Email Splatter

A few of the many boats using radio email are creating a problem, which affects not only other boaters but also all users of the HF radio spectrum: governments, military forces, and many other groups in the countries that we visit. We can easily fix this problem, and we should fix it before someone else does it for us.

The problem is radio splatter. On an SSB radio it sounds a lot like a Pactor email signal, but it can be heard on all frequencies up and down the HF spectrum. Most of us have heard this in crowded harbors. It is so common that HF nets ask boaters to refrain from using email during net operations. This helps the nets but does nothing for other HF users.

Splatter is NOT inherent in radio email. Most boats using radio email do not create splatter. Some email shore stations operate multiple radios simultaneously in the same room with no splatter. The cause of splatter is over-driving the radio by setting the modem drive level too high or using the radio’s speech processor during email transmissions. Splatter can occur with other modulation types as well, but email splatter is particularly annoying and easy to recognize.

If you use radio email, you can do two simple things to prevent splatter:
–         Set the modem drive level so that the radio produces no more than half its rated power during email transmissions
–         Always turn off your speech processor before using email.

Half of the rated power is ample for email, which requires much less power than voice.  For instance, setting the drive for 25 watts out during email, which is one-sixth of the normal (150 watts) rated power for marine SSBs, will rarely cause a failure to connect to a shore station at any time of the day or night. The Airmail software provides a simple on-screen setting for drive level. If you need help setting the drive level, ask another email user or a radio ham. This setting does not affect the radio’s power output using voice.

If you use radio email, you have an obligation to the other users who share the HF radio spectrum to prevent splatter. You also have a legal obligation. Your ship’s radio station license only authorizes you to transmit on the marine channels. Splatter occurs outside the marine bands, and it can easily be traced from the call signs embedded in email transmissions. Fixing the splatter takes much less time than responding to a citation.

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