Communications Design Alternatives SystemOperation Capability ControlCost $Complexity Radio Control Line of Sight < 3 m depth for Commercial RC Submarines Attenuation in Water = Signal Loss 8-Channel Tx & Rx + 4 Servos = $1100 Receiver & Antenna WireCable LengthNot RemoteSame as RCEntanglement SonarLong RangeDopplerSonar = $1,000+ Electronics = ? Too Complex & Expensive for Scope LightCable LengthNot RemoteFiber Optic CableToo Complex & Expensive for Scope Entanglement BadAcceptableGood

Communication Analysis

Communication Design Futaba 8UAPS and matching FP-R148DP Receiver (FM/PCM 1024) 8 Channels Available, RAV requires W output Receiver Power Gain = 0 dB MHz, ¼ wavelength whip antenna = 3.23 ft. long Signal Loss at MHz Refraction Loss = dB Attenuation of Chlorinated Water = ~300 dB/m Conductivity varies with Chlorine Concentration (Avg Value = 200 µMhos/cm) Antenna Design Metallic Interference from Aluminum Hull & Tail Use Shielded Coax Cable from Rx to RAV External ¼ wavelength vertical isotropic antenna Antenna Mast = 2.0 ft. X 1/4 in. Static Seal Antenna Rise above Surface to avoid Losses Run Propulsion Subsystems Test 6 in. below surface Run to 75% Underwater Fail-Safe Depth for Full-Systems Integrated Test (if Tested) Antenna Drag N at 7.5 knots 6.40 N at 5.0 knots 1.50 N partially submerged at 5.0 knots Fiberglass/Hollow Aluminum Rod Stress not an Issue

Communications – Testing Configurations [COMM 1] Nominal Config [COMM 2] Propulsion Test Config [COMM 3] Buoyancy Test Config

Communication Test Plan Range Test Move away from RAV until Signal Loss Distance Step Function Characterize Tx & Rx Stretch Goal - Repeat with RAV Underwater Quantify Rx Power Gain Underwater Quantify Antenna Design Parameters

Transmitter 30-60% efficient Modulates & amplifies carrier signal Feed Cable Path connecting Tx to antenna = loss Loss fxn of cable type, length, frequency More Higher Frequencies Propagation Path Attenuation Receiver Demodulates Isotropic Antenna Gain = 1 = 0 dB dBi = 10 log (antenna power gain/isotropic power gain) G = 4*pi*Ae/(lamda^2) Ae = eta*Aphys Directional Antenna Pointing Loss Propagation Path Loss (lamda/4*pi*R)^2

Coaxial Cable Attenuation & Power Handling Calculator Product Frequency (MHz) Attenuation (db/100 feet) Attenuation (db/100 mtrs) Average Power (kW) Run Length (feet) Total Run Attenuation(dB) Efficiency (%) Copyright ©2002 Times Microwave Systems All rights reserved.