PSK31 – PC/Laptop Test Notes
Comparison of two systems running MixW 2.03, direct connected via the audio connections. No RF involved.
PC System: Pentium III?, 400mHz, sound card: Creative Technology Ltd.
Laptop system: Gateway Solo 2500, Pent II, 400 mHz, on board sound hardware.
500Hz, PC System transmitting. Some 2,3, & 5th harm dist. No observable freq(phase) flutter on tuning indicator, also RST is 599
2.7 kHz, same setup. Note RST dropped to 499
4 kHz, Observable freq flutter and tuning indicator phase jitter has inceased enough to drop RST to 299
Audio connections reversed so that Laptop is sending to the PC. Note significant degradation as offset frequency is increased. R-1 at 4 kHz and signal is unreadable despite S-9 signal strength.
Laptop transmitting 500 Hz, RST is 599 but about 30° phase instability noted
2.7 kHz, RST has dropped to 199 with significant text errors making the call sign unreadable.
4 kHz , at least 180° of phase instability and signal is totally unreadable despite S9 signal strength.
Frequency stability tests with Spectrogram 6.5 Tools
A single tone and a PSK31 signal at 2.7 kHz was tested for frequency stability using the Spectrogram 6.5 software. Screen captures for both the PC and Laptop sound cards are shown.
Laptop transmitted signal at 2700 Hz. Freq deviation is about +/- 5 Hz for both single and PSK31 tones. The rate is about 1.1 Hz.
PC transmitted signal at 2700 Hz. Freq deviation is about +/- 2 Hz for both single and PSK31 tones. The rate is about 0.9 Hz.