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-----Original Message-----
From: <[email protected]>
Sent: Dec 14, 2021 10:11 AM
To: <[email protected]>
Subject: Re: [Yaesu-FT-980] FT-980 CW Filters and Notes ON GEN TX

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More assorted ramblings on the Aux Band ROM:

The device is listed as a TBP18SA030. Equivalent to an NS82123 and similar. These can be found on the auction site and via a few other sources...but the programmers may be a little harder to source.

When I was researching this project a while ago I ran across the following:



I bought a couple of them plus a programmer that supports the SST39SF010. If one leaves the Aux Rom socket empty, all the data lines should be set "High". Thus, to set a band segment one will have to program a "0" into the bit location. Per earlier comments, 5 bits should cover the entirety of the HF spectrum...leaving 3 bits for housekeeping stuff. I revisited the CPU Board this morning before typing out this reply and there doesn't appear to be anything special going on with the high (or low) bits of the band-data byte: All 8 are put on the bus and processed. Thus, any filter or VCO switching logic is probably done as a function of the CPU programming.

Those extra bits could be used to set the VFO (Ham or Gen) and for TX Inhibit. A bit of empiricism is going to come into play, one supposes. Given I can program the Flash ROM as many times as needed, I'm thinking of setting Bit 1 high, 2-5 low and 6 and 7 low...as a baseline. Then test and record. All 255 combinations could be tested sequentially and I just may do that to flesh out a data sheet completely.

There is still the matter of filter switching on the RF Unit (D70-D72) but I think I figured out what Yaesu did with regards to the control logic here. First things first: Getting the band segments recognized and the rig generating the correct LO/control signals.

73 - Fred, N8YX

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