In a 27 June 1950 internal CIA memo, the Communication Division Chief was directed to make 1205 RS-1 sets available at 9 different locations for issue to agents (along with 1225 RS-6 sets among others). North Korea had invaded South Korea 2 days earlier on 25 June 1950.
By 1965 the CIA noted that available stocks of their RS-1 sets were “diminishing”. By then, the US Army needed their own dedicated, small radio set as the GRC-9’s were both big for portable ops but also well into obsolescence.
The U.S. Army did utilize the basic design of the RS-1 as the functional basis for the new AN/GRC-109 to be supportable with standardized training, repair parts and depot maintenance within the Army supply and logistics system. The GRC-109 appeared about 15 years after the RS-1 sets first entered service. As a practical matter they were probably considered interchangeable (except for the burst keying capability) when available and as needed. The RS-1 sets and the GRC-109/GRC-109A’s were all made by different companies; reportedly RDR, NEMS, Admiral Corporation and Oklahoma Aeronautics respectively.
The main difference between the RS-1 and GRC-109 sets is the T-784/GRC-109 transmitter. The T-748/GRC-109 transmitter has the addition of the panel connector and internal circuitry for the “burst” high speed keying transmission capability. This new capability/connector required different antenna and keying connector position locations and labels versus the RS-1’s Type RT-3 transmitter.
Anecdotal evidence has GRC-109’s in Special Forces unit inventory as late as 1978. They were being overhauled at the Tobyhanna Army Depot as recently as 1983. The Department of the Army Radio and Radar Reference Data manual, FM24-24, dated December 1983 still listed the AN/GRC-109 as “Standard A” issue. The set continued to be listed in US Army Field Manual FM24-24 Signal Data References: Signal Equipment dated 29 December 1994.
Photo at left: A mid 1970’s photo of the US Army 10th Special Forces Group (E) team radio equipment laid out for inspection. In addition to the two complete GRC-109 sets, note the GRA-71 Code Burst keyers, the PRC-74 transceivers, PRC-25/77’s, PRC-90’s and the Homelite XLA115/1/400/1P gas powered, 400 cps AC Gensets for the GRC-109’s.
Accessory gear included the G-43 hand cranked generators, AC/DC power supplies, antenna bobbins, spare parts kits, camera kit, 7×35 and 10×50 binoculars. By the time of this photo, the PRC-74 was taking over the commo tasking formerly met with the GRC-109’s but the 109’s were still in active inventory.
It is clear that early in the Vietnam war the GRC-109 was a primary long-range communications workhorse of MACV-SOG operations (Military Assistance Command Vietnam – Studies and Observations Group). Prior to the stand-up of MACV-SOG in 1964, the CIA (and the US Army) would have used the earlier RS-1 sets in previous communications circuits in Southeast Asia in the late 50’s and early 60’s.
It can also be surmised that MACV-SOG units inherited some RS-1 sets from their predecessors and continued to use them for those missions post-1964 in Southeast Asia, when or where they were available. The historical record does not always differentiate between the sets in field use. From a “report writers” perspective, they may have been considered to be equivalent. The CIA’s RS-1 set was very likely in use by the US Army and others in that earlier time frame before communications doctrine changed to require the usage of “burst” and the GRA-71 high speed burst keyer and the AN/GSH-17 Receiver-Recorder system became available.
In those days, regular Line infantry units in Vietnam primarily depended upon the easy-to-operate tactical voice radio systems they had available, especially as the CW skills of many RTO’s atrophied along the way. This was especially true considering the limited geographical TAOR that most regular Army units operated within; and that was usually (ideally) within range of their supporting artillery (and VHF radio range).
Long range Division recon units in Vietnam may have had the GRC-109 in addition to the Special Forces units, but the unclassified/declassified record is so far silent on that. However, LOS VHF voice-to-relay sites or aircraft within South Vietnam would have dominated for regular infantry units, since it was easier, faster and we had air supremacy above that country. In contrast, the LRRP units in Europe routinely used the GRC-109 for their primary communications of Intel back to G2 at their base (Reference 38). However, they were training for operations “further east” in western Europe where air supremacy (and reliable VHF/voice aircraft relay) would not be assured; hence, HF.
The GRC-109’s were deployed to at least 28 SF camps and in fortified villages throughout South Vietnam as the only means of reliable comms back to HQ and, initially, between themselves for mutual support*. This was true especially in the “early days” and later on they were used as backup systems to the AN/FRC-93’s (Collins KWM-2) as those became available in fixed camps. The KWM-2’s were far more fragile and arguably far less “soldier proof” than the GRC-109’s however.
(*It should be noted that the sunspot numbers (an indicator of effective skywave HF communications) was at the very bottom of the 11 year cycle in October 1964. It began to improve for the next few years but was still relatively poor. The networks did the job despite poor conditions during those early years, a testament to the reliability of HF morse code communications and to the operators skills.)
Also see Peter McCollum’s excellent GRC-109 article here: http://www.militaryradio.com/spyradio/grc109.html It includes some photo’s of the GRC-109 in operational use with the US Army Special Forces in Europe and Southeast Asia.
The GRC-109 was also utilized as the primary communications set by Vietnamese personnel working behind enemy lines in unconventional warfare operations deep inside North Vietnam (Reference 1, MACV-SOG Communications). Notably for their long range but also because on-scene air support (and its inherent radio voice / relay possibilities) was not in operation.
The predecessor RS-1 was also likely used by US led recon teams operating in Laotian and Cambodian border areas (later to become SHINING BRASS recon patrols), initially as they took over those missions from CIA control prior to 1964. The GRC-109 was also used early and elsewhere in Southeast Asia, again taking advantage of the long range and ruggedness of this system. It was noted that Comms were dependable with this system however it was also noted that the weight of the GRC-109 set, especially with its heavy and bulky hand-cranked generator reduced the mobility of these men working on MACV-SOG missions.
For the complete article go to the link listed below.
Article from n6cc.com
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