MOTOROLA
FM
MOBILE 2-WAY RADIO EQUIPMENT
Part One, 1941-1957
Introduction
Please note that this page is new, and is regularly revised and added to. There are going to be some models not shown and some information missing, which will be added in time. The years given are usually approximate, as exact records are not publicly available if they exist at all.
The Galvin Corporation created what they argued was the first production AM broadcast car radio, in the early 1930's. Up through the mid-1930's, they also made specially modified car radios to receive police broadcasts, on a "to order" basis for nearby police departments. These were the days when the company was small enough that one could walk in off the street and have a special modification of a "stock" radio done almost "while you wait." Galvin began producing "Motorola" brand mobile AM police one-way radio equipment in 1937, with a modified broadcast automobile radio first called the "Police" and later dubbed the "Police Cruiser." In approximately 1939, Galvin introduced two-way operation with the T-69-20A mobile police transmitter, a VHF AM two-piece unit which operated in the 30-40 Megacycle range. Base station transmitters and receivers were also produced to communicate with this mobile equipment. The pre-war Galvin AM equipment is detailed on its own separate page, PREWAR MOTOROLA POLICE RADIO.
Deluxe Line (1940-1950)
In 1940, the Connecticut State Police adopted a VHF FM two way system in the 39 MHz band, manufactured by Fred M. Link's Link Radio Corporation. The Link contract was the first large scale two way FM VHF system in the country and was so successful that it was held out as a model for other departments to emulate. It should be noted that many articles, and Link's own advertising at the time, give the impression that Link was first with an FM VHF two way radio, but this is not actually the case. GE had purchased a license to pursue FM development from Major Armstrong, inventor of FM, and had produced working VHF FM equipment since approximately 1938, although it was essentially experimental without meaningful sales. This equipment had been examined by Professor Daniel Noble, consultant to the state police, however he found it "unsatisfactory" for reasons not fully disclosed. The Fred Link system was built to Noble's specifications, by modifying existing VHF AM equipment (the 8-UA receiver and 15-UBX transmitter.). Noble would shortly thereafter join Galvin Corporation and supervise the production of Galvin's own line of two-way FM radios, which not coincidentally looked very much like original Link equipment, and was in direct competition with it. This first line of Galvin FM equipment was dubbed the Motorola "Deluxe" line, and Galvin at that time ceased design of any new "Police Cruiser" receivers or T-69 series AM transmitting equipment (although production of both continued throughout the remainder of the 1940's.) Fred Link encountered financial difficulties and sold Link Radio in 1950, undoubtedly due to the competitive pressure from much better funded Motorola.
Once Motorola began producing FM equipment, they placed all emphasis on VHF FM and dropped advertising for conventional AM 2-Way products other than an occasional mention in brochures and advertising.
The Deluxe line consists of a two piece radio set, mounted in the trunk of the vehicle. Unlike the Link FM equipment, the Motorola equipment placed the vibrator power supply for the receiver inside the receiver cabinet, rather than in a separate external case. Perhaps by virtue of being approximately a year newer than the Link equipment, the Motorola was more advanced in design (as well as being more complicated.) The Deluxe line was produced from approximately 1941-1950, at which time it was replaced by the "Research" line, Motorola's new flagship two-way radio product.
During its production run, the Deluxe line was produced in many configurations and models, for both low band (40 MHz), mid-band (75 MHz) and (later) high band (150 MHz) systems, and was sold throughout the world. The equipment would later be referred to colloquially as "Coffin Units" or "Doghouse Radios" by the two-way radio trade.
The transmitters and receivers were labeled individually with their own model numbers, FMR- for the receivers and FMT- for the transmitters. After the end of the war, a "U" was added denoting high band VHF, for example FMTU-30D. There were various model numbers within this scheme; the FMAR-13V receivers, for example, were low band sets of a newer design than the original 1941 sets, used Loktal tubes and were called the "Precision Selectivity" receivers. The original low band receiver was the FMR-13V. There was also a unique chassis number, usually beginning with P8--- which identified the exact and specific chassis in use.
