Radio Selection



This application note contains observations regarding various radios that SailMail members have used.  If your experience differs from the observations listed below, please contribute to this application note by sending an email to


Icom M710, 700Pro, 710RT

These radios are very similar and are the best performing and most reliable radios used by SailMail members.  The M710 has a fancy display with more features, the 710RT has a remote head, and the 700Pro is the cheapest.  They all appear to be the same electronically and have the same functional specifications. 

The user interface is a bit awkward, and the radios are larger and heavier than most other marine radios.  These radios can be used on the ham bands, but are a bit tricky to adjust the frequency in that application.  If easy ham use is important for you, the AirMail software contains a utility that makes tuning an Icom easy, and Don Melcher at HF Radio Onboard sells software that runs in a Palm Pilot that makes tuning easy.

These radios can be remote controlled and have their frequency set for use on SailMail by the AirMail software, via a SCS PTC-II.  If you have a SCS PTC-IIe, IIex, or some other (non SCS PTC-II Pactor-modem) you can still remote control these radios, but you will need a second COM port on your PC.

The size and weight of the Icom radios turns out to be related to their biggest advantage.  These radios are built on a cast aluminum chassis with a substantial heatsink, they incorporate a large diameter fan, and are real "workhorses."  These are the only radios that we have tested that are capable of running continuously at 150W output.  The SailMail stations all use M710 radios which run at very high duty cycles for years and we have experienced only one failure.


Icom M802

This is Icom's newest SSB.  It has a remote head, which is handy for installation.  It has digital IF filters and DSC capability.   Pactor-III requires the full 2.8 kHz bandwidth, so the variable IF filters are not needed for SailMail, but the DSC capability might be useful someday.  As with all recent Icom SSB's, the M802 is rated for continuous 150W output.

The M802 will likely turn out to be a terrific SSB, and a great choice for SailMail.

There were a few wrinkles with the early production units that may be worth watching out for.     Details are in the application note on the M802. 

There is an application note on the M802 linked from the SailMail Primer that describes the use of the M802 with the PTC-IIpro HF modem.  Observations are welcome from early users; please send comments to


Icom M700

This is Icom's original HF marine radio.  This radio has a number of disadvantages for use with digital communications.

There is no accessory jack with the necessary AF input, AF output, and PTT signals.   The addition of an accessory jack will require you to have a radio technician modify the radio.  Most radio technicians will (sensibly) refuse to do this modification because they feel that it is pointless to work on such an old radio.   If you do decide to get the modifications done be sure to get the price quoted in advance, and then reconsider just replacing the radio.

Once modified, the M700 still is not ideal.  It is only capable of about 50 watts continuous output.


Icom M600

The Icom M600 will work fine for SailMail, but takes some work. 

The M600 did not come standard with an accessory jack with the necessary AF input, AF output, and PTT signals needed to hook up a Pactor-modem.  However, Icom used to sell a retro-fit kit for the M600 that was used to add an "accessory" connector.  We understand that the retro-fit kit is now unavailable from Icom, but some members have used M600's even without the Icom retro-fit kit by adding their own DIN accessory jack and wiring it into the connector that is inside the radio that was originally intended for use by the retro-fit kit.   They then plug their PTC-II modem into the new DIN accessory jack using a normal cable that marine electronics dealers sell to hook PTC-II modems to Icom radios.

The radio is fan cooled and so is capable of about 60 watts continuous output, which is fine if you use a PTC-II.   You need to set the audio drive levels  by setting PSK 120 and FSK 120 in AirMail's tools/options/settings/amplitudes.  Read the application note in this Primer on setting drive levels and check these settings yourself.  You don't want the radio to draw more than 10 amps of current from your 12 volt supply when transmitting.

There is a problem that some M600's have in digital use:  The symptom is that the radio will not transmit or receive after it gets warm.   The cure is to replace the unstable C228 trimmer capacitor with a ceramic equivalent and adjust the PLL lock voltage for 2 volts instead of 2.5 volts as stated in the manual.  There are details about this modification on the Icom website.

Thanks to Dave Kerr and Mary & Carl Heckrotte for suggestions for the M600.


SGC SG-2000

The SG-2000 does not come with a fan, and is not capable of continuous full power.  SGC isn't perfectly clear on the point, but after discussions with SGC one develops the impression that the SG-2000 is capable of 50 watts continuous RMS output without a fan kit, and 100 watts continuous RMS output with the #51-81 fan kit.   If you have a SG-2000 radio, you will have to carefully reduce the modulation levels to avoid causing the radio to go into high-temp power reduction.

SailMail members have reported that the SG-2000 is susceptible to interference from strong out-of-band signals.  The means that SG-2000 users often have difficulty using their radio if another vessel in the anchorage is using a SSB, even on a different band.

The SG-2000 can be remote controlled and have its frequency set by the AirMail software, via an SCS PTC-II.

The SG-2000 sometimes causes problems with laptops and Pactor-modems because it radiates quite a bit of RFI on its 12 vdc powerline.  Review the application note on the SG-2000 that is part of this Primer for suggestions on how to solve this problem.



We have only heard of two instances where members succeeded in making  Kenwood Marine radios work for digital service.  Most folks with Kenwood Marine radios have found it easier to replace the radio than to work through the problems.  The problems are rumored to be both slow (30ms) T/R timing and RF self-modulation.  The T/R timing problem is only evident if you are close to the SailMail station that you are trying to use.  If you get your Kenwood TKM-707 to work, it will only be capable of 50 watts continuous RMS.

There is an application note (linked to from the SailMail Primer) regarding the Kenwood TKM-707 that was written by a cruiser who has managed to make his Kenwood work, and who is happy with it.

Kenwood Ham radios are fine radios and work well for digital modes on the ham networks.



Get the accessory "Telex kit" that is sold to modify Furuno radios for digital applications, and read the special instructions that describe how to set the radio up for 10ms T/R timing.   If these modifications are made, the Furuno has been used successfully on digital modes, although it is only capable of 50 watts continuous RMS.

Furuno radios require an unusually high audio drive level.   If you have the original SCS PTC-II (no suffix), you will need to have your radio dealer modify the Pactor-modem  to allow the HF modem to provide sufficient drive to the Furuno radio.  Information on this modification is available from SCS's US distributor, Farallon Electronics.  The SCS PTC-II PRO and SCS PTC-IIe, and IIex modems do not need the audio drive level modification because they are capable of higher audio output as delivered.



The Sea 235 comes with a remote control interface that allows AirMail to control the radio via an SCS PTC-II or via an additional COM port on the computer.  Unfortunately, for a radio apparently designed for digital service, the Sea is incapable of running full power continuously.   In our tests, the radio reduced its output power due to over-heating after only 9 minutes of use with an SCS PTC-II running 70 watts RMS (140 watts peak).  Net, the Sea 235 appears to be a good radio, but you will have to run at about 50 watts RMS output. 

There is a fan kit for the SEA 235, part number CF235 at a list of $50.  It is a very good idea to get the fan kit for SailMail use, but even when using the fan kit, SEA recommends running at reduced power for email.

Unfortunately, the SEA 222 is not suitable for use with Pactor-II and the SailMail system. It lacks the connectors to interface to the modem and its switching times are most likely too slow.  If you have a SEA antenna tuner, you could continue to use it and upgrade to the SEA 235 radio.