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I'm in the process of applying for an FCC experimental certificate so I can be legal when I purchase a satellite generator.

I found a used (calibrated) generator on eBay and want to know if I need a dummy load on the RF outputs that aren't being used. The is one on the front limited to -110 dBm and the one on the back is labeled CAL/MON and is always on and transmitted at -48 dBm.

I understand those signal levels are VERY LOW. Do I still need a dummy load on the unused port?

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  • \$\begingroup\$ do you mean dBm ? Please add datasheet, etc. describing the generator, I would say in generic, to terminate every unused output. \$\endgroup\$ Feb 10 '17 at 18:02
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    \$\begingroup\$ What does the manual say? \$\endgroup\$ Feb 10 '17 at 18:16
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    \$\begingroup\$ With that low power, pretty much all 50 ohm terminators should be good enough as a dummy load. \$\endgroup\$
    – AndrejaKo
    Feb 10 '17 at 18:21
  • \$\begingroup\$ Yeah, that makes sense. Datasheet shows nothing about terminating unused outputs. \$\endgroup\$
    – Samee87
    Feb 10 '17 at 20:56
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After consulting with the manufacturer, a dummy load is not typically used on signals lower than -70dBm as a rule of thumb. To paraphrase the response I received, the VSWR due to an open load at such small signal levels does not negatively affect transmission line characteristics internal to the generator.

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  • \$\begingroup\$ No. you ABSOLUTELY MUST use a dummy load. I will add an answer shortly. \$\endgroup\$
    – Damien
    Apr 6 at 4:41
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YOU ABSOLUTELY MUST USE A DUMMY LOAD. NOT DOING SO HAS SERIOUS CONSEQUENCES

There is a famous GPS disruption event known as the Portland Spoofing Incident, ironically at the world's largest GPS conference.

It was caused by a professional signal simulator - broadcasting actual GPS power levels of roughly -130dBm - not being fitted with a dummy load.

Whilst it did not penetrate outside the building, it had several consequences:

  • Some phones set their date to 2014, which was the date of the GPS simulation.
  • Some phones were unable to perform normal function like fetching email because of the bad timestamp information.
  • Some phones were unable to recover without a factory fresh firmware reinstall.

So please use a dummy load.

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