Click BACK to Return to the Museum / Telegraph Web Page.


Click on photographs then click "GO BACK" to return to text.

The following accounts of the use of radios on ships in the early part of the 20th century were provided by Bob Shrader - W6BNB...

If you have any questions for him you may contact him by email at


Bob Shrader - W6BNB obtained his amateur radio license while he was in high school. In 1932 he went to Central Trade School to obtain his commercial telegraph and phone licenses.

In 1933 he went to sea as a radio operator for Dollar Line on round- the-world trips (6 times) and then trans-Pacific on other liners (12 times) then trips to Honolulu on Matsonia and one trip on a freighter to Panama and back.

In 1939 he became deputy sheriff for Alameda County at KPDA where worked phone, CW and did some patrol work. He was in charge of radio and electricity training of deck Cadets at U.S. Merchant Marine Academy at Kings Point, L.I. He returned to the sheriff's office in 1945. In 1946 he took over teaching day and night classes at Central Trade School, which later became Laney College.

In 1959 he wrote a text book "Electronic Communication" and other electronic and electricity texts for McGraw-Hill. In 1969 he retired and moved to Sebastopol with his wife and spent 3 years building a new home. He joined the volunteer fire department, ending up as Fire Chief of the Freestone Fire Dept. He then went on to Twin Hills FD as Director. He wrote "Amateur Radio, Theory and Practice", again for McGraw-Hill, did short stints with Hewlett Packard in microwave repair in 1957, and as tech writer in 1979. In 1991 he brought out the 6th edition of E.C. And most recently, he wrote "Fire Fighting, How It's Done" for Vision Books International, which will be published in July 1997.


Bob first wrote to me to ask me to identify a bug that he had owned for many years:

He wrote:

The old bug in this picture
has quite a history. It is shown with my Bunnell double-speed key above and my home brew sideswiper at the right..

On the first trip I made as rdo op around the world, the chief op got tired of my changing his adjustments and suggested I get myself a bug of my own. When we reached New York City I spent $ 6 to buy this little bug brand new.

The round-the-world trips started in late 1933 and I used it daily until 1939 at sea, then from '39 to '46 in police radio CW, then from '46 to '69 while teaching rdo communications at a trade school/junior college, and from '69 to date on the ham bands. In 1937 while on the SS President Hoover it was used to send the SOS while the ship was being bombed by Chinese airplanes. Really a sweet feeling old friend. Hi.

I am sorry that I can't tell you the address where I purchased the bug. All I remember was that it was on the North side of Cortland Street on the West side of New York City. It was in December of 1933 during a stop-over on my first trip around the world as a Dollar Line radio operator.

We started from San Francisco and went from there to Honolulu, Kobe, Shanghai, Hong Kong, Manila, Singapore, Penang, Columbo Ceylon, Bombay, Suez, Port Said, Alexandria, Naples, Genoa, Marseilles, New York, Boston, New York, Havana, Panama Canal, LosAngeles and back home. What a trip for a 19 year old kid!

We used 2 kW spark transmitters for the medium frequencies mostly. We also had a self-excited push-pull triode 1 kW HF and MF transmitter. We used TRF receivers for HF and an IP-501 regenerative detector plus 2-stage AF receiver for MF and LF. p> In 1937, while on our way to take Americans out of Shanghai due to the Sino-Japanese war, the 635-ft luxury liner SS President Hoover was at anchor in the Yangtze River, waiting for clearance to move into the Woosung River and Shanghai. All of a sudden we heard airplanes coming and then the sound of bombs dropping in the water and on our top deck.

The skipper turned to me and said, "Well, Sparks, I guess you better send an SOS." So I went into the radio room and flipped on the "1 KW" VT (Vacuum tube) transmitter set and with my trusty old Logan Speed-x bug sent a very fast SOS. Of course we were always told to send a 1- minute transmission of 4-sec dashes followed by 1-sec spaces before sending a distress call. With the planes still overhead I decided that information was for other conditions and I just let go with my bug. I knew that the ops at the Shanghai radio stations were very good operators and my 25 or so wpm sending would be no problem to them.

We later found out that the planes were Chinese and that they thought we were the Asama Maru, a big Japanese ship that was supposed to be in the area. How they could miss the 30-foot long American flag laid out on our top deck I don't know. But is was something to remember. We were not supposed to be at war! One dead and a few injured -- so we were lucky. Those Chinese pilots were not too great as they had a sitting duck with us at anchor there in the river.

The Dollar Line 2-kW spark transmitters in use at that time had fast operating QSK keying relays. The keying circuit only required a fraction of an ampere to key the many amperes in the primary of the spark transformer. I measured the Leach keying relay coil I have here that was used with spark transmitters and it reads 225 ohms, which in series with a 250 ohm resistor was used across the regular 110-V dc line aboard most ships in those days. The heavy duty keying contacts on the bug easily handled that amount of current, about 0.25 amps. We were handling traffic at speeds up to at least 30 wpm with no trouble with our spark sets.

In your last communication you suggested that information on old time equipment might be of interest. So here is some information about transmitters that I know of first hand - and some that predated me but that I know about.


