Receiver Circuit For Caravans

Just the job for a caravan is this sensitive medium and long wave receiver whose only power supply requirement is 100mA from a 12 volt car battery! Our contributor displays his customary ingenuity in producing yet another cleverly designed circuit which offers maximum performance from a minimum of components

 THIS ARTICLE DESCRIBES A SIMPLE hybrid circuit which will give good results on medium and long waves from a 12 volt supply and a normal car-type aerial. Current consumption is only of the order of 0.1 amp so that the receiver may be used for long periods without running down the battery. It is particularly suitable for use in a caravan when a 12 volt supply is available from the car battery. It can also be used as a car radio when the car is stationary, but the output is not sufficiently high for use on the open road except in a quiet motor car. It is ample for occasions when the car is stationary.          

Components List: Resistors (All fixed resistors 1/4 watt 10% unless otherwise stated) RI     2.7k R2     47k R3     1.2k R4     2.2M R5     220k R6     1M R7     150k R8     1M R9     330 R10    l00 ohm, 2 watts, 5% VR1  25k potentiometer, linear track VR2  5k potentiometer, pre-set Capacitors  C1     0.01 uF, paper  C2     0.1 uF, paper  C3     0.0l uF, paper  C4     l00 pF, silver-mica or ceramic  C5     330 pF, silver-mica or ceramic C6     0.01 uF, paper  C7     27 pF, silver-mica or ceramic  C8     l.000pF, paper or ceramic

C9     l00uF, electrolytic,  12V wkg.  VC1  800pF   variable,   solid   di-electric  Inductors L1, 2, 3 Coil unit (see text) L4   2.5mH choke, Repanco type CH1  L5   Primary (red and blue leads) of Repanco  transformer type TT53  T1   Output transformer, Repanco type TT5 Valves  V1/2   3Q5GT (DL33) Transistors TR1   MAT101 or MAT121  TR2   G.E.C. S5 or S6 (see text) Switches S1  (a), (b), fc),   3-pole 2-way S2       s.p.s.t. (may be ganged with VR1) Loudspeaker  3ohm impedance Miscellaneous 2 International Octal valve holders,  Ferrite rod 3 x 3/8in  Cabinet, etc.

The Circuit

The circuit is shown in Fig. 1. TR1 is a common emitter high frequency amplifier with the input untuned. A good transistor will give higher amplification, in these circumstances, than a valve, as its input impedance is low and it is reasonably well matched to the fairly low impedance of the aerial-earth system. No extra selectivity is offered by an untuned stage, but with a circuit designed to be used with an aerial only about 3 or 4 feet long, and incorporating a highly selective radio frequency transformer for medium waves, this is of little importance.

The tuning coil arrangements are unusual. The coil unit consists of LJ1 L2 and L3. These are wound to the dimensions shown in Fig. 2. L1 has 300 turns of 38 s.w.g. enameled wire wound in a single pile and with a tapping at 100 turns from the end remote from L2.  L2 and L3 use 32 s.w.g. wire. L2 has 50 turns, close wound, and L3 has 25 turns wound in a narrow pile. The coils are wound on a sleeve made of "contact" or similar paper-backed adhesive plastic on a piece of 3/8in ferrite rod, 3in long. Coverage will be from about 190 to 550 metres on the medium waveband, and from about 1,250 metres to well over 2,000 on the long waveband. Turns should not be removed from L1 in order to lower the wavelength coverage as this will result in L1 resonating with its self-capacitance within the medium waveband, and will render the receiver inoperative on the long wavelength end of that band.

If Fig. 1 is studied it will be seen that, with S1(a), (b), (c) in the lower position, L1 forms the collector load for TR1 and couples, on the "large primary" principle, to L2, which is the medium wave tuning coil.* This arrangement provides good selectivity and uniform coupling throughout the band. LS is the reaction coil for medium waves. The earthy end -

* It is conventional practice, on medium and long waves, for an aerial coupling coil to have a considerably larger inductance than the tuned coil. The aerial coupling coil, in company with the aerial-earth capacitance, then becomes broadly resonant below the low frequency end of the band covered, thereby boosting sensitivity at this end.—EDITOR.

