Online Amateur Radio Community Wiki

User Tools

Site Tools

Trace:
packet:transceivers_144pk

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
packet:transceivers_144pk [2025/07/08 09:30] – g7tajpacket:transceivers_144pk [2025/07/08 12:33] (current) – g7taj
Line 21: Line 21:
 {{:packet:switch_hl.jpg?400|}} {{:packet:switch_hl.jpg?400|}}
  
-Once in my hands ( a 400mile round trip back to my old QTH location, having just moved, which is coincidentally where Nick lives and I just happened to be there to visit family) and with all this information, it quickly lead me to work out that the binary counter driving the EPROM address lines and driving the synthesiser to setup the frequencies. What I didn’t know, is how.+Once in my hands ( a 400mile round trip back to my old QTH location, having just moved, which is coincidentally where Nick lives and I just happened to be there to visit family) and with all this information, it quickly lead me to work out that it was the binary counter driving the EPROM address lines and driving the synthesiser to setup the frequencies. What I didn’t know, is how.
  
 I removed the EPROM and dumped it and noticed some very repeated patterns. I removed the EPROM and dumped it and noticed some very repeated patterns.
Line 35: Line 35:
   * The EPROM was clocked via the RC NOR gate oscillator   * The EPROM was clocked via the RC NOR gate oscillator
   * This oscillator could be stopped by D7 of the EPROM going HIGH   * This oscillator could be stopped by D7 of the EPROM going HIGH
 +  * D4 - D6 were used to send the DATA, CLOCK and ENABLE signals to the NJ88c22
   * The reset circuit was triggered each time the channel switch position was changed, which would start the counter again from zero   * The reset circuit was triggered each time the channel switch position was changed, which would start the counter again from zero
  
Line 76: Line 77:
  
 I modified my C program to account for the PTT line changes and found that on TX the frequencies were correct but at RX they were low. But they were all low by 21.4Mhz, which sounded very much like a standard IF frequency! So that answered that, phew! I modified my C program to account for the PTT line changes and found that on TX the frequencies were correct but at RX they were low. But they were all low by 21.4Mhz, which sounded very much like a standard IF frequency! So that answered that, phew!
 +
 At this point, I was confident that I could change the data for a frequency I wanted. At this point, I was confident that I could change the data for a frequency I wanted.
 +
 A quick modification to the C program made a new EPROM image and I was ready to test. A quick modification to the C program made a new EPROM image and I was ready to test.
 On the bench, I plugged it into the dummy load and tested the channels according to what I had calculated from the EPROM image. They were all wrong :-? On the bench, I plugged it into the dummy load and tested the channels according to what I had calculated from the EPROM image. They were all wrong :-?
packet/transceivers_144pk.1751967028.txt.gz · Last modified: by g7taj