RECEIVERS

RECEIVERS

THE RECEIVER MATRIX COMES AFTER THE TEXT BELOW

Welcome to the Royal Navy's RECEIVER PAGE, but what is a RECEIVER?  Unlike the W/T transmitter side of the house, where a transmitter is defined as low or high power, main or secondary set - portable or transportable - fed from mains supply or batteries etc where a  transmitter is a transmitter,  that is not the case when it comes to reception!

To attempt to put receivers into a neat table without ambiguity {particularly receivers from the earliest days} is not an easy task and therefore it will not be attempted.  Receivers, like transmitters, started life as large pieces of copper sheets which {in the receivers case} were screwed to the bulkhead  in the silent cabinet [a part of the W/T office] onto which were attached components culminating with an inker,  designed to read minute fluctuations coming from coherers, thereby automatically transcribing the incoming signals.  There were no earphones or loudspeakers and operators did not use pencils and paper to read the Morse code.  In general, the standard of operating and the proficiency in the Fleet for reading Morse code was not good, in fact, it was the cause of great concern to many an admiral for a lengthy period prior to WW1. 

Over on the transmission side, we mention that to fully understand  that section {and the same comment applies equally here to reception} one must first read of the historical events and happenings before WW1, indeed from 1895 until 1913.  It is a big read but it is a prerequisite  if you are to avail yourself of the necessary background knowledge. 

Be warned that when reading the pre WW1 files from 1895 - 1913 {in two sections} you will sense an almost total bias towards transmission.  However, many of the trials and tribulations experienced, even though some were abject failures, obviously involved primitive receivers. That they have not bothered themselves too much with the detail, apparently concentrating only on transmitter power and transmitter aerials and almost ignoring propagation and receivers per se, is to be understood, because the receiver was, in the beginning, the "poor cousin"  of the embryonic wireless telegraphy age.  With the transmitter came the SPARK and the ARC age which lasted for a longish period of time, and during this period the receiver coped with them both without having to be changed.  Prior to the break through of heterodyning and the introduction of the valve, R&D on receivers moved relatively slowly from coherer to various forms of crystal detectors, and when not that, the problems of actually hearing the detected signal were addressed by establishing the "silent cabinet", the Rejector, the Acceptor circuits and the earphones.  One example of this was in the overcoming of atmospheric or locally produced interference at the receiver site.  Instead of the receiver being 'tweaked' to resolve the problem [or that a frequency change was ordered neither of which were possible] the problem was resolved at the transmitter end which was thought of as a panacea for all ills.  The resolution came by speeding up the rotary or the AC alternator providing power for the transmitter so that the Morse code note also went up and was more easily read than a lower note.  Typical of this was that a transmitter emitted a 400Hz [our mains voltage is delivered at 50Hz] Morse tone which was increased to say, 1000Hz to clear 'interference' but only for a limited period after which the power source was returned to a less alarming rate of r.p.m!

In these early days, that sheet of copper screwed to the bulkhead was given a name, a single letter of the alphabet, and it remained a TYPE 'A' receiver, component changes notwithstanding, for some considerable time until a new sheet of metal was exhibited at which time receiver Type 'B' was vogue.  When the Type 'C' receiver was introduced in 1910, at first in the mould of receivers A and B, [see PRE WW1 WIRELESS 1910 {1910.ONE.PDF FILE}]  using a state-of-the-art latest crystal detector, it was seemingly very successful. The Type 'C' receiver then went through the now customary changes until by 1912 it was neatly boxed as a stand alone piece of apparatus. It was still the sum of its parts, and regrettably, at least for us devotees, they spoke and wrote of the parts and not necessarily the sum. Because of this, we have very little text and just one small picture plus a schematic to remind ourselves of those times receiver-wise. You will see below the word heterodyning.  This is much too early to start thinking about heterodyne as in "superhet", and here they are referring to the mixing of frequencies to produce the AF [audio frequency] stage of the receiver, what we today, call the BFO [beat frequency oscillator] stage. 

