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Author Topic: HF freq.  (Read 5395 times)
Galaxy001
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« on: February 24, 2009, 07:01:17 PM »

What exactly are the HF freq for?  When would a pilot be in contact with someone receiving on an HF?  Is it kinda like a center over remote areas (ocean, etc.) that give optional service?  Thanks!

Zach
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sykocus
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« Reply #1 on: February 26, 2009, 09:55:42 AM »

I would say it's most commonly used over oceanic airspace yes. However on the Pacific side it's a requirement two have two-way HF contact to fly in class A airspace (which starts above 5500 over the water). I don't know the requirements in the Atlantic, but I'm sure they're similar. ARINC is a company that has two dispatch centers on each coast, they monitor the frequencies receive position reports from planes and pass them off to the controllers working them. Vice versa they take control instructions from ATC and relay them to the planes. HF radios are very susceptible to atmospheric interference so throughout the day the frequencies change.  Part of the NextGen ATC system and ADS-B that keeps getting talked about is CPDLC (controller pilot data link). CPDCL uses satellites (which are operated by ARINC btw) to allow the planes and controllers to directly send text messages to each other. It's taking over for HF communication, but still a large number of planes still use HF. I'm sure there's much more to it then that, but that's the part of it I'm familer with.
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Galaxy001
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« Reply #2 on: February 26, 2009, 11:24:06 PM »

Skyocus, thanks for the information.  I'm appreciative of any additions from other users.
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captray
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« Reply #3 on: March 01, 2009, 03:03:44 AM »

HF or High Frequency radio is left over from the early days of oceanic travel. It was used on ships and then aircraft. It is as reliable as an ADF receiver. Day time, Night time, weather and sunspots all effect it's operation.
The rule of thumb is; the higher the sun, the higher the frequency. The controlers, ARINC not ATC, will give you 2 freqs when you coast out. A primary and a backup, sometimes during changes in the atmosphere even the backup won't be usable. In that case use the chart, all freqs are listed or call another aircraft on the air to air freq, 123.45 or Guard 121.5 and ask what others have found out. They may be going Westbound when you are Eastbound or  vice versa.
Hope this helps!
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sykocus
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« Reply #4 on: March 02, 2009, 12:40:06 AM »

The controlers, ARINC not ATC, will give you 2 freqs when you coast out.

How do you get the first freqs from ARINC? Do you call from the ground before you takeoff? I'm just curious. Here, when we (ATC) have a plane leaving our airspace we give them the freqs when they're about 50mi from the first reporting point they make to ARINC. That's also the boundary of our airspace and usually our radar coverage.
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captray
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« Reply #5 on: March 02, 2009, 05:44:35 AM »

Good question, I always forget if you don't do this, it is all very strange!

Unlike domestic airspace, when you receive your ATC clearence on the ground (we are talking IFR) you are NOT cleared into Oceanic airspace. You are cleared to your coast out point generally the FIR (Flight Identification Region) prior to reaching the boundry you must get your oceanic clearence, this could be a route, GPS fixes or Lat/Long coordinates. This freq. can be the center freq. or it could be a VHF ARINC freq or it could be a discrete VHF freq for oceanic clearences only. It is at this time, normaly, you will be assigned a HF freq for the crossing.
Depending on where in the world you are these procedures are subject to variation. For example, when coming westbound from Europe if you will coast out into Shanwicks airspace there is a published  VHF freq. I have it written down in the aircraft. It is based on whether the aircraft is registered west of 30 degrees longitude or east of that line.

True story, I can't make this stuff up.
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sykocus
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« Reply #6 on: March 02, 2009, 09:43:39 AM »

Interesting. Out here it's not that complicated, at least for planes that depart from our airspace. They get cleared on the ground to their destination. Some ask for the freqs before they take off, but usually they're not able to make contact with arinc until they get airborne.
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bcrosby
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« Reply #7 on: March 04, 2009, 06:23:40 PM »

You can get some extremely detailed information on Oceanic Procedures here:

http://www.tc.gc.ca/CivilAviation/publications/tp14371/RAC/11-0.htm

It's for the Gander OCA.

HF channels for Gander Radio can be found here:

http://www.tc.gc.ca/CivilAviation/publications/tp14371/COM/6-0.htm#6-6-1
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Galaxy001
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« Reply #8 on: March 05, 2009, 01:22:45 PM »

Blake, thanks for the links, that does clarify a lot of questions.  It's certainly interesting how long it takes for old technology to become obsolete. 
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