Ugly Circuit Boards - for experienced electronics makers: Video posted Jan 12, 2025

Video posted Jan 12, 2025 :: https://youtu.be/-is1NowfrtA

Resources for 'Ugly Circuit Boards::

 

Above — Schematic of the so simple AF presented in the video.

Above — The so simple PA stage in a test bench setup: 1KHz signal generator, 8 Ω dummy load and DSO.

Above — Clean output FFT of the so simple PA when driven to 288 mW signal power across the dummy load.
 

Above — 2 users requested a higher power version with (hopefully) the same parts count. I employed 2  packaged Darlington emitter  followers -- the TIP122 / TIP127 pair instead of the 2N4401 / 2N4403 followers.

 

Above — I had to add 2 diodes to the PA bias stack, plus an additional DC filter capacitor  which increased the parts count by 3 items. The 22 Ω DC low-pass filter is now moved on the other side of the NPN transistor to avoid a big voltage drop across that resistor with the higher DC current drive of the 'big guns' PA pair. A 470 µF bypass cap gets added to the DC supply of the TIP122 to low-pass filter the output followers. 

 Above —  Clean output in time domain with the alternate so simple PA  driven to 700 mW signal power across the dummy load.

 
 
Above —  Clean output FFT of the alternate so simple PA when driven to 700 mW signal power across the dummy load.
 

My Voltage Tuned VFO - Have I gone crazy? : Video posted Feb 9, 2025

 Video posted on Feb 9, 2025 :: https://youtu.be/_SEzhTw6DcY

Resources for 'Voltage Tuned VFO'::

 

 

Above — Complete schematic of the voltage tuned VFO

 

 Above — Varactors on a scrap of PC board.  "Zoomed in heavily".

 

Above — Photo of the 3.5 MHz VCO ( voltage tuned VFO).

 

Above — Photo of a 5 MHz low pass filter I built 30 years ago using PL-259 connectors (PL-259 to BNC adapters in-situ). Currently most use SMA connectors, although some in the mid-to-late 2000's employed BNC connectors.

 

Above —  Some of my low pass "bench" filters. I also have band pass and high pass bench filters in my collection All filters I made after 2017 used SMA connectors. Most are not shown.

 

Above — Output of 3.5 MHz voltage tuned VFO into a 50 Ω terminated DSO channel.

  

Above — Output of 3.5 MHz voltage tuned VFO into a 50 Ω terminated DSO channel with the 5 MHz bench low pass filter in the signal chain.