1400 Bridge coax connection question

Unanswered Question
Jun 6th, 2009
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I have two AIR-BR1410A-A-K9 bridges that I need to use for connecting a vehicle to a building network. The bridge on the building will use the conventional mount and network connection. The other bridge is going on top of a vehicle (bigger than a UPS truck, smaller than an 18-wheeler). There are several existing coax runs from the interior of the vehicle to the roof of the vehicle. All runs terminate with an N connector inside and an NMO outside and are 50 ohms. I would like to use these runs for the Bridge, but the F-connectors/cables for the 1400 are 75 ohms.

Specifically, I want to put the injector inside the vehicle and use the existing vehicle coax runs and mount the bridge on the roof of the vehicle. I have found the F-to-N and F-to-NMO adapters. What kind of trouble am I going to run in to running the Ethernet and power over cables/connectors with mismatched impedance? I'll try to step through the entire run:

Ethernet 100Base-T and DC Power connects to the injector

F-type coax (75 ohm) cables from injector run 4 feet to connect to F-to-N adapter (not sure what the impedance is here)

F-to-N adapter connects to N connector at coax patch panel inside vehicle (50 ohm at panel connector)

Patch panel coax travels approximately 40 feet to roof-mounted NMO connector (50 ohm)

NMO-to-F coax adapter connects to NMO (not sure of the impedance here)

F-coax runs 10 feet to Bridge (75 ohm)

Will this work, or do I need to build a couple of transmatch stubs (I assume I would need one at each end)?

I have a good RF guy working with me on this project, but we are stumped since the coax carries the ethernet and power, not "normal" RF signals.

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scottmac Sun, 06/07/2009 - 05:47
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Should be no problem.

There will be some additional loss on the radio signal, there will possibly be a small amount of stress on the transcievers, but nothing it can't handle.

As for the power; it's DC, so there is no "impedance" to the conductors, just plain'ol' DC resistance ... which will be virtually identical between the two type of cables (50 and 75 ohm coax).

Good Luck


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