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4

I think I figured this out. By looking at VFO with an oscilloscope I could catch a brief glitch (~1.5ms) in the signal when the frequency is changed: It was hard to notice because you can't easily trigger on this. I had to manually trigger single captures while tuning for some time to see this. Then by googling "si5351 output glitches" I've found ...


1

Since it happens when switching frequencies, I suspect glitches of some form in the local or beat frequency oscillators' output. The mixers simply multiply the "signal" by the oscillator. Any noise or glitch in the oscillator outputs will be reflected in the mixed outputs. You may be more sensitive to BFO glitches, since the output is at DC, not a ...


3

Try powering the LM386 temporarily off a battery. if the popping stops, then the cause is a surge being conducted into the 386 from the supply that feeds the rest of your circuit. Normally, you would bypass the power input of the 386 to ground with a hefty electrolytic capacitor (50 to 100mfd) and then shunt that with a fast-acting cap (0.01 to 0.1uF) to ...


1

QRP simply refers to low output power. What modulation you use is up to you. Voice, CW, digital mode like JS8Call .... Using 5 Watts to contact a DX station in SSB is quite a thrill.


3

After a little bit of searching I discovered that this topology is called QER filter, where QER stands for Quasi-EquiRipple. This topology is attributed to Dr. Dave Gordon-Smith, G3UUR, who is also well-known for inventing a popular method (the G3UUR method) of measuring crystals. Apparently it was first described in The QRP Quarterly, Spring 2010 under the ...


1

The very best source of information that you'll find about making common-mode chokes is available at Jim Brown, K9YC's site http://k9yc.com/publish.htm. Download his PDF http://k9yc.com/RFI-Ham.pdf. RFI, Ferrites, and Common Mode Chokes For Hams Most recent update April 2019. This tutorial is directed specifically to RFI in ham radio applications. It ...


1

You build a few and measure them with a vector impedance meter.


3

If you purchase a radome antenna, like a Comet gp6, they are painted and can be painted again for color change ..using non conductive paint They are made of fiberglass which is not uv tolerant and will deteriorate if left unpainted. Pvc pipe is not uv resistant and should be painted. I've done this before and found a Rustoleum product spray on paint with ...


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