[amrcg]

Dear all

I am looking for information about the RF communications between sonobuoys and monitoring platforms (e.g. P-3C Orion). More specifically I would like to know the following:

1) What is the usual RF frequency band used for communications between sonobuoys and monitoring platforms? VHF?

2) Does the sonobuoys transmit the sensed noise to the monitoring platform using an analog modulation or are there any sonobuoy types that digitize the noise prior to transmission?

3) Does the transmitted data consist only on noise samples or is there any additional digital data resultant from pre-processing (e.g. direction of noise in the case of directional sonobuoys, SNR, GPS positioning, etc.)?

4) In the case of digital communication what are the most used communication protocols? Are there any specification documents?

5) What is the usual RF comm range? Does it impose practical limits to the area being monitored by a single platform?

6) What is the usual sonobuoy dropping pattern/procedure and what is the usual number of sonobuoys required to monitor a given area.

7) Could you specify your answers to the above with references to apecific sonobuoy models and manufacturers?

Where can I find detailed documentation on the above?

Thank you very much in advance.

Best regards,
Antonio Grilo

[NefariousKoel]

I'm guessing some of the answers you're looking for are classified.

[Looney11]

I know from experience that a lot of those questions are classified information

The only think i could dig up from our friends at FAS.org was

http://www.fas.org/man/dod-101/sys/ship/weaps/an-ssq-62.htm

[XabbaRus]

Yep quite a few seem classified though I guess some real navy guys can give clues if not definite answers.

[Sea Demon]

[Beer]

[compressioncut]

Question 1) is not classified - they transmit essentially in the FM band. There are restrictions on using them in certain areas because of it. You get some Mexican Radio station instead of the buoy on a channel or two at the SOAR range, for example. And occasionally taxi cab company comms from Vancouver in area Whiskey Golf, et cetera.

The rest of the stuff, um, well, no.

[amrcg]

Thanks a lot for all the answers. I'll definitely try to contact a P-3C Orion crew in Portugal. The reason of all this is that I am working on a way to improve RF communications in sensor networks.

Regards,
Antonio

[amrcg]

Does anyone know if there will be any range limits for RF communications between sonobuoys and monitoring platforms? I believe that in real life the usual frequencies (VHF or UHF) are high enough to place a significant limit on range.

Regards,
Antonio

[Nitro]

If I'm not mistaken, VHF and UHF are both LOS-dependant... If you've got a clear line-of-sight, and enough transmitting power, you can talk to just about anything. However, the LOS dependancy becomes an issue for anything located at ground/sea level due to the earth's curvature, which is why the VHF radio antenna on my sailboat is wayyyyy the hell up at the top of my 60-foot mast. Altitude = Range

Now, if you want to factor in any atmospheric "skip" you might get, you can open up a whole other can of worms... I pick up transmissions from a coast guard station more then 200nm away, with both land and sea between us, on a regular basis.

[Bill Nichols]

[amrcg]

[Scion]

The transmitter has a double setting on the family yacht - 5 watts for close talk - and 25 for long range.

[Smuook]

The power setting on sonobuoys are .25W for BT's and 1W for just about everything else. Although the life settings can be adjusted (up to 8 hours max on certain buoys) the RF coverage is based off line-of-site limitations as stated earlier in this thread. So basically, if you have a large pattern in the water you may have to be at a higher altitude to receive all the buoys. The transmitter power cannot be adjusted.

The sea state can also cause loss of coverage by washing over the bouy.... but it has to be pretty high.

[amrcg]