custom filter for ubitx 4

Richard E Neese

anyone have a schematic and or know where to find one for the v4 as it has the board headers for 1




not entirely sure 'what' custom filter opportunity you are referencing - but 'board headers' seems to be a clue. 

I remember there are pad features to interface with a second crystal filter - this topic has certainly been on the lit.  if you seek CW - a good CW filter is best at a much lower IF than 12 MHz.  its easy to make from lower frequency xtals - designs abound.  the 'bad news' - need to to add some firmware instruction to retune the BFO when doing CW.  it needs to be proven (if it hasn't been) - but it is possible that the SSB 12 MHz and a say 4.9 or 5 MHz CW filter could co-exist in parallel without switching. 

other v4 filters of interest - well something to reduce mixer spurious at 45 MHz.  v5 adds an LC filter.  I tried it on v4, in itself it does not have enough Q - so I suspect its part of a set of solutions.  adding a second 45 MHz xtal stage is popular - as reported here I tried it, it greatly reduced my CW transmit output.  I have since added SMT inductors with some shielding on the primary 45 MHz filter, so possibly it will work better - when I try it again. 

for CW and narrower bandwidth SSB - I am using a NESCAF audio filter that I am happy with.