HAM / SSB / SAT Phone

[s/v Jedi]

Originally Posted by osirissail

He said "speed of iridium is 2400 baud although if you purchase an AxcessPoint Wifi device or an WXA-200 router you can get over 3000 baud... Check this out."

Not Kbps. Kbps can vary with the protocol/process used to establish bit flip voltages/phases. It is better explained here: Baud versus Bits Per Second

Not in this case. The link stays 2.4kbps or kbaud, it does not become 3 kbps or kbaud.

ciao!
Nick.

[lsoltero]

Originally Posted by s/v Jedi

Hello Luis,

I have some questions for you, if you don't mind:

1. Iridium link speed. You write that connecting an AxcessPoint ir WXA-200 increases the speed from 2,4kbps to 3.0kbps. How does that work, as the satellite link that the phone has is 2.4kbps maximum? I think you have been misinformed and observed higher rate is the result of data compression, which a lot of devices, incl. Pactor modems, can do.

2. You claim the isatphone is 2.0kbps download and 1.6kbps upload. But Inmarsat claims the same 2.4kbps as Iridium. Are they lying?

3. You claim that satphones are 3 to 5 times as fast as Pactor 3. However, the satphones you reference are both 2.4kbps rate, while my Pactor modem is 2.7kbps which is actually faster than either satphone can provide. I regularly download gribfiles over Email and this is faster over my Winlink Pactor than it is over my satphone, which is conform the specifications.

4. You state Iridium will provide us with FREE email when we buy the AxcessPoint device. How does that work, do they send you cards with minutes as you use them? Or can you call a free number? Also, are there limits to this FREE service? Or is it not free and must we pay the regular full price for minutes used? Might it be that they just give a free email address like Hotmail, GMail etc. also do without the need to buy equipment?

thanks,
Nick.

Answers to your questions...

Iridium actually runs faster than 2400 baud application to application. What slows it down is contention for the PPP connection by other system and user level process that want access to the net. When measuring application to application transfer rates using the USB we routinely see between 12-18 Kbytes per minute over Iridium. This is true for both Macs and Pcs. When doing the same measurements with an AxcessPoint wifi we see transfer rates > 3000 baud 3118 being the record so far. However... note that your milage will vary depending on signal strength, occlusions, satellite handoffs etc.

Bottom line.. the firewall on the AxcessPoint Wifi and WXA-202 allow you to squeeze the most out of your connection.

2. Yes.. that is the claim... but we don't see that. The Isatphone is considerably slower than Iridium when measuring application to application transfers. There are some distinct advantages of iridium over isatphone here they are...
a. iridium has 20 second billing increments. Isatphone has one minute inclurements. This mens that you play for two minutes of airtime on isatphone if you rseession is 61 seconds long. Note the case with iridium.
b. It takes over 1 minute to bring up a ppp connection with isatphone. it takes 15 seconds for iridium. This means that in isatphone you blow a full minute of airtime before you transmit a single byte of data.
c. Iridium is considerably faster than isat. this is especially true on uploads.
d. iridium line turn around latency is 1.4 seconds. Its 5 seconds for isatphone. When you take into account protocol overhead this is a real killer. Take SMTP for example... SMTP requires 5 line turn arounds for setup and one additional line turn around for each email address. So... to send an mail with 5 recipients over isatphone takes 50 seconds of overhead before you send a single byte of data. with Iridium 14 seconds.

Using optimized compression software for both iridium and isatphone is essential.... However, without it isatphone just doesnt work.

3. I said on average.... You rarely (never) get 2400 baud out of pactor. A smoking pactor III connection gets you 10 kbytes per minute. A good connection gets you 5 kbytes per minute. An average connection 1-3 Kbytes.

AND the line turn arounds for pactor are dismal. Once you get it going in one direction it does ok but as soon as you have to turn the line around the protocol really slows down.

4. Free email does not mean free airtime. You get the software and an email account at iridium which allows you to do email with out having to subscribe to a service. i.e. free email. You still pay for the airtime. Free email is only available to users with 9555 or 9575 phones who also own an AxcessPoint Wifi device. Chekout the iridium.com or more info.

The email has been optimized for transfer over satellite phones and works very well. We should know since we did the implementation... AxcessPoint Mail & Web is powered by XGate. So... you get the same performance as you do with our XGate email software.

