H A R D W A R E C O N F I G U R A T I O N C H A P T E R 3
Enhanced 1W PEP Driver
The low power model incorporates a 1W PEP driver amplifier. The driver is between the new front end low
pass filters and the band pass filters on the BPF board, which yields increased harmonic suppression. The
driver circuit also allows for amplifier stability when driving capacitive loads and increases the gain to
reduce sound card drive requirements.
28MHz Transverter IF Takeoff
The RFE provides an internal connector for integration of the Down East Microwave 2M transverter IF
(DEMI144-28FRS). Only a single coax cable is required for both RF and TR control. The SDR1K-ENC
enclosure has mounting holes to allow either common or separate transmit/receive connections for
transverters. You can even set up the SDR-1000 to provide a dual 144/28MHz IF to cover all of the VHF
through microwave bands.
Key features of the DEMI144-28FRS are:
144-146MHz coverage
Unity gain receive conversion
4dB NF maximum
+17dBm double balanced mixer
Three chamber helical filter
100mW nominal linear output
Experimental Impulse Generator
An experimental circuit has been incorporated that creates a 4.5ns pulse for equalization of the QSD and
sound card quadrature path. DSP software will be written to calculate the impulse response of the circuit
and automatically correct for phase and amplitude imbalances between the channels. In theory, this will
provide dynamic opposite sideband rejection optimization.
Enclosure
The SDR1K-ENC enclosure is designed to accommodate expansion options including the Down East
Microwave 2M IF transverter and the 100W PEP HF linear amplifier and LDG Z-100 automatic antenna
tuning unit options. Rear panel connections are provided for the PC parallel control port, sound card
interface, 7 external control lines, split or common transverter RF connections, and QRP and QRO RF
connections. An AUX mounting hole is provided for the 10MHz reference clock option connector when
precision frequency control is desired.
4 FlexRadio Systems
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