A REMOTE STEERABLE
RECEIVING ARRAY FOR
1.8 MHz
GREG SMITH ZL3IX
REASON FOR THE
PROJECT
• TO STUDY SKEWING ON LONG
PATHS.
• TO AID THE RECEPTION OF WEAK
DX SIGNALS.
REMOTE STATION BLOCK DIAGRAM
Signal Combiner
160m Rx
438 MHz Tx
Duplexer
433 MHz Rx
Controller
Telemetry
Solar Power Supply
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
THE BEVERAGE ANTENNA
• Long low wire about 2-3m off ground
• Needs to be about 2 wavelengths long.
F
ARRAY OF BEVERAGES
NEEDS 330m X 330m
OR ABOUT 10 Ha
BROADSIDE ENDFIRE
ARRAY
BroadSide EndFire
ARRAY (ref W8JI www.w8ji.com)
100 m
21 m
100X21m BSEF ARRAY
REQUIRES ABOUT
1 Ha
E/W
NW/SE
N/S
NE/SW
92X38m BSEF ARRAY
ELEMENT CHOICE
• SHORT LOADED VERTICAL
• SHORT VERTICAL WITH Hi Z
BUFFER.
• SMALL LOOP
FET BUFFER
Q1
J310
Ant
Element
C7
100n
Q2
J310
R1
100R
C4
47p
L1
90u
C6
100n
R2
10k
R3
500R
C1
C2
270p 270p
C3
56p
R4
L2
220u
Output
75 ohm
T1
C5
100n
L3
220u
+13.6 V
REVERSE
COAX PHASE
DELAY
100n
ANT 1
T3
RL1
T1
220u
150
ANT 2
RL5
100n
100n
T4
ANT 3
T2
N/S
220u
RL2
150
ANT 4
100n
ANT 5
15
ANT 6
NE/SW
820
820
RL3
150
ARRAY
OUTPUT
T5
ANT 7
T6
ANT 8
E/W
RL4
SIGNAL COMBINER
SE/NW
From Antenna
Bandpass
Filter
14.4 MHz
TCXO
IF Xtal
Filter
3.579 MHz
Direct Digital
Synth
5.38-5.48 MHz
Product
Detector
IF
Amp
AGC
Xtal Osc
Audio
Amp
CONTROLLER
•
•
•
•
•
16F876 PIC
WIZ C
DECODES SERIAL CONTROL DATA
PROGRAMS DDS IN Rx
SELECTS CORRECT ELEMENTS FOR
REQUIRED DIRECTION
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
POWER SYSTEM
Solar Panel
Constant Voltage
Controller
Load
45 Ah
Lead Acid Battery
LOCAL STATION BLOCK DIAGRAM
Controller
433 MHz Tx
Duplexer
Telemtry Rx
Headphone Amp
438 MHz Rx
TUNER BLOCK DIAGRAM
Shaft Encoder
4x4 Keypad
16F876 Processor
LCD Display
4800 Bd Serial Data
THE UHF LINK
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
THE TELEMETRY RECEIVER
1850 Hz
-
16F876
PIC
+
300 BAUD
2150 Hz
Switched
Capacitor
Filters
4800 BAUD
PROBLEMS
• UNEQUAL ELEMENT PICKUP
-
PREAMP GAIN VARIATIONS
PROBLEMS
• UNEQUAL ELEMENT PICKUP
-
PREAMP GAIN VARIATIONS
PICKUP FROM COAX BRAID
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
TESTING
N
NE
NW
HOME
E
W
REMOTE
SW
SE
S
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RX array