Pactor Modem Practice

[Charlie]

Hello All:
I am interested in "practicing" with recieving SSB signals and grib files. I have a Pactor Modem on the boat that I have not installed yet and was thinking that I could buy either an SSB receiver to"listen" and download files while at home as a practice for a possible upcoming Atlantic crossing. On a recent trip from Cabo San Lucas to San Diego we used the weather forecasts on SSB to get our weather forecasts but did not know how to download grib files and had to rely on a buddy boat for that information. I am interested in practicing some more and was wondering if anyone had some advice on what equipment to get. I currently have an ICOM 710 (I think) on the boat that works well. I am debating between getting a home Ham set up and/or a portable SSB rcvr. The portable would stand as a back up on the boat should we loose our rig.

[Paul Elliott]

Somebody please correct me if I'm wrong, but I don't think you're going to have much luck receiving GRIB files with your pactor modem using just a receiver. The GRIBS aren't broadcast at a particular time, but are attachments to email that is being sent to a specific vessel. This email gets sent when that boat logs in.

You can use the modem's built-in WFAX demodulator with a receiver to decode the USCG WFAX radio transmissions, which are scheduled, but these are not GRIBS.

I would connect the modem to your 710 (a very good rig, by the way), make sure you have the proper licenses, and use this. You mention ham radio, so if your 710 has been opened up for the ham bands you can use winlink for testing, and you won't have to pay to join sailmail. You may want to join sailmail later though, depending on your success with winlink (I find sailmail to be more reliable). You don't have to be a member of sailmail to use their saildocs GRIB service.

[Krakato]

To properly use the PACTOR modem, it has to transmit as well as receive. The server (the mailbox you are connecting to) and the client (your modem) exchange a series of parameters as well as a checksum value to see that the packet that was exchanged was error free. If not, it will be retransmitted. So even if you are on the receiving end, your radio will still transmit a short burst about once a second or so.

Now that said, there is a way to put the modem into "monitor" mode in which you can listen into an exchange, but it will not be error corrected so depending upon signal strength you will loose about 20-80% of the content.

If you have your amateur radio license, use WINLINK 2000 and a free program called Airmail. With that you can practice as much as you want sending and receiving.

Hope this helps.

Cheers,
Mike
NW5M

[Charlie]

Originally Posted by Paul Elliott

Somebody please correct me if I'm wrong, but I don't think you're going to have much luck receiving GRIB files with your pactor modem using just a receiver. The GRIBS aren't broadcast at a particular time, but are attachments to email that is being sent to a specific vessel. This email gets sent when that boat logs in.

You can use the modem's built-in WFAX demodulator with a receiver to decode the USCG WFAX radio transmissions, which are scheduled, but these are not GRIBS.

I would connect the modem to your 710 (a very good rig, by the way), make sure you have the proper licenses, and use this. You mention ham radio, so if your 710 has been opened up for the ham bands you can use winlink for testing, and you won't have to pay to join sailmail. You may want to join sailmail later though, depending on your success with winlink (I find sailmail to be more reliable). You don't have to be a member of sailmail to use their saildocs GRIB service.

Originally Posted by mhward1337

To properly use the PACTOR modem, it has to transmit as well as receive. The server (the mailbox you are connecting to) and the client (your modem) exchange a series of parameters as well as a checksum value to see that the packet that was exchanged was error free. If not, it will be retransmitted. So even if you are on the receiving end, your radio will still transmit a short burst about once a second or so.

Now that said, there is a way to put the modem into "monitor" mode in which you can listen into an exchange, but it will not be error corrected so depending upon signal strength you will loose about 20-80% of the content.

If you have your amateur radio license, use WINLINK 2000 and a free program called Airmail. With that you can practice as much as you want sending and receiving.

Hope this helps.

Cheers,
Mike
NW5M

Thanks for the replies. I didn't realize that grib files rqd both a transmit and a recieve. Looks like it is a good idea to get my ham license but I don't know if I will have time.

[Paul Elliott]

Originally Posted by Charlie

Looks like it is a good idea to get my ham license but I don't know if I will have time.

You might find it quick and easy to get the license, now that there's no Morse code requirement. Take a look on-line at the requirements and sample questions before you assume it's not feasible.

[richardhula]

Originally Posted by Charlie

Thanks for the replies. I didn't realize that grib files rqd both a transmit and a recieve. Looks like it is a good idea to get my ham license but I don't know if I will have time.

I essence they don't but its the means by which they are derived that require first an email request, then after a short wait for the server to reply, another email to be received containing an attached grib file. Obviously email per se requires full two way communication.

As mentioned above you can use it in receive only mode with GetFax software to receive Weatherfax, RTTY, Navtex & CW broadcasts. Its even possible to configure PTC II to receive & store Navtex broadcasts without PC being present.