Click to enlarge


A.

Click to enlarge

B.

The text we have is on a very used piece of paper so a quick re-type is necessary.  Before giving it to you, you need to know that is the early days they took the literal functions of a receiver and named it so, whereas, a receiver still carries out those same functions today, but we call it pure and simple,  a receiver.  They called them "TUNER AMPLIFIERS" a statement today more fitting to transmitters than to receiver's, and when you get into the matrix below, your might be surprised to learn that the 'famous' receiver B28 was first introduced into the Navy as "Tuner-Amplifier B28".  The figures shown in brackets in the text below refer to the figures pointing to various parts of the receiver in the pictures A and B above.

This is what it says:-

"RECEIVER OUTFIT C

Date of Design: 1912 [that is the boxed version]
Frequency Range: 55 - 1400 kc/s
Receiver outfit C is a tuner outfit consisting of separate inductance and condensers wired up as shown in figure a [the schematic above].  Receiver Outfit C cannot, therefore, be used alone but must be used in conjunction with a detector [e.g., Board E] or an amplifier. It consists of four separate circuits:-

[a].  The Aerial circuit consisting of the aerial inductances [2] and [3] and aerial condenser [4].  This condenser can be short circuited on all except the higher frequencies.  If receiver Outfit C is used in conjunction with the aerial normally used for transmission the aerial transmitting inductances [aerial coil, mutual coil etc] are of course included in the aerial circuit.
[b].  The acceptor circuit consisting of the acceptor inductance which is the primary of the I.T.M. [Inductance Tuner Mutual] [9] and the acceptor condenser [5].  Another condenser [7] can be inserted in parallel with this condenser [5]  by means of a pattern 1549 switch [6].  The switch [8] is normally to be in the central position.
[c].  The Rejector circuit consisting of a number of fixed condensers [12] which can be switched in, in parallel, up to large valve, and small inductances [10] and [11].  This rejector circuit can be connected by means of the red switch [13].
[d].  The secondary circuit consisting of the secondary of the I.T.M.,  [14] and the secondary condenser [15] , across which leads are taken to the grid and filament of the first valve of  the amplifier [17].  Another condenser [18] can be connected in parallel with condenser [15].

The action of the circuit is very simple, provided the actions of acceptor and rejector circuits is understood.  The aerial and acceptor circuits simply act as two separate acceptors circuit in series, each tuned to the incoming wave [while the rejector circuit, if in use, and also tuned to the same wave, offers a high impedance to the required wave but a comparatively low impedance to interfering waves].  The latter, therefore, chooses the path of low impedance, via the rejector, in preference to the higher impedance of the tuned acceptor circuit.   The secondary circuit gives selectivity to the model and the coupling between the primary and secondary of the I.T.M., should be adjusted for best results.  The picture above to the right also shows the equivalent circuit [Normal] and the equivalent circuit [Rugby].

Amplifier M3B [17] is usually fitted with receiver Outfit C but note magnifier N9 [18] may not be fitted. In 2*-34 a cabinet fitting [25] is used to connect the receiving gear to the magnetic key.

TO TUNE THE RECEIVER OUTFIT C

Switch on the heterodyne unit K5 [bottom left picture B] using I.C.W. and adjust it to the required frequency.  Separate the primary [9] and the secondary [14] of the I.T.M. as far as possible.  Couple the K5 to the secondary and tune the secondary circuit.  Couple K5 to the primary of I.T.M., and tune acceptor circuit with switch [8] in position "K5 Tuning". Tighten the I.T.M., coupling and tune the aerial circuit.  Note that the red switch [13] may be used for short circuiting acceptor condenser [5] as stated below.
To receive very low frequencies e.g., Rugby, frequency 16kc/s.  Pattern 1549 C.O.S., [6] is put over to the connect condenser [7]  in parallel with the aerial capacity.  Pattern 1276A C.O.S., [8] short circuits the acceptor condenser [5].  The aerial and acceptor circuits are therefore now combined into one acceptor circuit of a high L.C., value which tunes to the low frequency of the wave which is being received.  The secondary circuit is used as before.  The rejector circuit cannot anyhow be used under these conditions, as it would no longer be connected across an acceptor circuit."

