N7RGWによる２バンド化へのスケッチ変更

2437New Possible Modifications for CS-series (or KN-Q7A) with Sandwich
n7rgw
May 16 3:59 AM

I came up with this idea while thinking about the options with the sandwich VFO.  Why not program the jumper closed for one band and jumper open for another band.  Then modify the two band-pass filter chains to work with both frequencies.

First: I modified a sandwich so that when the jumper (switch) is shorted, I get 40 Meters.  When the jumper (switch) is open, I get 80 Meters.  The sandwich does have to be powered off and restarted to make the switch.
Here is the code difference:

if (digitalRead(JP))  //JP10: Open - 80 Meter, Short - 40 Meter
 {
   op_freq = 3800000;  //set op_freq to the mid of the band
   band_high_limit = 4000000;  //set band high limit to 4.00 MHz for 80 Meter Band
   band_high_limit = 3500000;  //set band low limit 3.50 MHz
   bfo_freq = 8190100; //IF freq = 8190.1 kHz, BFO freq is around IF freq depending on LSB or USB, default to LSB
   bfo_low_limit = 8189500;
   bfo_high_limit = 8193500;
 }
 else
 {
   op_freq = 7200000;  //set op_freq to higher portion of the band
   band_high_limit = 7300000;  //set band high limit to 7.30 MHz
   band_high_limit = 7000000;  //set band low limit 7.00 MHz
   bfo_freq = 8190100;     //historical reason: for KN-Q7A kits IF freq = 8192 kHz
   bfo_low_limit = 8189500;
   bfo_high_limit = 8193500;
 }

This was for my older KN-Q7A with the 8.192 MHz IF.
The sandwich works great!

Next experiment was to look at putting two Band-pass filters in parallel (for a total of 4 in radio).  One filter was calibrated for 40 Meters and the other 80 Meters.  NOTE: This experiment has not been placed in the radio itself, yet.  Only 40 Meter or 80 Meter signals passed through as I had anticipated.  This would mean that I don't have to add a relay to switch the filters in and out.  I would just put them in parallel.  I am not certain as to the overall affect on the signal path such as impedance, etc. but it is an interesting step.

The frequency of the VFO (sandwich) should be able to select the appropriate signal coming through.  I will see what happens.

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