The transmitters were available in various power levels and power supply types, and included such numbers as FMT-16V for a 20 Watt vibrator powered low band transmitter, to the more common FMT-30D dynamotor powered 30 Watt transmitter. All of the Deluxe Line began as 6 Volt DC powered equipment, although some military applications were supplied with 12 Volt and 24 Volt power supplies. Eventually, some of the equipment was converted to 12 Volts in the field when American automobiles changed to 12 Volt batteries in 1956, although the majority were taken out of service and scrapped at that time. A twin 807 tube "high power" low band Deluxe transmitter (50 Watts) was available by some time in the late 1940's, although the current to run it on a 6 Volt system was extremely high and required a vehicle equipped with a high output generator or a first-generation Leece-Neville alternator.
The individual transmitter and receiver scheme allowed mixing and matching, to some extent. Fir example, a low band receiver could be used with a high band transmitter (rare) or more commonly, only a Motorola receiver or transmitter would be purchased, and the complement would be a Link or RCA or GE unit. For example, California Highway Patrol used the Motorola low band Deluxe transmitters with a Philco AM medium wave receiver, as well as the under-dash Motorola "Police Cruiser" AM sets. Other departments used a Wells Gardner AM broadcast radio sold under the trade name "Western Auto," which was modified by the Oakland, California Western Auto franchise for police use, and later mated it to only a low band VHF FM transmitter such as the Deluxe series.
A complete model would be numbered something like "FMTR-30D" or "FMTRU-30D," the complete model number apparently taking the transmitter numeric model number rather than that of the receiver. The complete model number only appeared in the manuals and not stamped on the equipment itself.
Shown below is the earliest Deluxe line design. Later versions had a pull-handle cover latch instead of the top mounted twist handles. Note that there are a couple of ways to tell a high band from a low band Deluxe set in old photos. The low band sets use prewar "Bendix" style antenna connectors which have a smaller tightening ring and are generally smaller in appearance than the more modern "UHF" Amphenol connectors, which were used on the high band sets. Also, on the high band transmitters, there is a small "coupling" screw adjustment hole located on the panel on the left end just above the antenna connector. The antenna connectors in the photo below with the legend "Mobile Transmitter and Receiver" can be seen to be UHF style, therefore those sets can be identified as VHF high band.
Note the installation below in a police car in the Philadelphia area circa 1948. Not a lot of tread left on that spare!
Dispatcher (1947-1952)
The Dispatcher was an "economy" series of two way one-piece radios created in approximately 1947, probably as a response to the FCC's opening the VHF "high band" 150 MHz channels in 1946, requiring that new police licenses be on that band absent a showing of need to still use low band. The Dispatcher was the forerunner of the Research Line, which would eventually replace the Deluxe series in the early 1950's. Unlike the Deluxe equipment, the Dispatchers were built using miniature tubes on two small channel-shaped chassis (called "strips" in the industry) and unitized into a single slide-in cabinet with an optional key-lock (called the "drawer" in the industry.) Dispatchers offered only a low power transmitter, in the 10 Watt range, and were available in either low or high band VHF. The Dispatchers were typically numbered FMTR-5(V) (low band) or FMTRU-5(V) (high band), and were known as the "5V" in the industry. Because of the small size of the strips in the Dispatchers, they were also mounted in black steel Harley Davidson "tubs" and placed in the saddlebag area of police motorcycles. The cables and control head for the Dispatchers do not interchange with the Deluxe line. The Dispatcher used a circular connector of the Cannon AN- series (later re-designated MS-) and the new Amphenol "UHF" connector for the antenna socket. Unlike the Deluxe Line, the Dispatcher control head could offer a micro switch under the microphone hang-up clip which would shut off the transmitter tube filaments when the microphone was hung up after use. The microphone hangs on the front of the control head itself in Dispatcher installations.
The Dispatcher "drawer" consists of only two chassis; the receiver chassis and the combined 10 Watt transmitter/power supply chassis which used 2E26 tubes in the transmitter power amplifier. The receiver used all miniature tubes and offered somewhat less sensitivity than the Deluxe line, and used a "derived" IF section which was not crystal controlled. The receiver had rather poor selectivity. The Dispatcher transmitter used a 2E26 output tube and the power supply consisted of a synchronous vibrator for the receiver and a non-synchronous vibrator for the transmitter, rectified by a 6X5 octal based rectifier. The Dispatcher transmitter was of course wideband FM, and like the Deluxe line, there was no deviation control offered.
