Difference between revisions of "RF Attenuators"
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== Attenuator Design - Rev 2 == | == Attenuator Design - Rev 2 == | ||
| − | * 6 dB resistor values in | + | [[FILE:ATTEN1_P1896-720PX.jpg]] |
| + | |||
| + | * 6 dB resistor values in above | ||
* [https://oshpark.com OshPark] clear soldermask "After Dark" | * [https://oshpark.com OshPark] clear soldermask "After Dark" | ||
** $4.40 for 6 cards | ** $4.40 for 6 cards | ||
| − | + | * Small/light enough to hang directly off fragile devices | |
| − | |||
| − | |||
| − | * Small/light enough to hang directly | ||
* SMA connectors | * SMA connectors | ||
** Male/female are good choices for direct connect to devices | ** Male/female are good choices for direct connect to devices | ||
| Line 121: | Line 120: | ||
** 1206 | ** 1206 | ||
*** 1/4W | *** 1/4W | ||
| − | ** 1% values | + | *** 1% values get good accuracy (approx. 2%) even though not exact to calculated values |
* Good bandwidth up well past RF | * Good bandwidth up well past RF | ||
Revision as of 15:49, 23 October 2021
Contents
Purchased Attenuators
Programmable Attenuator
Triple Attenuator
Homebrew RF Attenuators
30 dB Attenuator
- Built
- Standard 5% resistor values
- R1 = 820 in parallel with 22K = 790.6 ohms
- R2 = 2 paralleled 120 Ohm 1/4W resistors paralleled with 470 ohms = 53.2 ohms
- Flat from 0-30 MHz
- Measured attenuation is flat
- -30.01dB at 1 MHz
- -30.24dB at 30 MHz
- Input Impedance - 53.1 ohms, 21.3nF
- SWR 1.06
- 1/2W max (5VDC max, 0 ohm source)
- NanoVNA scan data
- LTSPICE Simulation
20 dB Attenuator
- Build
- Standard 5% resistor values
- R1 = 2 of 510 in parallel also in parallel with 8.2K = 247.3 ohms
- R2 = 2 paralleled 150 Ohm 1/2W resistors paralleled with 330 ohms = 61.11 ohms
- Flat from 0-30 MHz
- Measured attenuation is flat
- Input Impedance - tbd ohms, tbd nF
- SWR tbd
- 1W max (8.6 V max, 0 ohm source)
- LTSPICE Simulation
Attenuator Construction
- Single side copper clad PCB
- Approx 2"x1"
- Clean with steel wool
- Solder SMA connectors
- Use large alligator clips to hold while soldering
- Solder on sides only
- Cut "T" Shaped pads
- I used nibbler
- Center fits between connector ground pins
- Glue down pads with Superglue
- Solder center pin with big solder blob
- A bit too high for direct contact
- Verify raised pad does not short to ground
- Solder side resistor(s)
- Leave room for center resistor(s)
- Measure side resistors from pad to ground
- Should match value
- Solder center resistor(s)
- Verify no shorts between centers and ground
Attenuator Design - Rev 2
- 6 dB resistor values in above
- OshPark clear soldermask "After Dark"
- $4.40 for 6 cards
- Small/light enough to hang directly off fragile devices
- SMA connectors
- Male/female are good choices for direct connect to devices
- Resistors
- 1206
- 1/4W
- 1% values get good accuracy (approx. 2%) even though not exact to calculated values
- 1206
- Good bandwidth up well past RF
Parts
| Mfr. # | Manufacturer | Customer # | Qty | R1/R2 | Description |
|---|---|---|---|---|---|
| RK73H2BTTE17R8F | KOA Speer | ATTEN_03DB | 1 | R1 | Resistors - SMD 1/4W 17.8 ohms 1% |
| RC1206FR-07294RL | YAGEO | ATTEN_03DB | 2 | R2 | Resistors - SMD 294 ohms 1/4W 1206 1% |
| RK73H2BTTD37R4F | KOA Speer | ATTEN_06DB | 1 | R1 | Resistors - SMD 1/4W 37.4 ohms 1% |
| CRCW1206150RFKEAC | Vishay | ATTEN_06DB | 2 | R2 | Resistors - SMD 1/4Watt 150 ohms 1% |
| RC1206FR-0771R5L | YAGEO | ATTEN_10DB | 1 | R1 | Resistors - SMD 71.5 ohms 1/4W 1206 1% |
| RC1206FR-0797R6L | YAGEO | ATTEN_10DB | 2 | R2 | Resistors - SMD 97.6 ohms 1/4W 1206 1% |
| RK73H2BTTD1070F | KOA Speer | ATTEN_13DB | 1 | R1 | Resistors - SMD 1/4W 107 ohms 1% |
| RC1206FR-0778R7L | YAGEO | ATTEN_13DB | 2 | R2 | Resistors - SMD 78.7 ohms 1/4W 1206 1% |
| AC1206FR-07249RL | YAGEO | ATTEN_20DB | 1 | R1 | Resistors - SMD 249 ohms 1/4W 1206 1% |
| RK73H2BTTDD61R9F | KOA Speer | ATTEN_20DB | 2 | R2 | Resistors - SMD 61.9 ohms 1% |
| RK73H2BTTD7870F | KOA Speer | ATTEN_30DB | 1 | R1 | Resistors - SMD 1/4W 787 ohms 1% |
| AC1206FR-0753R6L | YAGEO | ATTEN_30DB | 2 | R2 | Resistors - SMD 53.6 ohms 1/4W 1206 1% |
| RC1206FR-072K49L | YAGEO | ATTEN_40DB | 1 | R1 | Resistors - SMD 2.49k ohms 1/4W 1206 1% |
| RK73H2BTTD51R0F | KOA Speer | ATTEN_40DB | 2 | R2 | Resistors - SMD 1/4W 51 ohms 1% |
| RK73H2BTTDD49R9F | KOA Speer | ATTEN_50_60DB | 2 | R2 | Resistors - SMD 49.9 ohms 1% |
| RC1206FR-077K87L | YAGEO | ATTEN_50DB | 1 | R1 | Resistors - SMD 7.87k ohms 1/4W 1206 1% |
| RC1206FR-0726K1L | YAGEO | ATTEN_60DB | 2 | R2 | Resistors - SMD 26.1k ohms 1/4W 1206 1% |
Measurements
- NanoVNA
- S21 gain
- 1-900 MHz scan
- Calibrated with cable on thru
6 dB Attenuator
- Flat from 1-600 MHz
- Higher attenuation past 600 MHz
- S21
- S11 from 1-900 MHz
40 dB Attenuator
- Flat from 1-600 MHz
- Higher attenuation past 600 MHz
- -39.9 dB at 14 MHz
- S21
- Flat from 1-30 MHz
- S21
- s11
- 1-900 MHz
- VSWR
- 1-900 MHz
DC Block
- Use same PCB
- Install 0.1uF cap between the two SMAs
- Leave off resistors to ground
- Sweep 50 KHz to 900 MHz
- S21 of -0.8 dB at 50 KHz
- S21 of 0.44 dB at 900 MHz
- Sweep 50 KHz to 900 MHz
- S11
Attenuator Charts
References
- Attenuator Calculator - Le Leivre.com
- Attenuator Calculator - Pasternak
- Heavily inspired by Alan (W2AEW) video
