Hiya All,
How important is ALC (Automatic Level Control) on your set while using FT8 or FT4?
Not that mutch…
KJ7E explains:
Where the claim was, driving the FT8 audio into a Icom IC-7300 SDR HF radio to the point of ALC action would cause flat top distortion. My response was, the conclusions made by the VK2HTV was based on the audio scope displayed on the IC-7300, which is just a software representation of the audio and not a derived from sampled RF and a real measurement. It also appears the flat top waveform distortion is just the vertical limit of the audio scope with the sensitivity settings he is using. An RF sample fed into an external Oscilloscope would be necessary to verify transmitted audio is being driven into distortion. So I thought I would demonstrate this on my SDR HF radio to show, the effect of driving the FT8 tones into the radio at audio levels well below the ALC threshold and up to max ALC. Not all radios are the same, my point here is, you cant trust the fake audio scope on the IC-7300, if you want to be sure whats going on, you have to measure this with external equipment.
See the Video below