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.

Signal Com biner 160m Rx

Duplexer

Solar Power Supply

438 M Hz Tx

433 M Hz Rx

Contro ller

Telem etry

REMOTE STATION BLOCK DIAGRAM

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

N E E D S 330m X 330mO R A B O U T 10 H a

A R R A Y O F B E V E R A G E S

BroadS ide EndFireAR R AY (ref W 8JI -

w w w .w 8ji.com )

100 m

21 m

BROADSIDE ENDFIRE ARRAY

100X21m BSEF ARRAY

R E Q U IR E S A B O U T1 H a

E /W

N W /S E

N /S

N E /S W

92X38m BSEF ARRAY

ELEMENT CHOICE

• SHORT LOADED VERTICAL

• SHORT VERTICAL WITH Hi Z BUFFER.

• SMALL LOOP

C 12 7 0 p

C 22 7 0 p

C 35 6 p

C 44 7 p

C 51 0 0 n

C 61 0 0 n

C 71 0 0 n

R 11 0 0 R

R 21 0 k

R 35 0 0 R

R 4

Q 1J3 1 0

Q 2J3 1 0

L 19 0 u

L 22 2 0 u

L 32 2 0 u

T 1

An tE lem en t

O u tp u t7 5 oh m

FET BUFFER

N /S

N E /S W

E /W

S E /N W

A N T 1

A N T 2

A N T 3

A N T 4

A N T 5

A N T 6

A N T 7

A N T 8

150

150

+13.6 V

ARRAYO UTPUT

150

820 820

15

100n

100n

100n

100n

220u

220u

T1

T2

T3

T4

T5

T6

C O A X PH A S ED E LA Y

R E V E R SE

R L1

R L2

R L3

R L4

R L5

SIGNAL COMBINER

BandpassF ilter

D irect D ig ita lSynth

5.38-5.48 M H z

IF X ta lF ilter

3.579 M H z

AG C

IFAm p

AudioAm p

Xtal O sc

ProductD etector

14.4 M H zTC XO

From Antenna

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 Panel45 Ah

Lead Acid BatteryConstant Voltage

Contro ller

Load

LOCAL STATION BLOCK DIAGRAM

Duplexer

433 M Hz Tx

438 M Hz Rx

Contro ller

Headphone Am p

Telem try Rx

TUNER BLOCK DIAGRAM

4x4 Keypad 16F876 Processor LCD D isplay

Shaft Encoder

4800 Bd Seria l 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

Sw itchedCapacitor

F ilters

1850 Hz

2150 Hz

+

- 16F876PIC

300 BAUD 4800 BAUD

PROBLEMS

• UNEQUAL ELEMENT PICKUP

- PREAMP GAIN VARIATIONS

PROBLEMS

• UNEQUAL ELEMENT PICKUP

- PREAMP GAIN VARIATIONS

- PICKUP FROM COAX BRAID

PROBLEMS

• FADING ON UHF LINK

- AIRCRAFT FLUTTER CAUSES DEEP SIGNAL FADES ON BOTH UP AND DOWN LINKS.

- SLOW FADING DUE TO GENERAL TROPOSPHERIC PROPAGATION VARIATIONS

•

• NOISE FROM COMMON Tx/Rx ANTENNA

- HOSE CLAMPS SERIOUS OFFENDERS

- METAL MOUNTING PLATE

- PVC TAPE UNDER U BOLTS

- COAX BRAID

TESTING

E

NE

N

NW

W

SW

S

SE

HO M E

REM O TE