If you haven’t considered these specs before, you should—and here’s why.
- Option to easily add 2-way telemetry. The reasons for having 2-way redundant telemetry are explained in the above article…a dual-telemetry system can always be cobbled together, but when the GOES transmitter is designed with this capability built-in, things are so much easier.
TCXO frequency controller. There are two types of frequency controllers (the device which keeps the timing of the transmitter accurate so transmissions always occur within the allotted 10-second window, kind of like the quartz crystal in your watch). The most common is an “OCXO” (oven-controlled crystal oscillator). They have several drawbacks, all of which can affect the reliability of your data. A TCXO:
- reduces the overall power consumption by eliminating the high current oven, eliminating the time and need for warm-up (which consumes a lot of power).
- is not vulnerable to breaking due to constant power cycling
- Health status data appended to transmissions. Premonition—the ability to predict the future—is a valuable power. Despite your best efforts, problems outside of your control are bound to occur…wouldn’t it be great to know before they happen so that you could prevent them and in effect change the future? Transmitting the health status of your station (as well as sending it to the logger) is one way to accomplish this. Watching the trend of battery voltage, VSWR, internal temperature, etc.) lets you literally see conditions which will lead to a failure. Before they do, either make a planned visit to the site (or remotely interact with your station to fix it—see #1 above.)
- Data redundancy. To make sure that no data is ever lost, you should have the option to have every data sent twice—once during the hour that it’s collected, and again with next data set sent. This ensures that if one transmission fails to be received, the data will not be lost.
- VSWR measurement available on-site after installation. A common issue with GOES transmission failures is a poor connection and signal path from the RF transmitter’s output to the antenna, both as a result of improper installation and damage to the RF connections over time. A technician should be able to verify the VSWR (signal quality) after installation so corrections can be made before leaving the site. Ongoing measurement and logging of this value is also helpful to see conditions that could lead to a failure—before they occur (see #4, above)
- Meeting all USGS and Environment Canada specifications. This really goes without saying, but not all GOES transmitters do, so it’s an easy way to weed out the one’s you shouldn’t spend any time on.
- Ability to keep accurate time for up to 28 days without a GPS fix. Internal clock accuracy should be sufficient to stay within a channel assignment for long periods without connecting to a GPS satellite.
- Free and easily accessible setup software. Software for setting up your GOES transmitter should be painless to obtain, install and use.
- Ability to request new data right before a transmission. Rather than the transmitter radio staying on continuously, listening for anything the logger sends, it can instead “sleep” between scheduled transmissions, waking up just before a transmission to request all new data from the logger. This saves a lot of power.