Difference between revisions of "RF Noise Generator"
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* C1 is connected Emitter of Q1 to GND to reduce power supply noise | * C1 is connected Emitter of Q1 to GND to reduce power supply noise | ||
* Higher noise than EMiRFD design | * Higher noise than EMiRFD design | ||
− | * Falls off | + | * Falls off straight line with frequency |
** Usable from 1-10 MHz | ** Usable from 1-10 MHz | ||
** -40 dBm at 1 MHz | ** -40 dBm at 1 MHz | ||
− | ** - | + | ** -80 dBm at 30 MHz |
* Nearly zero power supply current | * Nearly zero power supply current | ||
Revision as of 11:54, 9 September 2021
Contents
Design
- Useful as a filter test signal source
- Pass filters
- Crystal filters
- From Experimental Methods in RF Design
- Fig 7.72
- Described as "not flat"
- "Junk box" parts
- (2) 2N3904 transistors
- (2) 5V (nominal) zener diodes
- Noise figure -50 dBm @ 10 MHz
Schematic
Prototype
- Unique nodes in red
- Prototype on single sided copper clad PCB
- KiCAD zener packages have backwards silkscreen (will need to fix on OshPark PCBs)
Meaurements
- 12V, 43mA current draw
tinySA Measurements
- 1-30 MHz
- Power Off
- Power On
- 100 KHz-1 MHz
- Power Off
- Power On
- Lot more energy at ~400 KHz
- -30 dB
Rigol DS1054Z Measurements
- 50 MHz scope with mods
- UltraScope settings
- SCAL 1.00 V
- H 200nS
- FFT settings
- CF = 16 MHz
- 2 MHz start, 50 MHz stop
- RBW 416.6 KHz
- Background noise
- Generator off
- Average ~ -64 dB
- Noise Generator On
- Falls off with frequency, but better than -50 dB
- Measured performance per EMiRFD (predicted - 50 dB)
Better Design
- C1 is connected Emitter of Q1 to GND to reduce power supply noise
- Higher noise than EMiRFD design
- Falls off straight line with frequency
- Usable from 1-10 MHz
- -40 dBm at 1 MHz
- -80 dBm at 30 MHz
- Nearly zero power supply current
- Off
- On, 1-30 MHz
- On, 1-10 MHz
Build / Enclosure
- Used very old, but high quality chassis mount BNC connector
- Silver connector has a nice patina
- Built onto Single Side PCB material
- Acts as ground plane
- Pads cut from PCB material and superglued down onto the Base PCB
- Hot glued down into plastic enclosure