@N9KWK My understanding: A good handheld+monopole system will be designed with the effect Onno mentioned (ground circuitry + your body being the "other half" of the antenna) in mind. However, it is difficult to evaluate whether a manufacturer has done this, your antenna might or might not match the tested antenna very well, etc. So, there might be some circumstances where a "rat tail" counterpoise could help, but there are also some where it could hurt - it is difficult to make a statement in the general case. Experimentation is encouraged do some tests with your specific radios+environment and see what you find. But also, don't fret too much about it - it's certainly not guaranteed to improve your signal.
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