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The N1JEZ Simple GPS Stabilized 10 MHz Oscillator

Dave Robinson

WW2R

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The problem

• WA5TKU has told us how to ensure antenna alignment when roving, so what other variables can prevent a QSO?

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The problem

• WA5TKU has told us how to ensure antenna alignment when roving, so what other variables can prevent a QSO?

• QSOS can be lost due to not being able to know what frequency you are on!

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Solutions

• Use a rubidium standard• HP Z3801 10MHz GPS locked reference

is a solution but is costly and bulky• G3RUH and G4JNT have produced

solutions using 10kHz outputs from GPS boards (not 1PPS)

• I used cheaper, smaller N1JEZ solution

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Power InPower In10 MHz10 MHzBNC outBNC out

10 MHz10 MHzSMA outSMA out

DBDB--99RSRS--232232

InterfaceInterface1 PPS1 PPSLEDLED

GPS Ant InGPS Ant In

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SMDSMDVCVC--TCXOTCXO

InterfaceInterfaceBoardBoard

JupiterJupiterGPSGPS

EngineEngine

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Supports 4 Different VersionsSupports 4 Different Versions5 volt GPS 5 volt GPS –– 5 volt DIL5 volt DIL--14 VCXO14 VCXO

5 volt GPS 5 volt GPS –– 3 volt SMD VCXO3 volt SMD VCXO

3.3 volt GPS 3.3 volt GPS –– 5 volt DIL5 volt DIL--14 VCXO14 VCXO

3.3 volt GPS 3.3 volt GPS –– 3 volt SMD VCXO3 volt SMD VCXO

The Interface BoardThe Interface Board

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VC13H50BYVC13H50BY± 50 PPM± 50 PPM

± 200 PPM pull± 200 PPM pull

5 v DIL5 v DIL--1414

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Pletronics VC13H50BYSupply = 5.00 vdcN1JEZ - 2/15/2005

-2378-2220

-1693

-1100

-450

0170

845

1424

2063

2666

-3000

-2000

-1000

0

1000

2000

3000

CVR (in volts)

Cha

nge

Freq

uenc

y (

Hz)

10.000000 MHz2.35 vdc

0.5 - 4.5 v CVR2266 + 2220 = 4886 / 4 = 1222 Hz/v

0 0.5 1.0 3.5 4.0 4.5 5.01.5 2.0 2.5 3.0

Pletronics Voltage/Frequency Characteristic

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± 0.5 PPM± 0.5 PPM

± 3 PPM pull± 3 PPM pull

3 v SMD3 v SMD

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FOX 801BE-1000N1JEZ - 2/16/2005

-117

-78

-40

-5 0

29

63

-120

-100

-80

-60

-40

-20

0

20

40

60

80

CVR (in volts)

Cha

nge

Freq

uenc

y (H

z) 10.000000 MHz1.57 v

0.5 - 2.5 v CVR78 + 63 = 141 / 2 = 70.5 Hz/v

0 0.5 1.0 1.5 2.0 2.5 3.0

Fox Voltage/Frequency Characteristic

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ECS Osc Freq v Tuning Volts

VC-TXO 39SM

-100

-50

0

50

100

150

0 0.5 1 1.5 2 2.5 3

in (volts)

Chan

ge F

requ

ency

(h

z)

115 Hz per volt

10.000000 Mhz

BEWARE!

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WWHATHAT CCANAN YYOUOU DDOO WWITHITH IIT T ??

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Reference as a MarkerReference as a Marker10 MHz to 2500 MHz10 MHz to 2500 MHz

Reference for a Qualcomm SourceReference for a Qualcomm Source1152 MHz (2304 1152 MHz (2304 –– 24192 MHz)24192 MHz)2616 MHz (47088 MHz)2616 MHz (47088 MHz)

Reference for a Brick OscillatorReference for a Brick OscillatorSuch as CTISuch as CTI

Reference for CT1DMK lock boxReference for CT1DMK lock box

DSPDSP--10 Reference10 Reference

“Rectangular”Synthesizer Simple GPS

Stabilized10 MHz Osc

“Texas”Synthesizer

Programmed to2304 MHzDivide by 21152 MHz

Programmed to2616 MHz

WA5VJBLOG PERIODIC

ANTENNA

+18 dBm1152 MHz

+18 dBm2616 MHz

26-40 GHzWavguideDiode Detector

10 MHz 10 MHz

GPS Antenna

SMA diode DetectorRun Backwards

(RF in Meter Side)

2304MHz3456 MHz5760 MHz

10368 MHz24192 MHz

47088 MHz

The Use of a The Use of a SimpleSimple GPS Stabilized 10 MHz OscillatorGPS Stabilized 10 MHz Oscillator

Microwave Marker System

GPS StabilizedOscillator

W1FKF

2616 MHz 1152 MHz

47 GHz 10 GHz/24 GHz

10 MHz

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N1JEZ Startup from Cold (Rb Reference)

N1JEZ + Qualcom Synth+ Multiplier

5759.984

5759.986

5759.988

5759.99

5759.992

5759.994

5759.996

5759.998

5760

5760.002

0 20 40 60 80 100 120 140 160 180

Time (S)

Freq

uenc

y

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Frequency distribution ( sampled every 30S)

0

50

100

150

200

250

5759

.999

985

5759

.999

988

5759

.999

991

5759

.999

994

5759

.999

997

5760

5760

.000

003

5760

.000

006

5760

.000

009

5760

.000

012

5760

.000

015

Mor

e

0%10%20%30%40%50%60%70%80%90%100%

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Is the lock good?

• Can see status using Terminal program or TAC32 to inspect NMEA strings

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Initial GPS Power UpInitial GPS Power Up

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Less bulky alternative?

• Using PC is a bulky option• Can use a PIC to monitor NMEA string

and inhibit the output if not a good GPS lock

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GPGGA sentence (0,1,2)GPGGA sentence (0,1,2)GPGSA sentence GPGSA sentence –– second character = 3second character = 3

Use HDOP and PDOP values.Use HDOP and PDOP values. Beware Jupiter gives Beware Jupiter gives values with no satellitesvalues with no satellites

Measure VC line. Measure VC line. Beware loading effects! Beware loading effects!

Determining Lock StatusDetermining Lock Status

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NMEA Time problems• Time output by NMEA strings can be 1-3

seconds out. Acknowledged by manufacturer• Reason: Putting time information in the NMEA

strings is THE lowest priority activity of the Jupiter GPS board!

• Binary outputs from the GPS don’t have this problem, but cannot be used by time programs requiring NMEA strings (eg NMEATIME)

• One solution is to use the PIC doing valid lock detect function from the binary data and have it synthesise an NMEA string (like my Z3801 clock does). Work in progress

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References

G3RUH design• http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htmG4JNT design• http://www.scrbg.org/g4jnt/SimpleGPSDO.htmN1JEZ design• http://mysite.verizon.net/n1jez/osc/page5.htmlTAC32• http://www.cnssys.com/Tac32/