TCS Radio Set

Post under construction


The Collins TCS radio set includes the Transmitter Type COL-52245, Receiver Type CMX-46159, Loading Coil Type COL-47205, control box, shock mounts and one of several different power supplies.  It was the standard radio installed on U.S. PT Boats, landing craft, service craft, vehicles and shore installations as well as on large surface ships during WWII, the Korean war and into the Vietnam war. They may have been used in the odd aircraft as well. Some references to that (it is quite heavy).

These sets were aboard everything from mine sweepers, destroyer escorts, aircraft carriers and battleships, often serving as a Bridge radio or more often as a backup radio in Radio 2 or Radio 3 on the larger ships.  Many ships carried more than one.  These versatile, rugged sets also served through the Vietnam war era and then into the 1970’s in some installations.

After action reports from PT Boat squadrons in the South Pacific / Rendova AOR indicate that comms between the boats and from the boats to base were generally “satisfactory”. Enemy jamming was noted and was effective at times on 3785 kc, one of the operational frequencies in use. When HF radio problems occurred, the reports noted that TBY’s were used to good effect however weak batteries, beyond their “use by” dates, were a constant problem. Reference 54.

This set is currently operational at N6CC on the 75 and 40 meter AM phone bands as well as CW, utilizing a DIY AC power supply.  It sounds great on transmit and receive and has produced many 500 + mile voice contacts with simple dipoles and slant wire antennas, even further on CW.  Here it is loaded to 75 ma plate current on AM Voice putting about 900 ma of RF antenna current into a low impedance wire antenna.  It will also operate well on 160 and 30 meters, well within its 1500 – 12,000 KC range in 3 bands.

US Navy TCS Radio Set – N6CC

I bought this set in 1974 from the old Spectronix store in Chicago (they were happy to get rid of it – AM WAS DEAD – FM WAS KING!) but I just obtained the Transmitter and Receiver. I still don’t have the dynamotor power supply, remote control box or system cables but I am looking for them to complete my set some day. I do have the shock mounts in storage at present.

TCS Transmitter and PT-109

TCS Transmitter and PT-109

Above: My TCS Transmitter on display on Veterans Day 2013 at the Danville CA Veterans Memorial Building. You could see visitors’ lights go ON when they saw the transmitter WITH the model.

The receiver and transmitter antenna interconnect has BNC connectors and a type N for transmitter output. I don’t know if those were “stock” among the many configurations seen. My receiver also has the noise limiter kit installed. I find that to be quite effective on CW and especially so in the AM mode position. That was apparently added as a post-production upgrade.

NAVSHIPS Technical Manual 95322 (TCS-12) states that the transmitter power output measured at the PA tube plates is 40 watts on CW, 20 watts on phone.   Certainly an odd way to measure power output but it further states that approximately 60% of those levels are actually delivered to the antenna.  This of course is the result of the output network inefficiently coupling RF power into the electrically short antenna.  Depending upon the actual antenna used, your mileage may vary.

MZ-1 Radio Jeep

Above: Mark’s superb MZ-1 Radio Jeep equipped with a TCS radio supporting USMC ground operations. Camp Delta at Tower Park Military Vehicle Collectors of California annual camp out.  Note the dual rear wheels to handle the extra weight and to enhance mobility across beaches. That louvered box between the seats is a mechanically-powered generator for the radio set. Runs from an engine power-takeoff.

TCS set in the MZ-1 Jeep

TCS-9 Antenna Loading Coil

Above: The TCS-9 Antenna Loading Coil, Navy Model COL-47205. Built by Collins, this well worn veteran was restored at some point in its life by the San Francisco Naval Shipyard “Shop 67″. Good thing; it has seen many years of service since then as well. This coil was used with the TCS transmitter when driving an electrically-short antenna on the lower frequencies. For example, the 20 foot whip on Elco and Higgins class PT Boats. It is simply a series-connected 97 microhenry air core coil with a 6 position tap switch; set it for maximum antenna current while tuning the TCS transmitter. Although the TCS output coupling network was designed for a 20 foot whip, it needed some additional inductance to tune-out the capacitance of these short antennas when operating on frequencies between 1500 and 3000 KC.

