A REMOTE STEERABLE RECEIVING ARRAY FOR 1.8 MHz

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A REMOTE STEERABLE RECEIVING ARRAY FOR 1.8 MHz

• GREG SMITH ZL3IX

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REASON FOR THE PROJECT

• TO STUDY SKEWING ON LONG PATHS.
• TO AID THE RECEPTION OF WEAK DX SIGNALS.

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REMOTE STATION BLOCK DIAGRAM
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ANTENNA DESIGN REQUIREMENTS.

• BEAM WIDTH NOT EXCEEDING 60 DEGREES.
• MUST BE STEERABLE TO COVER ALL COMPASS POINTS
• MUST FIT INTO A REASONABLE SIZE, eg 1 HECTARE

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THE BEVERAGE ANTENNA

• Long low wire about 2-3m off ground
• Needs to be about 2 wavelengths long.

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BROADSIDE ENDFIRE ARRAY
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100X21m BSEF ARRAY
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92X38m BSEF ARRAY
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ELEMENT CHOICE

• SHORT LOADED VERTICAL
• SHORT VERTICAL WITH Hi Z BUFFER.
• SMALL LOOP

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FET BUFFER
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CONTROLLER

• 16F876 PIC
• WIZ C
• DECODES SERIAL CONTROL DATA
• PROGRAMS DDS IN Rx
• SELECTS CORRECT ELEMENTS FOR REQUIRED DIRECTION

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UHF Rx/Tx

• Rx - MODIFIED DEVELOPMENT MODEL TB8100
• 500 mW WHEN ASLEEP
• Tx - TM8100 PA
• CTCSS TONE TO SWITCH ON
• LACK OF CARRIER FOR 4 s, OR A DIFFERENT CTCSS
  TONE, SWITCHES SYSTEM OFF.
• DATA LINK 4800 Bd RAW RS232

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POWER SYSTEM
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LOCAL STATION BLOCK DIAGRAM
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TUNER BLOCK DIAGRAM
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THE UHF LINK
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TELEMETRY

• PARAMETERS - 160m RSSI, UHF RSSI, Batt Volts,
  Solar Volts.
• SUPERIMPOSED ON AUDIO
• 300 Bd FSK, Tones at 1850 and 2150 Hz
• Telemetry has HP filter at Tx
• Audio has LP filter at Rx

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THE TELEMETRY RECEIVER
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PROBLEMS

• UNEQUAL ELEMENT PICKUP
• - PREAMP GAIN VARIATIONS

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PROBLEMS

• UNEQUAL ELEMENT PICKUP
• - PREAMP GAIN VARIATIONS
• - PICKUP FROM COAX BRAID

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PROBLEMS

• NOISE FROM COMMON Tx/Rx ANTENNA
• - HOSE CLAMPS SERIOUS OFFENDERS
• - METAL MOUNTING PLATE
• - PVC TAPE UNDER U BOLTS
• - COAX BRAID

• FADING ON UHF LINK
• - AIRCRAFT FLUTTER CAUSES DEEP SIGNAL FADES
  ON BOTH UP AND DOWN LINKS.
• - SLOW FADING DUE TO GENERAL TROPOSPHERIC
  PROPAGATION VARIATIONS

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TESTING
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