EVX-5400 in race car

[BDixonRacer]

Hi, we have been using EVX-531 and EVX-534 for car to pit communications in road racing applications for a few years. We are going to try some endurance racing and so we bought a EVX-5400 to mount in the car. I am having some trouble getting this radio set up. I have the programming cables and software for all of these radios. I purchased a harness from www.RacingRadios.com to use with the mobile unit, but it was setup for use with a Motorola CM-200D. I changed the connector to the DB-15 shell for the EVX-5400 and attempted to make the proper connections.

The audio transmitted from the EVX-5400 is great.
The audio in the earphones from the EVX-5400 is terrible. There is a constant hum and there is no way to change the volume. The audio received is somewhat garbled as well.
The speaker on the front is always active and I see no way to disable it in the programming software, but maybe I missed the setting somewhere.

Any suggestions?

Thanks!
Brandon Dixon

 

[devicelab]

Brandon, it sounds like the wiring could be off and/or the earphones are not fully compatible. It could be an impedance issue and may require a matching transformer to get the best audio output.

Check Page 4 of the EVX service manual for a detailed explanation of the wiring. You can download the service manual from my link: https://www.dropbox.com/s/q0onsxyhkiwic6b/Vertex_EVX-5300_5400_serv.pdf?raw=1

As far as the volume is concerned, I believe most manufacturer's leave this up to the external accessories to control this level and thus the audio level is fixed from the radio itself. This is by design.

To disable the front speaker, I wonder if a termination plug on the loudspeaker jack would work..? I don't believe that would affect the audio output from the 15-pin port.

Hope this helps!