- of LI is taken to the positive filament pin of V2 to reduce the voltage available for TR1 to about 9 volts. La and L3 have their earthy ends taken to positive, and not negative, battery line, to facilitate the special reaction-cum-volume control method used. C3 completes the r.f. circuit and provides a short r.f. path for VC1. With S1 (a) (b) (c) in the upper position, L1 is still the collector load for TR1, but is now also the long wave tuning coil. The collector is tapped into it to reduce damping by TR1. The reaction coil is now L2

V1 and V2 are pentode output valves of a type which are frequently advertised in this magazine. Filament voltage is supplied via RI0. V1 is a leaky-grid detector. It will be found to work very efficiently with the small h.t. voltage available for it. R.F. for reaction purposes is taken from the anode through 5 to the slider of VRi. As the slider of VR1 is moved in an upwards direction, the part of the track between C5 and the reaction coil is reduced and reaction increases. At the same time the d.c. voltage available for V1 increases, since VR1 is across the battery. At the minimum position, V1 is deprived of anode and screen-grid voltage, and no signals are passed. As may be seen, V1 is a triode so far as reaction is concerned, its anode and screen-grid being joined together for r.f. signals. It will be found that a smooth   control   from   zero   to oscillation point results.

L4 is an anti-breakthrough choke to prevent any possibility of a powerful medium wave station forcing its way through on to the long waveband.

 The low frequency anode load is L5, which is the primary of an inexpensive transformer designed for coupling a crystal pick-up to the input of a common emitter amplifier. The winding has a very high inductance, this being well maintained with the small current passing through it in the present circuit. It is shunted.by a 220k ohm resistor, R5, to prevent threshold howling. Far greater amplification is possible by this method than by using resistance coupling, especially when only 12 volts are available for V1.

The amplified signal appearing across L5 is fed to the grid of V2 by means of C6. R7 and C7 maintain stability. Negative feedback is provided by R6.

Valve-Transistor Coupling

The arrangements for coupling V2 to TR2 involve a new circuit developed by the author. V2 will have a very high output impedance. Provided it is found possible not to damp this output impedance, V2 will offer a very high degree of amplification despite the limitation of less than 12 volts high tension. TR2 is connected as a common collector large signal amplifier. In this configuration it is capable of providing good current amplification. No voltage amplification is offered, as there is 100% negative feedback of voltage inherent in the operation of a common collector amplifier which, incidentally, results in unusually good quality. Quite considerable voltage amplification is, provided by the two pentodes so plenty of power is available from TR2. A common collector amplifier must have an output load which is not too low, to maintain its current amplification and high input impedance which, in favourable circumstances, is similar to the output impedance of a pentode. It follows, therefore, that direct coupling from a pentode valve to a common collector transistor power amplifier is both practicable and highly efficient, provided a transistor is chosen which gives satisfactory results with a base current equal to the anode current passed by the pentode.

It will be seen that the input of TR2 forms the output load for V2. This is a most satisfactory load as it has a high impedance to a.c. (the signal) and a low resistance to direct current. A snag, however, remains to be overcome. Although the resistance to d.c. of V2 forms the bias arm from the negative supply line to base, the path from base to the positive line remains open. There is, therefore, a state of affairs which can lead to thermal runaway, and the normal solution of a resistor between base and positive arm is ruled out as it would cause hopeless damping of the load offered to V2. The answer to the problem is to abandon any idea of current stabilisation and adopt, instead, a form of power stabilisation. That is to say, we allow the current passed by TR2 to vary but arrange that any increase in current is accompanied by a corresponding decrease in voltage available, the power remaining substantially constant and within the limits allowed for the transistor. This effect is produced by R9/C9 is a bypass for the signal.