It appears that there was no specific speaker supplied with the Dispatcher series; initial models seemed to have been supplied with the square louvered speakers later used on the Research Line radios of the 1950's. Some sets were ordered without speakers, as it was popular at the time to make use of a broadcast radio speaker mounted behind the grille of the car's dashboard at its intended place. Few fleet automobiles were purchased with radios (or even heaters!) so the space was available and represented a cheaper and better alternative to the purchase of a stock Motorola speaker.
The Dispatcher was widely used in taxi fleets and small police departments, but was produced only for a few years, approximately 1947-52. The low transmitter power and rather dismal receiver sensitivity on VHF high band limited the Dispatcher to small geographical areas. Most Dispatchers seem to have been made for the VHF high band range. Additionally, new FCC restrictions on stability and narrower channel spacing were on the horizon, and Motorola chose to discontinue the Dispatcher and bring out a totally new model rather than attempt to upgrade the original design.
The model name "Dispatcher" would continue to be used over and over again in succeeding years on newer models, for example the "Transistorized Dispatcher," the "Industrial Dispatcher," the "Airport Terminal Dispatcher" and the "Solid State Dispatcher."
The 1948 photo below shows an FMTRU-5V mobile leased to a police department
by the Bell System. In the northeastern states, the Bell System was
heavily involved in leasing two way radios and mobile telephones to police and
fire departments. Apparently the Bell System felt that handsets were
better than microphones, and the majority of installations featured a handset,
such as in the photo below. This made for somewhat of an odd appearance,
since the 5V head is unique in having a microphone hanger on the front panel.
Research Line (1949-1952)
The Research Line was introduced in 1949 to replace the aging Deluxe equipment and was the basis for one of the most successful and reliable two-way radios in history, as well as one of the most prolific. The Research Line was an extension of the concepts introduced with the Dispatcher sets, namely one-piece radio "drawers" using individual strip-chassis, with all-miniature tubes in the receivers. Unlike the "5V" Dispatchers, the Research Line was available in many configurations and with many different receiver or transmitter chassis combinations.
RECEIVERS:
The receivers offered in the Research Line included "Unichannel" and "Sensicon" types. The Unichannel receiver was a narrower chassis version, less expensive, but with nearly the same performance specifications as the Sensicon. The Sensicon receiver was the most expensive version, was on a wider chassis than the Unichannel, and offered more options such as multiple channels and a carrier operated relay. In the VHF high band version, the Sensicon receiver had tunable cavity "pipes" in the front end (Sensicon "A".). Both types of receivers featured Motorola's new "Permakay" IF filter, for "Precision Selectivity," although they could be ordered without it (few were.)
TRANSMITTERS:
The transmitters were available in power levels from 10 to 60 Watts, the higher powered transmitters having a wider chassis and using an 829B or two 2E26's as the final amplifier/s, and were referred to as the "A" series transmitters.
Depending upon the chassis selection, the Research Line sets could be purchased in a 10" wide cabinet or a 15" wide cabinet (or specially ordered in an even wider, 17" case !). All Research Line mobiles used the same control head, although that control head was available in many different configurations. The Research control heads are recognized by their white ribbed knobs with black pointers and the "squelch" and "volume" nameplates being riveted to the panel plate. Research was produced from approximately 1951-late 1955. Research also was the first series to offer a 450 MHz UHF radio, near the end of Research model production in approximately 1955, the T44-1.
POWER SUPPLIES:
The power supplies were available in vibrator, dynamotor and AC Utility (desktop base station.) The dynamotor power supply was used on the highest power models as apparently the vibrator design was not up to the task. The lower power models ( FMTRU-41V, FMTRU-40V for example, were vibrator powered.)
Research Line heads:
Typical Research heads appeared as the one below,
and were usually found with the louvered speaker and mike shown. Handset
models were also available, as were heads with special small multi-frequency and
multi-tone knobs in the center area (by special order.) The head shown
below was a special model with a switch to turn off transmitter filaments to
save battery power in a 6 Volt vehicle, and was probably used with a 15"
width high-power Research mobile.
The microphones were a standard Shure carbon mobile microphone of the CB-12 variety.
