packet:transceivers_144pk
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| packet:transceivers_144pk [2025/07/11 14:49] – g7taj | packet:transceivers_144pk [2025/07/29 06:29] (current) – g7taj | ||
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| ====== Wood & Douglas 144 PK 144Mhz packet transceiver ====== | ====== Wood & Douglas 144 PK 144Mhz packet transceiver ====== | ||
| + | A reverse engineering project by G7TAJ | ||
| A post by Nick G4TAI on the OARC forums about a boot sale find, turned into a few discussions about it as he was wondering how it worked and if it would be possible to change the frequencies. It was on the old 1980’s 144Mhz frequencies. A few discussions later and I agreed, for a few beer coins, to take it and see what I could find out as a little interesting project (I always want to know how things work inside the box, even from a young age). | A post by Nick G4TAI on the OARC forums about a boot sale find, turned into a few discussions about it as he was wondering how it worked and if it would be possible to change the frequencies. It was on the old 1980’s 144Mhz frequencies. A few discussions later and I agreed, for a few beer coins, to take it and see what I could find out as a little interesting project (I always want to know how things work inside the box, even from a young age). | ||
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| 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, testing with the original EPROM, 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 :-? |
| So I double checked the switch connections and EPROM data lines and found that there was a jumper, JP5, that pulls A2 and A3 to ground if bridged, which it was. So I adjusted the address lines in the program and re-ran it and the frequencies matched, wahoo! | So I double checked the switch connections and EPROM data lines and found that there was a jumper, JP5, that pulls A2 and A3 to ground if bridged, which it was. So I adjusted the address lines in the program and re-ran it and the frequencies matched, wahoo! | ||
| - | With the new found addresses, I wrote a new EPROM image. I only had a 27c256 to hand and so I wrote it to both 128k sections. Pulled it out of the programmer and plugged | + | With the new found addresses, I wrote a new EPROM image. I only had a 27c256 to hand and so I wrote it to both 128k sections. Pulled it out of the programmer and pushed it into the socket on the board. I tentatively powered it up, watching for magic smoke, which there wasn’t any, thankfully! |
| With a jumper wire for activating PTT, I had the H/H set to 144.950Mhz and went for it. And it only went and bloody worked! I quickly connected a set of headphones to the audio out and repeated the test from H/H to 144 PK on RX and it was working as well. JOB DONE! | With a jumper wire for activating PTT, I had the H/H set to 144.950Mhz and went for it. And it only went and bloody worked! I quickly connected a set of headphones to the audio out and repeated the test from H/H to 144 PK on RX and it was working as well. JOB DONE! | ||
| Well, not quite. I wanted to test it on packet, after all, that’s what it was designed for! So I unplugged my Motorola GM350 from the NinoTNC and plugged in the 144PK with the lead that came with it (5 pin DIN to standard 9pin TNC connector, as used by Kantronics and the standard that the Nino also uses). | Well, not quite. I wanted to test it on packet, after all, that’s what it was designed for! So I unplugged my Motorola GM350 from the NinoTNC and plugged in the 144PK with the lead that came with it (5 pin DIN to standard 9pin TNC connector, as used by Kantronics and the standard that the Nino also uses). | ||
| - | “C MB7NSC” I wrote at the node prompt. The TX light lit and the H/H screeched and “Connected to MB7NSC” appeared. It connected and on 5watts, over 63kms. Wow, impressive. I did a few more test over the air, getting nodes lists, going to GB7IOW and posting on this wall there etc | + | “C MB7NSC” I wrote at the node prompt. The TX light lit and the H/H screeched and “Connected to MB7NSC” appeared. It connected and on 5watts |
| < | < | ||
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| * The frequency of the EPROM clocking would be nice to know. My scope is in one of a million cardboard boxes from the house move, so I have no idea what its running at. The resistors are 223’s, so 22k. The capacitor is something I can’t measure. This would enable me to determine the startup timing from RX to TX and visa-versa. This may be <10ms or maybe far more, which wont make much difference at 1200baud (as my tests works just fine with no change on my normal TXDelays etc) but it might at a higher rate. | * The frequency of the EPROM clocking would be nice to know. My scope is in one of a million cardboard boxes from the house move, so I have no idea what its running at. The resistors are 223’s, so 22k. The capacitor is something I can’t measure. This would enable me to determine the startup timing from RX to TX and visa-versa. This may be <10ms or maybe far more, which wont make much difference at 1200baud (as my tests works just fine with no change on my normal TXDelays etc) but it might at a higher rate. | ||
| * Its programmed for 25khz. I can change this to the NJ8822 but the front end will no doubt be hardware LC filtered for that. More investigation needed | * Its programmed for 25khz. I can change this to the NJ8822 but the front end will no doubt be hardware LC filtered for that. More investigation needed | ||
| - | * What is the audio path like for 3600 or 9600 ? < | + | * What is the audio path like for 3600 or 9600 ? < |
| < | < | ||
packet/transceivers_144pk.1752245386.txt.gz · Last modified: by g7taj