END OF TUNING

Wasn't that thrilling ? Well maybe not, but you have just witnessed the forefront of receiver technology as used in the Royal Navy and in a sophisticated receiver which could boast good frequency coverage [it is a LF/MF receiver - called NORMAL operating] capable of also receiving VLF called RUGBY operating], good detection, and, in common with all equipments of those times, could handle either ICW or CW emissions. However, the text tells us that a 'NOTE MAGNIFIER' could not be used with this set.  A 'Note Magnifier' is used on a receiver which doesn't have a "powered AF stage" and is an external unit with an interface for earphones and/or loudspeaker connection which is connected into the Detector Stage of the receiver.  Did you spot in the paragraph immediately before the commencement of the tuning instructions the bit about "2* - 34" ? This receiver, as you will see, was, in its many forms, the most ubiquitous piece of equipment the Royal Navy ever had. It got to Model C34 before it became obsolescent [note - not obsolete]. It then continued, now with a second letter of the alphabet added to the letter 'C', from Outfit CE to CR but this time as a valve set using a valve as a detector as well as for amplification.

Many separate parts [components] were made as tuners, amplifiers, detectors, rejectors, acceptors, and any or all of these parts could be offered up to replace older parts across the board of receiving kits.  This meant that a so and so part could find its way into a Communications Receiver or into a Direction Finding Receiver, where, in the latter case they added a goniometer and in the former, an inker for transcribing Morse code messages.  Some sets doubled as standard receivers and D/F sets and when you see in the matrix below the D/F Receiver SF, you will see that it has two quite separate frequency ranges, one for D/F and one for "other reception."  Many of you will be familiar with sets like the FH4 or FM11, FM12, where, in all cases their basic receivers, receivers like the FMB, were stand alone TRF's which could have been employed in other types of radio receivers. However, apart from the earliest of D/F equipments which are covered in the matrix below, D/F equipment is dealt with under its own section on this site.  Navigation radio receivers are covered under their own section.   This "mix and match" approach to receivers proper was also used in documentation and the first file in the scuttle matrix below tells something of the haphazard way in which items of equipment were named. Incidentally, this file also applies to the transmit side and it is the first file shown on that matrix too. The next file in the matrix below simply gives a list of all the receivers used from year dot right up to and including ICS2 [with a 1980 cut off].  This matrix will not show receivers which were an integral part of an equipment considered to be a transceiver, and to find those receivers, one needs to trawl the transmitter matrix.

