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We have an issue with regulatory testing where our lab reported EIRP varies significantly between separate labs who have tested for FCC and another country. The test methods are quite different. The lab that tested for the FCC filing used a radiated method where the DUT power was measured then a signal generator and known value antenna are used to replace the DUT. Power is adjusted on the signal generator until the same power is read at the RX antenna. That power setting is reported as the EIRP. The second method involves a straight radiated measurement without substituting any other equipment. As a result one of the labs reported 6uW while the other reported just under 2mW.

We are currently working with the labs to see if there was an issue with either test methodology where we could retest. Has anyone experienced similar issues when using different labs, and how did you ultimately solve the discrepancy?

Thanks

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  • \$\begingroup\$ So you are comparing conducted vs radiated? Exactly how would comparing conducted vs radiated help? Are you filing for unintentional or intentional radiator? \$\endgroup\$
    – Voltage Spike ♦
    Commented Jun 18, 2019 at 19:06
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    \$\begingroup\$ For FCC 15.b they specify how the testing is to be done. Radiated RF/EMI is always done via an antenna, I've never heard of that being done conducted. Conducted is for noise conducted back onto the mains supply, and a LISN will be used to measure that. \$\endgroup\$
    – Aaron
    Commented Jun 18, 2019 at 21:30
  • \$\begingroup\$ There are two methods that are specified by the two different countries. There is a radiated method where the DUT is powered up and a measurement of the power is taken. The DUT is then removed and a signal generator and known gain antenna are used. The power of that system is changed until the same reading is obtained. That is reported. \$\endgroup\$
    – GLM
    Commented Jun 19, 2019 at 17:39
  • \$\begingroup\$ Did you fail one of the measurements? \$\endgroup\$
    – Leroy105
    Commented Jun 19, 2019 at 18:12
  • \$\begingroup\$ We did not, but according to IEC 60601-1-2 we need to report our power. However, we have two different test labs that report different results, so which do we publish? Of course that's a rhetorical question and the answer lies more in getting a correct result instead of choosing out of the two we currently have. \$\endgroup\$
    – GLM
    Commented Jun 19, 2019 at 21:47

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