming, Colorado and New Mexico. Thus, there are many more misplaced W call signs than K call signs.
Of course, KDKA and KQV come to mind. Philadelphia has KYW. What other misplaced call signs are there, e.g. W’s west of the Mississippi and K’s to the east? Of course, one can google it and get an answer, however there is one that is pretty obscure.
Reflecting the state of the economy in Detroit, WDTW went silent on January 1st. Less than two weeks later, the towers come down:
Thanks, Chris R for the video link.
The license has been donated by Clear Channel to MMTC (Minority Media and Telecommunications Council), but not the land or towers. It remains to be seen whether the station will return to the air, however, given the costs involved and the economic conditions in Detroit, that is unlikely.
The station signed on in 1946, moving to 1310 KHz with full time operation in 1948. Back in the day, it was a flame throwing top 40 station and is purported to be the source of the “Paul is dead” rumors that surrounded the Beatles in the late 60′s. Much more history at Keener13.com.
Take pictures of your favorite AM stations now because tomorrow, they and all their history may be gone.
I found a 1981 Continental Electronics equipment catalog at an old transmitter site. These finds are great if one is interested in history and looking at the way things used to be done. This particular transmitter is a 2,000 KW (2,000,000 watt) medium wave unit:
Continental Electronics D323C, Circa 1981
I believe most units like this were destined for use by government broadcasters either the middle east or western Europe. I know there were several 1,000 KW medium wave stations in West Germany at one time. The Continental transmitter is basically two 1,000 KW units (323C) combined. They used a modified version of Doherty modulation, that is called “Screen and Impedance,” which accurately describes how it works. More information from the Continental Catalog can be found here: Continental D323C. The tubes (or valves depending where you are located) used in the D323C were 4CW25000A tetrodes as modulators and IPA the final was a pair of X2159, which is an impressive tube.
EIMAC X-2159 water cooled power tetrode
The tube sat anode up. The filament, grid and screen connections are underneath. Cooling water was pumped through the two connections on the top at about 130 gallons per minute depending on the plate dissipation. With a 30° C rise, that equals about 96,000 BTU per minute. The D323C had a dissipation of 400,000 watts for the carrier tube and 240,000 watts for the peak tube (640 KW total) under 100% modulation. That equals about 2 million BTU per hour. Notice the lifting hook, this tube weight in at 175 pounds. Tube date sheet here.
Continental no longer makes medium wave transmitters, their closest high powered broadcast product now is the 418/419 and 420 HF (shortwave) transmitters. The 420D does a wimpy 500 KW using a solid state modulator section.
I remember in the early 1990′s when I was at the Harris plant in Quincy, they were working on a 1,000 KW solid state DX series AM transmitter for Saudi Arabia. It had to be liquid cooled, which added another layer of complexity to an already complex system.
I don’t know if there is much call for 2 MW medium wave transmitters anymore as there are more efficient ways to reach remote populations and I can’t even imagine what the electric bill would be like.
This is a trip down memory lane. Someone has taken the time to preserve and document Radio Shack, its founding, history and all of the catalogs printed from 1939 to 2005. The website archive is Radio Shack Catalogs.
I remember reading these very catalogs cover to cover, when they came out in the mid 1970′s. At that time, this stuff looked expensive and in relative dollar terms compared to today, it was. We had one of these computers in our “Math Lab” in 9th grade:
Radio Shack catalog, TRS-80
In fact, when I found one of these computers stashed away in the corner of a transmitter site, I had a flash back of Mr. B scowling as yet another student made a mistake plotting x/y coordinates on the backboard.
Historic VLF (Very Low Frequency) station SAQ Grimeton will be on the air to celebrate United Nations Day on October 24th at 10:30 UTC (6:30am EST) on 17.2 KHz CW. This station was established in 1922 and is the last radio station in the world employing an Alexandersontransmitter. More information at their website.
This is a great 2011 video of a tour of the station, including transmitter start up:
It is great to see that old gear come to life and transmit a message. The electric motor/generator sounds like a jet engine spooling up.
Before solid state or even hollow state rectifiers, motor generators were used to create the DC voltages needed to transmit high power radio signals. This method was used by high powered Naval shore stations through WWII and beyond.
By way of comparison, an average CW operator can send and receive Morse code at about 20-25 words per minute. A good CW operator, about 30 words per minute and a Russian CW operator, somewhere near 50 words per minute. This was the main wireless data transmission method until Radio Teletype came into widespread use in the 1950s. Here is a comparison of data speeds through the years:
75 Baud/100 WPM
100 Baud/133 WPM
Switched 56 (Switchway)
The Morse Code (CW) and Radio Teletype data rates are not a direct comparison, as most radio teletype systems use 5 bit Baudot code instead of 8 bit ASCII. Morse code varied in length from one to five bits, if one thinks of each dot or dash as a data bit. Back in the day, before “Netcentric” mindset, we used mainly radio teletype to communicate from ship to shore. A premium was placed on brief, concise, operational communications. Everything else was sent via the mail.
It is quite amazing to see the increase in data speed, which directly correlates to information exchanged (or the ability to exchange information) in the last 90 years.
To receive SAQ Grimeton, one needs a VLF receiver or converter capable of receiving 17.2 KHz and a very quite receiver location. There are many VLF hobbyists that will be tuning in.
I have covered numbers stations before. This is a radio program from BBC Radio 4 first broadcast in 2005. It is an interesting look what is known and not known about various numbers stations around the world.
Somebody working to preserve a record of past work:
Some of these have familiar looking cabinets and tube arrangements. They all look like classics to me and it is good that they are being saved. I noticed at the end of the video there is a Harris MW10A. As for the RCA Ampliphase transmitters; I maintained a BTA5J in Harrisburg PA on 580 KHz. It was reliable enough, but I could never keep it sounding good for more than a couple of days.
Every year on July 12, the Maritime Radio Historical Society (MRHS) commemorates the end of commercial Morse code use in the US. I have a soft spot for Maritime Radio, as that is where I began my radio career. For nearly one hundred years, ship board radio operators, “sparks” communicated with land based stations using Morse keys and relatively simple low powered transmitters. The skills gained by a good CW operator could only be attained by time spent sitting watch.
In order to remember those who did that service, several former coastal radio stations fire up transmitters once a year on July 12th. This year’s frequencies are:
Festivities begin at 8pm eastern time. In addition to those frequencies, K6KPH will be on the air on 3550, 7050 14050 and 21050 KHz.
KPH, KFS and KSM are all operated from Point Reyes National Park, transmitters are on Bolinas. This is a video of the transmitter gallery in Bolinas:
Other video of Bolinas Facility:
Former KPH receiver site, Point Reyes National Park:
This is a former coastal station site in Cape Cod, which was torn down:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
~1st amendment to the United States Constitution
Any society that would give up a little liberty to gain a little security will deserve neither and lose both.
The individual has always had to struggle to keep from being overwhelmed by the tribe. To be your own man is hard business. If you try it, you will be lonely often, and sometimes frightened. But no price is too high to pay for the privilege of owning yourself.
Everyone has the right to freedom of opinion and expression; this right includes the freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers
~Universal Declaration Of Human Rights, Article 19
...radio was discovered, and not invented, and that these frequencies and principles were always in existence long before man was aware of them. Therefore, no one owns them. They are there as free as sunlight, which is a higher frequency form of the same energy.