Note that there are some advantages to subscribing to a comercial service over getting the email for from from iridium. Iridium only allows access to the email through their airtime. You can't use webmail or an internet connection to check for mail. The system also only works for the 9555 and 9575. XGate on the other hand allows you to use wifi, cell phones, satellite phones, and other connectivity methods to get your mail. So although you might pay $20 per month for xgate the flexibility might offset the cost.


take care.

--luis

[Paul Elliott]

Luis, are you using the term "baud" correctly here? I know it's become (wrongly) synonymous for bits/sec, but as I'm sure you know baud is the symbol rate, not the effective bit/sec throughput.

I've no doubt that the bit/sec throughput is significantly improved through the use of satphone-aware protocols. This is why I use XGate instead of native PPP for my Iridium email. The difference is staggering, especially when dealing with a marginal connection.

[s/v Jedi]

I am sorry Luis but you are wrong and I am not good in bringing that more subtil. Your or anyone elses applications do not increase the raw link speed of Iridium above 2.4kbaud. PPP and other applications are irrelevant, because whatever you do, it all has to go through the 2.4kbaud satellite link. The satellite link is not faster tan 2.4kbaud; you are mixing that up with the signalling overhead but that is the same for all media discussed here (Pactor 3 is also 3.6kbaud before signalling overhead) so we only use the net link speed. Also, special devices or hardware that you sell do not improve the satellite link speed.

All that you can do with devices and apps is data compression and data filtering in order to optimize what goes through the 2.4kbaud. That is good enough, no need to claim the impossible.

As for Pactor: my link is never smoking but almost always faster than 2.4kbaud. It probably makes a difference that I am on Winlink2000 and not SailMail. The links I have also perform equally in both directions. Your bad experiences must have been caused by bad SSB installations and Pactor 2 instead of Pactor 3 links. Or by ignoring propagation tables. I agree that this can be highly inconvenient which is one of the reasons we have a sat system besides the SSB.

ciao!
Nick.

[lsoltero]

Originally Posted by Paul Elliott

Luis, are you using the term "baud" correctly here? I know it's become (wrongly) synonymous for bits/sec, but as I'm sure you know baud is the symbol rate, not the effective bit/sec throughput.

I've no doubt that the bit/sec throughput is significantly improved through the use of satphone-aware protocols. This is why I use XGate instead of native PPP for my Iridium email. The difference is staggering, especially when dealing with a marginal connection.

The answer is yes...

Baud is a measure of performance. It means bits per second. You can also use the number of bytes transferred in a minute as a measure of performance. The number of bits in a byte vary. When speaking of serial communication you have a number of bits transferred in a burst. These bits include a sync, data, stop, and parity. There are about 10 bits in a byte.

When talking about performance I like to use the bytes transferred in one minute between the client application running on the remote PC and the sever. In the end this is what really matters. How much data do you get to transfer in one minute of airtime.

so here is a nice equivalence....

15 kbytes in one minute is the same as 2400 baud.

This allows you to convert easily convert between bits per second and bytes per minute.

Also note that your application to application transfer rate is usually slower than advertised transfer rate for the medium. This is because there is protocol overhead (i.e. PPP, error correction, retransmit) that are not taken into account when publishing the numbers.

Inmarsat advertises 2400 baud for their transfer rates... But by the time you include the overhead you get less than that. On average we see about 10-12 kbytes per minute down on Isatphone. this translates to (12/15) * 2400 --> 1600-1920 baud. hence my statement that isatphone is 2000 baud down.

Iridium also advertises 2400 baud... However... we routinely see more than that... On average iridium transfers data application to application (that is XGate application to application... other protocols are much slower do to line turn arounds) of 15kbytes per minte--> 2400 baud. This means that iridium must be running faster than 2400 baud since you get that rate application to application which also includes overhead. It gets better...

We have seen 3118 baud over iridium. this means that application to application transfer rates of 19.5 Kbytes in one minute which is almost 2x Isatphone. To get this transfer rate you must have perfect signal, not occlusions, and a firewall that prevents other applications from competing with your bandwidth.

As stated previously standard protocols dont work well over iridium or isatphone because of the latency of the link. Internet protocols have a lot of send data/receive ack interactions each of which takes 1.4 seconds of dead time overhead for iridium and 5 seconds for isatphone. XGate removes these which is one of the reasons performance is so much better. XGate also compresses and plays other tricks to optimize transfer speeds.

Tale care.

