Archive for the 'Weak Signal Modes' Category

Picaxe GPS NMEA-0183 Decoder

Published on February 25, 2012 in Electronics, Projects and wspr. 0 Comments Tags: , , , , , , , .

There has been some interest in the Picaxe GPS NMEA-0183 Decoder which I use to time the keying of my wpsr beacon.
The Picaxe chip decodes the time data in the $GPGGA sentence from the GPS unit and then print the UTC time on the lcd display. In addition it set a output at the start of every even minute for keying the wspr beacon. That’s all it do with the current 18X chip.
I am planning an upgrade to the 18M2 chip which is a lot more powerful and has got more functions then the current 18X chip.
With the 18M2 I am planning to display some of the other GPS information, like position, signal strength, number of satellites, etc.  It’s not that the 18X chip can’t do this extra information bit. But these task will put a lot more strain on processing and communication so I fear the accuracy of the keying will suffer.

Picaxe GPS NMEA-0183 Decoder

 >> Download full size scheme <<

            ; *****************************************************************
            ; ************************* Picaxe Project ************************
            ; *****************************************************************
            ;     Filename:         GPSDO Display unit v0.4.bas        
            ;     Date:             25.02.2012
            ;     File Version:     0
            ;     Written by:       LA6TPA Geir Aarnes
            ;     Function:         Decode NMEA data from GPS unit
            ;     Last Revision:    4
            ;     Target PICAXE:    18X
            ; *****************************************************************
            ;
            ;     Revision history
            ;
            ;     Intitial code                 GPSDO Display unit v0.1.bas
            ;     First working version         GPSDO Display unit v0.2.bas
            ;     WSPR trigger added            GPSDO Display unit v0.3.bas
            ;     Code cleanup                  GPSDO Display unit v0.4.bas
            ; *****************************************************************          
                       
            #Picaxe 18X
            SETFREQ m8
           


            symbol GPS_RxD    =     0                                   ;NMEA data from GPS module
            symbol GPS_1PPS   =     pin7                                ;1PPS signal from GPS
            symbol GPS_TxD    =     B.0                                 ;NMEA data to GPS module
            symbol WSPRtrig   =     B.1                                 ;Triger output for WSPR tx start
            symbol tByte00    =     b0                                  ;Byte for temorary data
            symbol LcdByte1   =     b1                                  ;Byte used by LCD routine
            symbol LcdByte2   =     b2                                  ;Byte used by LCD routine
            symbol tByte03    =     b3                                  ;Byte used by LCD routine
            symbol tByte04    =     b4                                  ;Byte for temorary data      
     
            gosub init                                                  ;initialise LCD
           
            pause 10000                                                 ;wait for GPS to boot
            serout GPS_TxD,T4800_8,(13)
            serout GPS_TxD,T4800_8,("$PRWIILOG,???,V,,,",13,10)         ;turn off all GPS output
            serout GPS_TxD,T4800_8,("$PRWIILOG,GGA,A,T,1,0",13,10)      ;activate GGA sentence
           
            let LcdByte1 = 1                                            ;set b1 to ‘clear display’ instruction
            gosub wrins                                                 ;send instruction to LCD

main:       serin GPS_RxD,T4800_8,("$GPGGA,"),B8,B9,B10,B11,B12,B13     ;wait for $GPGGA then receive 6 bytes into B8..B13
           
           
            ;debug
           
           
            IF b13 <> "0" THEN GOTO LBL01                               ;Check lower part of seconds, skip if not == 9
            IF b12 <> "0" THEN GOTO LBL01                               ;Check upper part of seconds, skip if not == 5
            tByte00 = B11 - 48                                          ;Read lower part of minute and convert ASCII to binary
            tByte00 = tByte00 & %00000001                               ;Mask bit 0 which indicates an ODD minute
            IF tByte00 <> 0 THEN GOTO LBL01
           
            high WSPRtrig
            pause 500
            low WSPRtrig
           
           
           
           
LBL01:      LcdByte1 = 1
            gosub wrins
            LcdByte1 = "U"
            gosub wrchr
            LcdByte1 = "T"
            gosub wrchr
            LcdByte1 = "C"
            gosub wrchr
            LcdByte1 = " "
            gosub wrchr
            LcdByte1 = b8
            gosub wrchr
            LcdByte1 = b9
            gosub wrchr
            LcdByte1 = ":"
            gosub wrchr
            LcdByte1 = b10
            gosub wrchr
            LcdByte1 = b11
            gosub wrchr
            LcdByte1 = ":"
            gosub wrchr
            LcdByte1 = b12
            gosub wrchr
            LcdByte1 = b13
            gosub wrchr
           
