I recorded this plot with my HP 3586A Selective Voltmeter while the FT-1000 was driven by two tones at 1kHz and 1.2 kHz respectively, with an outpout power of 50W. It took 7 minutes to make the plot under computer control via the GPIB bus (Link 1). When set to 20 Hz bandwidth, the 3586 is pretty slow...
The tones are generated by my (old) Thinkpad 560x laptop computer through the sound card and my Tone Generator program (Link 2), driving the Packet input of the transceiver.
The carrier frequency was set to 28.6 MHz. It is down by almost 60dB from the modulation, good!
This is a plot of the output from the sound card (same settings as it was driving the FT-1000) recorded with the HP 3586A (the HP 3586A goes down to 50Hz carrier frequency, with as narrow as 20Hz resolution bandwidth so it makes a nice audio spectrum analyzer too.)
The frequency is in MHz (that's what my program is designed to output..) But in fact the plot is from 500 Hz to 2.5 kHz. I will try to redo it later with a nicer scale.
You will notice a few things:
- The sound card generates very low intermodulation products (-60 dBc or better), which is quite unexpected, but it also generates fairly high harmonics of the audio frequencies, which are only about -25 to -30 dBc. I did not try different output levels to see the effect on harmonic levels. The output level from the sound card when the plot was made was about -10 dBm, as can be seen on the plot.
- The FT-1000 was set in the Packet mode (LSB) which is the default for RTTY and PSK31 also, so the spectrum is inverted.
- The harmonics from the sound card go through the filter of the FT-1000 quite well, which explains why higher frequencies are used for RTTY. If I had used 2 kHz and 2.2 kHz tones, the harmonics would have been at 4 kHz and above, outside the SSB filter bandwidth. Even the 3rd harmonics are quite visible on that plot, but they were not plotted in the sound card output (I need to redo that plot).
- The 3rd order intermodulation products from the FT-1000 are at about -30dBc, which is not too bad.
This is the ON click.
This is the OFF click.
The transitions are way too fast, the ON transition is about 1mS, and the OFF transition is only about 300 uS. The recommended transition time for smooth CW is 3 to 5 mS.