[hpsdr] preselector control

[Graham Haddock]

Hi Henry:

Well, we are not far enough along to split the project yet.

Initial work will be focused on verifying that the topology we are
considering can be made to work over the frequency range, and whether we
can use solid state switches and still make the filter performance,
or whether we need to go to relays.

Packaging and control decisions will come later, after we know how big it
will be, and how sensitive the inductors are to picking up local fields.

By going from a ten section fixed tuned preselector to a continuously
tuned preselector, we have gone from something where a simple
SPI bus was fine, and a small CPLD was overkill, to needing
a small CPU or a large CPLD and a fairly large lookup table,
or some clever algorithms to train and manage it.

--- Graham

==



Henry Vredegoor wrote
> Hi All, Francis, Graham,
>  
> I think a nice solution would be to have a number of options (or 
> "split" this project into 2 sub-projects?)
>  
> - Make a filters-only board-section (let's call it "Alex-Filter") with 
> some clear junction to the control section to have simple control, 
> like e.g. Francis' parallel port control solution
> - Make a filter-control board-section (let's call it "Alex-Control") 
> with a more or less "intelligent" control circuit (I2C, CLPD and the 
> like)
>  
> Both on the same PCB, as "one board"
>  
> - If you want an Atlas based Alex, leave the board as-is and populate 
> fully.
> - If you want the Alex-Filter remote controlled by Alex-Control cut 
> the board at the junction and populate both boards fully, put 
> Alex-Control in an Atlas card slot and wire it to the remote Alex-Filter
> - If you want to have the parallel port solution cut the board at the 
> junction, populate only Alex-Filter and do not use Alex-Control (save 
> it for other control related functionality) and interface/wire it to 
> the parallel port
> - If you want to have Alex-Filter controlled by some other means 
> within HPSDR (e.g. other existing on board CLPD, other I2C), cut the 
> board at the junction, populate only Alex-Filter and interface/wire it 
> to the appropriate interface.
>  
> I think this would give people the most flexibility?
>  
> Henry.
>  
>  
> --*
> *


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