Peter wrote:
HF could be done with much more compact gear than it is today IF you want to receive-only. There are too many airports (c. 10k I think) to continually broadcast all the tafs and metars every 30 mins at a low data rate, but one could have a service whereby you program a route (before departing) and you get a constant feed of airport data within say 200nm of it.
Or you could just buy an ADL-120 at low cost and get good value inflight weather, winds, infrared, radar and text messaging. It won’t help you surf the net but who cares.
As usual there is no free lunch. Globalstar offers higher bandwidth than Iridium but I still think the ADL110B / ADL120 / ADL130 concept is the best overall package:
- Moving to Globalstar would mean nearly doubling the size of the devices as the Globalstar chip is much bigger than the Iridium hardware. As far as I can tell it would also no longer fit in the ADL110B round panel mount enclosure.
- In the past Globalstar lost several satellites and it took long to replace them. In the meantime service was intermittent and this situation would have been a nightmare. Iridium has got spare satellites in the orbit and seems more robust.
- While one small Iridium antenna can also be used as a GPS source for the ADL device with one thin antenna cable. As far as I can tell this is no longer possible with Globalstar so the device would have two antennas or a big special combination antenna with two cables.
- Some planes are already equipped with Iridium antennas which can be just plugged in. This is usually not possible with Globalstar.
- Due to the nature of the device with the ADL you only pay for data which actually got through. With most other systems like Globalstar etc. you will also pay for transmissions which got interrupted half way etc.
- For Iridium I can offer affordable 3 day trip kits. So far as I think this is not possible for Globalstar.
- The Globalstar coverage is ok for European use but I have quite a lot of pilots flying globally so changing to Globalstar this would reduce the ADL usage area
- Very short message for tracking purposes are very affordable with Iridium which is why the 10 minute tracking is complimentary with all ADL subscriptions. Using other networks like Globalstar this would probably not be possible.
So in the end Globalstar would provide more bandwidth but so far I think the Iridium ADL deals with the low bandwidth in such an efficient way that it is still the best solution for the task at hand.
www.flightsafetyaustralia.com/2015/11/tablets-of-wisdom/
Just for information, for some reason in Australia the national Telecom Telstra have enabled their 3G/4G cell towers to point upwards so that you can get a good signal at say 35,000ft….this means that products like Ozrunways (also available in Europe btw) ruining on a tablet with sim can overlay weather on the moving map….also such OR users are automatically providing their GPS position back to the server which is then uploaded to all other users…sort of like TIS-B in the US… And due to the uniquely Australian requirement to carry CASA approved charts and AIP enroute supplements, OR has the market cornered such that almost every aircraft is using it….food for thought if we could just get a few masts pointed skywards!
It’s often held forth on the other channel (OK, the other, other channel) that allowing aerial connections to cell towers will cause the entire planet to implode upon itself or something. Despite this, good 3G connections can be had at altitude throughout most of the US, New Zealand and now apparently Australia. Despite this flagrant disregard for the future of human civilisation, none of these places seem to have imploded just yet.
Obviously the ‘authorities’ in Europe take the matter much more seriously, ensuring that you have to descend below 1500’ (in UK and Northern Europe at least) in order to pick up that part of the chart that you omitted to download before takeoff, and of course giving you the alternative solution of just reading the road signs on the motorway.
So can anyone here speak to the subject of why I can get good cellular data at 10,000’ in densely populated California, but zilch at 2000’ in the home counties? Is it just population density, or the absence of mountains, or something else? Answers please on an email or something but only below 1500’ N of 50 deg N.
Until December i only had (Vodafone) 3G. Now i changed my contract, and on my flight Sunday i realized that with 4G i have a much better connection. Worked fine up to 6500 ft … but have to test at higher altitudes the next time!
allowing aerial connections to cell towers will cause the entire planet to implode upon itself or something. Despite this, good 3G connections can be had at altitude throughout most of the US, New Zealand and now apparently Australia. Despite this flagrant disregard for the future of human civilisation, none of these places seem to have imploded just yet.
Well, yes, it’s pretty obvious that if that was true, it would take only a few people on an airliner who forgot to turn their phones off to sabotage the entire cellular network(s) down below – which obviously is not happening.
So, obviously, there is software in the cellular system which prevents this happening, and it must have always been there. So all those dire warnings must have always been rubbish, because airliners have been around a lot longer than cellular networks.
Whether you actually get a usable connection (for sms, voice, data) from high-up is a different matter.
It seems pretty evident that the more brief a connection is needed for the job, the more likely you are to succeed.
Hence, SMS, with its short packets, has always worked fairly well, at all GA altitudes. It used to work better on the old phones which could retry say every 10 seconds; modern phones try a few times and then abandon it (unless you hack the firmware). SMS needs only a basic GSM connection, no internet.
