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Troubleshooting the MHST

If one constantly repeats the same test repeatedly without changing a thing, then why would you expect a different result each time you run the test?

I have another homebrew SDR transceiver that closely resembles the MSHT. It too uses QUISK and an identical mainboard. The same Driver, and Final and a steerable single BJT amp. The single difference is this one uses the SDR LLC interface while the MHST uses the Pi Pico. The actual QUISK rig selection for the Pi Pico is the VWS Package and for this one it uses the Soft Rock USB. 

The Pi Pico uses the Si5351 and the SDR LLC the Si570. The Pi Pico turns out a quadrature LO at frequency directly and the SDR LLC is at 4X and run through a 74C74 D Flip Flop which results in a 1X Quadrature signal stream.

SDR Using the SDR LLC Controller and Soft Rock Package
 
Yesterday was spent comparing the two rigs, The SDR LLC does not have that nasty signal that exits with the Pi Pico. The SDR LLC produces a single transmitted output at the correct operating frequency. The externals to the Mainboard, i.e. the same two sound cards are used with both rigs, so any difference is the QUISK hardware specific software and or bad components on the main board. This may be a ADE-1 issue.

So, using essentially the same mainboard what could cause the issue with the Pi Pico? A bit of Noodling through the scenarios we get the two items as above, the hardware specific software (VWS versus Softrock) and one or both bad ADE-1's on the mainboard. The LO drive level to the ADE-1's was checked and they were consistent from board to board.

A brute force test would be to decouple the SDR LLC controller from the 2nd unit and sub in the Pi Pico. This would resolve several questions. If it works sans the SDR LLC Controller and VWS Package, then we know it is a mainboard issue with the MHST. If it displays the same erroneous signal, then we have two possibilities with the Pi Pico board or the VWS package. 

The reverse is a check too if we can get the MHST to work with the SDR LLC then that proves the mainboard is OK and that narrows the choices to the Pi Pico and the VWS package. 

Since both alternatives involve some dis-assembly and temporary hookups, which of the two options is better to arrive at the answer.


Green Board Lower LH Corner is the SDR LLC Board


Them That Know Can Make Things Go!

73's
Pete N6QW

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