The typical speaker was as shown below, although this speaker was also available in a gray wrinkle finish. The mounting intent was that a single hole would be bored into the vehicle firewall, the threaded rod placed through it, and a nut in the engine compartment securing the speaker. Research was the last series to use this curious speaker mounting, an apparent throwback to 1930's auto radio mounting schemes, since even the Deluxe series used a modern "trunnion" dash or firewall mounted "U" bracket.
Also curious is that none of the paint color schemes of the speakers match the control head or microphone paints!
THE STRANGE TU 215 MYSTERY SPEAKER:
This is a speaker you won't see pictured in the service manuals but they do exist! The TU 215 speaker makes use of the "inside out" voice coil and magnet assembly used on Motorola TV sets of the late 1940's or early 1950's. This style speaker has the voice coil and magnet on the front side of the cone instead of behind it, making for a very compact speaker. For some reason Motorola decided to discontinue production of this style speaker, and sent the excess inventory to the Communications Division where they were made into mobile radio speakers with open, flocked grilles on front and rear. These were shipped during the approximate period of 1953-1955 and seem to all be undated. I had never seen one until quite recently, when two of them came my way. They are not as robust as the speaker above and may have had a short lifespan.
Typical Models:
It is almost impossible to list all the model combinations which were made in the Research Line. The most common ones were the "41V", the "80D", and the "140D" series.
41V: The FMTR-41(V) and the FMTRU-41(V) were the smallest and possibly the most popular sets of the Research Line. They were in a 10" wide case and featured the Unichannel receiver with a 10-15 Watt level transmitter, with a third chassis containing the separate power supply. The 41V used a vibrator power supply with a selenium rectifier, and was available in one or two channel models. Unlike its predecessors, the 41V has an adjustable deviation control on the transmitter. The 41V was available in either 6 or 12 volt versions, but not both in the same chassis. Unlike any other equipment either prior to it or contemporary with it, the 41V was available in either a dash mount or a trunk mount configuration, as well as a desktop base station.
40V: The FMTRU-40V is an interesting set which appears to have been made from production scraps and primarily for the VHF high band taxicab market . It seems to have been intended as an improved version of the older Dispatcher "5V" series and probably was one of the least expensive models. It consisted of a wide chassis high band Sensicon "A" receiver, mated to a Dispatcher transmitter/power supply combination, in a 10" wide cabinet. This is unusual in that the Dispatcher equipment was already discontinued at the time the 40V was being sold. Evidently Motorola had a surplus of Dispatcher transmitter/power supply combinations left over. The choice of a Sensicon A receiver rather than a Unichannel receiver is also interesting; evidently the set was designed to be used in urban areas with a high concentration of interfering signals and intermodulation distortion, which only the Sensicon A receiver with its cavity-pipe front end could deal with. Otherwise, had a Unichannel receiver been used, the set could have been significantly narrower and compact. Most of the FMTRU-40V sets seem to have been sold in the San Francisco, California area to taxicab operators.
80D and 140D: These were the industry standards in the 1950's and made in the greatest quantity.. The FMTR- or FMTRU-80(D) and FMTR- or FMTRU-140D are 15" wide cased mobiles which usually used Sensicon receivers with high power transmitters. In some instances, a less expensive "Unichannel" receiver was used. The 80D used a pair of 2E26's while the 140D used a single 829B in the transmitter power amplifier. The 80D was nominally a 30 Watt transmitter while the 140D was nominally a 60 Watt transmitter. The power supply used a vibrator for the receiver and a dynamotor for the transmitter. The Research Line enjoyed widespread popularity and such a long service life that most of them were converted to 12 volts after the auto industry switched battery voltage standards in 1956, and many were also converted to comply with "narrow band" FM requirements mandated by the FCC in the early 1960's. In the mid-1960's, Motorola even offered a field modification kit which replaced the vibrator/dynamotor power supply in the 80 and 140 series with a 12 Volt transistorized power supply, which included a heat sink which bolted to the front panel and instructions to overstrike the model number on the ID plate to read FMTR-140(T) or FMTR-80(T) as appropriate. The chassis used in these mobiles were also used in all manner of upright cabinet base stations, desktop base stations, repeaters and so forth.
