Updated 30th of August 2007. Release of FlashForth V2.1 and move to SourceForge.
Flashforth is now distributed via sourceforge.
--> Go to SourceForge
The NMEA time display is now parsed correctly.
Source : navtex1_5.txt
Some bugfixes have been made.
Since I had some 16F870’s lying around, I had to make version for
In the process some new features were introduced.
Building note: The version of the HW with the 6 kHz intermediate frequency has better selectivity and sensitivity.
schema1_3.gif board1_3.gif place1_3.gif navtex1_3.txt navtex1_3.hex
Some low quality pictures.
For Toshiba controller T6963 based LCD displays,
with 240x64 pixels,
which gives 8 rows of text with 40 characters
Example of a suitable display module: http://www.hantronix.com/down/64gs242p.pdf
Reception frequency 518 KHz FSK
Intermediate frequency about 6 KHz or 18 KHz depending on the exact crystal frequency.
IF Audio output, which can be used to trim the RF stages and IF stages,
by using a PC audio spectrum analyzer.
Local Oscillator signal generated by the PIC Pulse Width Modulator.
FSK demodulator using the PIC capture function.
Note that the CRYSTAL constant in the program may need to be changed
depending on the real crystal frequency. I use a serial resonant mode 18432 KHz crystal.
It resonates on 18439 KHz.
NMEA display decodes GLL, VTG and APB messages.
NMEA serial speed is 4800 baud
This circuit is currently in use aboard my boat,
it has worked now continously for 3 summers.
Current consumption is 35-40 mA
Version 1.1 has the opamp and the comparator switched with eachother.
The 1.1 version was found to have bad sensitivity, and bad dynamic range.
It was due R13 having the value 0.
This caused wideband noise from the comparator output to be coupled to the mixer input.
With R13 = 10K, the sensitivity is so good that the RF amplifier can be removed.
To ensure good performance, the top side of the PCB should be used as a ground plane.
A new improved version 1.2, with the RF amplifier removed, is introduced below.
This will reduce possible overloading problems.
Also the opamp and comparator are now correctly used.
The inductors are standard chokes, available ready made from for example ELFA.
No need to wind anything :-)
The pin out of the LCD control lines and the keyboard lines have changed,
therefore a new software version is provided.
schema1_2.gif board1_2.gif place1_2.gif navtex1_2.txt
Very nice small radio for listening to
5,9 - 18 MHz.
455 kHz IF.
Uses dual gang capacitor and a 1:36 geared reduction drive.
This circuit has been built and debugged 27.11.2001
TCA440 SW radio
Fits the above SW receiver.
455 KHz IF offset.
This circuit has been built and debugged 27.11.2001.
The first intermediate frequency is 45 MHz.
This is a project I actually have built, and it is in use all the time.
This is another project which actually is ready and working.
I have made some modifications to my Sat 700.
These have mainly to do with improved sensitivity,
and strong signal tolerance of the whip antenna amplifier,
and a proper AGC which works with SSB.
Comments & Questions to: mikael.nordman-at-pp1.inet.fi