Continuing from the first post, another student from the Advanced RTO Course has been running a series of tests on the various digital modes for sending busts of data. The advantages to this should immediately be obvious- as I teach in the RTO and SIGINT Courses, your voice is the most exploitable piece of information you can give an adversary. But on top of that, the time of transmitting is far, far shorter than when using voice. Coupled with the operating techniques we cover in the basic RTO Course, you’ll be a hard target even with dirt cheap gear such as a Baofeng UV-5R, a data cable, and a cheap laptop.
Here’s what “R” sent:
OK, this is where I have been heading on the digital modes…
My assumptions were a one-try transmission, no acknowledgement, no fills.
That means no ARQ (Ack/Nak) modes, which are the ones that come closest to guaranteeing error-free reception. The only other choice is FEC, which relies on interleaving and/or redundant data to enable error-correction by the recipient. I therefore only considered digital modes that used FEC, except for DominoEX which has a reputation for reliablility without FEC due to the tone frequency difference carrying the information rather than the tone frequency itself.
Transmission needs to be completed as quickly as practical which works at
cross purposes to reliability. Extensive field trials in varying conditions
would give a good idea of the crossover point under different conditions but
I do not have that experience yet.
My best guess was to pick modes and data rates that were in the faster 50% or better of options. I then made a dummy report and timed the transmission time for each. This was with the RSID turned off.
Best times were:
MFSK128 @ 8 seconds
DominoEX_44 @ 9 seconds
Thor 100 @ 11 seconds
Olivia 4-2K @ 14 seconds
MFSK64 @ 14 seconds
MT63-2KL @ 17 seconds
Olivia 8-2K @ 18 seconds
DominoEX_22 @ 18 seconds
Several others were tried and took longer. I stopped experimenting at 30 secs, which is still pretty darn fast compared to voice.
The link worked best when the dual watch function and battery save functions were turned off in the transceivers. I also had to adjust digital squelch levels and volume levels when switching between some modes. This is a weakness of the simple setup, as a radio with a dedicated data port can have the volume levels set and they stay put until changed.
On/off/volume, not so much.
Will send the sample message next so you can confirm this if you want.
Sample message encrypted via One Time Pad:
135 DE 168 // 001 // CYRIL //
01001 00108 59859 85949 34100
10859 33508 10810 81290 00212
61261 26402 22122 12214 02280
28028 07163 35335 33521 05405
76386 38638 69450
Think about how long that would take via voice versus data. Its all about your techniques that back up your tactics. What are you doing with your time? Put some arrows in your quiver and really learn how to operate.