This is how FPV jammers are often field-checked in Russo-Ukrainian war. It doesn't test frequencies or spectrum quality, but is a useful indicator, that jammer is actually emitting (has power and is turned on), so you can be sure, that if it's up to spec and covers frequently used frequencies at your location - it actually tries to do it's job, instead of being a costly paperweight.
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This is how FPV jammers are often field-checked in Russo-Ukrainian war. It doesn't test frequencies or spectrum quality, but is a useful indicator, that jammer is actually emitting (has power and is turned on), so you can be sure, that if it's up to spec and covers frequently used frequencies at your location - it actually tries to do it's job, instead of being a costly paperweight.