US Coast Guard

[KB8UYC]

Hi all,

Was trying to monitor a US Coast Guard event near Detroit the other day and I put in the VHF frequency and was hearing a bit, but I put in 11.494.00 USB and I heard nothing but what sounds like screeching or bubbles under water every once in a while. I am assuming at this time that it is encryption and or data packets being passed.

Does anyone know if this is a valid Coast Guard Frequency??

 

[ColoradoRedlands]

That freq is part of the Customs & Border Protection HF-ALE network. You can occasionally hear some plain voice traffic, but most of what you will hear is encrypted voice and a variety of data traffic that sets up calls and monitors propagation.

Many agencies are allowed to communicate on that network, the USCG being one of the main players.

 

[HM1529]

Hi all,

Was trying to monitor a US Coast Guard event near Detroit the other day and I put in the VHF frequency and was hearing a bit, but I put in 11.494.00 USB and I heard nothing but what sounds like screeching or bubbles under water every once in a while. I am assuming at this time that it is encryption and or data packets being passed.

Does anyone know if this is a valid Coast Guard Frequency??

Your "bubbles under water" sound was likely the ALE (Automatic Link Establishment). ALE capable equipment will try to establish the best comm link over a set of frequencies.

Detailed info can be found here:
http://wiki.radioreference.com/index.php/ALE

 

[CapnJon]

That was me in the tub making bubbles and keying up the rig at the same time! LOL D'oh! Just had to say it!

 

[SkipSanders]

Actually, it sounds like the typical USCG rolling code scrambler used on HF. IIRC, it's a time division band split type thing, moves the bits of talk around in time, and maybe frequency as well, rapidly. I couldn't find an example of it on the best digital samples page to refer to, though.

 

[KMTC]

Just in case you dont have these already....

237.90 AS DETROIT AIR OPS 2
326.15 AS DETROIT GRND OPS 1
345.00 AS DETROIT AIR OPS 1
379.05 AS DETROIT GRND OPS 2
381.80 AIRCRAFT PRIMARY

 

[SkipSanders]

To update the USCG HF encryption, it's KY-65 'Parkhill' type. A somewhat poor (weak audio) sample can be found on this page:

Encryption/Vocoder Samples