Topband: EIRP Measurement

W2XJ w2xj at
Wed Feb 22 08:50:42 PST 2012






That is not what I said. The skywave would only be stronger if field
measurements on the ground were used to determine power due to various
ground losses, ground conductivity, etc.  when an RF ammeter is used for
measurement (standard practice for MW installations) The maximum EIRP
before ground losses is at the zero degree azimuth. Skywave will have a
lower EIRP.

Having designed and built MW facilities for over the last 40 years, I
and anyone else who has can attest to the irregularity in field strength
when radials are measured. When the measurements are matched to the best
fit ground conductivity curve the variations in signal strength above
and below the theoretical can be significant in many cases.

On 2/21/12 8:58 PM, Rick Karlquist wrote:
>  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
>  _______________________________________________
>  UR RST IS ... ... ..9 QSB QSB - hw? BK

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