Suppression of ideas

I found this video called Empire of Noise about broadcast radio jamming. It seems to be about ten years old and is a post-cold War documentary about the jamming of radio signals by the USSR, Warsaw Pact counties, and China.  It is an interesting look into the extent and expense that governments will go to suppress counter thoughts and ideas.

The video is quite long, and there are stretches of jamming noise that can be annoying, but perhaps that is the point.  It is worth the time if interested in history and radio broadcasting.  You know what they say about history; those that do not understand history are destined to repeat it.

A few of the highlights:

  • The former Soviet Union had the most extensive jamming network of anyone on Earth.  There were groundwave jamming centers in eighty-one Soviet cities which consisted of approximately 10-15 transmitters each in the 5 KW covering the medium and shortwave frequencies.
  • Each groundwave jamming station consisted of a transmitter site and a receiver/control site.  The receiver site possessed lists of frequencies to monitor, when objectionable material was heard, the jamming transmitters were turned on.
  • There was a skywave jamming network consisting of 13 jamming stations with 10 or more 100-200 KW transmitters in each.  There were some transmitters in the 1,000 KW power range.  These were located in Krasnodar, Lvov, Nikolaev, Yerevan, Alma-Ata, Grigoriopol, Sovieck, Novosibrisk, Tashkent, Khanbarovsk, Servdlosk and Moscow (some of these names may have changed).  These operated in a similar fashion to the groundwave jammers.
  • After the sign-off of government stations, Soviet jammers sent a blanketing signal on the IF frequency (most likely 455 KHz) of receivers to effectively block them from receiving any station while USSR government stations were off the air.
  • Baltic states had 11 jamming stations with approximately 140 transmitters
  • Ukraine had approximately 300 Jamming transmitters.
  • Warsaw Pact countries had extensive medium-frequency jamming networks.
  • It is estimated it takes about 20 times the transmitted power to jam any one signal.

The entire jamming network was hugely expensive to equip and operate, costing several tens of millions of dollars per year.

It is interesting that the US position in all of this was:

Everyone has the right to seek, receive and impart information through any media and regardless of frontiers.   Jamming of radio broadcasts is condemned as the denial of the right of persons to be fully informed concerning news, opinions and ideas.

Sounds perfectly reasonable.  The free exchange of ideas and information over the internet is something that should be guarded carefully and should not be restricted or censored.  Perhaps somebody should inform Congress.

Restoration work on an RCA transmitter

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 the transmitter start-up:

These units were designed to be switched on and run at 100% duty cycle for 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 a 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 sideband (ISB), which means that either sideband 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.

Radio Shack catalog archive

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-1970s.  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
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 flashback of Mr. B scowling as yet another student made a mistake plotting x/y coordinates on the backboard.

Tandy TRS-80 Model 4D computer
Tandy TRS-80 Model 4D computer

Ahhh, memories.  Enjoy!

SAQ Grimeton

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 (6:30 am EST) on 17.2 KHz CW.  This station was established in 1922 and is the last radio station in the world employing an Alexanderson transmitter.  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:

CW20 WPM8.3
CW35 WPM14.58
Radio Teletype*75 Baud/100 WPM41.6
Radio Teletype*100 Baud/133 WPM55.41
Async data300 Baud300
Async data1200 Baud1200
Async data9600 Baud9600
Switched 56 (Switchway)56KB56,000
DS0 (POTS)64KB64,000
ISDN64KB X2128,000
DS1 (T-1)1.54 MB1,540,000
DS3 (T-3)45 MB45,000,000

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 the “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 quiet receiver location.  There are many VLF hobbyists that will be tuning in.