US Armored Cavalry in Vietnam - Radio Net

THE RADIO NET - Page Title
US RADIO COMMUNICATIONS


Since the majority of the information for this page was supplied by Veterans of Bravo Troop, 3/4 Cavalry I will use their Radio Net as the example for this section.

Call Signs

On the whole, radio call signs were changed about once a month for security reasons so the following is only valid for a small period of time and would have changed frequently.

The Squadron's call sign was 'Saber' and the 3 Line Troops in the Squadron were 'Saber Alpha', Saber Bravo and 'Saber Charlie'. The Squadron Air Cavalry Troop had it's own call sign, 'Centaur'.

The Squadron CO was 'Saber 6', however Squadron Communications was 'Saber 33' because the Squadron Executive Officer (XO) was 'Saber 65'.

The Bravo Troop HQ call sign was 'Saber Bravo 6' (the CO's vehicle) and the Troop Commo track was 'Saber Bravo 65'. Other vehicles in the HQ Platoon were numbered 'Saber Bravo 41', 'Saber Bravo 42' and so on.

Within each troop, taking 'Bravo' as the example, the 3 Platoons were numbered 10, 20 and 30, so that the call sign of the Commander of '2nd Platoon, Bravo Troop' would be 'Saber Bravo 20'.

All other vehicles in the 2nd Platoon would be numbered as the platoon number plus 1 - 9. For example, the vehicles of 2nd Platoon, Bravo Troop would be numbered 20, 21, 22, 23, 24, 25, 26, 27, 28 and 29.

Radios and Frequencies (Pushes)

The Troop HQ (Saber Bravo 6) carried two radios. One of these was on the Squadron frequency (called a PUSH in the 'Nam) and the other was on the Platoon's frequency. In this manner the CO could communicate directly with Squadron HQ and with each of the Platoon CO's in his Troop. During a firefight however, the CO would communicate on the Platoon Push whilst the Troop Commo Track (see below) would be dealing with communications to and from Squadron. Squadron Radio Net - Schematic

In addition, the Artillery Forward Observer (FO), who was usually riding with the Troop CO, also had his own radio (AN/PRC-25) which was on the Artillery Pushes to the supporting artillery units. When there was no attached FO the job usually fell to the CO or he would assign it to the communications section who would have to change frequencies on one of their radios, usually the one that Squadron was on. One thing the communications section did learn very quickly was how to read a map and use PO's (Points of Origin), these were assigned by Squadron prior to the troop taking to the field and they would vary according to the different Fire Support Bases in the AO (Area of Operations).

If it was necessary to call for Air Support to deliver air strikes, then either the Troop CO or the Commo track would call up an O2 Bird-dog FAC who would then take care of getting any air strikes necessary. If the troop was in deep trouble then there was a universal call-sign, 'Broken Arrow', which denoted a US unit in imminent danger of being overrun. When transmitted, this would result in every aircraft in that entire sector converging on the location no matter what their previous orders were, it was not used very often.

Each Troop in the Squadron had a Commo Track (Saber Bravo 65) which was the main communications center for that troop. This track carried two multi channel radios, one was set up on the Squadron frequency and the other was set to the Troop frequency, the RTO on the commo track would monitor both radios. A secure, encrypted radio was also carried by the section but the Commo Sgt was the only one allowed to install the encryption key.

All three Platoons in the Troop were assigned a frequency and the individual Platoon Leader's track had a single multi channel radio which had the pushes of the platoon and the troop in it. The Platoon Leader could communicate with his own platoon and either the Commanding Officer or the Commo Track, but not Squadron.

All the vehicles in the Platoon were equipped with a single radio on the Platoon frequency.

Crypto Codes

The only ones able to contact Squadron was the CO or the Commo track and that was due to the fact that both the CO and the Commo track had to authenticate by means of a crypto code for which only the CO and the Commo Sgt had clearance, Stanley Homiski wrote,

"The crypto codes were used by the Commo Sgt or the CO in order to enter the Squadron Net, they came from a book that changed every month. The way it worked was that upon signing on to the Squadron Net, the Squadron RTO would ask for authentication by giving the entering RTO or CO a line,  for instance he would say Line Alpha ( just because A is the first letter of the alphabet it would not be the first line of the Authorization code) That was governed by the Date say 25 July, the Day say Sunday and the Hour and minute you signed on the Net. The code was only good for that particular sequence. There was a formula that was followed to calculate the proper line that the Squadron RTO had requested. The actual authentic code would be read back to the Squadron RTO from the line he requested, due to the fact that the code was based on day, month, day of the week, hour and minute there were conceivably hundreds of letter combinations that could only be used once... "


SAMPLE RADIO TRAFFIC

Presented below is the radio traffic concerning a hypothetical move from the Saigon area (Tan Son Nhut) back to the 25th Infantry Division Base Camp at Cu Chi for a three-day stand down. The Main Supply Route (MSR), QL 1, ran from Saigon to Tay Ninh.

The lead element and the trail element would report their positions to the Troop Commo Track, who in turn would report the positions to the Squadron Commo Track. On the maps would have been marked certain locations which were designated as Check Points (Charlie Papa).

Map Check Points along Main Supply Route (MSR)

Main Supply Route - Tan Son Nhut to Cu Chi

  • Tan Son Nhut ( Charlie Papa Tango Sierra November)

  • The first bridge NW of Saigon ( Charlie Papa Lincoln)

  • The second Bridge NW of Siagon (Charlie Papa Lima)

  • The village of Phu Trung (Charlie Papa Papa Tango)

  • The village of Cu Chi (Charlie Papa Charlie Charlie)

  • Ambush gate at Cu Chi Base Camp (Charlie Papa Alpha Golf).

