Saturday, March 19, 2011

Der Nauen Crosses the Pond

I'm pleased to report that a pair of passive, Epstein-Joly-Arco (EJA) frequency-doublers are currently producing an output power of 100mW on the 20m CW band. The saturable reactors for these multipliers employ four, 1960's-era, magnetic computer memory core ferrite toroids.

The excitation for these multipliers is presently provided by a BUL128 bipolar transistor that I once salvaged from a compact fluorescent lamp. Some of you may recall my use of this transistor in my Das DereLicht transmitter and receiver projects. While this low-gain, high-voltage/current transistor was never intended for use at RF, I found that it worked reasonably well at frequencies below 4MHz. At 7MHz and above, the working efficiency of this transistor is impractically low. In fact, that's the reason I chose to use it in the transmitter of this 20m radio. 

An oscillator drives a power amplifier made from a BUL128 transistor to produce an output of 1.0 watt at 3.5MHz. This energy is delivered to a tandem pair of EJA frequency-doublers. The first doubler produces 360mW of RF output at 7MHz. The second doubler delivers 100mW at 14MHz. The total passive frequency-multiplier conversion loss is 10dB.

Last week I paired this 20m transmitter with a straight, two-transistor regenerative receiver to form a rig that I've named, Nauen.

My first contact with the Nauen came on Tuesday evening, when W3HZZ answered my CQ from Atlanta, Georgia. When I went up to the house later in the evening I found that receivers in the Reverse Beacon Network had captured a good many of my calls. The most distant receiver that heard me was PJ2T's station in Curacao!

The DX propagation was considerably worse the next day. However, on Thursday evening I was pleasantly surprised to hear G3NWR reply to my CQ on 14.059kHz. The conditions were such that we only managed to exchange signal reports, nevertheless, my little Nauen prototype had crossed the pond! 

G3NWR is the call sign for the Wirral Amateur Radio Society club station. MØATZ was at the key for our QSO. Colin later wrote

"Your RST was indeed a 559 – it was a lovely signal and I was surprised to hear the /QRPp at the end of your call as it was moving the meter quite well this end! 

Later, when I checked the Reverse Beacon Network, I noticed that both a half-hour before, and twenty minutes after my UK contact, the receiver at OL5Q in the Czech Republic had picked up my calls.

                 
These photos of my prototype transmitter were taken shortly after my QSO with G3NWR.The second photo is a close-up view of the tandem EJA frequency-doublers.


W4OP and NØUR both kindly made an audio recording of my 100mW signal. Please click here to listen to my signal as received by NØUR at a distance of 1642km.
Nauen Log 

W3HZZ       559/569      Atlanta, GA        1520km     5w to G3RV
W4OP         589/579      Glenville, NC      1329km    12w to Optibeam
W7CNL      549/549      Boise, ID            3445km     90w to 5el Yagi
K9FO         549/539      Momence, IL      1266km     AT Sprint at 5w
W6EOD      459/559     Swansboro, NC   1106km    Elecraft KX1 at 2w
W4OP         599/589     Glenville, NC       1329km    200w to Optibeam
N4HS          569/589     Lanet, AL            1649km    2w to 3el Yagi
N4HS          559/559     Lanet, AL            1649km    2w to 3el Yagi
G3NWR      559/559     Wirral, UK           5005km   80w to 3el Yagi
KØIIS          569/?         Davenport, IA       1478km
NØUR         559/559     Ellendale, MN        1642km    2w to 3el Yagi
W3HZZ      559/549     Atlanta, GA           1520km    10w to G5RV
KO1U/M    569/449     Abbeville, SC         1381km     50w mobile
NU8S         569/449     Loveland, OH        1097km    5w to Yagi
WA9ETW  559/319     Monticello, WI      1362km     ATS-3 @ 3w
WA9BXB  599/339     Brookfield, IL        1253km     500w to Yagi
N1KW      569/549     Homer Glen, IL       1270km    DX60 & invee
N1ZX        569/599    Stuart, FL               2000km   

I would like to thank everyone who listened for my signal. A special note of thanks is due to DL3PB. Peter returned home from work on two evenings and set up a temporary 20m antenna in order that he might hear me.

