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Output > ERP
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Author:  Atomic Taco [ Sat Jul 23, 2016 11:17 am ]
Post subject:  Output > ERP
http://wireless2.fcc.gov/UlsApp/UlsSear ... ey=3301972

Definitely not the first time I've seen the output power greater than the ERP. Are they assuming almost a 50% loss between the repeater and the antenna!?
Author:  N7QOR [ Sat Jul 23, 2016 2:55 pm ]
Post subject:  Re: Output > ERP
Atomic Taco wrote:
http://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=3301972

Definitely not the first time I've seen the output power greater than the ERP. Are they assuming almost a 50% loss between the repeater and the antenna!?


Assuming, or perhaps actually calculating

There are many reasons that an outcome like this could occur
Author:  nickcarr [ Sat Jul 23, 2016 2:57 pm ]
Post subject:  Re: Output > ERP
Atomic Taco wrote:
Definitely not the first time I've seen the output power greater than the ERP. Are they assuming almost a 50% loss between the repeater and the antenna!?


Nah the 40w value just refers to the output power of the transmitter -- that the frequency is assigned to. The 2nd value (Max ERP) just refers to what the FCC is "certifying" them to use. So they must comply with that. Ideally, if the system were designed efficiently, then you'd have 40w transmitter probably reduced to only 10w into low-loss coax but a high-gain, roof-mounted antenna. This would save energy and allow for future expansion. (Of course, it's usually 40w into cheap antenna and cheap coax == high loss == 25w ERP...)

Technically, the station is supposed to be under the 25w ERP no matter what (and they can be fined if they're not) but it's not like the FCC has the man-power to check every transmitting station. Usually it would be a secondary violation. i.e. if they're at full 40w of power and ERP is more like 80w ... and they're stomping on Joe Blow Towing... then they could get cited for causing interference and using above their allowable transmitting power.
Author:  chpalmer [ Sat Jul 23, 2016 9:55 pm ]
Post subject:  Re: Output > ERP
Ive got a single antenna combiner system with 4 repeaters connected to it at a customers location. Receive Transmit on same antenna.

The repeaters can transmit at 45watts and are turned down to 40. The loss through the combiner is enough (due to the design) that I get 6watts per channel on the output. With a 6dB antenna and no loss in the feedline Id only have 24watts ERP. But calculating the 1.2dB of loss of the feedline Im more around 18watts ERP.

Truthfully the "Power Out" on an application and license are largely ignored by the FCC these days. They really want to know and control the "ERP". (told that by an FCC engineer)
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