AC Utility: The AC utility was a desktop base station configuration made from an FMTR-41V series mobile configuration, using a built-in speaker and control panel along with an AC power supply in place of the mobile power supply. Full sized tabletop base stations were also marketed, although it was probably more common to see base stations built into 6-foot racks with separate remote controls.
AM Options: Many large police departments still used medium frequency AM for their car to station frequency into the late 1950's (Los Angeles even into 1965!), but the old medium wave separate Police Cruiser receivers were no longer produced after about 1949. To address this market, Motorola offered a medium frequency AM receiver strip which could be used inside a Research Line case instead of a Unichannel FM VHF receiver, either with a companion VHF FM transmitter or by itself as a one-way setup. That AM receiver was the P-9075, which was also available in a motorcycle version in a Harley Davidson steel saddlebag box.. A typical configuration might have been an FMTR-5(V) style motorcycle radio, with this AM receiver instead of the usual VHF FM receiver. The model numbers of such sets are not known to the author, but may have been something similar to "FMTR(A)-5(V) or perhaps "FMT(A)R-5(V)SP-xxx." This receiver chassis was built at least through the end of 1955 and probably was carried mainly to accommodate the Los Angeles Police Department, which did not abandon AM on medium wave frequencies until 1965!
Research model numbering change: In approximately 1954, the model numbering scheme was changed from the FMTRU- type numbers to ones usually beginning in "T43G-1, T44A-6 or T51-1", although the equipment otherwise appeared identical. At the time of this change, the T44-1 UHF mobile was introduced, which was in a 15 inch housing and continued with few changes into the new "Twin-V" series after 1956, other than being re-badged "Twin-V" with a model number change to "T44AAV." A number of new models were introduced with various power levels and other options, these being referred to here as the "Second Generation" Research Line, as follows:
Second Generation Research Line (1953-1955)
The Research Line rather quickly evolved from the initial offerings of the "80D" and "140D" sets to a wide variety of configurations in 1953, in addition, Motorola changed the model numbering scheme, abandoning the FMTR- style system to one of a series of numbers such as T51-1 or T43-1, being further expanded to such numbers as T51G-1. In 1954, a UHF radio, the T44A-6 was also developed. Differing series of chassis became available, now the "A" or "G" line series. The "A" series chassis were essentially the same as in the FMTRU-80D or -140D equipment, including the famous "Sensicon A" receiver. The "41V" series mobile chassis strips were discontinued at this time and the "41V" was replaced by the T41G or T43G series radios, using the same housing but featuring the new "Unichannel" style "G" chassis for both transmitter and receiver. The wider cased higher power radios were also available with the "G" series "Unichannel" chassis inside, in which case blank metal filler chassis strips were added to fill the space in. The array of available configurations in the second generation "Research Line" was large. As mentioned, most of the Research Line mobiles were capable of either 6 or 12 Volt operation by the selection of appropriate cables and jumpers on the chassis, but apparently for marketing reasons, Motorola chose to rename the standard mobile radio line the "Twin-V" in approximately late 1955, even though it was largely unchanged from the second generation Research equipment.
Portable Sets:
Motorola's portable sets were offered in two models, starting in 1947. The portables are probably most appropriately called Research Line portables rather than Dispatcher or Deluxe portables, although they actually have nothing in common with either equipment series.
FHTR Series (1948-1956): The lower powered portables were the FHTR- series (FHTRU- for high band). They make use of subminiature wire-lead tubes in individual modules, and were powered either by a pair of 2 volt wet cell batteries with a vibrator power supply in a large battery box, or several 67.5 volt "B" batteries and a string of "D" flashlight cells in a smaller "dry battery" box. The FHTR series was available in one or two channel models, and could be ordered with extra transmitters or receivers inside for broad band operation. There was no speaker, only a handset which hung on a cradle across the top. Most handsets appear to have been supplied by Roanwell. There was no squelch in the receiver on most models, although it was an option, with the squelch control a screwdriver adjust potentiometer located inside the power supply.. Evidently the additional battery drain of the constant noise in the earpiece during no-signal conditions was offset by the savings in not using an additional tube and module for the squelch function. The FHTR- modules and basic design were incorporated into a custom made forest service semi-portable repeater station called a "lookout radio," which as the name implies, was used in forest service lookout towers throughout the country. This series appears to have been discontinued by 1956, although sometime around 1953 the model number was changed to H11-1 and H13-1.