  • Cav Motor Pool at Cu Chi (Mike Papa)

For the sake of brevity only a limited number of check points are given and in reality there would have been many more along the route. 

Elements Involved

Yellow = Lead Element (Saber Bravo Lead)
Aqua = Trail Element (Saber Bravo Trail)
White = Bravo Troop Communications (Saber Bravo 65)
Red = 3/4 Squadron Communications (Saber 33 )

The radio traffic would go something along these lines (the call signs were repeated twice initially, after the first call the call sign was used only once);

(LEAD) Saber Bravo 65, Saber Bravo 65 this is Saber Bravo Lead, Saber Bravo Lead over 
(COMMO) Saber Bravo Lead this is Saber Bravo 65 over
(LEAD) Saber 65, Saber Bravo Lead Charlie Papa Tango Sierra November over
(COMMO) Saber 33, Saber 33 this is Saber Bravo 65, Saber Bravo 65 over
(SQUADRON) Saber Bravo 65 this is Saber 33 over
(COMMO) Saber 33, Saber Bravo Lead Charlie Papa Tango Sierra November, over
(SQUADRON) Saber Bravo 65 Saber 33, Saber Bravo Lead Charlie Papa Tango Sierra November, over
(LEAD) Saber Bravo 65, Saber Bravo Lead Charlie Papa Lincoln over
(TRAIL) Saber Bravo 65, Saber Bravo 65 this is Saber Bravo Trail, Saber Bravo Trail over
(COMMO) Saber Bravo Trail this is Saber Bravo 65 over
(TRAIL) Saber Bravo 65, Saber Bravo Trail Charlie Papa Tango Sierra November over
(COMMO) Saber 33 this is Saber Bravo 65, Saber Bravo Lead Charlie Papa Lincoln Saber Bravo Trail Charlie Papa Tango Sierra November over
(SQUADRON) Saber Bravo 65 Saber 33, Saber Bravo Lead Charlie Papa Lincoln, Saber Bravo Trail Charlie Papa Tango Sierra November over
(LEAD) Saber Bravo 65, Saber Bravo Lead Charlie Papa Lima over
(TRAIL) Saber Bravo 65 Saber Bravo Trail Charlie Papa Lincoln over
(COMMO) Saber 33 this is Saber Bravo 65, Saber Bravo Lead Charlie Papa Lima, Saber Bravo Trail Charlie Papa Lincoln over
(SQUADRON) Saber Bravo 65, Saber 33 Saber Bravo Lead Charlie Papa lima, Saber Bravo Trail Charlie Papa Lincoln over
(LEAD) Saber Bravo 65, Saber Bravo Lead Charlie Papa Papa Tango over
(TRAIL) Saber Bravo 65, Saber Bravo Trail Charlie Papa Lima over
(COMMO) Saber 33, Saber Bravo 65, Saber Bravo Lead Charlie Papa Papa Tango, Saber Bravo Trail Charlie Papa Lima over
(SQUADRON) Saber Bravo 65, Saber 33, Saber Bravo Lead Charlie Papa Papa Tango, Saber Bravo Trail Charlie Papa Lima over
(LEAD) Saber Bravo 65, Saber Bravo Lead Charlie Papa Charlie Charlie over
(TRAIL) Saber Bravo 65, Saber Bravo Trail Charlie Papa Papa Tango over
(COMMO) Saber 33, Saber Bravo 65, Saber Bravo Lead Charlie Papa Charlie Charlie, Saber Bravo Trail Charlie Papa Papa Tango over
(SQUADRON) Saber Bravo 65, Saber 33, Saber Bravo Lead Charlie Papa Charlie Charlie, Saber Bravo Trail Charlie Papa Papa Tango over
(LEAD) Saber Bravo 65, Saber Bravo Lead Charlie Papa Alpha Golf over
(TRAIL) Saber Bravo 65 Saber Bravo Trail Charlie Papa Charlie Charlie over
(COMMO) Saber 33, Saber Bravo 65, Saber Bravo Lead Charlie Papa Alpha Golf, Saber Bravo Trail Charlie Papa Charlie Charlie over
(SQUADRON) Saber Bravo 65, Saber 33, Saber Bravo Lead Charlie Papa Alpha Golf, Saber Bravo Trail Charlie Papa Charlie Charlie over
(LEAD) Saber Bravo 65, Saber Bravo Lead Mike Papa (3/4 Cav Motor Pool) over
(TRAIL) Saber Bravo 65, Saber Bravo Trail Charlie Papa Alpha Golf over
(COMMO) Saber 33. Saber Bravo 65, Saber Bravo Lead Mike Papa, Saber Bravo Trail Charlie Papa Alpha Golf over
(SQUADRON) Saber Bravo 65, Saber 33, Saber Bravo Lead Mike Papa, Saber Bravo Trail Charlie Papa Alpha Golf over
(TRAIL) Saber Bravo 65, Saber Bravo Trail Mike Papa over
(COMMO) Saber 33, Saber Bravo 65, Saber Bravo Trail Mike Papa over
(SQUADRON) Saber Bravo 65, Saber 33, Saber Bravo Trail Mike Papa over
(COMMO) Saber 33, Saber Bravo 65, request permission to leave the net over
(SQUADRON) Saber Bravo 65, Saber 33 permission granted out

This is an example of the typical radio traffic that went on during a move to base camp it also happened when the Troop was escorting convoys and the like.

For an example of the sort of radio communications that could be expected during a fictitious engagement see Air Strike and Fire Mission also by Stanley Homiski.


SOURCE

Mr Stanley Homiski, Communications Sergeant, Bravo Troop,  3/4 Cavalry (1968-1969)


For further information on communications see Radio Equipment

For an explanation of US infantry radio operations see Radio Communications

More information can be found by looking at RTO's


 

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