Buckshot,Splatter and Scopes


Bob, K2CU said:

"While working on the Precision AM Detector, I discovered just how many of the guys on AM over modulate in the negative direction, cutting off their carrier on voice peaks, and splattering up the bands". 

Tom, K1JJ's reply:

Yes, it's easy to take it for granted that everyone has a scope and closely watches their negative peaks for carrier cut-off.

You are correct...even a perfectly clean AM transmitter will double or triple it's normal bandwidth by hitting greater than 100% negative.

What do we do? Have a "modulation percentage check week" where a number of guys with scopes on their receivers give out good and bad reports to everyone on the AM bands...to make awareness? That would probably work.

I think some of us sometimes bury our heads in the sand thinking that if no one says anything bad about our audio then we MUST be clean...and keep turning it up until someone does.

Maybe the problem is that most AMers are too polite to say anything about a spattering signal and just let it go..the easist way to avoid conflict.

About splatter and normal side products - the word "splatter" has always meant a negative connotation to me. I hear it said on the bands often... "there is splatter coming from the AM QSO 4kc away"...HA!

I think the term "splatter" should be grouped with the words "buckshot" and "garbage". "Normal side chatter" is more accurate if they are clean and we are too close in... There's better terms out there too.

Finally, back to the main point... it should be an AMer rule to have a scope in the shack monitoring the RF transmitted waveform...no other way to know what's going on. Like flying blind without it.

Almost like driving a car with ice covering the windshield until someone beeps the horn at you.
Everyone NEEDS a decent scope! - and watched like a hawk.

Everyone splatters at one time or another. Believe me, I've done my share in the past without knowing any better. But, what we do about preventing it in the future is what sets us apart.

It's simply a matter of making sure that the center of our carrier never becomes a thin line on the scope, as well as the peaks staying rounded and not flat topping...easy!

Tom, K1JJ

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