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HELP uBITX v4


Curt
 

Rubens

I have a v4, with stock firmware. Press the main tuning knob, it has a push button also. This brings up a menu. Scroll by turning the main knob. One selection relates to frequency. Press again when you find it, then use knob to select frequency corresponding to your chosen band. I think this is nice, others do not so they add a touch screen.

Curt


Evan Hand
 

Here is the section of code that is from the version 4.3 Nano code:
================================================================================================
/**
 * Select the properly tx harmonic filters
 * The four harmonic filters use only three relays
 * the four LPFs cover 30-21 Mhz, 18 - 14 Mhz, 7-10 MHz and 3.5 to 5 Mhz
 * Briefly, it works like this,
 * - When KT1 is OFF, the 'off' position routes the PA output through the 30 MHz LPF
 * - When KT1 is ON, it routes the PA output to KT2. Which is why you will see that
 *   the KT1 is on for the three other cases.
 * - When the KT1 is ON and KT2 is off, the off position of KT2 routes the PA output
 *   to 18 MHz LPF (That also works for 14 Mhz)
 * - When KT1 is On, KT2 is On, it routes the PA output to KT3
 * - KT3, when switched on selects the 7-10 Mhz filter
 * - KT3 when switched off selects the 3.5-5 Mhz filter
 * See the circuit to understand this
 */

void setTXFilters(unsigned long freq){
 
  if (freq > 21000000L){  // the default filter is with 35 MHz cut-off
    digitalWrite(TX_LPF_A, 0);
    digitalWrite(TX_LPF_B, 0);
    digitalWrite(TX_LPF_C, 0);
  }
  else if (freq >= 14000000L){ //thrown the KT1 relay on, the 30 MHz LPF is bypassed and the 14-18 MHz LPF is allowd to go through
    digitalWrite(TX_LPF_A, 1);
    digitalWrite(TX_LPF_B, 0);
    digitalWrite(TX_LPF_C, 0);
  }
  else if (freq > 7000000L){
    digitalWrite(TX_LPF_A, 1);
    digitalWrite(TX_LPF_B, 1);
    digitalWrite(TX_LPF_C, 0);    
  }
  else {
    digitalWrite(TX_LPF_A, 1);
    digitalWrite(TX_LPF_B, 1);
    digitalWrite(TX_LPF_C, 1);    
  }
}
 
======================================================================================================
 
So for the 10m band, all are off.  For 20m just KT1, for 40m KT1 and KT2, and for 80m all of the KT1 to KT3 relays are on.
 
If all of the bands EXCEPT 10m is working, AND you have a v4, THEN I would look at the KT1 circuit and the relay.  Most likely that is where the failure is.  One of the 10m LPF coils could be open.  This could be verified on the v4 by measuring the resistance between the antenna output and ground without power.  It should be close to zero ohms for both shield and center pin.  The other possibility is that the relay is always on, or stuck in the on position.  To verify that would require you to trace the circuit checking for continuity where it is not expected.
 
73
Evan
AC9TU


Rubens Kamimura
 

Evan and Group

How do the selections of relays KT1, KT2 and KT3, or TXA, TXB and TXC work in uBITX v4?

How are frequency bands selected?

73's
Rubens
py2pvb