The guide recommends spike length of 1 or 2, depending on the frequencies used. What are the pros and cons of a spike length of 4? The only mention of higher spike lengths in the the guide says: a Spike Length of 24 as shown wouldn’t be a good value.

So hopefully this explanation resonates with you. If not, we can try various other means to explain.

We have 1024 points to describe the waveform.

With a simple square wave, 512 are used to denote 100% positive, then the last 512 points are used to denote 100% negative.

Now when we add spikes, they are added at the start of the leading edge of a waveform's maximum positive and/or negative points, depending on settings. (+ Spike, -Spike)

With a simple square wave, you only get two spikes. When you have multiple wave cycles in use, things can get more interesting.

Anyhow, with a spike length of 2, the first 2 of the 512 data points are used to denote 100% positive, then the remaining 510 points are used to denote the positive at the ratio you are using. A ratio of 2, means that the spike is twice the rest of the power, so you will note the rest of the square wave's positive side is at 50% power.

Same goes for the negative portion of the waveform.

If we use a number like 32, the spike ceases to be a spike. Now we are applying a 100% positive signal for 1/16th (32 of 512 data points) the time, before power drops off to 50% (ratio 2).

If you were after a stair step effect, then use of the length 170 would allow the first 3rd of the square wave to be at 100%, then the remaining 2/3 would be at 50%.

The idea though behind a spike is a brief momentary burst of power over the nominal amplitude. When we do this, we create a rich set of harmonics. If you have a spike length set too long, then the effect is weakened.

Therefore, a value of 1 or 2, maybe 4 works well.

Furthermore, if you have multiple wave cycles in the waveform, then you have less data points to describe each cycle. So keep this in mind if you use large values for the length, to create interesting wave forms.

To give you an idea what I mean, let's say you set your wcm to 5. Now each square wave only has 204 points to describe the square wave - 1024 / 5. If you used a spike length of 170 still, it would be more data points than available due to the 1/2 point being only 102.

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