--luis

[lsoltero]

Originally Posted by s/v Jedi

I am sorry Luis but you are wrong and I am not good in bringing that more subtil. Your or anyone elses applications do not increase the raw link speed of Iridium above 2.4kbaud. PPP and other applications are irrelevant, because whatever you do, it all has to go through the 2.4kbaud satellite link. The satellite link is not faster tan 2.4kbaud; you are mixing that up with the signalling overhead but that is the same for all media discussed here (Pactor 3 is also 3.6kbaud before signalling overhead) so we only use the net link speed. Also, special devices or hardware that you sell do not improve the satellite link speed.

All that you can do with devices and apps is data compression and data filtering in order to optimize what goes through the 2.4kbaud. That is good enough, no need to claim the impossible.

As for Pactor: my link is never smoking but almost always faster than 2.4kbaud. It probably makes a difference that I am on Winlink2000 and not SailMail. The links I have also perform equally in both directions. Your bad experiences must have been caused by bad SSB installations and Pactor 2 instead of Pactor 3 links. Or by ignoring propagation tables. I agree that this can be highly inconvenient which is one of the reasons we have a sat system besides the SSB.

ciao!
Nick.

Hello Nick,

I beg to differ with you.

We have been in the vessel communication business for 10 years (global marine networks was founded in aug 0f 2003). I have personally been in the vesel communications business since Aug 1, 1996 when I purchased and installed my very first pactor modem on my vessel in trinidad. In the year 2000 I did over 3000 emails over pactor while in the western carribbean.

GMN also ran the XNet HF network for 5 years. This network consisted of 7 pactor 3 stations in the Caribbean, US east coast, and Europe.

All of the figures I have posted here are measured averages for application to application transfers.

Our experience (which is considerable given then thousands of customers we provide services to) is that
1. advertised transfer rates for the different carriers seldom map to application to application transfers.
2. Iridium does better than either pactor or isatphone although the advertised rates for all are about the same.
3. For iridium we typically see 2400 baud (applcation to application) which maps to 15 kbytes in one minute. This means that on average the raw transfer rate for iridium is > 2400 baud.
4. For isatphone we typically see 10-12 kbytes per minute down which translates to an application to application transfer rate of 2000 baud which means that isatphone is close to their advertised medium rate of 2400 baud.
5. With pactor your average connection is way slower than 2400 baud. I spent a full month back in 2006 doing benchmarks between our TN and Florida shore stations. When conditions were perfect we could observe 10 kbytes per minute of data transfer application to application which maps to 2000 baud which means that the medium baud rate was close to 2400 baud. However... there are many factors that affect pactor including atmospheric and installation related. On average our customer were getting < 5 kbytes per minute and many in the 1-3 Kbytes per minute. The per user figure varies dramatically from day to day and connection to connection. Satellite phones give you much more consistent behavior.

Take care.

--luis

[medicrene]

If you already have a Ham Radio with the capability to use the upper side band, then why waste money on a sat phone. I had a sat phone and it was great to call people (including the CG) in an emergency, but to get internet on a sat phone will be expensive in that you will need to have a phone that can do that (mine does not).

If you have a ham or SSB on the boat now, try tuning into some weatherfax frequencies in your area (they are posted on the NOAA marine weather website). If you can hear the beeps, then buy a demodulator (about 120 dollars) and get the system working.

The Witchdoctor

[lsoltero]

Let me add one more note...


On my desk I have two pactor III modems wired back to back. When transferring directly without an HF radio running balls to the wall we see 10 kbytes per minute (or 2400 baud) application to application. So under absolutely perfect conditions a pactor system will run slower than what we observe over iridium in the field (15 kbytes per minute application to application).

All of our test are conducted XGate (including those on pactor) so the application to application protocol is consistent for all measurements.

take care.

--luis

[lsoltero]

I hate to beat a dead horse... But here is a sever log session showing that it is possible to get a raw application to application transfer rate > 2400 baud over iridium.

Mon Nov 28 11:33:00 2011 [39847-1322479980] /tmp
Mon Nov 28 11:33:00 2011 [39847-1322479980] Debug flag = 1
Mon Nov 28 11:33:01 2011 [39847-1322479980] cmd: "login weather4d XXXX i1.0.0080 1 0"
Mon Nov 28 11:33:01 2011 [39847-1322479980] looking up weather4d
Mon Nov 28 11:33:01 2011 [39847-1322479980] chk: srv=0, cln=0, numfiles=1, chksum=38966, ini=39932
Mon Nov 28 11:33:01 2011 [39847-1322479980] passwd file: logged in weather4d IRIWIFI 0
Mon Nov 28 11:33:02 2011 [39847-1322479980] cmd: "xget 0"
Mon Nov 28 11:33:02 2011 [39847-1322479980] Processing mail for weather4d /home/weather4d
Mon Nov 28 11:33:02 2011 [39847-1322479980] hdr: 1322478605.M95503 86617 from=query-reply@saildocs.com to="weather4d"
<weather4d@myiridium.net>
Mon Nov 28 11:33:03 2011 [39847-1322479980] Sending server.x.bz2 58477 1
Mon Nov 28 11:36:07 2011 [39847-1322479980] ACK
Mon Nov 28 11:36:07 2011 [39847-1322479980] Done processing mail for weather4d
Mon Nov 28 11:36:08 2011 [39847-1322479980] cmd: "BYE"
Mon Nov 28 11:36:08 2011 [39847-1322479980] Done.


