With all the various electronics equipment becoming such a part of radio controlled flight these days, it should come as no surprise when one or more of these electronic goodies doesn't play well with the others. Put another way, this plethora of electronics can cause electromagnetic interference between the components and modules on the aircraft. The UHF telemetry transmitter can interfere with the GPS receiver. It is not uncommon for FPV cameras to generate noise in the UHF spectrum which means the long distance UHF receiver can be desensitized which greatly reduces the range. Other components such as electronic speed controllers can interfere with the flight controller. Some video transmitters have been found to splatter their signal across multiple channels which means another pilot's aircraft could be interfered with when flying at the same field or event. Any one of these could situations can result in one losing control of the aircraft and a resulting crash. As if this wasn't enough, some of the aircraft use Wi-Fi and Bluetooth for providing updates to the craft. This all adds to the possibility of one thing causing a problem for another.
How do we fix this kind of problem? One option is to use a spectrum analyzer. A spectrum analyzer is an electronic device that helps the user check for proper operation and troubleshoot the various RF devices on the aircraft and the flight-control ground station. The bad news is that commercial high-end spectrum analyzers are traditionally expensive and bulky, in the order of several thousands of dollars, and you usually need experience to master them. The good news is that a combination of firmware and modern hardware has produced spectrum analyzers that are much cheaper, handheld in size, and very affordable (some as low as $99).
I recently purchased such a handheld spectrum analyzer. Since I was looking to be able to check the RF signals used for RC aircraft, I decided on the RF Explorer 6G Combo, manufactured by seeed. It is one of more than a half dozen models made by seeed. With it, I can check the old style 72 Mhz RC transmitters and the newer 2.4 Ghz transmitters too. I can also check the 5.8 Ghz video transmitters that stream live video from the aircraft back to the pilot. From the company's sales brochure, "RF Explorer offers 90% of what a high cost unit will do for RF digital band communication at 5% of the cost." I purchased the 6G Combo through one of seeed's U.S. partners, Nuts About Nets.
This 6G base model covers the 5.8 Ghz RC frequency range. It will display any signal found between 4.85 Ghz and 6.1GHz. With the help of an internal expansion module, the "combo" part extends the range by covering 15MHz to 2.7GHz. This allows me to look at signals from the 72 Mhz RC transmitters, as I previously said, along with the 433 Mhz long range RC transmitters, 915 Mhz telemetry radios, 1.2 Ghz video downlink radios, and 2.4 Ghz RC transmitters. The 6G combo pretty much covers everything in the RF spectrum that is used for radio controlled flying.
The unit will run for approximately 16 hours using the internal LiPo battery which can be recharged via the USB port. A good quality USB signal/charging cable is supplied with the spectrum analyzer. The spectrum analyzer can be used while it is being charged. The user can replace the battery should it be necessary. No need to send it back to the factory.
Handheld operation of the spectrum analyzer is accomplished through a well conceived menu system which is implemented by just 7 keys on the front panel. Several of the keys also provide for shortcut operations depending what the current mode happens to be. This bypasses the need to go access the menu system for certain functions.
The 6G Combo model comes with 3 antennas. Left to right, the Nagoya NA-733 telescoping antenna, the 2.4 Ghz antenna, and the 5.8 Ghz antenna. All models use standard SMA connectors for antenna and cable connections. Many of the current RC aircraft antennas can also serve double duty for use by the spectrum analyzer. This saves a few dollars which is great!
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