I don’t find voice works well at all, but obviously you have the other problem in that unless you can feed it via the headset, it’s a bit useless in the cockpit…
As for data, 4G is finally making things work sort-of usefully because establishing the connection (DHCP etc) is about 5x faster than on the older 3G / 3G+HSPA. It seems to happen in under 1 second so you have a pretty good chance of getting something done. Whatsapp, Telegram, even small emails can work. With 3G the setup would take 5 seconds and at 150kt you often lost the connection soon after that.
But whether the towers point high up must be country dependent. In the UK they don’t seem to, but in mountainous areas (S. France for example) they always have done and I was running dial-up connections there, for minutes at a time, in 2004 at FL080.
in Australia the national Telecom Telstra have enabled their 3G/4G cell towers to point upwards so that you can get a good signal at say 35,000ft
They must have also done something to facilitate rapid handovers between towers. I don’t know if any 3G/4G specialist will have the details (I know several of them read EuroGA and have previously posted) but I recall the 4G system deals with this issue very differently to 3G (and GPRS, etc).
Peter wrote:
I don’t find voice works well at all, but obviously you have the other problem in that unless you can feed it via the headset, it’s a bit useless in the cockpit
I have been able to call an airfield in Germany from around FL080 over northern France when we realized that we would arrive just after closing time. They agreed to stay open a bit longer. That was with a bluetooth headset, and the whole call took around 1 minute and was completely clear and stable.
Have you noticed that those horrible pulsing noises (rat-a-tat-tat) are absent these days. The prevalence of 3G and 4G means that 2G is rarely used. Since the later generations broadcast RF continuously (CDMA and OFDMA), rather than using timeslots (TDMA), there is no pulsing of RF transmissions and hence much less interference.
One reason for the improved coverage is the deployment of lower frequency spectrum, made available from the switch off of analogue TV. Bands at 700 and 800MHz provide longer range than the higher frequencies, so are good for rural and less densely populated areas. When combined with the superior technical performance of 3G or 4G, signal range and penetration (as well as speed) are much improved.
Dealing with a single device flying slowly across the countryside (say at 100 knots, not that much faster than automobile traffic) would likely be easier than handling a large block of co-located devices hurtling at several hundred knots. You can imagine that a high speed train crossing between cell sectors places a lot of strain on the system to handover all sessions quickly. Likewise, a planeload of 200 active phones.
Disruption to the cell network on the ground from fast moving airborne planes did used to be a problem and one reason why cellphones weren’t used onboard. I’d assume that technical improvements have been made to circumvent that.
Have you noticed that those horrible pulsing noises (rat-a-tat-tat) are absent these days. The prevalence of 3G and 4G means that 2G is rarely used. Since the later generations broadcast RF continuously (CDMA and OFDMA), rather than using timeslots (TDMA), there is no pulsing of RF transmissions and hence much less interference.
I am no expert on GSM but I think the reason is different.
About 15 years ago mobile phones would radiate continuously while you were making a voice call. This was when concerns were raised over the cancer risk, because 400mW or so next to your head would in theory heat up the brain a little bit. But this mode also resulted in a poor battery life.
Then came DTX (discontinuous transmission) whereby the data got packaged and sent out with a low duty cycle.
Then the networks started stretching how often a phone “logs onto” the system. Nowadays a phone sits there silently listening, and goes active for a second or two every 10 mins to log on, report it’s position to the system, etc. The power output is variable in AFAIK 255 steps; the weaker the incoming signal, the more power it sets for the outgoing. These measures makes it possible to make a smartphone which more or less works for, ahem, 1 day 
But the old ones e.g. the Nokia 6310i did 2 weeks between charges.
In the aircraft, one gets the noises in the headset when the phone is logging on to the system – every 10 mins or so. That’s if it is getting a GSM signal. If it isn’t (which is the case most of the time at altitude) it won’t be transmitting anything at all.
One reason for the improved coverage is the deployment of lower frequency spectrum, made available from the switch off of analogue TV. Bands at 700 and 800MHz provide longer range than the higher frequencies, so are good for rural and less densely populated areas. When combined with the superior technical performance of 3G or 4G, signal range and penetration (as well as speed) are much improved.
I don’t know the answer but are they using the 700MHz band for 4G (LTE) data? I would have thought that the data rate on 4G (10-20mbits/sec possible in some places e.g. Germany) would need a higher frequency carrier.
I don’t find voice works well at all, but obviously you have the other problem in that unless you can feed it via the headset, it’s a bit useless in the cockpit…
(Connected to Headset via Bluetooth!)