TR2 must be a high amplification output transistor which will tolerate l00mW and, in order not to be damaged while VR2 is being adjusted, up to 30mA current. The author recommends the G.E.C. S5 or S6.* For maximum power, bearing in mind the function of R9 and the impedance of the output load, TR2 should pass about 10mA. For this it will require a base current of from about 50 to 150uA depending on its amplification factor. It is necessary, therefore, for V2 to be set up to pass this current, and the necessary adjustment is made by VR2, which controls grid bias. If a milliammeter is available it should be inserted between T1 and the positive line, and VR2 adjusted so that 10mA is registered. If no milliammeter is available adjustment can be done by ear, using a powerful station and adjusting for maximum volume without distortion. If grid bias is too great, both V2 and TR2 will be short of current and there will be distortion. If grid bias is too small a heavy current will pass through TR2 and,

* The S5 and S6 (or GET.S5 and GET.S6) transistors do not appear in the normal lists, but are available as surplus items at very low cost. The author obtained his from Lasky's Radio, 207 Edgeware Road, London, W.2. A possible alternative in the present circuit would be the ACY18 or ACY21.— EDITOR. 

because of R9, it will be short of voltage and again there will be distortion. R9 will prevent damage to TR2 whatever the setting of VR2.

Loudspeaker Requirements

It is recommended that a good loudspeaker be used and that it be mounted in a separate box to avoid any possibility of microphonic howling due to the large amount of audio frequency amplification.

Nothing longer than a normal car aerial should be used. Earthing is automatic through the battery. The receiver should be insulated from the metalwork of the caravan or car and may then be used whether the negative or positive side of the battery is earthed. There is some advantage in using a metal case for the receiver, since this prevents direct pick-up of a very powerful signal by the coil unit. The lead to the aerial should not be screened, since this will reduce input as a result of losses due to self-capacitance which cannot be "tuned out" with an untuned input stage. There is no need for screening, either, with a stationary engine.

The circuit will be found surprisingly sensitive. In South Devon, the Home, Light and Third programmes, together with four Continental stations, can be received in daylight at good volume, and about 30 alternative programmes are offered after dark.

Radio Constructor Vol.10, No.9 (1966)

5 Watt Transmitter (USA - 1922)

 AN EFFICIENT 5 WATT TRANSMITTER (Alpheus Hyatt Verrill - 1922)

For those who wish a more powerful and efficient set for sending this is to be highly recommended. Under favorable conditions it should have a range of from 25 to 40 miles. Moreover, it is not an expensive set to make and, exclusive of batteries, should not cost over $35.00 to $45.00. ($45 = to $800 2024)

The accompanying diagram Fig. 60, makes the wiring very plain, A being the aerial, B the ground, C the ammeter, D the inductance, E the variable condenser, F the fixed condenser, G the grid-leak, H the modulation transformer, I the 6 volt battery, J the microphone, K the grid, L the plate, M the rheostat, N the choke-coil, O the rectifier, P the current transformer.

Although practically every part of this set can be made, with the exception of the ammeter, rheostat, microphone, and modulation transformer coil, still it is almost as cheap and much more satisfactory to purchase the current transformer, the variable condenser and the choke-coil. The inductance D is easily made, the plate coil being wound with No.18 cotton insulated wire on a cardboard tube three and one-half inches in diameter, using twenty-six turns and is tapped at the thirteenth turn. The aerial coil is the same size of wire, but with only eight turns. The space between windings or turns should be about one-half inch. The choke-coil may be purchased as such, but an ordinary spark coil—using the secondary winding —may be used and an old Ford spark coil with contact-breaker screwed down may be used for the modulation transformer. The ammeter used should be one of low reading scale or, if desired, an ordinary 3 volt flashlight bulb may be used instead. The ammeter, however, will give far better results. 

The grid-leak is an ordinary lead pencil leak of medium soft lead. The most difficult part to make is the current rectifier, but even this is very simple and consists merely of eight pint fruit jars filled with a solution of ordinary borax in the proportion of half a pound of borax to ten pints of water. In filling the jars avoid having any undissolved borax or sediment in them, and fill only about three-fourths full. 

Borax bridge rectifier (shown Fig. 61)

The plates consist of alternate lead and aluminum strips, eight of each alternating as shown in Fig. 61, and with each plate 5 x 3/4 inches. With this rectifier and the current transformer P, an ordinary 110 volt, 60 cycle electric current may be used, or without these, two or three B-batteries may be used instead, but this is far more expensive and does not give as good results. Before using this outfit the rectifier must be treated to form the plates, which is accomplished by connecting an ordinary 50 watt incandescent bulb and letting the 110 volt current run through it for ten or twelve hours.

