Hat Yai HFDL and Gander VOLMET on 13270 USB 17:50 6 Nov 2019

[jasmine]

this is more a question about aeronautical frequencies which are used by multiple things. like i've noticed i can hear both the Hat Yai, Thailand HFDL data transmissions and Gander VOLMET at the same time. is this normal? if i can hear it wouldn't air traffic wanting to hear Gander VOLMET also hear the HFDL data? i presume most airlines have a better radio and antenna than mine.

[Looking-Glass]

Many frequencies on HF have a multiple use in the aeronautical band, HFDL is often shared with normal MWARA/RDARA/LDOC voice traffic frequencies and is usually allocated to countries in different continents as to afford "minimal interference" but Mother Nature and propagation often put sway to this.

Another example of "sharing" is EIP Shannon Aeroradio in County Clare, Ireland which uses 3.413MHz USB, this frequency is also shared with San Fransisco ATC in the USA for normal voice working of aircraft in the MWARA CEP-3 region.

Similar is 6.532MHz which is shared with Shannon Radio for HFDL in Slot-10 and also allocated and used by San Fransisco ATC for MWARA CWP-1/2 voice traffic.

If you haven't already done so, print off a copy of Civilian Aero/Military HF Frequency List, updated every few months, it's not 100% accurate, some active frequencies are not listed and I have found the odd error but beside that it's excellent value to have on the table near the radio.

The Brown Monitoring Post: Civilian Aero/Military HF Frequency List via Google will get you there, last up dated 18th August 2019.

Good luck...

[Josh]

On being able to hear hf sigs a professional site can't, it all depends on propagation conditions, what, if any, angle of radiation the ionosphere is supporting at the moment for all parties involved. If the sphere is supporting long path and you are at a hop point of that path you will hear the sig while a HFDL site not at a hop point might not, even with millions worth of antennae and receivers.

An issue with HFDL is if there's almost any interference at all, the HFDL sig is corrupted at the decoder, especially if it's a tone, but that doesn't stop HFDL freqs from being used by other services such as the meteo sig. I often have 8912 tuned in and decoders set for HFDL and ALE as 8912 is used by Riverhead NY for HFDL and USCG for ALE.

[jasmine]

thank you Looking-Glass and Josh! i really appreciate the detailed responses. and yes, i was doing some HFDL decoding and plotting with Plane Plotter (21 day free trial). so amazing but i did wonder if voice comms on that channel was messing up my decode of hat yai. good info.

[Josh]

I had a decoder running ALE and HFDL on 8912 since I posted above, here's the take so far;

[2019-11-06 23:04:36]
[2019-11-06 23:04:36] [NORMAL MODE][TWS][D05][EOM]
[2019-11-06 23:04:38]
[2019-11-06 23:04:38] [NORMAL MODE][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][TWS][D05][EOM]
[2019-11-06 23:06:32]
[2019-11-06 23:06:32] [NORMAL MODE][TWS][N10][EOM]
[2019-11-06 23:06:35]
[2019-11-06 23:06:35] [NORMAL MODE][TWS][N10][TWS][N10][TWS][N10][TWS][N10][TWS][N10][TWS][N10][TWS][N10][TWS][N10][TWS][N10][EOM]
[2019-11-06 23:09:21]
[2019-11-06 23:09:21] [NORMAL MODE][TWS][K16][EOM]
[2019-11-06 23:09:27]
[2019-11-06 23:09:27] [NORMAL MODE][TWS][K16][EOM]
[2019-11-06 23:11:33]
[2019-11-06 23:11:33] [NORMAL MODE][TWS][J07][EOM]
[2019-11-06 23:29:39]
[2019-11-06 23:29:39] [NORMAL MODE][TWS][D69CBP][TWS][D69CBP][TWS][D69CBP][TWS][D69CBP][TWS][D69CBP][EOM]
[2019-11-06 23:29:43]
[2019-11-06 23:29:43] [NORMAL MODE][TWS][D69CBP][TWS][D69CBP][TWS][D69CBP][TWS][D69CBP][EOM]
[2019-11-06 23:31:33]
[2019-11-06 23:31:33] [NORMAL MODE][TWS][D47][TWS][D47][EOM]





HACARS mode: 2  Aircraft reg: .N477AV
Message label: Q0  Block id: 8  Msg. no: S58A Flight id: AV0062
Message content:-

----------------------------------------------------------[06/11/2019 23:02]
HACARS mode: 2  Aircraft reg: .C-FGEO
Message label: SA  Block id: 3  Msg. no: S64A Flight id: AC0118
Message content:-
0EH230156SH/
----------------------------------------------------------[06/11/2019 23:03]
HACARS mode: 2  Aircraft reg: .C-GEZD
Message label: SA  Block id: 9  Msg. no: S83A Flight id: TS0517
Message content:-
0LV230320H
----------------------------------------------------------[06/11/2019 23:04]
HACARS mode: 2  Aircraft reg: .N975AV
Message label: SA  Block id: 1  Msg. no: S70A Flight id: AV0086
Message content:-
0EH230714VHS
----------------------------------------------------------[06/11/2019 23:08]
HACARS mode: 2  Aircraft reg: .N459AS
Message label: Q0  Block id: 4  Msg. no: S68A Flight id: AS0851
Message content:-

----------------------------------------------------------[06/11/2019 23:11]
HACARS mode: 2  Aircraft reg: .N852FD
Message label: _  Block id: 2  Msg. no: S61A Flight id: FX0003
Message content:-

----------------------------------------------------------[06/11/2019 23:12]
HACARS mode: 2  Aircraft reg: .N509DN
Message label: SA  Block id: 8  Msg. no: S86A Flight id: DL0583
Message content:-
0LV232229SH/
----------------------------------------------------------[06/11/2019 23:23]
HACARS mode: 2  Aircraft reg: .G-VRAY
Message label: Q0  Block id: 7  Msg. no: S66A Flight id: VS0118
Message content:-

----------------------------------------------------------[06/11/2019 23:28]
HACARS mode: 2  Aircraft reg: .G-VRAY
Message label: _  Block id: S  [Uplink]
Message content:-

----------------------------------------------------------[06/11/2019 23:38]






On a like note, it's best practice to fire up your HFDL decoders every once in a while so they can update their tables if need be. They do this over the air if given the chance.

[jasmine]

On a like note, it's best practice to fire up your HFDL decoders every once in a while so they can update their tables if need be. They do this over the air if given the chance.

thanks!

[Josh]

Something I forgot to add about hearing what others can't. When your transmitter is in an aircraft at 25k ft over a saltwater ocean and you are feeding a fairly efficient antenna with 2kw of hf, you have a far more effective transmitting system than pretty much any ground based transmit site.