           
            goto main        
           


           
init:       let pins = 0                  ;Clear all output lines
            let b4 = 0                    ;Reset variable b4
            pause 200                     ;Wait 200 ms for LCD to reset.
            let pins = 48                 ;Set to 8-bit operation.
            pulsout 3,1                   ;Send data by pulsing ‘enable’
            pause 10                      ;Wait 10 ms
            pulsout 3,1                   ;Send data again
            pulsout 3,1                   ;Send data again
            let pins = 32                 ;Set to 4-bit operation.
            pulsout 3,1                   ;Send data.
            pulsout 3,1                   ;Send data again.
            let pins = 128                ;Set to two line operation
            pulsout 3,1                   ;Send data.
            let b1 = 12                   ;Screen on, cursor off instruction
            gosub wrins                   ;Write instruction to LCD
            return

wrchr:      let pins = b1 & 240           ;Mask the high nibble of b1 into b2.
            high 2                        ;Make sure RS is high
            pulsout 3,1                   ;Pulse the enable pin to send data.
            let b2 = b1 * 16              ;Put low nibble of b1 into b2.
            let pins = b2 & 240           ;Mask the high nibble of b2
            high 2                        ;Make sure RS is high
            pulsout 3,1                   ;Pulse enable pin to send data.
            return

wrins:      let pins = b1 & 240           ;Mask the high nibble of b1 into b2.
            pulsout 3,1                   ;Pulse the enable pin to send data.
            let b2 = b1 * 16              ;Put low nibble of b1 into b2.
            let pins = b2 & 240           ;Mask the high nibble of b2
            pulsout 3,1                   ;Pulse enable pin to send data.
            high 2                        ;Back to character mode
            return

>> Download source code file <<

Picaxe wspr beacon up and running again.

Published on February 15, 2012 in Electronics and wspr. 0 Comments Tags: , , , , .

I have put my wspr beacon on the air for a test after the latest modifications. And so far it look promising.

Here is a picture of the mess :-)

Picaxe wspr beacon. Bottom: Picaxe and DDS-60 :Top from right: 10MHz LPF, tripler and amplifier for clocking the dds-60 @ 30MHz

 

 

10MHz – 9 Section Lowpass Filter

Published on February 10, 2012 in Electronics, Projects and wspr. 0 Comments Tags: , , , , , , .

Here is a small update regarding my band hopping picaxe controlled wspr beacon.
I took the beacon of air the other day to do some revisions to it’s circuitry. And in this context figured out that I was in need for a filter to clean up the square wave shaped signal from the 10MHz reference oscillator, the GPSDO MKII. I did a little googling and found an interesting circuitry drawn by Jerry Mulchin – N7EME. The reason for needing this filter is that I have a passive frequency trippler for clocking the DDS-60 @ 30MHz, and this tripler need a sine wave to work right.

There is still some work to be done before I can put the beacon back on air. But as they say in broadcasting; Stay tuned, will be right back after….

PCB measures 60x20 mm and parts are SMT

Schematics

Measuring reflection (S11) with the minivna. Return loss is more than 26dB @ 10MHz.

Measuring transmission (S21) with the minivna. 1dB insertion loss @ 10MHz and cout-off at 12MHz.

More Opera

Published on January 17, 2012 in Opera. 0 Comments Tags: , .

Been testing Opera for few days now. And I must admit there has been some head-scratching. :-)
First of my microham digi keyer II which is hooked up with my TS-2000x did not produce much results. This duo works great in other modes but not with opera. I’m not sure what causes this but I suspect that my USB hub may be the problem. Anyway, I changed to my second digi keyer (mk1) and the FT-1000mp and the results began to show.

I have not yet enough experience to say anything about it’s ON-Air performance.
The software itself is very CPU hungry but this may me rectified (I hope) in later revisions. In fact new revisions are commeng all the time, sometimes several in a day.

Testing Opera

Published on January 14, 2012 in Opera and Weak Signal Modes. 0 Comments Tags: , .

Last night I tested for the first time the new weak signal beacon mode opera. It only ran for a few hours and I think there must be something wrong for I have had several clearly audible signals here but only one decode.
I will let it run through out the night to see if I can catch something.

Opera screen capture