Another point to remember is always to disconnect the high voltage current from the plate when not in use and when using the set always light the filament in the tube with the low voltage battery before turning on the high voltage current. The switch on the microphone circuit also should always be thrown off, thus disconnecting the phone from the battery, when not in use. To tune this set it is only necessary to adjust the variable condenser until the ammeter or flashlight shows the highest reading.

The author:-

Alpheus Hyatt Verrill, known as Hyatt Verrill, (23 July 1871 – 14 November 1954) was an American zoologist, explorer, inventor, illustrator and author. He was the son of Addison Emery Verrill, the first professor of zoology at Yale University. He authored numerous works on natural history and science fiction.

Radio Postcards

This image is silk banner           

1920s visions of future that came true

Armand Taylor 'Jewel' radio

 The Jewel Radio 

(by Gerry Wells in BVWS Bulletin 2002. Colour images are my radio)

	Very few people will have heard of Tuskite. Very few people in the radio trade will have heard of it either. If you lived in or around Marsh road in Pitsea, Essex and had a Vange 3 number telephone then you would have been aware of the factory that called itself Armand Taylor & Co Ltd. You would also be aware of a peculiar smell that emanated from this factory. What you could smell was the process of Bake-lizing paper to form what is commonly known as Paxolin.
	The factory is run by a charming lady called Josephine.

 I can only assume that she is the daughter of Armand Taylor. In 1957 this very worthy company decided to produce a radio set called the Jewel. I get the impression that they intended to make about five thousand of them: in actual fact only 1000 were produced. I worked through out from the serial numbers. They were all six figure and started with 111000, I have never found anything beyond 111999.

 Up until March 2001 I had only been aware of one: that is in Jonathan Hill's 'Radio Radio' figure 785. It was on the 23rd February that I had a telephone call from Josephine. She informed me that she had a factory that had been out of use since 1957. She further stated That she wanted to sell the factory but it was full of radios and unwanted stock.

 She said that she had a possible buyer but she would have to get the factory completely emptied. It had to be done in a hurry and I could have it all for nothing; all I had to do was collect it. I Told her that I was off on holiday The following Monday, down to Lakeside on Hayling Island.

 I Telephoned John Thompson who had a very large Citroen hatchback car. He agreed to contact Josephine and collect the contents of the factory. He cleared everything. He made seven journeys from Pitsea to Dulwich. When I came home a week later, I found my whole dining room two feet deep in clag.

Gerry & helpers re-assemble stock

There were about 200 incomplete sets and oils of cases. They were all rejects, in tact about 20% of the first run. I think at this point in 1957 they decided lo stop production and padlock the factory.

 Although they were very fine little sets they were all valve-ed and the transistor was on  It's way in. In spite of the fact that I have been continually involved with radio for sixty years, I have not met anything like this sort of design before. The designer was one hell of a genius.

 If you examine the accompanying circuit you will wonder what the blazes is going on. If you take a close look at the chassis you will be convinced that the man behind it was no ordinary set designer.

 The set is quite usual for the first three valves ie: DK92, DF91 and DAF91. It has a small Three-waveband coil pack that they designed and made themselves and 2 IF transformers that looked odd, two wires came out of each end and their trimmers were on the side of the cases.

 You would then spot a weird object that was where the tuning condenser would normally be. This object was their own patent tuning system. It was about the same size as a normal tuning gang.

 It consisted of 2 oval pieces of Paxolin or Tuskite, A layer of very fine neoprene or latex (the sort That is usually found in clinics) was glued to the copper sheets on the drum. A strip of copper sheet was fixed to the drum, but well insulated tram the inner copper strips. It is wound round about one and a half Turns and returned to a shaft with a slot in it and wound round until it is fully wound. A drive cord was fitted to the shaft with a big knot and the other end wound round the drum against the spring. The copper outer was then earthed.

 I have played with this device for hours to see how it worked and have tested it for capacitance and losses. It gave a good 500 pF on each half and didn't seem to be too lossy.

 As you will see the rest of the set is fairly conventional apart from The output stage and power supplies The three battery valves have their filaments in series and are placed across a resistance network in the cathode of the UL41 output valve. A small amount of anode to anode feedback is applied to the output stage.

