Racing radios PTT booming

Hi all,

So I’ve recently purchased a complete 2 way radio setup from Racing Radios. It is for our endurance go karting team.

I am in Australia and only after purchasing it found out the radios supplied were not in compliance for use in Australia which was completely my fault.

I’ve since purchased a pair of Motorola SP476 handsets. The original radios supplied were BPR40’s.

The kit consists of a headset with speakers and mic for the crew person and ear buds and a mic for the drivers to have in their helmet.

My big problem is that when the PTT button is pressed by the driver (its a steering wheel mounted PTT) the crew person is getting a loud boom almost “DOINK” like noise.
The exact same thinf is happening to the driver and when the crew person releases their PTT (mounted into the headset) the driver gets the same noise but twice as bad as they are wearing ear buds inside their ears. The worst of the noise seems to be as the PTT is released or no longer depressed.

The quality of the transmission is quite good while the PTT is depressed but as song as it is released it gives an almost instant headache due to the loud booming noise (I tested them 3 hours ago and my ears still slightly ache)

The noise is exactly the same either with the SP476 or the BPR40’s.

I would love to get some insight from anyone who might understand why it does it and if there is a way to eliminate it or at least minimise it. Otherwise it’s back to the drawing board and finding a different system as it is almost unbearable.

Thanks :slight_smile:

Just to add a bit more info to this, when using the radio PTT the loud “doink” noise at the end of the transmission doesn’t exist. It is only heard when you introduce the supplied external PTT on the vehicle as well as the headset PTT. It is only heard by the receiving radio.

Hope that helps explain a bit more and if anyone could give some insight.