Saturday, March 12, 2011

Some Early-Modern RF Alternator History


The above postcard bears a photograph of the Grossfunkstation at Nauen, Germany as it appeared in 1941. A combination reflecting pool/transmitter cooling pond is located in front of the main radio station. The building was designed by a prominant achitect of the day; Hermann Muthesis. German industrial architecture of this period is still celebrated today.  

By the mid 1920's the RF alternator had emerged as the most efficient means of generating high-power VLF energy. By then even the last hold outs had replaced their arc transmitters with alternators. 

Telefunken installed 400kW magnetic frequency-multiplied RF alternators at Kootwijk Radio and at Torra Nova near Rome. They installed a 150kW alternator at Prado del Rey (Madrid) and a 100kW station at Funabashi in Japan. Telefunken stations were also erected Malabar and Monte Grande. The last great alternator of this type was the 500kW station built at Nagoya, Japan.   

Both the installation and the operating costs for a 200 to 400kW RF alternator represented a huge expenditure. Despite the ever-increasing demand for commercial international wireless services, as the shortwaves gradually became available the primary workload for the VLF alternators shifted from commercial to military operations. In his, History of International Broadcasting, Vol. 1, James Wood remarked

"Paradoxically, the cable telegraphy, whose demise had seemed so clear two decades earlier in 1906, outlived long-wave wireless telegraphy. This was attributable to two factos: the huge costs associated with high power, long wave installations, and the increase in commerical traffic from 1920 onwards, which gave a larger market." 

Indeed, the operational cost ratio for several kilowatts at shortwave using vacuum tubes as compared to several hundreds of kilowatts needed at VLF would have spelled the demise of the big alternators by 1930, had it not been for two saving graces.

Firstly, the transmissions from high-powered VLF stations suffer less disturbance due to changes in propagation than those at shorter wavelengths. 

Secondly, it had been discovered before the First World War that submarines submerged to a depth of 2 to 3 meters could continue to receive the signals from these VLF "powerhouse" stations. 

Following the First World War, the station at Nauen, Germany was run by Transradio A.G. (Radio Trans-Ocean Ltd); with Telefunken as the majority shareholder. Despite the worsening economic situation in Germany, the station was steadily upgraded. A model of the station as it appeared in 1920 may be seen here and here.

In 1931 this charming photograph was taken from the heights of the transmitter towers at Nauen (not a safety belt in sight!). In January of that year the Reichspost took over control of the station. The VLF RF alternators were refurbished in 1937. 

In a series of articles titled, Funkgeshichte, Dr. H. Richter described the VLF transmitters that were used for U-Boat communications in the early years of the Second World War 

"Eine große Bedeutung für die fernführung der deutschen U- Boote hatten auch die Längstwellen, die von den Booten mit ihren Peilrahmen- Antennen auch noch unter der Wasseroberfläche empfangen werden konnten. Am Anfang des Krieges stand dafür nur der Sender Nauen auf der Hauptbetriebswelle für U- Boote (Wellenlänge 18130 m = 16,55 kHz) mit einer Leistung von 300 kW zur Verfügung. Nach der Besetzung Frankreichs kamen noch drei weitere Längstwellensender dazu, St. Assise mit 300 kW, Croix-d´Hins bei Bordeaux mit 360 kW und Kootwijk (Niederlande) mit 120 kW. Der Sender Nauen und die beiden französischen Sender waren Maschinenfrequenzsender, der holländische ein Röhrensender." 

Up till the occupation of France, the RF alternators at Nauen were the main VLF transmitters available to the Kreigsmarine. Later, two French RF alternators as well as the Kootwijk Radio transmitter at Apeldoorn in the Netherlands were pressed into service. Herr Richter states that the later was a vacuum tube transmitter. However, I wonder about this given the Dutch 400kW VLF RF alternator was said to have remained in serviceable condition until the Germans themselves destroyed it upon their retreat.

In his book, Funkführung der U-Boote in der Praxis, Arthur O. Bauer describes the workings of the passive frequency-multiplied Telefunken RF alternators that were used to issue orders to the U-boat fleet


The RF alternators at Nauen are said to have been dismantled by the Soviets at the war's end. Whether they were ever placed on the air again remains a mystery. Fortunately, the Soviets decided not to follow through with their original plan to blow up the grand, old Muthesius building. The structure is used to this day as a radio transmitter.