that as 58K in 3 minutes...

that is a raw throughput speed of 3118 kpbs which is significantly higher than 2400 kbps.

Note that this is not the effective throughput which was 4700 kbps for this transaction it was the RAW throughput. That
is about the highest figure raw transfer rate that I have ever seen over Iridium.

The transfer was done using an iPad, iridium AxcessPoint Wifi, XGate from a boat in the middle of the Atlantic during the Arc.

--luis

[osirissail]

Bits, Bytes, Baud, all too much for me. How long each system takes to load a NOAA weather fax wind/wave chart is what I care about.

Originally Posted by medicrene

. . . If you have a ham or SSB on the boat now, try tuning into some weatherfax frequencies in your area (they are posted on the NOAA marine weather website). If you can hear the beeps, then buy a demodulator (about 120 dollars) and get the system working.
The Witchdoctor

You don't need to buy a demodulator for weatherfax charts if you use JVComm32 (free from: JVComm32 - Download page )

Any HF receiver with USB SSB capability can supply the signal to your computer/lapbook/netbook's microphone input jack. Then your computer's sound card demodulates the signal and JVComm displays the chart on your screen.

[lsoltero]

easy...

take the size of the file compressed...( i.e. use the windows compress feature to compress the size and then view the size in windows explorer using the detail view ) and then device that by 15000.

So... if a wefax is 25kbytes then that would take 1.7 minutes over iridium.

a grib file containing 3 days of wind forecost every 6 hours (i.e. 12 forecasts) the size Caribbean sea takes about 1 minute over iridium.

--luis

[stevewrye]

Wow, way over my head I'm afraid. What about quality of end result with pactor or sat phone? A friend with SSB/pactor says he hates the quality of the download, has a hard time reading wind barbs as they are almost always a blur. Any truth to that?
I guess I don't mind paying a few bucks a day on a long passage for 3 days of 500 millibar and surface maps if I can press a button anytime of day and in a few minutes have what I need.

[lsoltero]

Originally Posted by stevewrye

Wow, way over my head I'm afraid. What about quality of end result with pactor or sat phone? A friend with SSB/pactor says he hates the quality of the download, has a hard time reading wind barbs as they are almost always a blur. Any truth to that?
I guess I don't mind paying a few bucks a day on a long passage for 3 days of 500 millibar and surface maps if I can press a button anytime of day and in a few minutes have what I need.

Pactor, Iridium, Isatphone, etc... are all digital modes of transmission. Pictures downloaded using these technologies are perfect.

Your friend must be using the WeFax demodulator built into the pactor modems and receiving his weather faxes using fec mode... this method of receiving digital data is error prone and time consuming. It leads to blurry pictures with lots of drop outs taking about 15 minutes per image to download. 6 weather faxes can take almost 2 hours to download.

Receiving the same images over a satellite phone usually takes about 1 minute per image. And you can get these anytime you want without having to get up to meet the schedule.

--luis

[conachair]

Originally Posted by stevewrye

Wow, way over my head I'm afraid. What about quality of end result with pactor or sat phone? A friend with SSB/pactor says he hates the quality of the download, has a hard time reading wind barbs as they are almost always a blur. Any truth to that?
I guess I don't mind paying a few bucks a day on a long passage for 3 days of 500 millibar and surface maps if I can press a button anytime of day and in a few minutes have what I need.

Just recieving weatherfax via a ssb, you should probably get a better quality or at least the same as this. Plenty to see the isobars & fronts. For free Which over a few weeks adds up to quite a few beers

[SoonerSailor]

You'll get much better weather fax images by retrieving them from the email based Saildocs service via Pactor OR Satphone than you will by receiving them over the air line by line with a SSB radio and fax demodulator.

There wont be any difference in the images between Pactor and Satphone, they are both just digital pipelines.