Josephine (owner in 2000)

The power supply is unusual. It employs a mains transformer that has a 250V primary and a 100V secondary tapped at 40 volts to light up the UL41, A simple voltage double-er circuit is employed to give an HT+ of 220 volts using Two small, nasty selenium rectifiers called Sen Ter Cel (a cleaned up name for KB). (nasty because when faulty gives off poisonous fumes)

 It is then smoothed in the usual way and a 40mA pilot bulb is in series with the rest of the set This bulb flickers m time with the music and is placed on the forehead of the figure of an Asian woman, which forms the main part of The Tuning dial.

 Most of the 200 sets had case parts missing. There were no lop plates that hold the case tube into place with chrome plated dome nuts (1/2 CWT of dome nuts) The case is an oval tube 8 inches by 8 inches. It has a pattern of 3/4 inch holes punched in it on either side. The whole tube is covered with cloth, a wide variety of cloths had been used, a great many tartan patterns and a lot of caravan curtain styles. I think a few country and western shirts crept in as well.

 A few case tubes were unusable, well nibbled or covered in a white fungus. The first thing I had to do was make up the oval top plates. I used 1/4 inch MDF for this and covered them in brightly coloured felts.

 The cabinet case outer tubes were quite easy to form up, I made up a solid wooden mandrel and bought several rolls of the heaviest lining paper that you can get. I cut up the rolls on a fine-bladed circular saw. This meant that I could get eight cases out of each roll. I then coated the paper with wallpaper paste and rolled them over the mandrel, fixed them with string, then took them off the mandrel before they had realized what had happened.

 I stood then in rows to dry before putting them on a jig to punch holes in them, I got Eileen to go round to all the local shops to get any suitable material. She did very well and even came back with cloth with teddy bears on.

 It now came to the time to make the set work and see how well it performed. I picked a set out at random and gave it to one of our little old men to take home to his prefab in Lewisham, Ted did a first class job on it. He told me that it performed very well and sounded very fair. He was kind enough to draw me out a first class circuit diagram with all the component values on it. 

 Although Ted has been in the radio repair trade all his life and is seldom beaten, he did state that this set was rather like a City and Guilds test piece with every fault known to man in one chassis. He had to admit that it was beautifully put together and the soldering was perfect even if the UL41 valve holder was back to front and the electrolytes were in backwards.

 Up to date (2001) I have completed about fifty of them and sold a few, given a few away as presents and made sure that everyone at the museum has one whether they want one or not.

Short video of my radio that once belonged to a factory family owner and kept in box most of life

Vintage battery Radio Power Pack

 

This unit will work for most 4 valve battery radios from the past. It utilizes components available to the modern builder. High voltage transformers with extra windings for valves and no longer made. But transformers for low voltage transistor circuits are common. This unit uses 2 x 20v secondary's, but a 15v type will also work well.

HT circuit

This uses a voltage multiplier arrangement x 4. Each diode will rectify 1/2 of the AC waveform and then discharge it across first capacitor and so on until 90 volts is achieved. Similar circuits were used in television receivers to generate EHT voltage for the CRT. Also used in neon high light voltage circuits. The output voltage is stabilized by C & R at the end of circuit.

LT Circuit

LT is stabilized by a modern i/c circuit arrangement known as a Buck Convertor, mainly made in China and can be found on-line for as little as 50p each. The LM2596 is supplied with all the components needed for it to work handling output current up to 2 amps, more than needed for most 1.5, 2, & 4 volt radio batteries. The chip operates at 40 megahertz and can create large amounts of radio interference. The answer is to install inside a small tobacco type tin that has been earthed. Make sure external holes are tiny as at that high frequency the signal will escape.

I've covered the mains terminals with cardboard to isolate from stray fingers.

The HT and LT circuits were made on Vero strip boards with pre drilled holes. Bridge diode can be any that can handle low voltage up to 3 amp current. Similar units sell on-line made in France around £60, but made by yourself can be done for as little as £20. 