The previously mentioned Telefunken alternator at Yosami, near Nagoya, Japan was saved from the scrap heap early-on for the same reasons that the German alternators remained in service throughout the Second World War. Originally installed for the purpose of commercial oversea wireless signaling, this largest of all RF alternator stations was nearly obsolete by the time it went on the air in 1929.

The station was eventually taken over by the Japanese Navy and used primarily for communicating with their submarines until the end of the war. I believe the callsign of this station was JNI3. After the war the US Navy took control of the station and changed the callsign to NDT. The US Navy used this station for its own submarine communications from 1950 until 1993.

Happily, after 60 years of on-air operation one of the two alternators - along with its ancillary equipment - has been moved to a permanent museum. In May of 2009, the IEEE commemorated the station with a dedication ceremony.


JA2DJN has posted some wonderful photos of the well-conserved Yosami transmitter here. Be sure not to miss the complete schematic diagram of the station which may be found here. The photo of the RF output feed-through insulator at the rear of the original building reminds me a giant spark-plug!

Another fine photo collection may be found here. I especially like the wrist-diameter Litz wire inductors set into those gorgeous, teak-wood frames.

The Telefunken E-378S "All-Wave" receiver provides a good example of the type of equipment that was used to receive VLF transmissions in this time period. This regenerative receiver was nicknamed "Brotkiste," or "breadbox," for obvious reasons. These receivers were standard issue on Kreigsmarine ships and U-boats up to the end of WW2. For example, the E-378S receiver can be located (#10) above the operating table on the starboard side of this Type-XXI, U-boat radio compartment. The above two links are taken from the web sites that may be found here and here

The E-378-S also had a place of prominance in the radio room of the Graf Hindenburg. Please click here and here.    

Tuesday, March 8, 2011

An Unexpected Turn of Events

An gift from a friend turned up in my mailbox two weeks ago. It was an envelope containing some 1960's-era computer magnetic memory ferrite toroids. The cores measure 1.9mm in diameter with a thickness of 0.5mm. These are somewhat larger than other magnetic memory cores that I've seen from that time-period.


The B/H loops shown in the above photo were made at 100kHz. Both loops are identically scaled. The left-hand loop was taken from the best of my junkbox collection of ferrite cores. The right-hand loop was made from the computer memory core. Please notice the knee at the onset of saturation for this semi-hard ferrite material is considerably sharper than for the soft ferrite loop shown on the left. Given the areas inscribed by both loops are comparable, the sharp-kneed computer memory core ought to be a more efficient harmonic generator.

I wound 98 turns of 0.09mm diameter enameled wire on one of the computer memory cores. The inductance measured 134uH. Swapping this for my previously used "junk-box" toroidal-core inductor in the 700kHz to 3.5MHz frequency multiplier, the RF output power jumped from 250mW to nearly 350mW! The total, two-stage (35x) frequency multiplier efficiency had increased to 10.8% (9.8dB conversion loss). 

 

My original intention had been to move forward on the project by including a 9x multiplier stage in front of the 100kHz -> 700kHz frequency multiplier. However, I now began to wonder if it might be possible to raise the final working frequency to 7MHz. With this in mind I began working on a plan for a frequency multiplier to follow the 3.5MHz stage.
 

A frequency doubler using a pair of DC-biased magnetic saturable cores was invented by J. Epstein in 1902 and refined by Maurice Joly in 1910. Shortly thereafter the great radio pioneer, Georg Graf von Arco, employed a cascade of these multipliers for use in Telefunken's enormous station (callsign, POZ) located in a swamp outside the village of Nauen, Germany. 

The first frequency-multiplied RF alternator of this type was installed there in September of 1912. In June of 1913 the engineers at Telefunken installed a similar transmitter at a sister station (callsign, WSL) on Long Island, at Sayville.

