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Measurement results Rev 1.4

Sensitivity

for 10dB SINAD filter bandwidth SSB (200 Hz - 2.7 kHz)

f / MHz Ue / µV Pe / dBm
0,4 1,0 -107
1,5 0,7 -110
3,5 0,7 -110
7,1 0,76 -109
14,1 1,0 -107
21,1 1,0 -107
28,5 0,95 -108

Strong signal behavior

f / MHz IP / dBm comment
7,1 1,5 (Tr1 original, R15 not fitted)
7,1 8,5 (Tr1 reverse, R15 = 200 R, sensitivity 9 dB worse)

(DK5DN, 25 June 2012)

Measurement results Rev 1.0

The most important measurements in brief:

  • TOI (IP3): -10dBm at 21.2 MHz 2-tone procedure
  • Sensitivity: -106dBm for 10dB SINAD at 2.7 kHz bandwidth SSB 40m - 15m

Strong signal behavior

  • limiting in op amp at Pe = -32 dBm at 14 MHz
  • intermodulation TOI (IP3) = -10 dBm at 21.2 MHz

Sensitivity

for 10 dB SINAD SSB at 2.7 kHz bandwidth

fe/MHz Pe/dBm
0.05 -77
0.1 -88
0.2 -96
0.5 -102
1.85 -105
3.65 -106
21.2 -107
29.5 -104

All measurements taken with Winrad with noise reduction

Note from DK5DN: Apart from TOI, all values are good to very good compared with other SDRs. The relatively poor value of -10 dBm can be blamed on the preamp. It is optimized for good sensitivity and short antennas, but not however for strong signal robustness. You can't have everything at the same time! If the FiFi SDR is driven with powerful antennas, the strong signal robustness can be improved by modifying these component values.

Measurement results Rev 0.2

  1. sensitivity: -117 dBm at 10 MHz with 2.3 kHz bandwidth (SSB) for 10dB SINAD without noise reduction, R21/24 = 56k
  2. sensitivity: -123 dBm at 10 MHz with 2.3 kHz bandwidth (SSB) for 10dB SINAD with noise reduction, R21/24 = 56k
  3. overmodulation: Pe = 32 dBm; same conditions as 1.
  4. sensitivity: -115 dBm at 10 MHz with 2.3 kHz bandwidth (SSB) for 10dB SINAD without noise reduction, R21/24 = 27k
  5. sensitivity: -121 dBm at 10 MHz with 2.3 kHz bandwidth (SSB) for 10dB SINAD with noise reduction, R21/24 = 27k
  6. overmodulation: Pe = 26 dBm; same conditions as 4.

The overmodulation occurs in the op amp. The amplification can be halved by changing R21/R24 to 27k; this leads to a raising of the overmodulation level by 6dB. With the resultant sensitivity loss of 2dB the dynamic range increases by 4dB.

Last modified 5 years ago Last modified on Jul 16, 2012 3:46:06 PM