Preselector control

[dl2ebv]

Hello Simon,
there are a lot of new SDRs with high bandwiths now and comming.
But as they use a huge bandwidth the lack of band-filtering and without filters they will be exposed to high summing signals and maybe suffer from intermodulation.
It is fine to have a broad spectrum visible but to have good reception of DX-signals in a dedicated band the receiver should have a preselector/bandfilters.

I work with Heinz Stampfl, HB9KOC, on an external preselector for the Shortwave bands.
He has a nice version WaveStar with 8 bands up to 30 MC/s prepared in kit-form which will be available by funkamateur.de soon.
I prepared the firmware for this preselector; the problem was that Heinz had the hardware ready before I could do the programming.
But I was able to program the ELAD-interface used between ELAD-SDRs an the ELAD-preselctors (SPF-08) which uses a simple SPI with a shift register in the preselector.

With ELAD it works fine and now I made an additional ARDUINO-interface to combine it with SDR-Console using CAT.
So the WaveStar will work with SDR-Console and with the interface also the ELAD-SPF-08 will work with SDR-Console and other than ELAD-SDRs.

But I think the way using CAT is not very fine.
I have to poll the active receiver 1 to 2 times a second...

It would be nice to have an definition-table in SDR-Console similar to that used in ELAD-SW2.
Here you can define frequenzy ranges for the control of the individual filters in the preselector.
Especially using the SFE-interface-table (each band uses full 8 bit for adressing) which is much better than that for SPF-08 (only 8 bands, using a 1-of-8-bit-code).
That means a definition-table with bandstart, bandend and the filter-number.
When the RX-frequency goes in the range of a band the filternumber should be send as a serial-data (on COM: and with USB-serial-interface to the preselector).
Could also be a ASCII-sequence like a CAT-command.

That would be a very versatile interface for each possible preselector (the preselector equipped with an Arduino to switch the filters in which way it is ever needed, as serial communication or with a parallel 8-bit word...).

With the new ELAD FDM-S3 (and also with ELAD FDM-DuoR) it is not possible to use the SPI-interface with the ExtIO-socket as those units use internal filters.
As best preselectors would have to use more than the possible 8 (or even 7 plus the bypass-board) a CAT-interface comming from the software would be versatile.

What do you think of that idea?
Any change to realize that in future?

vy 73, Ernst, DL2EBV

[Simon G4ELI]

A good idea, I assume the command is an ASCII string?

I can honestly say that spending a few days coding this doesn't really get me very enthused at the moment .