Originally Posted by goboatingnow
well pactor III sometime does
"After protocol overhead, PACTOR-III achieves an effective throughput of up to 2722 Bit/s without compression. If plain text is transmitted, the built-in Pseudo Markov compression allows an effective throughput of up to 5200 Bit/s"
Iridiums " effective throughput" with compression is 9600 bps
You guys are looking at theoretical values. In the field the effective throughput is much less for pactor than iridium. Iridium effectively transfers about 15Kbytes of raw data per minute. A really good pactor III connection will do 10Kbytes per minute. However, you usually see in the 1-5Kbytes per minute range out of pactor III. The other thing to keep in mind is that line turns arounds with pactor III are deathly slow. With iridium you have 1-3 seconds. For pactor III its 10 seconds or more.
The big win with Iridium is consistency. no matter where you are on the planet you can expect to connect quickly and have consistent data rates. With pactor its a toss up whether you will event get connected. with HF you have station contention, user contention, ionosphere propagation issues, grounding and RF issues, and....
Users that can afford to pay for airtime over iridium rarely if ever use pactor.
With pactor you can do one thing... e-mail.
with Iridium you can
1. call home to say hello to family
and friends on special occasions
2. call 911 as you abandon ship into your life raft and discuss the matter in person with emergency
3. receive voice calls (caller pays if they initiate the call)
4. receive free 160 character e-mail SMS mesgs
5. do all of your e-mail (compression based software highly recommended)
6. receive all of your weather
(compression based service highly recommended).
7. browse the internet in a pinch...
you can do this any time day or night anywhere on the planet. The phone consumes 400 mAmps when running so power is never an issue. Installation
is easy and requires that you plug
the phone into a USB phone of your PC. Put the phone in a location where it can have a clear view of the sky. That is it. Simple as 1 2 3.
With HF... well lets not go there. Let just say that installations can be lengthily, expensive, disruptive, and problematic.
Anyway... that is my 2 cents worth... And BTW... you might say that I don't know what I am talking about with pactor and HF but I ran 2 stations on the XNet association (TN and Puerto Rico) in a network of 7 stations that ran pactor III exclusively for 5 years... the 1 - 5Kbyte per minute figure comes from sitting in front of computers
running bench marks day after day year after year over the network and also dealing with customers and monitoring their traffic.
Take my word for it... Iridium is MUCH simpler and faster to use than pactor...
Iridiums throughput can be much higher than 9600 baud with compression. It just depends on what you are transmitting. Here is a sample from our logs
where a user transmitted 70070 Kbytes which compressed down to 3.2Kbytes (ie 25X compression) in 15 seconds... (which is typical for iridium).
Wed Sep 29 15:58:44 2010 [83610-1285775919] cmd: "xsend client.x.bz2 3255 0"
Wed Sep 29 15:59:07 2010 [83610-1285775919] Relaying file=client.x size = 70070
For this one transfer the effective baud rate was 52kbs. It all depends on the compressibility of the date.
BTW... i have used pactor modems and HF radios for sale
if anyone wants them.