Category Archives: Pactor modems and connecting to them

Pactor Modems and connecting to them

Glossary of SCS Pactor Modem model numbers

SCS model numbers and pactor modes are confusing.   Current modems in production are the PTC-IIIusb and the P4dragon, and are recommended.    Any previous PTC-II, IIe, IIex,  IIpro, or IIusb modem can be licensed to use the Pactor-III  protocol for a fee (paid to an SCS dealer or to SCS, not to SailMail) but can’t be used for P4.   Pactor-III transfers data 3-4x faster than Pactor-II with good signals, and is slightly faster than Pactor-II even with weak signals. P4 is somewhat faster still, particularly with strong signals.  We strongly encourage all members to use at least Pactor-III.  SailMail’s stations are all capable of all modes including Pactor-4.  We expect that PTC-II-family modems (licensed to use Pactor-III) will continue to be used by most SailMail members because of the significantly lower cost. But for those with greater communications needs, Pactor-4 offers a way to increase capacity.  Pactor-III mode was developed after the PTC-II and PTC-IIe were introduced, and was an “option”– part of the newer firmware-updates but had to be “unlocked” with a purchased license-code.  For later modems this Pactor-III license-code was keyed to the modem’s electronic serial# (ESN) and was transferable with the modem. For earlier modems, all PTC-II’s and early production PTC-IIe units, without an ESN, the original policy was for SCS to issue a license code that was keyed to the user’s callsign. This license-codes are not transferable to a new owner and are no longer available.  If you have a PTC-II or early PTC-IIe that does not have an ESN (i.e. no barcode sticker on the bottom), it may be possible to have the modem retrofit with a hardware ESN.  contact Gary at Farallon Electronics to find out.  If it is possible, the ESN retrofit and P3 license will cost around $350.

Leave the modem selection in AirMail set to your modem model number.  If your modem has indeed been upgraded to Pactor-III mode then Airmail will detect that, and use it.

The best way to find out the Pactor-III status is to connect the modem to the computer (no radio needed), open Airmail and open terminal window, and wait a few seconds for the modem to initialize. The initialization string will show the modem serial# is there is one, and the Pactor-III license status.

SCS Pactor Modem Guide

Model numbers are shown on the front panel, e.g. PTC-IIe or PTC-IIpro. The original PTC-II was an all-metal box, the later modems have gray plastic bezels around the front-panel. (Current SCS modems– DR-7400/7800 and PTC-IIIusb) have black plastic bezels).  The early modems were all PTC-II models of various sorts which may or may not have been upgraded to enable Pactor-3 mode.  No PTC-II or PTC-III modem of any type can be ungraded to run P4.    All SailMail stations support Pactor-II, Pactor-III, or P4.

From oldest to newest (see below for explanations of terms):

PTC-II (no suffix, original all-metal box):
Serial, TTL radio control, P2, No ESN.
PTC-IIe: Serial, No radio control.
Early PTC-IIe’s have no ESN (no bar-code label on bottom), P2
later PTC-IIe have ESN (same as PTC-IIex), P2/P3*
PTC-IIex: Serial, No radio control, ESN, P2/P3*
PTC-IIpro: Serial, full radio control, ESN, P2/P3*
PTC-IIusb: USB, full radio control, ESN, P2/P3*

The current modems (PTC-IIIusb, DR-7400, DR-7800) are all USB.  The PTC-IIIusb supports Pactor-II and Pactor-III.  The DR-7400 and DR, support Pactor-III and P4.(no license-code needed),   Again, all SailMail stations support P-II, P-III, and P4.


Serial: 9-pin serial computer interface, generally requires a USB/serial adaptor (we currently recommend any of the devices with a FTDI chip set, e.g. search Amazon for “FTDI RS232”

“TTL radio control” is the original 8-pin “control” connector, TTL (0-5 volt) radio frequency-control only, compatible with M700pro, M710 (not M802).

“Full radio control” is 13-pin “control connector”, either 0-5v or RS232 levels, compatible with pretty much any recent radio to set frequency.

ESN: Electronic serial #, stored internally and also on a paper bar-code label on the bottom of the modem. It is used as the “key” to an optional Pactor-3 license (unlock-code). Early modems without ESN can be upgraded to add the ESN chip, only a few have been.

