Re: K5BCQ uBITX Relay Switched LPF/BPF board


Now if one does all that and really wants 20 and up spurs and all....

Simple add an inline (between radio and antenna jack) 28mhz low pass filter.
and leave it there.  If it well made it will be invisible (low loss) and at worst
it catches harmonics like the old school TVI filter.  It does not fix the spur

So the deal for the relays then is:
KT1 selects 20m filter via TXA
KT2 selects 40m filter via TXB
KT3 selects 80m filter Via TXC
none selected is straight through
and the external always inline 28mhz LPF is doing the work.

 * Select the tx harmonic filters
void setTXFilters(unsigned long freq){
  if (freq >= 20000000L){ 
    digitalWrite(TX_LPF_A, 0);
    digitalWrite(TX_LPF_B, 0);  // 10m straight through
    digitalWrite(TX_LPF_C, 0);
  else if (freq >= 14000000L){ 
    digitalWrite(TX_LPF_A, 1);
    digitalWrite(TX_LPF_B, 0);  // 20M
    digitalWrite(TX_LPF_C, 0);
  else if (freq >= 7000000L){  
    digitalWrite(TX_LPF_A, 0);
    digitalWrite(TX_LPF_B, 1);  // 40m
    digitalWrite(TX_LPF_C, 0);    
  else {
    digitalWrite(TX_LPF_A, 0);
    digitalWrite(TX_LPF_B, 0);  // 80m
    digitalWrite(TX_LPF_C, 1);    

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