[hpsdr] Alex Filter Switching Frequencies

[Lyle Johnson]

Hello Phil!

Welcome back!

> ...The current logic is:-
>
> For the HPFs
> if (frequency < 1.5MHz)  bypass
>
> else if (frequency < 6.5MHz)  1.5MHz HPF
>
> else if (frequency < 9.5MHz) 6.5MHz HPF
>
> else if (frequency < 13MHz)  9.5MHz HPF
>
> else if (frequency < 20MHz)  13MHz HPF
>
> else 20MHz HPF
>
> and for the LPFs
>
> if (frequency > 29.7MHz) 6m LPF
>
> else if (frequency > 21.45MHz) 12/10m LPF
>
> else if (frequency > 14.35MHz) 17/15m LPF
>
> else if (frequency > 7.3MHz) 30/20m LPF
>
> else if (frequency > 4MHz) 60/40m LPF
>
> else if (frequency > 2MHz)  80m LPF
>
> else 160m LPF

I suggest something more like this for the LPFs:

if (frequency > 32.0 MHz) 6m LPF

else if (frequency > 22.0 MHz) 12/10m LPF

else if (frequency > 15.0 MHz) 17/15m LPF

else if (frequency > 8.0 MHz) 30/20m LPF

else if (frequency > 4.5 MHz) 60/40m LPF

else if (frequency > 2.2 MHz)  80m LPF

else 160m LPF

My thinking is that the LPF is probably not rolling off immediately at 
the band edge, so allow lots of room for MARS operations, etc.  Just as 
the HPFs don't switch at a band edge, the LPFs need not switch there, 
either.

73,

Lyle KK7P


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