The first transmitters, around the turn of the century, were open-gap spark types. The 500-cps ac was stepped up by a transformer and fed across a spark-gap in series with a primary coil which developed 1000- cps damped waves that were fed to the antenna. The resonant frequency of the antenna did most to determine the transmitting frequency. In the teens the gaps were often just open, or rotary types and made a terribly loud noise and generated a lot of ozone. In the 20s the gaps were made into many very short gaps in series, each being surrounded by copper enclosures, with mica insulators between copper holders so that each gap unit was not shorted. These were called quenched gaps because the noise was quenched, and so was the ozone.

Shipboard spark transmitters were usually built behind vertical bakelite panels sitting on top of the operating tables. I remember one ship's mate coming into the radio room to shoot the bull with us. He made himself very comfortable sitting on the desk top and leaning back against the spark transmitter while we talked. His rear end was pushed up against the 2-ft wide quenched gaps which stuck out in front of the panel. When the ship was called, the operator on watch forgot about the mate and switched on the spark transmitter to answer. Boy did that mate jump! A 2-kW spark transmitter, which was very loosely coupled to the antenna to provide a not-to-wide signal (30 kHz at 100 miles?), could be used for trans-Pacific communications with no trouble under reasonable conditions. They can operate on all frequencies.

Spark transmitters were no longer used by U.S. ships after WW2, although some foreign ships used them for many years after that.

In the teens the arc transmitter was developed. A dc electric arc has negative resistance across it. So, if an antenna-to-ground circuit is interrupted by putting an electric arc in series with it, the negative resistance of the arc makes up for the positive resistance of the antenna circuit wire and the radiation losses, so the antenna oscillates at its fundamental 1/4-wave frequency. These rigs put out nice clean unmodulated CW on lower frequencies. Most of them used back-shunt keying, meaning that when the key was down the signal was transmitted by the antenna at its resonant frequency. When the key was up the keying relay shunted the arc circuit to an LC dummy load tuned to some other far removed frequency so the operator could copy the station who was answering on the transmitting frequency.

The arc transmitter was going all of the time but only on the desired frequency when the key was down. These rigs were very good on higher wavelengths but down on the ship calling and distress frequency of 600 meters (500 kHz to youngsters) they sounded pretty burbly. Because the arc worked best in an alcohol or hydrogen atmosphere, when they were first struck by their operator, if there happened to any oxygen in the sealed arc chamber the result was an explosion and the top would swing back on its hinges. This threw out a sooty whiff that would show up as a black stripe across the chest of the operators white uniform. They did not like that. Arcs were not used at sea after the '30s although hundreds-of-kilowatt rigs ashore communicated during WW2 over long distances on frequencies lower than 50 kHz.

The only arc transmitter that I used was the one we had set up in our radio class room at the old Central Trade School in 1932. We had it explode.

We also gave local commercial stations KPH and KFS some QRM when we would key it. But they knew the instructor so did nothing about it.

I have worked other stations on 500 kHz who were using arcs.

There was something else I forgot to tell you about in the way of old time tranmitters, the ones that used VTs.

In the late teens vacuum tubes became large enough to be used in transmitters. By the mid-'20s an old spark transmitter was converted into a "P-8" transmitter. Two push-pull 204A triodes were installed in place of the quenched gaps in a self-rectified Colpitts oscillator circuit. It put out something over 100 W in the MF range. Later MOPA rigs were at sea with a Master Oscillator and a Power Amplifier. Power outputs were becoming greater. By the '30s Globe Wireless (not to be confused with the present Globe Wireless) had a 2-Gammatron triode self-rectified push-pull oscillator tranmitter for both HF and MF operations. By use of a Variac on the front panel the power output could be adjusted from a watt or two up to 1 kW. Its 500-Hz ac power source was doubled to a 1000-Hz output modulated CW, a really nice signal to copy. Also, it was over 100% modulated so it was pretty broad. This was advantageous because the receivers at that time drifted badly as did the transmitter. By this time LF operations had dropped off to almost nil at sea.


Original receivers at sea were either solid-state crystals or other simple diode type rectifiers. They could only be used to pick up modulated signals so they were usable with spark signals and MCW transmissions. In fact up to this date SOS and other emergency sets are supposed to use MCW to assure the signals are audible on any kind of receiver, should they be tuned to zero-beat with the transmitter.

In the teens triode oscillators were beginning to be used as the detectors. Besides operating as a diode in the grid circuit they also provided amplification in the plate circuits. This was the well known "regenerative detector" system. In oscillation it would beat against incoming signals providing a beat-tone to be heard in the earphones. With a 2-stage amplifier it could provide enough amplification for loudspeaker operation.

Being an oscillator and coupled to an antenna it also radiated a constant CW signal that could be heard for several miles. At sea all operators monitored the distress frequency of 500 kHz constantly. As result, any time a ship would pass by within a few miles its weak whistle signal would be heard. Once when sending in an arrival message to the coastal station at Colombo, Ceylon I keyed my receiver to send the message. The operator at the dock station would not believe me. When I turned on my 2-kW spark set and repeated the message he believed me! His ears must still be ringing. During WW2 the German subs would monitor 500 kHz and when they heard the weak whistles they would find the ship and sink it. With an RF amplifier in front of the detector this was not a problem. That was the demise of the regenerative detector at sea. In the mid-'30s superhets began to find their way into ship communications.

73 W6BNB Bob


Click BACK to Return to the Museum / Telegraph Web Page.

For more information contact:

Bob Shrader W6BNB

e-mail address: (Please eliminate the SPACES when you type this email:) w6bnb @