Denmark's Oldest Radio Station

If you google VYL eventually you will find the 1973 United States Hydrographic Office publication Radio Navigational Aids (Atlantic and Mediterranean Area) ... it lists off: VYL Lightship, Denmark 55° 24' 25" N. 7° 33' 38" E. continuous and it's range is listed at 50 miles, It's frequency 289.6 kc/s , A2

Characteristic	Minutes
(Interrupted by a long dash)	1
Silent	1
2 repetitions above signal	_  4__
Period	6

The List of Lights, Radio Aids, and Fog Signals from 1963 gives somewhat more color with the additional notation: "Red hull, white cross on sides, "VYL" in horizontal stroke of cross, 2 masts." But then a 1915 copy of List of Radio Stations of the World lists OXC as the call letters and Vyl, Denmark as the location. Also a 1935 copy of the Shortwave Listener specifically lists the call letters as OUY on both 1.818 and 1.622 Mc. But they do list an OXC on 1.819 Mc in Ringsted, Denmark. This long history and change of call signs poses a problem, compounded by the fact that I cannot read Danish.

With some luck I found both the old and new URL of a museum dedicated to this radio station www.oxa.forsvaret.dk and www.oza.dk. (The former is offline but thanks to the Wayback Machine, we have a copy from 2013.) So lets get back to the United States Hydrographic Office. IN 1935 they list all the radio navigation beacons in Denmark: OUX, OUZ, OUY, OUB, OUT, OUK, OUR, OUE and OUU. I think it's safe from this format to assume the call sign is not VYL. Sources refer to Vyl Station which is the lightship, not the radio station.

The first marine navigational radio in Denmark was installed on the lightship station Vyl in 1899 and also at the same time on the lighthouse at Blavandshuk, so that observations from Vyl could be received ashore. (Vyl is not the ship but the location.) Various ships held that position including Motorfyrskibet Nr. I. This was ship-to-shore radio, not exactly a broadcast but radio nonetheless. The 1939 Edition of US Hydrographic Office publication Radio Navigational Aids makes clear that this is OUY, thus disentangling the two call signs.

On September 1st 1908, the War Department signed on OXA, Denmark's first real coastal radio station.  It was based in a wooden house at Frederiksholm at the Holmen Naval Station. Later came OXB Blavand Radio in 1914, OXZ Lyngby Radio in 1917, OXP Skagen Radio in 1945 and OYE Ronne Radio in the 1950s. The book The Bow and the Spark (Buen og gnisten) by Lise Bock describes that early scene [Roughly translated from Danish]:

"The Danish Navy had been broadcasting since the first attempt with spark transmitters back in 1898. One of the first permanent installations was installed in the Blåvandshuk lighthouse and on the Vyl lighthouse ship on the west coast of Jutland in 1901. Equipment came from the German AEG developed by Arco and Slaby. Afterward, the Navy destroyed a some warships, and in 1905 they set up a radio station on the islet in Kolmenhavn where the Danish fleet was based... The station was then referred to as Denmark's first coastal radio station..."

On that website is a picture of one of their early crystal sets: Wireless Specialty Apparatus Co. type IP-76. In 1910-1914 the most widely used type in the US Navy. It was used at OXA during World War I and up to the mid 1920s. It's labeled Amerikansk Krystalmodtager which means American Crystal Receiver. They also used equipment from Marconi, Slaby Arco, Skovmand & Pedersen, and Telefunken. OXP was decommissioned in 1993, and OXB in 1996 both to be controlled remotely by Lyngby Radio OXZ. Likewise, OXA served the Royal Danish Navy and the merchant fleet until the late 1940s and then it's building sat disused for half a century. Today, all remaining maritime emergency radio stations in Denmark are controlled by Lyngby Radio.

In 1991 the Danish Navy decided to relocation operations away from Holmen and to close the naval station. The modest wooden building now seemed doomed to demolition to make room for new development. In 2000, a small group of people interested in radio history decided to restore and relocate the station. With the permission and support of the Defense Department, OXA moved from Frederiksholm to Nyholm. The project was completed in October 2003. The station then reopened as a museum of Denmark's oldest coastal radio station Kobenhavn Radio OXA. [LINK]

PBI RNAV

"In general, the FAA chooses names that are noncontroversial," said FAA spokeswoman Laura Brown. I think that's a good policy in general for a federal agency. So it comes as no surprise to anyone who has been watching the news over the last few weeks that a Donald Trump-themed navigation point would need to be re-named.