Pre 1914 Radio Communication

	1: Marconi Wireless Cabin on Board the "Tongue" Lightship. The Trinity Brethren were among the first to recognise the value of Marconi's invention to those who go down to the sea in ships. Ten years ago they ordered the equipment of the East Goodwin Light-vessel with wireless apparatus. Communication with South Foreland Lighthouse, 12 miles distant, was most satisfactorily maintained. The '' Tongue " installation is typical of the many lightships now fitted.
	2: Schooner "Volunteer." Chartered by the Newfoundland Government in 1902, for the purpose of erecting Marconi stations along the coast of the Labrador. The ship was used as a stores and dwelling place by the engineers fitting up the installations, who had to carry out their work in weather, and under conditions, of Arctic severity.
3: Mr. Marconi and Assistants at Cape Breton Station. The illustration shows Signor G. Marconi with five of his assistants outside the High-power Wireless Telegraph Station at Cape Breton, Nova Scotia, and gives some idea of the severity of the weather conditions under which Sig. Marconi and his staff carry on their work at times. Mr. Marconi is the third figure from the left.
	4: G. Marconi. Born at Bologna, 1874 Married 1905, daughter of Lord Inchiquin. Carried out first experiments in wireless telegraphy at Bologna. Same first tested in England between Penarth and Weston. In 1899 established wireless communication between France and England, and Trans-Atlantic service between England and America in 1907. In addition to the warships of the British and Italian Navies, most of the ocean liners have the Marconi apparatus.
5: Marconi Station at Banana, Congo Free State. This station was erected by the Marconi Company in July, 1901, to the order of the Congo Government for communication with a similar station at Ambri-zette, Angola, and was operated by natives, illustrative of the ease with which the Marconi apparatus can be mastered and worked. Station now dismantled.
	6: Marconi Station at Niton, Isle of Wight. Erected by the Marconi Company in 1901. Situated on the most southern point of the island. Many early experiments were carried out there. The station has a working range of 150 to 200 miles, and carries on a public telegraph service with ships voyaging between the United States and London, Germany, France, and Holland.
7: Messina  Station. The station at Messina, destroyed in the recent lamentable catastrophe, was illustrative of the multifarious usages to which Marconi's invention may be put. Connecting, as it did, the Italian Peninsula, by means of the similar station at Eeggio di Calabria, with Italy's largest neighbouring island, the service of the Italian State and Sicilian Railways was considerably accelerated. The station is being refitted.
	8: Cape Cod Station. Erected in 1900, this station transmitted direct to a similar station at Poldhu, in Cornwall, England, 2,800 miles distant, an inaugural message from President Roosevelt to His Majesty King Edward, in January. 1903. The poles carrying the aerial wires are now replaced by the familiar lattice work towers. It has provided since 1904 a daily news service to the principal Trans - Atlantic liners.
9: Wireless Telegraph Motor Car. The illustration shows the first application of the Marconi system to moving stations. This steam motor car with its light zinc cylinder serving as an an antenna, was able to communicate, as long ago as 1900, with a corresponding station up to a distance of over 20 miles. Moving stations carried by mules or light field carts now provide instant means of communication up to more than 100 miles.
	10: Cape Breton Station. Erected by the Marconi Company in 1902 for Trans-Atlantic communication, but has since been rebuilt. Now carries on constant communication, day and night,- with station at Clifden, Ireland, transmitting public messages, and supplying a daily news service to Atlantic liners for publication on board. The view is taken from seawards in mid-winter.
11: South Goodwin Lightship. Situated at the southeast corner of the Goodwin Sands. Was equipped with wireless telegraphy in May, 1905, by order of Trinity House. Communicates with stations at Dover and North Foreland. Has been of great service in summoning assistance to vessels in distress on the Sands. Six lightships in all have now been equipped with wireless telegraphy.
	12: John 'Jack' R. Binns. Born at Brigg, Lincolnshire, on 16th Sept., 1884. Entered Marconi service as ship telegraphist at the age of 20. By his devotion to duty he was the means of saving 2,000 lives on the S.S. "Republic," when in collision in the Atlantic, remaining at his post for nearly 50 hours. For this he received an address from the Mayor of Peterborough, and a special presentation from the Directors of the Marconi Company.

13: Jack Binns' Cabin on the "Republic."  The illustration depicts the wireless cabin on the S.S. "Republic" from which Jack Binns sent out his now famous call " C.Q.D.," which brought help from all quarters to the "Republic " after her collision with the S.S. "Florida." On the left are the transmitting instruments and key, and on the right the receiving instruments and recorder. The cabin was partially destroyed in the accident.