Shown below is an FHTRU series pack set with the optional wet battery rechargeable power supply. Two clear plastic-cased 2 Volt wet batteries are inserted at each end of the power supply case, through panels in the bottom cover. A small vibrator power supply then provides the high voltage DC to the pack set.
FPTR Series (1950-1957): The higher powered portables were the FPTR-series, and came in a much larger and different case than the FHTR- sets. They were introduced in 1950. The FPTR units had a large chrome handle across the top and offered a speaker/microphone combination rather than a handset, as well as room for multiple transmitters without increasing the overall original size (unlike the FHTR series which became quite a bit larger to accomplish the same thing.) They also offered squelch in the receiver as a standard feature, although that squelch was a relay-operated type rather than an electronic design. Like the FHTR units, there was a battery box across the bottom where large B batteries resided. The FPTR units use most of the same modules as the FHTR- sets. The FHTR equipment seems to have been discontinued at the introduction of the Research Line, but interestingly, the FPTR- equipment continued to be sold at least through 1956 after being re-numbered as the P11-1 (low band) or P13-1 (high band). Some are painted with gray wrinkle paint, while others are a silver-gray hammertone finish. I am not sure which is newer. An accessory AC-DC power supply was offered, which connects to the Cannon external power connector on the top panel of the equipment. Note that the microphone in the example below is a slightly later model; the one used with this model originally should be a round style made by Shure, rather than the Turner manufactured item shown here. I am not aware of a wet battery rechargeable power supply being offered for this model, as it was with the FHTR series shown above. These sets are surprisingly rare today compared to the FHTR style shown above.
Apparently the chrome handle was originally conceived to be a different shape. See the article below from the August, 1950 issue of Mechanix Illustrated:
Handie-Micro Talkie: Perhaps one of the strangest and most obscure Motorola products of the 1950's was the Handie Micro Talkie, made with various model numbers and introduced in late 1953. The name is somewhat of a misnomer as this radio is actually only a portable transmitter, containing wire lead subminiature tubes, "B" batteries and the first use of the rigid loop "railroad" antenna which also doubled as a handle. In 1955 this antenna must have looked very "space age." They were used where it was only necessary to have a transmitter, such as in rail yards where a receiver feeding a PA system rebroadcast the signal from the Handie Micro Talkie over loudspeakers, or in logging where the same basic system was used. The housing is a sturdy metal one. The majority of these, if not all, were VHF high band and the power level was 50-100 milliwatts. A late 1950's example was found carrying the model number Z13ULN. An interesting and apparently short-lived application for drive-in car hops is shown below, from the December, 1955 issue of Popular Science. Note that it mentions a system for communicating back to the car-hops but fails to mention that the Handie Micro-Talkie was only a transmitter, hence the need for signal lights. The Handie Micro Talkie was replaced in approximately 1961 by the all-transistorized pocket transmitter series H11NBC and H13NBC series.
MOTOROLA MODEL NUMBERING SYSTEM, 1942-54
(Deluxe, Handie Talkie, Dispatcher and Research)
Typical model numbers broken down, for complete sets:
"FMTRU- 30(D) " would be the model number of a complete set, as follows: F= FM equipment, M= Mobile, TR = transmitter and receiver, U = "UHF" (150-174 MHz), 30 = model series, D = dynamotor. The FMTRU-30D would usually consist of the FMRU-16V receiver and the FMTU-30D transmitter.
"FPTR-1" would be the model number of a "high power" speaker type pack set, low band, as shown above. The "H" as in FHTR-1 would refer to a low power handset model, as shown above. The letters mean: F= FM equipment, P= Pack set (H=Handie Talkie), TR=transmitter and receiver, 1= Model series. No suffix after the "R" means low band. A "U," as in FPTRU-1, would be a high band unit.
Further, "S" = Station, as in FSTR-80BY.
Individual unit model numbers would be as the following examples:
FMR-13V would be a low band FM receiver only, vibrator powered, 13 series, low band (no "U.")