Above is a RNAV map for PBI airport. While not all of those navigation points are Trump-themed, several of them are: DONLD, TRMMP, UFIRD, BRTHR, IVNKA, and AMNDA. These are the navigation points for pal Beach International Airport in Palm Beach Florida. Trump bought property there, built an estate and a golf club back in 1985. But he has fought with the airport non-stop since then, even filing a $100 million lawsuit against the county and accusing them of routing flights over his property as an act of retaliation. The spats have made him popular with no one in Palm Beach.

Every Airport has a number of RNAV beacons and navigation points to help guide planes in safely to the runway. At PBI their ATIS (Automatic Terminal Information Service) is on 123.75 Mhz, APP CON 9Approach Control) is on 128.3 and 317.4 Mhz, GND CON (Ground Control) on 121.9 and 257.8 Mhz and CLNC DEL (Clearance Delivery) on 121.6 and 284.6 Mhz. Sometimes that's abbreviated as C/D.

If you look at some other US airports, you'll see a pattern with the frequency allocations. From 108-118 MHz is where you'll hear the beeps of navaids (aeronautical navigation aids). From 118-137 MHz is the actual aeronautical band, where the tower to aircraft chatter ocurrs. But 128.825-132 MHz is assigned to commercial aviation and is in heavy use as well.

The coordinate names are used for a type of instrument area navigation, called RNAV. The points entered into the computer should be five letters long and must be unique to that airport. Ideally, they relate to the area where the coordinates are located. Both DONLD and TRMMP are pretty self evident. UFIRD is "You're Fired" his catch phrase from his crappy TV show. BRTHER is probably "Birther" since Trump is a deranged bigot. IVNKA is Ivanka, his daughter. The tricky one is AMNDA, which if you have paid attention to his TV program, you might know that Amanda is both his and Ivanka's personal secretary.

The other navigation points: CRYER, UTLEY, FINNS, PYRUT, AHABB and BAYBE seem unrelated.

NADIN

NADIN is an acronym that stands for National Airspace Data Interchange Network. It was used by the airlines to input flight plans into the National Airspace System (NAS). These flight plans are routed to the relevant air traffic control sites. But I first heard of NADIN from one if it's failures. The Availability Digest had a short write up on a multi-hour outage:

"Without a filed flight plan, a commercial airliner can’t fly. This was painfully demonstrated on Thursday, November 19, 2009, when the FAA’s1 National Airspace Data Interchange Network (NADIN) failed at about 5:30 AM Eastern Time and was down for three hours..." 

The system processed an average of 1.5 million messages per day, but by 2002 was already obsolete and was beginning to break down due to technical issues. In August of 2008 a single corrupt file header took out the system for 90 minutes. In 2009 the head-end in Atlanta crashed three times. Other government agencies were concerned the aging system wasn't hardened against "terrorist cyber-attacks." Eweek published the following stinging comment

"International intelligence analytical firm Stratfor reported a similar system outage back in 2000. Another was reported in June 2007 in addition to the Aug. 21 and Aug. 26 crashes. Those are the ones we know about; we don't know how many others were never made public information."

NADIN was an old-school mainframe based telecommunications network designed to aggregate and distribute air traffic  data. First proposed in 1975, the system went live in 1989 on a pair of Phillips DS714 mainframes.  It was intended to integrate the Aeronautical Fixed Telecommunications Network (AFTN) and their "Service B Network" because those were " near saturation." Remember this isn't just radio communications this is also the filed flight plans!

 Management of NADIN was awarded on a non-bid basis [source] to ASQ, Inc in 2002. This awarded contract included both NADIN1, and it's packet switching network (NADIN2). But what really needed to happen was a full replacement. In 2009 that happened. Lockheed Martin engineers built a more robust and redundant virtualized system on a series of  Stratus FTserver 6400s. Whew.

Radio Navigation

In several previous posts about radio navigation I've mentioned beacons, and that airplanes use them as points of reference. In one detailed post about Amelia Earhart I even roughly described the "boxing" maneuver aircraft use to orient their course.  But the particulars of this technique eluded me. Recently I found a simple 8 page student document from 1942 that comes complete with diagrams that describe four different ways to do so with a simple RDF (Radio Direction Finder) system. Later ADF (Automatic Direction Finder) systems had motorized antennas.