14: First Type Transmitting Apparatus. The illustration shows one of the early induction coils and oscillators used by Mr. Marconi for the production of Hertzian waves as employed in wireless telegraphy. The discharge which sets up the ether waves takes place between the two large brass balls, which are partially immersed in oil. , This type has been considerably improved upon.

15: Marconi  Syntonic Receiver.  Invented by Mr. G. Marconi. By its means several wireless messages can be received at the same moment. Two or three, each "tuned" to a different wave, will, if connected to the same "aerial" wire, pick out and record the particular message transmitted by the station using the same '' tune." It is thus possible to receive English, French, and German messages at the same time, each on its own instrument.

17: Marconi Station at Holyhead.  Opened for communication with ships entering and leaving Liverpool, in 1901. From left to right is: Coherer receiver in screening box (front opened), transmitting "jigger," Morse inker with battery of Leyden jars behind, transmitting key, and induction coil by means of which the oscillations, or waves, are created. Stations of this type have a working range of from 150 to 200 miles.

18: Marconi Cabin.  A typical Marconi installation on board ship. The instruments shown are, reading from left: Receivers, Morse recorder, Leyden jar battery, transmitting key, and transmitting coils. These sets enable regular commercial communication to be conducted at distances up to 200 miles, the messages being received on a tape. In the latest type, the messages are received by sound through telephones at much greater distances.

19: Marconi Magnetic Detector.  Invented by Mr. Marconi in 1902. Based upon the change taking place in an iron band travelling between two magnets, when affected by Hertzian waves, which causes a sound in the receivers similar to a telegraph buzzer. Records signals at 3,000 miles. The simplest and yet the most perfect wireless receiver yet invented. Rapidly replacing old coherer receiver where paper tape records are not required.

20: Marconi  Portable Wavemeter.  Invented in 1908 by a member of the Marconi staff, for the measurement of electrical oscillations ox-waves employed in wireless telegraphy. By varying the adjustment until the loudest signals are heard in the telephones, the wavelength is indicated automatically on a scale. Weighs 6 lbs., and only measures 9 ins. by 4 ins. by 6 ins. One of the most useful contributions to the art of wireless telegraphy.

22: Marconi Wireless Cabin on Atlantic Transport Liner.  One of the earlier type installations. The vital portions of the apparatus are duplicated (see two induction coils or transmitters at extreme ends of picture, and the two coherer receivers in screening boxes on the left). In centre is Morse recorder, Leyden jars, and, in front of coil, the transmitting key.

23: Receiving Room (High-power Station, Clifden).  The illustration shows an operator at the High-power Marconi Station at Clifden, Ireland, receiving a message from Glace Bay. Nova Scotia, over 2,000 miles away. Receiving is done by sound through a pair of telephones similar to those used by telephone switchboard operators, and ia carried on at a speed of about 30 words a minute.

24: First Type Lecture Apparatus.  One of the early sets of apparatus used for lecture purposes. To the right is the coherer, tapper, and relay, and on the left a call bell with telegraph sounder. The component parts are the same as in the commercial receiver, but more compactly arranged with the view to easy portability.

	Marconi Receiving Apparatus on an Atlantic Liner. Reading from left to right, the instruments are : Special side lever transmitting key, screening box containing coherer receiver, on which stands a tape wheel; behind is a switchboard carrying starting and regulating switches, voltmeters, ammeters, pilot lamps. The tube from top of screening box is the switch throwing receiver in and out of action by means of the side lever of the key.
	21: Marconi Wireless Telegraph Station, Bari, Italy.  Erected by the Marconi Company for the Italian Government. Now forms part of the Government network of stations for public service with similar station at Antivari (Montenegro) and other places. The two towers support the aerial, consisting of a number of wires arranged in the shape of a fan, point downwards, which lead into the instrument room.
	25: Italian  Portable Marconi Station. This automobile Marconi station is intended for military purposes. It has a working range of 100 miles, and can be brought into action in ten minutes. In addition to propulsion, the engine is used for raising and lowering the aerial elevator on. the roof, and for generating current for the apparatus. Messages can be transmitted and received while travelling at half speed.