Nearly the entire August, 1919 edition of the Telefunken Zeitung was devoted to the history of the Nauen station. Dr. Walter Dornig (who went on to co-develop the Schmidt-Dornig shock-multiplier transmitter that I'm presently using on 80m) explained on page 65    

"Die Versuche mit statischen Frequenz-Transformatoren hatten äußerst günstige Resultate ergeben. Erreichte Wirkungsgrade von ca. 90 Prozent veranlaßten Telefunken im Jahre 1912 einen 150 kW Hochfrequenz-Generator für 8000 Perioden in Auftrag zu geben und
gleichzeitig eine Versuchsanordnung für 100 kW Antennen-Energie mit vier Frequenz-Verviel-fachungs-Transformatoren zu bauen.  Diese Anlage ergab bei den ersten Versuchen mit zwei Verdopplungs-Stufen  (8000 auf 16000 auf 32000 Perioden = 9400 m Wellenlänge). Hiermit wurde an die Telefunkenstation Sayville bei New York am 18. Oktober 1913  3°° nachmittags — also bei Tageslicht auf der ganzen Strecke — das erste Telegramm gesendet und dort fehlerfrei aufge- nommen.  Damit war der erste drahtlose Tagesverkehr mit Amerika eröffnet."

Dr. Dornig is reporting favorable results with the 
Epstein-Joly-Arco (EJA) frequency multiplier. The stage efficiency had reached 90% in the first transmitter to be installed at Nauen in 1912. They used a pair of these passive multipliers, doubling first to 16kHz and then again to 32kHz. By the use of these frequency multipliers, on October 18, 1913 the first error-free, daytime radio message between Germany and the United States was exchanged; thus opening the link between Germany and the US to commercial radio-telegraph traffic.

The British cut Germany's transatlantic cables
only hours after the start of WW1 in Europe. In her book, The Guns of August,  Barbara Tuchman wrote

"... from that moment on, Germany was sealed off from direct cable communication with the overseas world, and the burden of communication fell on Nauen, the powerful German wireless station a few miles outside of Berlin."

The radio link between Nauen and Sayville was also to be of immense historical significance in the lead-up to the United State's entry into the war. For example, the press speculated that secret messages, such as the order to sink the Lusitania and the infamous, Zimmermann Telegram, were transmitted from the station at Sayville.

In hopes of uncovering these secret messages, a Sayville radio amateur, Mr. Charles Apgar, made the very first off-the-air sound recordings and delivered them to the U.S. Secret Service.



Following the war, Hiram Percy Maxim lobbied the U.S. Congress using Mr. Apgar's exploits as a prime example of why radio amateurs should be allowed back on the air.
 

Grosssender Nauen was invaluable to the German war efforts. For example, the transmitter at Nauen played a part in the fascinating and true story of the SMS Wolf.

British commandos captured or destroyed all of the German colonial wireless stations soon after the war began. Strange as it seems, the takeover of the Sayville, New York station represented the first U.S. military action of the First World War, when a contingent of armed U.S. Marines marched from the train station to commandeer the radio station.

On March 2, I wrote to some friends

"Today's tests went extraordinarily well. Using my Karl Schmidt 80m transmitter as the exciter, I measured the 7MHz output RF power just shy of 150mW!  During this test the 80m input power was just over 300mW. Thus, the EJA frequency doubler stage-efficiency is approaching 50% (3dB conversion loss). These numbers are astonishing. In fact, these would be considered quite good results for a varactor-based frequency doubler. I was just saying a few days ago that I would have been happy to make as little as 10 to 40mW of 40m power. Needless to say, I've been kicking up my heels here! Please see my photo of the 3.5MHz input and 7MHz (unfiltered) output waveforms."


"Aside from the unexpectedly high efficiency, the circuit is stable and the unfiltered output waveform is remarkably clean right out out of doubler. I had it running into a quarter watt, 50 Ohm load resistor all afternoon. I couldn't resist touching this resistor from time to time, just to feel the warmth. Again, the last semiconductor used in this transmitter is working at 100kHz. A total frequency multiplication of 70x is being produced by three historical circuits employing passive, saturable core inductors.
"

My EJA frequency doubler is nearly an identical copy of the one used in the big Telefunken transmitters. A schematic of the Nauen transmitter may be seen here on page 67 (Seite 67), figure 61 (Bild 61).

On the evening of March 3rd, I used my Schmidt-EJA transceiver (mit gain-less receiver) to answer a 40m CQ from VE1BHH. Peter replied from Wolfville, Nova Scotia (657km) with a 569 report. The historical circuitry last used at Nauen on 32kHz was now back on the air!

Please click here to hear my 40m signal (over some fairly high QRN) at W1TXT's on-line Connecticut receiver. 

Der Geist der Nauen lebt auf!