I may be out of the loop on this one, exactly what is an E.Bitx??
Can you point to a manual?
What DDS chip?
Do you have source code for the DDS?
There are several different kits coming out of India, it's a big place.
Not unexpected that you would start hearing noise when VFO is near the BFO.
Could be phase noise in those oscillators.
Could be some sort of non-linearity in the demodulator.
Could be that you are expecting more from this radio than it is capable of giving.
>? 3)? On putting CRO leads on BFO and VFO connected , changing either the BFO or VFO frequency
>? in DDS individually, I see both the frequencies incrementing and decrementing!
Sounds wrong, but then I don't know anything about the E.Bitx
Are you sure this measurement result is correct?
Slight changes in frequency would be hard to detect with a CRO (oscilloscope),?
how far are you changing these frequencies?? How are you measuring the frequencies?
Jerry, KE7ER
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On Tue, May 18, 2021 at 09:42 AM, <arorasimran@...> wrote:
I am building a E.Bitx purchased from India and here are the symptoms
1) VFO frequency =? BFO frequency? +-few Khz produces a strong radio like static when Q3 base is touched ie rx (side which connects to IF filter while going towards the Phase Detector)
2) With the VFO and BFO connected and BFO tuned to 9.96Mhz, Q3 does not have that kind of potential static noise. However If the BFO is tuned close to VFO frequency, a considerable amount of gain in the static noise and vice a versa.
3)On putting CRO leads on BFO and VFO connected , changing either the BFO or VFO frequency in DDS individually, I see both the frequencies incrementing and decrementing!
4)Step6 as Described in the manual of EBITX does not really do the job as expected. (this sounds very diecy)
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Things tried so far,
1) replacing transistors ( BTW BC550C in the IF amp ie q3 and nearby RX transistor gives a lovely gain, the transistors are 500Hfe
2) tried voltage references, all seems correct.
3) Trifilars in PD section and one that accepts signal from vfo had 9 turns, got them 8. No scene
4)Porting the code for Raduino for pinouts of EasyBitx. Held the PTT switch on low to enable RX, Pot moves the VFO freq dial nicely. Did not put the other pot for BFO. Also is there a way to have Raduino ported for 20meters so that I can totally eliminate doubt for a buggy DDS firmware?
what should I do now?
Simran
