A $20 SDR is a nice piece of kit to add to your base station laptop. It’s a receiver and spectrum analyzer. It will allow you to see with your own two eyes on your computer screen what is going on in your radio frequency environment. Use it for finding interference before you fly. You can also use it as an ADS-B receiver! (real time aircraft “radar”).

RTL SDR Hardware – An “RTL” is low cost to get into because they are re-purposed USB TV Tuners, retails for $10-$20. Plugs into your laptop with a small USB dongle and antenna. These RTL’s only receive, no transmit. Right now they come in two varieties. Search EBay or Amazon for USB DVB-T, RTL2832U  R820T or RTL2832U E4000. You won’t find these in stores in the US, because they are originally for foreign TV reception. These cheap RTL dongles are perfect for monitoring a RC 433MHz LRS and 900MHz or 1258-1280MHz (1.3GHz) video signals!

They also double as ADS-B receivers! Using this guide, a R820T and a home made 1/2 wave rubber duck (.035 mig welding wire) for 1090MHz, I tracked over 100 miles across mountains!

• R820T chipset. Frequency range is 24 – 1850 MHz, with no gaps. Newest available. $20.
• E4000 chipset. Frequency range is 52 – 1700 MHz, with a gap from 1100 MHz to 1250 MHz. Some might go up to 2200 Mhz. Do not use an E4000 due to gaps, might not work on your video channel.

Whichever one you decide on buying, it will need an upgraded antenna because the tiny TV antenna that it comes with isn’t very good and will barely pick up a FM radio station. And locate the antenna away from any laptops or other electronics, they all make noise. Look up: Discone antenna – Omni, covers a lot of frequencies, easy to build. Or you can just us a regular VHF/UHF television rabbit ear which is what I use. Additionally you can get an up-converter so that you can monitor higher microwave frequencies like 2.4GHz, but can be expensive and unnecessary for long range FPV.

 SDR Software

• SDR# (SDR Sharp) – For Windows 8, 7 and XP. Easy to use and setup. Quick start guide and nice wiki at: http://rtlsdr.org/softwarewindows
• HDSDR – Linux and Mac. Not easy to setup with an RTL.
• GNU Radio – Linux. Very powerful, has many software filters and processing capabilities.

Other Spectrum Analyzers / SDR Hardware – Costs $150 to $6000, but also may have transmit capability and cover more frequencies. Examples: HackRF, BladeRF, Winradio, FlexRadio, RF Explorer 3g, BK Precision, USRP