P3*: Units with an ESN *may* have been upgraded to P3 with a license code, most were. These license-codes are transferable to a new owner. The code itself will be stored in the modem (unless somehow erased), and can be checked or retrieved from SCS via email (

A modem with ESN, but which was never upgraded to P3, can be upgraded with the purchase of a license-code, cost is around $200 (contact Gary at Farallon Electronics in Calif,

Exceptions: Early, non-ESN modems could originally be used in P3 with a different code that was keyed to the user’s callsign. These codes are NOT transferable, and no new callsign-codes are being issued by SCS. It *may* be possible to upgrade these modems first with the addition of a ESN chip, then by purchasing the P3 license code, cost for all that will be around $350– contact Gary at Farallon.  If buying a non-ESN modem (PTC-II, early PTC-IIe) it is important to determine whether it has the ESN upgrade chip. For PTC-IIe, check for the bar-code label. Without the ESN the modem can only be used in P2 mode, works just slower. Upgrading to ESN (and P3) is expensive, check with Farallon and consider that in the price.

ESN modems may or may not have been upgraded to P3. If so, the license code *should* be stored in the modem: Connect to a computer, start Airmail and configure modem-type and com-port correctly, open terminal window and confirm that it initializes. The initialization message will show 13-digit ESN and Pactor-3 license status.

Alternately open a terminal program (Hyperterm or Airmail’s dumb-terminal window), hit ESC to get a “cmd” prompt, type the “LICENSE” command to see the license-code (if stored). The command “SYS SERN” will show the serial#.

Troubleshooting USB problems

Most new computers do not include RS-232 serial ports, and a USB/serial adapters is the most common way to connect serial devices such as a Pactor modem or a GPS. Most USB/serial adapters are reliable but unfortunately there are enough bad ones out there to cause a lot of problems. Our current favorites are any of the adapters that use the “FTDI” chipset, for example the Sabrent  CB-FTDI or search Amazon for “FTDI RS232”. Many others also work fine, just be sure that drivers are included for whatever version of Windows you are using.

If you are having problems with a serial device connected with a USB/serial adapter, here are some troubleshooting tips.

First, try to enlist the help of whoever you purchased the adapter from. If it was a Comp-USA store or a low-budget local vendor, then you may find this approach unrewarding. File that away for next time, and keep reading…

The first step in troubleshooting any system is to simplify it as much as possible. If you have multiple devices connected, then remove all but one and focus on that. If you are connecting through a USB-hub (multiple USB ports connected to a single USB-connector on the computer) then remove that, and plug your USB/serial adaptor directly into the computer. Be methodical, take notes, and simplify the configuration to the minimum and get that working before adding other devices.

Next, open Airmail’s Options window (Tools menu) and click the connection tab. Select each com-port in turn and note the description. Find your device and make sure that it is selected. The most common problem is having the wrong COM-port number. Also make sure that the baud-rate is set correctly, some USB adaptors do not like 115200 baud but all should be happy with 57600. (PTC-IIusb modems always use 115200 baud, and Airmail’s “Getfax” fax companion will be happier at 115200 if the modem-firmware is current).

If the device is not visible in Airmail’s options window com-port list, then open Windows Device manager: Right-click on “my computer” and select properties, or open Windows control-panel and select “System”. Click the “Hardware” tab and then the “Device Manager” button. Look for yellow question-marks, this would indicate a device whose driver did not load properly. If you find one of these then you need to identify the device, get the appropriate drivers and then right-click on the device and “update drivers”. Next find “Ports”, expand that (click the little “+”) and look for your USB/serial adaptor. If found, note the com-port number. That same com-port number should appear in Airmail’s Option window (remember to re-open the options window after changing devices), if not they it did not install properly.

If still no luck then make sure you have the correct– and latest– drivers for your USB/serial adaptor. Go to the manufacturer’s website, click on “support” or “dowloads” and find the drivers page. Download the driver-files for your device, save then in a “drivers” folder and then go back to device-manager (above) and try updating the drivers.

If still no luck then you may just have a turkey, see the comments above about Keyspan single-port adaptors or Edgeport multiport boxes. Or find a dealer who can supply an adaptor that they will stand behind, and will help you with if things don’t go according to plan.

Also worth noting: Some adapters assign com-port numbers according to the device serial number, so that a given adapter will always be “COM4” for example. Alternately, some devices assign COM-port numbers according to which USB-socket the adapter is plugged into. In this case moving an adapter from one USB socket to another will cause things to stop working. So a good rule of thumb is to always use the same USB socket for each adapter.

Good luck and good sailing!
Jim Corenman