[hpsdr] Interfacing LP Filter for Pennywhistle

[Sheldon Hands]

Subject: [hpsdr] Interfacing LP Filter for Pennywhistle


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>
> I have a HF Projects LPF100 switchable LP filter that I plan to use with 
> Pennywhistle until ALEX  is available.
>
> There appears at least two methods to interface, but realistic 
> documentation is lurking in a location that I have not yet discovered.
>
> Approach 1 would be to use the Penny 25 pin connector J6  and connect 
> "OC0 - OC6" [referred to in the manual as both "J6 Receive Pins" 1 - 7 and 
> "J6 Transmitt Pins" 1 -7] to the relays on the LFP100.  Seems straight 
> forward except that I can not find on the schematic if pin 25 "OCREF" is 
> connected internally on the Penny board or if it must be connected on the 
> LPF interface side - The ULN2003 would like this connected to the supply 
> voltage.  My interest here is twofold and includes another application to 
> interface to the THP  HL-45B as an FT-817 [decoded output].
>
> Dick Faust K9IVB
>

I just use the Penny lines to pull down a PNP switch using BC640 transistors 
to give high side or 12v on for the relays. It would very easy and tidy on 
some veroboard as you can use SIL packs for the biasing. Pin 25 is not used 
here.
Shel CT1IZU 


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