The first technique is called "Loop Orientation."  In using a loop antenna the loop "faces" bi-directionally. So after reaching a proper airspeed the first instruction is to set the loop indicator parallel to lateral axis of the airplane. Then the airplane is gently banked to find the first null. By holding this position, the azimuth dial can now be set. After holding that course the loop can now be rotated to find a second null. the angular difference between the 1st and second nulls determines the distance from the radio transmitter using the following formula:

Ground speed x time between nulls = distance out  / angular difference between the nulls.  For example that could be 130 mph x 3 minutes / 45 degrees. That's 8.6 miles. The use of "angular difference" is merely triangulating a location.  The document goes on to describe Radio Boxing, which further orients the path starting with the above calculations.  You can download this document at the link below

HERE

GEE

In 1935, the British began developing GEE. It was developed by Robert Watson-Watt at the Air Ministry and introduced by the Royal Air Force (RAF). The idea of hyperbolic navigation known in the 1930s, but the first trials didn't happen until 1941.  Starting in 1942 these radio signals were used to guide the WWII carpet bombing of Germany. Germany began it's attempts at jamming the GEE system in 1943 but these were largely ineffectual. So what's hyperbolic navigation?

Hyperbolic navigation is a class of radio navigation systems based which determines position based on the  microsecond difference in timing between the reception of two signals.  While you need three points to triangulate a location in 3 dimensional space, the surface of the earth is effectively a 2 dimensional plane. But hyperbolic navigation requires the plotting all of the potential locations of the receiver for the measured delay. This produces a series of hyperbolic lines (a parabola) on a chart. Taking multiple measurements narrowed this down. GEE was the first such system. 

Imagine two terrestrial radio stations located 186 miles apart. At light speed (the speed radio signals travel) their signals can reach each other in exactly 1 millisecond. So Station A emits a pulse, this pulse is received at Station B and it triggers the transmission of another pulse 1 ms later. But a ship in motion at a third location will receive these at odd intervals because of the distance from each station. But knowing their interval, they can plot a circle around each transmitter, and at their points of intersection (parabolas) they can determine their possible location down to a set of two. Then they had to use traditional navigation to pick which of the two. The source of that problem... is time.

In order to measure the exact time it took for a signals to reach the receiver, the receiver must know the exact time the signal was transmitted. But reliable millisecond time-keeping wasn't possible in the 1930s. The most common clock to use with GEE was a crystal oscillator. But that drifts about 1 to 2 seconds in a month. That may sound trivial, but 2 seconds is a distance of 372 miles... that's the difference between Bermuda and the Carolina coast. That's a big deal. (This problem wasn't overcome until the advent of atomic clocks in the 1960s.) So instead of absolute time, differential time was used. Your distance from the two transmitters was unknown, but the difference between their signals was measurable on an oscillograph and the delay curves were available on a chart.

GEE signals were all sent on the same frequency which made it difficult to distinguish the original signal from the response signal. Chains of GEE stations were built in the UK, France and northern Germany. Ultimately it was replaced by VOR systems and LORAN. Some of the British GEE equipment was used in the later GEE-H system which operated at the 20-80 MHz range. The last GEE chain was shut down in 1970

The irony in all this is that hyperbolic navigation was originally developed by Germany. Meint Harms lectured on the topic as a masters student at Seefahrtschule Lübeck, a navigational school. After becoming a professor of Mathematics, Physics and Navigation at the Kaisertor in Lübeck he began to demonstrate models of the system which he patented in 1932.

Low-Frequency Navigation Stations

Your vocabulary word for the day is "Multilateration." Rather than mangle the defintion I am taking it directly from Wikipedia.

"The process of locating an object by accurately computing the time difference of arrival (TDOA) of a signal emitted from that object to three or more receivers. It also refers to the case of locating a receiver by measuring the TDOA of a signal transmitted from three or more synchronised transmitters."

It's like triangulation, except distances are determined by the time it takes a radio signal to travel a known distance. LORAN-C stands for LOng RAnge Navigation. LORAN-C is just one version of Loran. It was preceded (of course) By LORAN-A and LORAN-B. LORAN-D was used exclusively by the United States Airforce. LORAN-A transmitted on 1750 kHz, 1850 kHz, 1900 kHz and 1950 kHz. the System wasn't very accurate and LORAN-B was a phase comparison variation that tried to improve on the model. There was infact a LORAN-F system that Motorla experiemnted with. This was never launched. the migration to a digital "eLORAN" system has already begun. More here.

The present LORAN system is harshly effected by weather, and changes in solar radiation including sunrise and sunset. Most LORAN-C transmitters use mast radiators insulated from ground with heights between 190 and 220 meters. Some of these stations broadcast in excess of 1000 kW. They each broadcast a precisely timed 1Hz signal and all of them are perfectly synchronized to UTC within 100 nanoseconds.

