Quite good FSK 600Bd/850 signal centered on 10405 KHz from Australian Defence Force (ADF/MHFCS), heard some days ago around 1630z using iw2nke KiwiSDR (center Italy). As reported in UDXF logs by Eddy Waters [1] [2], Australian Defence Force has changed the previous dual channel system (ISB) to two single channel with 4 KHz spacings: the lower of the 2 frequencies has a speed of 600 baud, while the higher is 50 baud. The shift in both cases is 850 Hz. As in the waterfall above, I did not hear the 50bd FSK signal 4 KHz above (i.e. on 10409 KHz): maybe it's missing? Eddy also logged 10405 KHz frequency reporting ADF MHFCS Humpty Doo as location of the Tx.
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| Fig. 1 - main parameters |
After arranged the demodulated stream into a 7-bit format, it's possible to detect the presence of the sequence called "Fibonacci bits" originated by the polynomial x^31+x^3+1 and which reveals the use of KW-46 crypto device (Fig. 2) as per STANAG-5065 Annex-A:
"Encryption and decryption sall be provided by KW-46 interoperable cryptographic equipment operating in the 6.0 Stepped Digital mode. Encryption by the KW-46 equipment sall be coded in the 7-0 unit SART-TOP ITA2 alphabet. Encryption by the KW-46 equipment will result in bits 1 through 6 being encrypted and bit 7 (STOP) being replaced with an unencrypted and deterministic Fibonacci bit", where "Fibonacci bits = Deterministic unencrypted bits used by the KW-46 interoperable cryptographic equipment to provide synchronization defined by the polynomial x^31+x^3+1."
"Encryption and decryption sall be provided by KW-46 interoperable cryptographic equipment operating in the 6.0 Stepped Digital mode. Encryption by the KW-46 equipment sall be coded in the 7-0 unit SART-TOP ITA2 alphabet. Encryption by the KW-46 equipment will result in bits 1 through 6 being encrypted and bit 7 (STOP) being replaced with an unencrypted and deterministic Fibonacci bit", where "Fibonacci bits = Deterministic unencrypted bits used by the KW-46 interoperable cryptographic equipment to provide synchronization defined by the polynomial x^31+x^3+1."
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| Fig. 2 - 7-bit frame delimited by KW-46 sync bit |
As reported here, the lower signal in ISB mode was called "Rockwell CPU100", don't know if such nickname is still valid.
Humpty Doo Transmitting Station is situated on an almost 800 hectare parcel of land near Middle Point and is located approximately 50 kilometres east/ south east of Darwin. Run and point google Earth to 12°36'39"S 131°17'28"E.
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| Fig. 3 - Humpty Doo Transmitting Station |