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Old April 4th 17, 08:41 PM posted to rec.radio.amateur.moderated,rec.radio.amateur.digital.misc,rec.radio.amateur.space
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Default [N6PSE] DXpedition communications technology


n6pse

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DXpedition communications technology

Posted: 03 Apr 2017 03:39 PM PDT
https://n6pse.wordpress.com/2017/04/...ns-technology/




The assortment of communications gear used in addition to HF.

I am often asked how Dxpedition teams communicate with their Pilot stations
and upload their logs to Clublog from the far flung and remote locations
that we visit. *In this Blog entry, I will describe the data and voice
technology available to enable a Dxpedition to communicate with the outside
world in addition to the HF radio gear.

When operating from a Fly in/Hotel venue, communications are usually pretty
straightforward. We can use a local SIM card in our cell phone for voice
communications for the outside world. Most hotels have some form of
Internet/Wi-Fi that is available for Skype calls and uploads of logs to
Clublog.

Although, as we found in Iraq and Eritrea, the Internet speeds were
insufficient to handle daily log uploads and we had to use other means to
upload our logs. In Asmara Eritrea, a BGAN was used to upload logs as the
hotel internet was too slow to achieve an effective data rate.

Operating on a remote island is much different than a fly in/hotel
situation. Voice communications are generally done via an Iridium satellite
telephone. Iridium operates a satellite constellation of 95 active
satellites used for worldwide voice and data communications. These
satellites are in low polar orbits at 485 miles above the earth. Iridium is
optimized for voice calls and they work pretty well. Data handling is
limited to short text messages. Larger messages and files can be
transmitted via BGAN (see below)



Our Iridium Extreme 9575 satellite phone.

The Intrepid DX Group uses two Iridium phones for extra redundancy.

In addition to Iridium phones for voice calls, we employ a DeLorme In Reach
SE for simple text/data communications with our Pilot stations, friends and
family. The DeLorme In Reach also uses the Iridium network and has global
coverage. The In Reach SE also has a built in GPS and can send coordinates
at regular intervals using the beacon function. Our In Reach SE was
attached to the antenna structure of the RV Braveheart and provided hourly
beacons and map positions of our travels to South Sandwich and South
Georgia Islands. Using the DeLorme IPad application, the In Reach SE was my
primary means of communications with our VP8 Chief Pilot-Tony EA5RM.



Our DeLorme InReach SE provided real time text and GPS beaconing.

We also use a Skyroam global Wi-Fi hotspot for our travels to exotic
foreign countries that have cellular networks. The Skyroam takes the
headaches out of finding and negotiating Wi-Fi networks. In can allow up to
five devices to connect as a Wi-Fi hotspot using the local cellular network.



Our Skyroam global hot spot.

For managing robust data communications such as file transfers, log uploads
and email, a pair of Hughes BGAN terminals are deployed for +1 redundancy.
BGAN stands for Broadband Global Area Network. This network consists of
three Inmarsat satellites in a geo stationary orbit over the earth. This is
line of sight technology and is optimized for moving data. Data speeds of
half a megabit per second are possible under ideal circumstances. From
South Sandwich and South Georgia Islands, we were only able to make limited
contact with the satellite based over Tunisia as it travelled in a figure
eight pattern throughout the day. We found that we could only make access
at the same precise time each day.



This map shows the coverage foot print of the Inmarsat satellite network.

While voice calls are possible over Inmarsat, the quality is poor as
compared to Iridium. It’s important for the Dxpedition organizer to
understand the limitations for BGAN/Inmarsat as it moves data whereas
Iridium is optimized for voice and does a poor job with Data as Iridiums
data rates are about 1/10th that of Inmarsat.

BGAN terminals work in locations where there is no wireless service. They
work on land or sea. An external antenna can be coupled to the terminal to
use on a ship or to receive signals outside while the terminal is used
indoors.



We use two Hughes BGAN terminals for redundancy.

BGAN service is very expensive with rates of $4 to $7 per Megabyte
transferred. The data usage for our VP8STI/VP8SGI Dxpedition was over
$1,500 to update our logs once a day to Clublog. BGAN terminals cost from
$2,000 to $12,000 or more.

So, to effectively move voice and data, the Dxpedition Leader must acquire
Iridium and Inmarsat knowledge and equipment to meet the ever-increasing
expectations placed upon the Dxpedition team for daily log uploads and
effective communications with Pilots and others.

What do you think?

*



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