Highly portable, low cost SDR instrument for RF propagation studies

Software Defined Radio (SDR) instruments can be used to replace bulky and expensive spectrum analyzers for RF field measurements. Using commercial off the shelf (COTS) equipment a low cost, portable SDR instrument for measuring RF propagation has been created and tested. In the UK, parts of the VHF spectrum have been re-purposed for the use of Internet of Things devices, the instrument developed here is designed to meet the use-case of performing an urban propagation study in VHF and UHF Short Range Devices bands in a fast and low cost manner. Design of the hardware and software is discussed, as well as the calibration of the instrument. Results of a test propagation study are given for the completed instrument. It is shown that the SDR instrument is capable of performing the study to a high degree of agreement with a commercial spectrum analyzer, thus validating the approach. Readings of received power taken by the instrument are shown to agree with readings taken at the same locations with a commercial spectrum analyzer to within an average of 1.4dB at 71MHz and 1.1dB at 869.525MHz. From the measurements taken log distance models were able to be produced with a path loss exponent of 2.44 and log normal shadowing standard deviation of 8.5dB at 71MHZ and a path loss exponent of 4.06 and log normal shadowing standard deviation of 8.8dB at 869.525MHz.