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HF radio check on the ground

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HF radio check on the ground

Old 31st Mar 2020, 10:10
  #21 (permalink)  
 
Join Date: Feb 2000
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prickly
Some people’s area of operations means that they just can’t comprehend having to make a taxi call on HF in an airliner at an untowered airport 1000+ miles from anywhere.

Last edited by compressor stall; 31st Mar 2020 at 11:20.
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Old 31st Mar 2020, 14:26
  #22 (permalink)  
 
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Originally Posted by prickly View Post
WTF? do I assume you would suggest there is no point checking the mags before take off because they may not be serviceable later?
I would suggest if you are operating around the Central Pacific, no HF, no go. So a pre take off HF check is essential. SELCAL however is a luxury.

WOW. Strong reaction. So in your case you find out one of your mags doesn’t work and you press on regardless? How many flights did you cancel/delay for unsatisfactory HF/SELCAL check on ground? There are many airports around the world where reaching someone while on the ground and shielded by terminals and mountains with HF is difficult.

Fly safe!
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Old 31st Mar 2020, 14:37
  #23 (permalink)  
 
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Shanwick Radio don’t charge for HF radio/selcal checks.
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Old 1st Apr 2020, 08:45
  #24 (permalink)  
 
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Originally Posted by jjj2 View Post
WOW. Strong reaction. So in your case you find out one of your mags doesn’t work and you press on regardless? How many flights did you cancel/delay for unsatisfactory HF/SELCAL check on ground? There are many airports around the world where reaching someone while on the ground and shielded by terminals and mountains with HF is difficult.

Fly safe!
jjj2 - the point he's making that still seems to be lost on you is that there are parts of the world that you need to know the HF is working so you can leave the ground. Europe and USA aren't those places normally. There's no point spending 5 mins hunting through the frequencies trying to work out which one is working and getting your call out when stationary with the engines turning. Better to have comms sorted prior to start so when you taxi you give the CTAF traffic call and then straight away the actual taxi call to ATC HF on a frequency that worked 5 mins ago. And yes, if HF didn't work, it may be rather prudent to delay or even cancel - although satcom now alleviates that somewhat.
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Old 1st Apr 2020, 13:03
  #25 (permalink)  
 
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Originally Posted by Uplinker View Post
We are not allowed to use our cellphones at petrol stations, and they are much lower power devices.

HF ground testing has probably been safety audited, but just a thought: The distance from your aircraft fin, (where the HF antenna usually is), to your fuel tank vents is not much different to those of the aircraft next door, on some ramps.
Re: at Petrol stations - that advice is now changing as cellphone payment options are spreading. (Money talks :-) )

However, there was a recorded case of a Ham radio operator causing an explosion at a petrol (gas) station in Southwestern Ontario way back in the 60's. I remember reading about it in the press, so it is not an apocryphal story. Ham mobile rigs are typically 100-200 Watts, similar to aircraft HF. And then your ADSB is 150 Watts at 1090 MHz, much more energy than HF. So I would say that anywhere you can set mode S you can safely use HF.

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Old 1st Apr 2020, 13:37
  #26 (permalink)  
 
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Originally Posted by Uplinker View Post
We are not allowed to use our cellphones at petrol stations, and they are much lower power devices.

HF ground testing has probably been safety audited, but just a thought: The distance from your aircraft fin, (where the HF antenna usually is), to your fuel tank vents is not much different to those of the aircraft next door, on some ramps.
Fair point but the B747-100/200 had their HF antennas on the wing tips right next to the fuel vents.
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Old 29th Jan 2021, 02:32
  #27 (permalink)  
 
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The HF test refueling restriction is a leftover from the probe and wire days. HF transmissions won’t cause an explosion any more than a cell phone will at a gas station. People should be taught more to ground themselves before fueling a car than worry about a cell phone.

If HF transmissions were a danger, you’d find more information on it. You don’t.

Yes, Airbus restricts you from doing it, but I’d say it’s more out of a liability concern. If you ask anyone there, and I have, you’ll find o one has an an answer.
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Old 29th Jan 2021, 02:58
  #28 (permalink)  

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Originally Posted by matkat View Post
Fair point but the B747-100/200 had their HF antennas on the wing tips right next to the fuel vents.
Not only that, but the HFs on the classic 747s transmitted @ 300 Watts, twice the power of the ham above that blew up a gas station.

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Old 29th Jan 2021, 11:28
  #29 (permalink)  
 
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Originally Posted by Uplinker View Post
We are not allowed to use our cellphones at petrol stations, and they are much lower power devices.
This has more to do with getting people to focus on the task at hand, refueling safely, and then crossing the forecourt to pay without getting run down, than it has to do with ignition sources.
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Old 29th Jan 2021, 11:46
  #30 (permalink)  
 
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The voltages present on a HF antenna can be rather large its caused by the black magic in the antenna tuning unit. The number insulators and size on a ground based antenna should give you a clue however for the same power the induced voltages on VHF and above are much smaller but the energy of the electron will be greater ( Lenz and Planck)

If no one can come into accidental contact with the antenna or aircraft( grounding issues) then i'd say your fine to test if your not sure leave it alone until you're away from everyone. I've known ship radio officers come up on the ham bands to test their kit
.
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Old 29th Jan 2021, 12:16
  #31 (permalink)  
 
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Aircraft refuelling during other aircraft's HF operation on the ramp has presumably - hopefully - been safety audited.

The HF transmission from your own aircraft is less likely to cause problems to your own aircraft because there is a conductive electrical path between your own HF system and your aircraft structure to equalise any electrical charges.

The problem can arise when two conducting bodies are not electrically joined - potential differences or static charges can arise. This is why your fuelling tanker connects an 'earth' wire to your aircraft before connecting the fuel hose: it forces both aircraft and tanker to the same electrical potential so there is no potential difference between the two, which could otherwise cause sparks and possible ignition when the fuel hose is connected and disconnected.

Two aircraft side by side on the ramp are not electrically connected to each other, and they have insulating rubber tyres, so a potential difference could arise - for example by one aircraft using a high power RF transmitter. As I say, hopefully, this has been considered - I always understood that HF and RADAR etc should not be used on the ramp, i.e. in close proximity to other aircraft.
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