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Yes, the ALC indicator does tend to go to full scale and into the red zone with compression on, but that doesn't mean it isn't creating splatter. Here is what I see on an Agilent 8924C analyzer hooked to the 7K's HF antenna output via a 30 dB attenuator, with 300 Hz sample bandwidth with a span of 40 KHz. The audio source was a stock HM-151 mic with a long AHHHH. Mic gain was set at 35% with two narrow bars of ALC showing when compression is off.

With compression on, running 80 watts PEP on 14.2 MHz and with the ALC showing all green bars on, I see splatter +/- 20KHz or more from the sideband peak (carrier frequency + 1.5 KHz for USB) at -40 dBc (40 dB below carrier, which is the peak sideband level in this case).

Assuming I was running a full 100 watts, which is 50 dBm, then the IMD products are 50 dBM -40dB = 10 dBm. Free space path loss at 30 miles from the antenna is aobut 90dB, so stations within 30 miles would receive my splatter at 10 dBm-90dB = -80 dBm, which is a little more than S9 on the S-meter on a 7k with the pre-amp on. If you are running an amplifier, the problem is of course worse.

This splatter exists when the ALC exceeds 50% of the green bars on. At 50% ALC, the splatter is below about -55 dBc. Below 30% ALC I could not see any splatter above -65 dBc.

Which is why I don't use compression often and am very careful with the mic gain and background noise levels when I do. I have too many ham friends that share the bands within a 30-mile radius.

Steve, W3AHL