FMT-30D would be a low band FM transmitter only, dynamotor powered, 30 watts
MOTOROLA MODEL NUMBERING SYSTEM, 1954-57
(Research, early Twin-V, Handie Talkie, Transistorized Dispatcher)
For some reason, Motorola briefly changed the model numbering scheme to a rather less informative one than used previously, during production of the "second generation: Research Line as discussed above, and this scheme only lasted a few years. It was as follows:
T43G-1 would represent a VHF high band 24 Watt mobile radio in 10" case. The "T" signified trunk mounting, the "4" being a 20-40 Watt power level, the "3" meaning 150-174 MHz band, the "G" representing "Unichannel" G series chassis "strips" inside, and the "-1" standing for whatever variation in that series the unit represented. Typical first letters could have been "H" for Handie Talkie or "P" for pack set, "D" for dash mounted radio, "M" for motorcycle, "R" for railroad, "X" and "Z" for special and industrial uses, "B" for base stations, "Y" for repeaters, "L" for desktop "Consolette" base stations, and a few others. An "A" suffix meant a wide-cased mobile using the "Sensicon" receiver and the larger "A" series transmitter.
Other models would have been deciphered as follows:
First (letter): D=Dash mount mobile, P=Pack set portable, H=Handie Talkie (smaller pack set,) R=Railroad, F=Fire engine version (rare,) W=Western Electric mobile phone, M=Motorcycle, S= Servicar three-wheeler. And a few others.
Second (digit): Power level. 1=Low power, to about 1 Watt. 2=Power to 2 Watts. 3= Power to 10 Watts. 4=Power to 25 Watts 5=Power to 50 Watts.
Third (digit): Frequency band. 1=Low band 30-50 MHz, 2=Mid Band 70 MHz, 3=High band 132-175 MHz, 4=UHF 400-470 MHz.
Fourth (letter): Type of strips inside. G series or A series, for example.
Fifth (digit): Combination of strips within that series, options included, etc.
It becomes obvious that this system is too limited in scope and as a result it only lasted a few years, replaced with the system used for the next forty years, which had numbers such as T43GGV-1100C, etc..
TWIN-V ERA, 1956-61:
MOBILES:
By late 1955, Motorola had begun production of an upgraded Research Line, called the Twin-V series, named so because of their ability to work in either 6 or 12 volt vehicles depending upon the selection of power and control cabling. The American auto industry had begun the switch to 12 volt batteries in 1956, and by that time practically all Motorola Research mobiles were 6 or 12 volt compatible. This was accomplished by split transformer primaries and dynamotors with dual windings.
Much of the Twin-V series differs little from the original Research Line, except for an expanded choice of optional receivers and transmitter power levels, and that all mobile models were capable of either 6 or 12 volt DC input. The transmitter and receiver strips from the Research Line were slightly upgraded to feature more modern tube types, but were otherwise variations of the same theme. The original Research Line mobiles, in the second generation type numbering scheme, continued to be made for a few years into the Twin-V era, probably simply to exhaust existing stock. The typical service manual, on the cover page, will use the words "Research Line" as well as "Twin-V" simultaneously.
The original Twin-V control head appeared with the lamp lenses of the Research heads :
The "normal" most common Twin-V control head appeared as shown below, note the opaque plastic lamp lenses as opposed to the glass versions shown above.
Typical examples of the narrow and wide cased Twin-V mobiles are shown below.
Note that in the above advertising photo from Motorola's Reconditioned Equipment Department, they have placed a Research series control head with the later "wrong" knobs on it, with a Twin-V mobile 10" drawer, apparently in an attempt to recycle everything and use up obsolete parts. The correct control head would have been the Twin-V style as shown on the 15" mobile above it (although they are electrically identical.) One of the former employees of the reconditioning department from that time has advised me that the radio drawers were separated from their accessories at trade-in time and all underwent reconditioning in separate operations, never to meet again.
By 1958, the Twin-V era equipment had begun to be replaced by the "T-Power" equipment, which was Motorola's last fully vacuum-tubed mobile. Twin-V equipment was still being sold from existing stocks until approximately 1962, although it is believed that full production actually ceased about 1959. The T-Power equipment will be discussed in Part Two. In 1959, Motorola also introduced the Motrac series, a completely new design with a fully solid state receiver and hybrid transmitter, which is covered in Part Two.
