Longitudinal　mode　ultrasonic　guided　waves　(UGWs)　in　prestressed　seven-wire　steel　strands　have　an　inherent　notch　frequency　property　covering　a　frequency　range　of　less　than　100　kHz.　If　UGWs　having　such　a　frequency　range　are　used　to　inspect　the　strand,　the　inspection　instrument　may　fail　to　detect　small　defects　due　to　difficulties　in　predicting　the　notch　frequency.　Therefore,　it　is　more　appropriate　to　design　a　miniaturised　instrument　that　can　excite　and　receive　UGWs　covering　a　frequency　range　of　far　more　than　100　kHz　for　on-site　strand　inspection　applications.　In　this　study,　an　FPGA-controlled　instrument　is　developed　to　test　its　UGW　detection　performance.　The　boost　circuit　operates　in　a　frequency　range　of　0.1-1.5　MHz　to　produce　a　parametric　burst　of　square　waves　with　a　low　distortion　content.　The　detected　UGW　signal　is　then　filtered　by　a　low-pass　filter　and　amplified　by　a　two-stage　programmable　gain　pre-amplifier　with　a　maximum　amplification　of　80　dB.　The　long-range　strand　inspection　results　show　that　the　proposed　instrument　provides　a　signal-to-　noise　ratio　for　the　detected　UGW　signal　of　6.06　dB　after　the　UGW　has　propagated　for　56　m　in　the　strand.　The　influence　of　a　notch　defect　on　the　extent　of　mode　conversion　between　the　L(0,1)　and　F(1,1)　modes　and　the　amplitude　of　the　signal　reflected　from　the　notch　are　analysed　based　on　the　short-time　Fourier　transform　(STFT)　results　from　the　detected　UGW　signals.　The　variation　in　the　UGW　signal　spectrum　that　is　induced　by　a　notch　with　a　cross-sectional　area　loss　of　1.13%　can　be　identified,　indicating　the　high　UGW　detection　performance　of　the　developed　instrument.