Re: Hi-Per-Mite Center Frequency


John Kirby
 

 qcx audio filter from CW to ssb es ft8 es WSPR / RX
The QCX is already setup to TX WSPR (menu driven) but must be time synced with WWV to within +/- one srcond.

The QCX can also be enjoyed as a general coverage SSB HF receiver

... reff :  qcx manual 1.08    # 5.7 ...CW filter

The QCX audio filter is a very well designed CW filter therefor can not pass SSB voice or FT8 or WSPR

You will need to bypass OR modify the QCX onboard CW audio filter to enjoy QCX SSB :

To bypass....
Locate R27 and R29.
Lift (unsolder) the leg of R29 that connects to R27.
Lift (unsolder) the plus (+) leg of C21.
I found it much easier to cut the trace between C21 (+) and IC9A (pin 1).
Solder a jumper from the now open pad at R29 to C21 (+) pad.
 then  plug your new outboard SSB filter into the PHONES jack.

All other QCX functions work as designed to include CW at a much wider bandwith.

Take  lQQk at this site
 http://www.bowdenshobbycircuits.info/opamp.htm
Drop down to  "2nd Order Opamp Filters" where the example is 200 Hz
...then... plug in your choice of freq for example 2500 Hz.

I also have first hand experience here...
>>>>http://www.circuitstoday.com/band-pass-filters<<<<
I plug these  math equations into EXCEL
then built several BPF ... to include a >variable< CW band pass filter
THAT WORKED FIRST TIME :>))

72, 73
John
N3AAZ 

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