As mentioned, the TCS was used well into the Vietnam war by many different types of vessels. During that era it was principally used as a backup to more modern equipment. But it STILL saw primary service in PT Boats. These were the PTF’s (Patrol Torpedo Fast) that were built in Norway for the US Navy and used in special warfare operations off the coast of North Vietnam. Later PTF’s (hulls 17-26) did not carry the TCS in Vietnam. See the “Fast Patrol Torpedo Boats” post elsewhere on this blog for more PTF details.

Radio Room TCS Set, Nasty Class PTF

Above: A photo of the Radio Room aboard a Nasty Class PTF of the 9-16 hull number series. Built in Norway based upon their “Tjeld” Class PT boats, the PTF’s 9-16 boats were built to US Navy specifications, the hulls and propulsion being essentially identical to the Norwegian design.  It appears that the TCS shock mount is itself shock mounted.  These boats (and crews) took a tremendous pounding while at-speed in heavy seas.  Oddly, the equipment to its left appears not to be shock mounted – it may have been installed or placed temporarily.  Its’ power cord suggests a temporary lash-up.  (Official US Navy Photograph)

Above we see the TCS mounted vertically on the port side of the boat under the 20 mm gun mount. Forward is to the right. Note the TCS antenna loading coil on the forward bulkhead above the TCS. Also shown is the AN/URR-13 UHF receiver mounted high and an unidentified large chassis with control box below it, likely a UHF transmitter or possibly an IFF set. The TCS was used aboard the Vietnam-era PTF boats until the GRC-109, and later the Collins ARC-94 (618T-*) replaced them. That is likely the TCS dynamotor power supply mounted on the deck underneath the operating table. PTF’s were used extensively in Vietnam and they relied upon HF radio to coordinate their operations with the US Fleet assets as well as their base back at Da Nang. Those operations were typically about 250 miles north of the DMZ, mostly over salt water. No problem for the TCS.

Nasty PTF (Official US Navy Photograph)

Above: A Nasty Class PTF, one of the earlier boats that was equipped with the TCS Radio sets in Vietnam.
The TCS was also used aboard submarines. Here is the installation aboard the USS Bowfin, SS 287 at Pearl Harbor, Sept 2003.

USS Bowfin SS 287 TCS Radio Set N6CC






















Above: The USS Bowfin’s TCS mounted vertically on the Radio Room aft bulkhead; the AC power supply mounted on the deck underneath. Note the use of SO-239 “UHF” coaxial connectors on the transmitter and receiver.  (It looks as if they got the coax cables from the receiver and the antenna reversed on the transmitter connectors.)
Glad to see there were no KenYaeIc rice boxes in that museum ship radio room – the ultimate insult to a proud ship and its courageous crews.

TCS Radio Set Mobile

They are also found in modern mobile setups. This belongs to my buddy Andy and is demountable for campsite use. He installed the proper remote control box at the Coxswain’s helm.  A good look at the 2-dynamotor power supply and its dyno’s.  The TX dyno on the left, RX dyno on the right.
Well, stuff happens. The BFO in my receiver failed for no apparent reason after several decades of normal operation. (It has had the Noise Limiter modification installed.) I had isolated the fault to the BFO oscillator can, Z-204. The fault was probably caused by an open or shorted fixed-value, 455 kc resonating capacitor; the stage otherwise works fine as the detector/1st AF amplifier. Very difficult to remove the can shield or that module due to inaccessible mounting screws, solder connections etc. (poor serviceability in this receiver layout). What to do?

So as a temporary “field expedient”, I built a crystal controlled BFO operating in the middle of the receiver passband, 455 kc. It operates when the “Reception” switch is in either the CW or CW Noise Limiter position. It works well.

TCS Receiver crystal BFO circuit


Above: The  bread board circuit while being tested (All Hail the Junk Box!).

I used a 2N3823 N Channel JFET oscillator transistor, a series resonant 455 kc crystal (CR-25B/U) and a 12 volt, 3-terminal regulator to feed it. It is powered by a well filtered half-wave rectifier circuit fed by the 12 VAC filament string from my DIY AC power supply. The oscillator draws 3 ma DC.

With the receivers’ broad IF passband, it works fine in CW or in receiving either USB or LSB. The front panel CW Pitch control is, of course, inoperative now but that is really not necessary for casual CW operation.
Good to go, for now…

Improvise, adapt, overcome.