A chain of LORAN-C radio navigation stations transmitting pulse-coded signals on the same frequency. Provides navigation location and timing services for air, land and marine users. The Loran-C system serves the 48 continental states, their coastal areas, and parts of Alaska. Each station has a Group Repetition Interval and has an ID number starting with GRI to indicate which chain they are a part of. Obviously in order to determine your location through multilateration you need at least 3 of these stations. That's why you'll see the same ID three or more times below. Inside the United States, the following stations broadcast:

GRI 7960 - Tok, AK
GRI 7960 - Narrow Cape, AK
GRI 7960 - Port Clarence, AK
GRI 7980 - Carolina Beach, NC
GRI 7980 - Raymondville, TX
GRI 7980 - Malone, MS
GRI 8290 - Gillette, WY
GRI 8290 - Baudette, MN
GRI 8290 - Havre, MT
GRI 8970 - Dana, IN
GRI 8970 - Malone, MS
GRI 9610 - Gillette, WY
GRI 9610 - Las Cruces, NM
GRI 9610 - Raymondville
GRI 9610 - Searchlight, NV
GRI 9940 - George, WA
GRI 9940 - Middletown, CA
GRI 9940 - Searchlight, NV
GRI 9960 - Nantucket Island, MA
GRI 9960 - Carolina Beach, NC
GRI 9960 - Caribou, ME
GRI 9990 - Attu Island, AK

Strangely in 2008 George Bush Jr. threatened to shut down the highly effective LORAN system. Instead after much hand-wringing the administration of the LORAN system was transferred from the Coast Guard to the Dept. of Homeland Security.

Radioman 2nd Class

"CAUTION! NOT TO BE ENTRUSTED TO THE CARE OF ENLISTED MEN!"

It sounded subversive, a peek behind a curtain of some kind. So I ferreted it home, and over many days, scanned it one page at a time into a PDF. It was the 1940 edition, so I have no doubt that in fact enlisted men can freely read this completely out of date 69 -year-old radio navigation text.

Radioman 2c is a designation under the artificer's branch. It that sets pay grade, an insignia, and indicates a set of positions that person may hold. Like most military positions to move up in rank one must pass a test. This is the instructors exam with answers for the Radioman 2c exam. There's a little more information here.

Radioman was a rating for United States Navy and United States Coast Guard enlisted personnel, specializing in communications technology. The rating was created in 1921 and was used continually until it was merged with Data Processing Technician into the Information Systems Technician. The Radioman was not just a DJ, what they called a Broadcast Operator, but also teletype repairmen, Crypto operators, supervisors, Distro Operators and every other job that fell under the qualification.

You can get all 34 MB if you
DOWNLOAD HERE

Flight Service Station

A Flight Service Station (FSS) is air traffic radio station that provides pilot information regardingg weather and possible hazards along flight route. When researching this try not to confuse it with the other FSS (Fixed satellite System) It's kind of like traffic information radio for air travel. an AFSS is an Automated Flight Service Station. 58 are automated.

But an FSS may also give communication services and Visual flight rules search and even rescue assistance to the plane in flight. FSS also relay Air traffic control clearances, creating Notice to Airmen, receive Instrument flight rules, flight plans and monitor Navigation Aids. More here

This page contains a roster of all existing Radio and Flight Service facilities between 1920 and 1978. Information provided below was published in the "Airways" - End of Seat-of-the-Pants Flying, by H. Dale Heister and published in 1978. Click here.

Your nearest FSS can be found by telephone with the number 1-800-WX-BRIEF (992-7433). pilot en route may also hail a FSS using the common frequency of 122.2 MHz. Every station has its own discrete frequency, generally between 122.3 and 122.6 MHz, so two stations aren't picking up the same pilot.

The First Radio Beacon

A radio beacon is non-directional transmitter that usually transmits a constant signal on a licensed radio frequency. Before the days of VOR, GPS, LORAN, beacons were used with direction finding equipment to find ones relative bearing to a known location. The beacon being the known location.

There are a few different kinds of radio beacons. There are amateur radio beacons that are used to test propagation of radio signals. At sea, there are marine beacons, though largely phased out. In aviation they use a beacon called Non-directional Beacon (NDB). These are used to help find airports.

In 1921 the first non-directional radio beacon (N.D.B.) went into service. It was operated by the Bureau of Lighthouses to assist marine navigation. A manual radio direction finder that was light enough for airborne use was developed in 1934 for these very NDBs. They were the core of navigational technology for decades.

By June 30, 1955, there were 173 NDBs operating in the United States. Since then a variety of much more dependable and accurate systems have been developed. The current plan is to decommission these beacons over the next few years as they are replaced with newer supposedly better technology. But at least today NDBs still pepper the landscape. These that still remain in service are kept as an emergency backup system in the case that these more "sophisticated" modern systems fail. Old obsolete technology is always more sturdy somehow...