Bulletins from the Pacific Packet Radio Society - page 078

6B. Wire U8 pin 2 to U1 pin 26 (Al3).

6C. Wire U8 pin 3 to U1 pin 27 (Al4). Pin 3 could alternatively be hooked to ground if no additional EPROMs are going to be used.

This completes the 2732 modification. Plug in a 2732 with some good software in it and give it a try.

Additional Memory

These modifications leave room for further additions to both the EPROM and RAM space. To add more EPROMs might require some swift work, as additional EPROMs cannot be piggy-backed. One approach might be to kludge sockets onto the back of the boa rd , and wire them to the present sockets, except for the chip-select pins. They are hooked to the remaining enable outputs from U8 (pins 11, 10, 9, 7) as required.

The RAM is easier to expand. Just piggy-back the additional 2114 chips on top of the present ones (U1 9 to U26) except for the chip selects (pin 8), which go to U27pins 11, 10, 9, and 7. This will double the RAM on the board from 4k to 8k.

Make sure you remind whoever burns your EPROMs which ones you are using and that your RAM is now at 8000-8FFF hex. Happy packeting!!!

FILE QST.82.05.20.0.W2FPY

Den,

I just spoke with Tom Clark, W31WI, concerning the interim modulation standard. I'm afraid I've committed a faux pas by even suggesting AFSK FM techniques for Phase III-B. Unless you've got an EME quality station, it's unlikely that' you'll squeek even one packet through without a bit error. We need to do the following:

1. Do the link calculations for the previously proposed and now inoperative standard (I'll do this on my end, too, and we'll compare notes).

2. Come up with a liveable modulation scheme, even if it means building an AFC loop to track the doppler shift.

3. Do link calculations for the new standard.

4. Build some prototype hardware. This is a tough one ... I think we can justify the work by pushing the baud rate up in the terrestrial packet activity. I'd like to have a direct hand in this one.

Other subjects of conversation included holding a Workshop

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