I’m not a hardware guru like John, so I cannot fully answer your question about the advantages of the StarTech ExpressCard serial adaptor compared to a USB-Serial adaptor (especially a Belkin adaptor).
On Zygote, we use two serial ports, one to accept electronic nav data (GPS, wind speed and direction, water speed, etc) and one to control the Pactor modem (including allowing the software to change the tx/rx channel on the SSB).
We first tried two USB-serial adaptors. Not Belkin brand, that’s for sure. I found the USB-serial adaptor could handle the electronic nav data flow, but not the other crucial function of handling whatever communication goes on between the Pactor modem and the iCom SSB (and which includes the aforesaid changing of tx/rx channels).
Our StarTech ExpressCard COM ports do everything we want, without any hiccup. I figure that if your Belkin USB-Serial adaptor works for you, you’ve no need to change.
I acknowledge that USB ports (and USB-Serial adaptors) are more sophisticated than even just two or three years ago. USB 3 is much faster at data transfer than USB 1, for example.
Is Lang wanting to compare Sailmail + Pactor setup with an Iridium satellite receiver? Or some other sat receiver system?
We initially thought that Iridium would be useful. Our Iridium kit cost us (several years ago) about the same as our Pactor modem. And if you guess that the reason we later bought our Pactor modem was because of our dissatisfaction with Iridium, then you’re right.
Our experience with Iridium was before the US military became a heavy user of Iridium (ie before the US adventures in Iraq and Afghanistan convinced Iridium to move sats to give better coverage in the tropics).
When we used Iridium, we found that its use for data comms (ie e-mail, GRIB download, weather fax etc) everywhere (ie tropical and temperate latitudes) was too slow to be useful. Seriously - just too frustating to use.
I have a personal history of starting in PC comms using the CP/M operating system, ie at about the same time that MS-DOS started, using modems that boasted of compliance with the Hayes smartmodem command set, when 300 kbits/sec was acceptably good and 512 kbits/sec was something to boast about on the BBS. That’s bits, not bytes/sec! And my experience with Iridium data was at about that speed level, because of frequent check-bit failure, meaning that a set of data packets were sent and re-sent multiple times before one set got through cleanly.
We found that Iridium voice comms was acceptable in temperate latitudes (it was great at 27 South), but hopeless in the tropics (in our case, that was from the Equator to 19 deg South). We also found that in RF-busy locations, the Iridium was useless (we were in Botany Bay, near Kingsford Smith Airport in Sydney, Australia, and so obviously being swept by air traffic control radar occasionally and close to transmitters of whatever HF or VHF commercial heavy airliners use - and could just manage to make a telephony connection to a landline, but not to make sense of the speech).
Let me point out that I was not naive and had equipped Zygote with a software program that calculated where the Iridium sats were and so could tell me when I could expect better comms (and I refreshed the sat data for that program too - but data comms was still too slow and uncertain to do e-mail). SSB HF has its time/frequency limitations and optimums too (eg trying to shoot a signal to a destination with the setting sun behind that destination is a recipe for sure failure), but I never failed in any 24 hour period to do e-mail and download GRIBs etc via Pactor over SSB HF).
I acknowledge that Iridium coverage is now much better in the tropics and sub-tropics than 5 years or so ago. And that the price of stabilised antenna for sat comms from boats is much lower than in the past (but I’m not sure than any of the stabilised sat comms antenna gear is really meant for a BCC-sized vessel with the battery power available to us).
I won’t comment on the cost of Iridium services - I’m out of date with what’s on offer now.
What convinced me to switch to Pactor and Sailmail was, of course, the excellent contact I maintained with you on BCC Calliste. We proved that for ourselves on Zygote and confirmed that apart from the excellent service from Sailmail (GRIBs, e-mail) we had better Weather Fax with the Pactor than when we used either the PC sound card or a proprietary hardware device to demodulate weather fax.
In US waters, you will have many more sat comms options than just Iridium, of course. That probably goes for the N Pacific too.