Topband: EIRP Measurement

Rick Karlquist richard at
Tue Feb 21 17:58:21 PST 2012

W2XJ wrote:
> If you can find a used FIM 22 it goes from 200 KHz to 550 KHz. That said
> I can not see determining EIRP by field measurement. There are just two
> many variables and a degree of engineering skill not posessed by the
> average amateur. The various national authorities must have a means of
> measurement accessible to the average operator and is easy to enforce.
> Then as I stated previously there is the interference problem. The
> signal measured along the ground will be less than at higher angles.
> Skywave interference will be greater because the real EIRP will be
> exceeded and by a large amount in some cases.

The RF ammeter test merely measures the total radiated power.
It does not account for the effective signal strength at some
skywave angle.  If it is true that the skywave is stronger than
the ground wave, then the power would need to be backed off,
but there is no way to determine how much to backoff without
a helicopter field measurement.  It would depend on ground conductivity,
so there would be no way to calculate it or model it accurately.

Rick N6RK

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