Now unlike Naval transmitters which almost to a set were kept out of the reach of civilians radio amateurs [RADIOHAMS] although of course some found their way to these collectors, yes and users, but only after they had been declared fully obsolete by the Service and even then only small to very small sets, several Naval radio receivers started their lives as commercial products and were jointly used by the Navy and by these knowledgeable and dedicated amateurs.  Perhaps the finest two examples of this, although there are others, is the Marconi superhet CR100 {in various versions and I am thinking about version 4] and the Racal RA117 [again in various versions and here we are talking about version E].  Enthusiasts searching this page for these sets will be unlucky because the navy has never had a set called a CR100 or a RA117E !  Whilst we 'old hands' are as fully familiar with these names and the workings of these sets as we are with all other equipments used in the navy, many in the navy are not,  and since it is a regimented organisation, all personnel of whatever rank or branch, call the same 'thing' the same name so that we ALL know what we are talking about.  Apart from equipment bought 'off the shelf' for quasi naval communications, and here consider sets like the 689 for communicating with commercial shipping organisations/ships or sets which are installed into warships working in a largely civilian environment [survey ships] or our RFA's with a part commercial fit and part RN fit - the "Globespan" transmitter is a good example - few, if any, commercial procurements have not been altered [some extensively] before being put to use in the Royal Navy.  Using the name printed on the front of a piece of kit regardless of its origin or use is quite acceptable [in fact, normal] in the informal sense, but this site, where possible, is about the Royal Navy and thus by implication, formal. After all, I have met very few people in the navy over a long period who have called the lovely Marconi transmitter the NT204, other than a transmitter Type 640, but I do meet people who insist on talking to me about RA 117's.  The fact of the matter is that kits like CR100's and RA117's were not up to the standards required by the Navy and so had to be modified.  Once ready for naval use they assumed a naval name, and the Marconi kit became a B28 and the RA117 became known as the CJK receiver, but in actual fact, just a part of that receiver, albeit, the most important part!  Racal RA17's have been used in other receivers like the CHB for example.  Their Lordships, in their wisdom, had decreed that all naval receivers should be named from the group letters of CAA to CUZ, which confused people when the B28 joined the Fleet.  The name B28 stuck, throughout its life, and CR100 wasn't used [certainly not by the rank and file] and more to the point, nor was Outfit CDC the correct name for the set given it by the Admiralty. Now, most of us, when referring to the Navy, refer to the sharp end, the sea going fraternity, but we had a large world wide SWS [Shore Wireless Service] serving our many foreign W/T stations, and into those went little old receivers like the B28.  Only when in a ship,  was its correct name the CDC and when fitted ashore it was an Outfit CDL.  From the same rationale, the B29 [also a Marconi receiver but a TRF and not a superhet and also with a CR prefix which we won't mention] became a CDF at sea and a CDM ashore. The CDC and the CDF were replaced by a wonderful receiver called a B40 [yes, a naval name] but more correctly a CDW at sea for all time, and, wait for it, first off a CAQ ashore, which later became a CAY ashore when their control system were up-dated.  The Naval Stores Branch supplies the equipment and the W/T Branch uses it.  There would be little point in asking the Stores for a B40: they wouldn't understand the request. Having multiple names within the navy [never mind the civilian/HAM input] led to a 'belts and braces' approach to documentation where the phrase "CDW/CAQ/B40" {quite unnecessarily} became the norm.  Whilst on the subject of nomenclature, there are several other occasions where a receiver has two names.  One example is the "B46/B47/CAJ-CAP" Receiver! When it is used in conjunction with a Transmitter Type 612 to form a circuit, it becomes a B46 and B47 [different frequency ranges] but when it is fitted separately as a normal shelf-mounted receiver it is either a CAJ, CAK, CAL, CAM, CAN, CAO or a CAP depending on where and with what aerial it is associated.  Hence, you will find reference to B46/47 under Transmitter 612 on the Transmitter Maxtrix, and for CAJ-CAP below: Similarly, quite a few receivers missing from this matrix can be found in the D/F Outfits matrix.   Finally, on this subject, when you get to the D/F page, be open minded,  for we need to establish an answer to the question WHEN IS AN FH4 NOT AN FH4 ?

By now, you should have gathered that far from being pedantic the navy has a specific nomenclature,  although we have to admit that you need a degree in logic to follow the plan.

So, if you are looking for popular receivers like for example B28, B29, B40, B41, you will find them grouped with formal/informal names under the  CAA to CUZ range, and if you are looking for a  CR100, a Racal 17 or 117 etc, look at their commercial websites [any and all] for details of those OEM's [Office of End Manufacturer], or better still,

have a look at this website  KEITHS VINTAGE RACAL SITE, because Keith Rawlings was the original webmaster of our Collection and what he doesn't know about the RACAL product is not worth knowing about.

The list of receivers {remember, from 1895 until 1980} in the matrix below, is not exhaustive, and some are omitted because of their close similarity to those listed. By and large the matrix is representative of 85 years of naval receivers, and whilst it is designed as a reference library it is also published to whet your appetite for even more detail about the W/T equipment used by the navy both ashore and afloat.

  
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