Hytera PD/MD785 “Waterfall” noise

I love the Hytera PD785 and MD785 radios. When compared to my Motorola DP4800 and DM4600, it only took me a few hours to decide that I prefered the Hytera but there was one thing that I didn’t like, the ‘comfort squelch’ as Hytera call it.

The ‘comfort squelch’ is a waterfall/hiss noise that is present on transmissions. If a user stops talking then the hiss is audible and I guess its intention is to let you know there is still a signal. Anyway, it’s not good but there is an easy fix.


This modification involves open case surgery on these expensive sets. They are small and easy to break so don’t attempt unless you are either very skilled or don’t mind breaking it or melting plastic parts.

There’s no need for a big long post about this. It’s very simple. You just add a resistor inline with the speaker and then turn the audio gain up in the CPS.

I went with a 47 Ohm resistor in the MD785. Just take the head off the radio and solder it in.

The PD785 is a little more difficult as it has less room and the speaker is attached with a flat ribbon cable. You need to remove the case screws (2 on the back and one on each side) and remove the castle nuts from the antenna connector, volume and channel selectors.

Then you can remove the radio chassis and install the resistor on the speaker. I tried several and settled for 120 Ohms. I also placed a small piece of insulation tape over the area where the resistor connected to the ribbon cable.

That’s it. A very simple mod but a little tricky. Worth doing if you dislike the hiss!

2 Replies to “Hytera PD/MD785 “Waterfall” noise”

  1. Hi
    I have an MD785 with a destroyed ingintion sense circuit. I can’t find any good quality pics of a circuit board or circuit diagrams to be able to work out which components have been burnt out.

    Would you be able to take a pic of your radios PCB and send it to me?


  2. Next time I need to take it apart I will take some photos and post them on my site.

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