What are T / A positions on 100 MHz radio dial?

[Machalot]

The 100 MHz selector dial on the radio has position called T and A.  What are they for?  The flight manual doesn't help much. Here's the only place I could find them mentioned (pp. 131-132).

 

 

 

Edited Sunday at 10:26 AM by Machalot

[mayo25]

In real AN/ARC-164 radio, A is used to enter the active mode, i.e., anti-jamming, frequency hopping mode. T is used to receive Time-of-day, to sync the time, which is used for active mode.

 

In DCS, T acts as 1, enabling to use the frequencies in 1xx MHz range, which can't be used on real radio (UHF only, 255-399MHz). I don't think A has any function.

Edited Sunday at 03:48 PM by mayo25

[Machalot]

On 2/21/2021 at 6:01 AM, mayo25 said:

 

In real AN/ARC-164 radio, A is used to enter the active mode, i.e., anti-jamming, frequency hopping mode. T is used to receive Time-of-day, to sync the time, which is used for active mode.

 

In DCS, T acts as 1, enabling to use the frequencies in 1xx MHz range, which can't be used on real radio (UHF only, 255-399MHz). I don't think A has any function.

 

Thanks.

 

Any idea why your text is gray-on-gray?  It's almost the same color as the Dark Theme background, and I can only read it by highlighting it.

[Frederf]

There is a whole side of NATO radio communications you don't see in DCS. Have Quick is a type of radio communication where the frequency used is changed several times per second. Users on the same "net" are using the same pattern of frequency changes so they can remain in communication. Others which are not using this pattern perceive this signal as essentially useless noise.

 

To be in contact with someone else on a HQ net you need three things:

• World of the Day (WOD)
• Time of Day (TOD)
• Communications Channel (Net)

WOD is a password expressed as 36 digits which is issued to the radio operators for example one day. Everyone would be issued this code in theater. In the ARC-186 it is entered as the presets 15-20. The actual presets are still available for normal radio use separately. The electronics just use these entries to program the radio. We'll take example WOD: 287.400 297.600 314.300 359.100 376.000 300.050.

 

TOD is simply a clock synchronization. The frequency changes happen so quickly that each radio must be synchronized to the pattern of changes precisely. The correct pattern at the wrong time will not allow communication. In this ARC-186 radio the TOD sync will come from a radio source which is providing by receiving a reference pulse. Normally the radio syncs to the first TOD signal it hears and ignores all others. The "T" position of the dial is spring-loaded and allows setting a new TOD sync. The radio can become the source of a TOD if needed. The radio can pass on TOD that it has to another radio if needed.

 

Net is the particular channel for communication so that multiple lines of communication can happen at once. When everyone's radio is configured correctly they will share the WOD, TOD, but be grouped in different nets as needed. Nets are designated by AXXX.YY with XXX being 000-999 and YY being 00, 25, 50, 75 to denote the group of frequencies used. In theory there are 4000 nets available, 1000 in each of the four frequency groups although the fourth frequency group "75" is not in use. The operational HQ training nets (according to this manual anyway) are A00.Z00 with Z being 0 1 2 3 or 4 for a total of five. In addition there are HQII frequency-managed training nets A0X.X25 through A0X.X25 where XX is 00 through 15 for a total of sixteen.

 

The combination of WOD and Net produce a frequency change pattern which repeats according to the TOD synchronization. There are two kinds of nets: training and combat. In the training mode the frequencies used are the ones entered in 15-19. In the combat mode the frequencies used are greater in number. The data entered into preset 20 determines if training mode is used and the rate of hops. An entry of 300.0XX sets training mode with the last 00, 25, 50, 75 determining hop rate. If a different frequency is entered in 20 then combat mode is used.

 

===

 

Change Radio Mode

• Set MAIN or BOTH
• Set PRESET
• Set CHAN 20
• Set frequency XXX.XXX
• Press PRESET (single beep if TOD signal present)

XXX.XXX Mode Codes:

• 220.000 Verify/Operate Mode (all operations except WOD load, erase, and manual TOD entry)
• 220.025 Load MWOD Mode
• 220.050 MWOD Erase Mode
• 220.075 FMT Load Mode (HQII 16-frequency)

TOD and WOD entry can happen in any order. A solid tone or alert tone (repeated beeps) indicates that TOD/WOD not set correctly when switching to active mode.

Before using Active Mode set radio to verify/operate mode. Net number can be set with frequency selector dials in MANUAL or by preset channel in PRESET.

CHAN 20 is not available as a preset channel since it is used to enter specific radio commands.

 

Load WOD

• Enter Load MWOD Mode
• CHAN 20
• Frequency 300.050
• Press TONE (beep)
• CHAN 19
• Frequency 376.000
• Press TONE (beep)
• CHAN 18
• Frequency 359.100
• Press TONE (beep)
• CHAN 17
• Frequency 314.300
• Press TONE (beep)
• CHAN 16
• Frequency 297.600
• Press TONE (beep)
• CHAN 15
• Frequency 287.400
• Press TONE (beep)
• CHAN 14
• Frequency 3XX.000 (XX as date tag for WOD)
• Press TONE (double beep)

Repeat above to load additional WOD (retains last six entered).

Verify WOD Load

• Set MANUAL
• CHAN 20
• Frequency 3XX.000 (XX day to check if WOD in memory for that day)
• CHAN 19
• CHAN 20
• Beep confirms WOD is loaded for entered day, silence if not
• Repeat for all other days to check

Receive TOD (Automatic)

• Set MANUAL (or PRESET) to receive TOD on manual frequency (or PRESET channel)
• Set frequency (or CHAN) to TOD source

Set Manual Current Day (if TOD source with date not available)

• Enter MWOD Load Mode
• Set MANUAL
• CHAN 01
• Frequency 3XX.000 (XX as current day)
• Press TONE (beep)

Verify TOD

• Set radio to non TOD source as needed to avoid interfering with other users
• Press TONE
• TOD signal followed by standard tone indicates TOD reception, standard tone only indicates TOD not received

Receive TOD (Manual)

• Set radio to TOD source as above
• Turn switch to "T" momentarily and return to "3" or "2" for reply
• Listen for beep indicating TOD signal within 60 seconds
• If no signal repeat with squelch off or try different TOD source

Self-Start Radio Clock as TOD

• Set MANUAL
• Hold switch in "T" position
• Press TONE
• Release "T" switch
• Verify TOD if desired

Send or Pass On TOD

• Tune frequency to TOD recipient
• Press TONE

MWOD Erase

• Enter MWOD Erase Mode
• Press PRESET (beep)
• Set MANUAL
• Press TONE (beep)
• All WOD are erased

FMT Load (HQII 16-frequency training)

• Enter FMT Load Mode
• Set MANUAL
• Enter first training frequency
• Press TONE
• Set CHAN 19
• Enter second training frequency
• Press TONE
• Continue entering frequencies decreasing channel each time until all 16 frequencies are loaded (CHAN 5 will be last)
• Editing of any particular frequency is possible out of order or later

 

[captainHelmet]

Well I learned something new today.  That was really interesting.