SPEAKER MIKES!
For some reason, during the Twin-V era, Motorola offered a normal-appearing mobile microphone which was actually a speaker-microphone. Instead of the usual carbon cartridge of the time, a small paper-coned speaker element and transistor amplifier was placed inside the microphone. The speaker-microphones can be recognized by the front section being a dark gray color with the rear half a flesh-tone color, while the standard microphones are the opposite scheme.
PORTABLES
The venerable pack set FPTR series (briefly re-numbered P11- and P13-) were replaced in early 1957 by the partially solid state "Transistorized Dispatcher" chassis pack sets. Motorola never referred to these pack sets as "Transistorized Dispatcher" but the chassis sections within were what was used on the new motorcycle and industrial radios. Instead, the tag says "Handie Talkie FM Radiophone." The first generation receivers were fully solid state other than two subminiature tubes in the IF section. The transmitter was primarily subminiature tubes (1AD4) with subminiature 6397 driver tubes for the high band version. The low power versions ended with a 3B4 (low band) or three 6397's (high band) power amplifier. For the first time, power levels were 1 Watt for the low power set and 5 Watts for the high power. All high power sets used a 2E24 tube as the PA tube. The 2E24 is an instant-heating version of the 2E26. All tubes in these sets were instant-heating, which in reality meant that the operator would depress the push-to-talk switch and then wait approximately one second for the tubes to heat, before speaking. These pack sets were available in three main power configurations - - dry batteries, nicad battery with built-in charger, or AC power (portable base station.) The transistors were Germanium types and the circuit boards were an early generation phenolic type with thick traces.
The center section is the transmitter-receiver chassis area, the bottom section is the battery or power supply, and the top section holds only the speaker and controls. These were also available in a handset model, and continued to be made through about 1966 with various refinements, such as the receiver finally becoming fully solid state. A special model for the US Coast Guard was made which had both a handset as well as the speaker, in contrast to the standard handset model which deleted the speaker.
They were purchased in large numbers by forestry agencies, fire departments, civil defense and the military. They are very reliable and reasonably easy to work on, the chassis sections folding out like the pages of a book for service. The transistors are all metal cased early Germanium types, and the boards are positive ground. In the nicad-DC models, the power supply is a DC-DC converter so that the output is isolated and unrelated to the input, thus placing the case in contact with the grounded metal body of a 12 Volt negative ground vehicle will have no effect.
Typical early numbering of these at the end of the second generation Research era (early 1957) would be H21-1 or P33-1, although since the majority of these pack sets were manufactured during the Twin-V era and later, the numbering would typically be H21AAM-1100 or H23AAM-1100, for example.
A few of these sets were available as special orders with multiple transmitters or multiple receivers for broadband operation. Quantities of these radios were leased to the U.S. government during the early years of the Vietnam conflict, and delivered to Saigon, where Motorola maintained a service depot near the airport. The government of the Republic of Vietnam also purchased quantities of these radios, as did the now defunct government of 1950's Cuba.
Shown below is a high power (5 Watt) VHF high band pack set, and a low power )1 Watt) VHF low band pack set. Both with ni-cad power supplies. The dry battery power supplies on these models are recognizable by the lack of a hinged door on the side of the power supply (where the charging and external power cables connect.)
Narrow Band conversions:
In 1962, the FCC required that all VHF low and high band systems be "split channel," i.e. the maximum frequency deviation of the transmitter was limited to 5 kHz and channel spacing was reduced from 60 to 30 kHz. A great deal of the equipment still in service from the 1950's was retired at this time by its owners rather than being converted to narrow band, especially since American cars had changed to 12 Volts in 1956. The cost to convert an older radio to both 12 Volt operation and narrow band was often more than the equipment was worth. The availability of partially transistorized equipment further eroded the interest in keeping any of this older equipment, such that much of it was gone by the early 1960's.
Equipment which was converted to narrow band using kits supplied by Motorola should display a silver sticker or nameplate with the letters "CC" followed by the new type acceptance number for a narrow banded radio. Equipment so marked usually shows up every once in awhile today.
This page created by Geoff Fors, Monterey California. Copyright 2000, all rights reserved.
Ver. 6/29/2010
