During the net, it was noted that Robby EI3GGB had quite a loud buzzing noise on his audio. His voice blocked out the buzzing/hum but the sound was very noticeable in between his words.
Rob was using a TYT MD-380 handheld with a magmount antenna on 70cms.
The buzzing sound sounded very much like mains hum, as if he was using a battery charger at the same time as when he was transmitting. He tried switching from the mains power supply to just a battery pack on its own but to no avail.
Through a process of elimination, we eventually traced the problem back to an external speaker mike.
It would seem that the problem is the RF signal on transmit is getting into the speaker mike and causing interference. We don't know yet whether the RF is getting into the electronics in the microphone or via the lead and into the radio.
Robby bought the 'Kenwood' speaker from China but it's not clear whether it's the real deal or just a clone. Hopefully the RF interference can be cured by using a simple clip on split ferrite core which Robby is going to source.
If you are using DMR and people start saying that your audio is distorted, noisy or buzzing then try removing the speaker mike if you have one.
2 comments:
Ferrites are not the answer. Owen duffy does a neat internal mod on converting mics for dmr use with an inductor https://owenduffy.net/blog/?p=12850
A ferrite core is an easy first step for anyone to take and if it works, it works. Modifying the inside of the mic is fine if someone is comfortable doing that kind of mod.
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