The Hytera MD785(G) DMR transceiver works great out of the box, both analogue as digital. But there is one problem. Noise coming out of the speaker. Even when the tansceivers audio gain botton is set to zero. When the squelch opens, noise can be heard. There is no way to fix this in the firmware of CPS codeplug by programming.
The modification is to put a 22 Ohm resistor in serie with the speaker. So, hardware needs to be mobified. The good news: The modification is easy and no SMD needs to be soldered. Just remove the front of the MD785, carefully remove the flatcable and put a 22 Ohm (variable) resister in series with the red speakerwire. That’s all.
Now reprogram you radio and set the speaker output level for both analog and digital by +2 or +3 db as compensation for the resistor you’ve just placed. Upload the codeplug and you’re done. The noise is gone.
Step 1: remove the front and *carefullly* remove the flatcable if you need more space.
Step 2: Put a 22 Ohm (variable) resistor in serie with the red speaker wire. Adjust the resistor if you feel the need to do so by a few Ohm.
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Thanks guys for great tip! I tore into one of these radios to made audio section design changes, but too much surface mount stuff. Hytera refuses to acknowledge this problem for the MD782 USA model.
You note a 22-ohm fixed or variable in the narrative, but 220 ohm in the picture. Which one is correct? I suspect the 22….
Author
Thanks for noticing. It should be 22 Ohm. And the modification should also work fine for the MD782 (US) versions.
Hi
I have done the mod I can’t see where in the CPS I need to adjust please can you assist me in telling me where I need to adjust.
Hello Randy,
Where can I find the section in the code plug to reprogram the radio and set the speaker output level for both analog and digital by +2 or +3 db?
Have you found where the setting is for output level? I can not find it either.
Did you ever find out where the setting is for the oudio output ?
Did you ever find the section in the codeplug for the speaker output?
I got a Harris Momentum HDM150….basically a Hytera MD782….everything else seems to work fine but no digital audio out for receiving and transmitting…anyone know what is wrong with the unit…?
I use an external speaker in my moble mounted MD782, and I don’t hear the hiss there. I do hear it on the MD782 that I have in my Ham shack.
Hytera amazes me, they want to sell as many radios as possible, yet they refused to acknowledge this problem.
Does the 22 ohm resistor lower the noise, or completely remove it. If the resistor lowers the volume, an you increase the volume to compensate, is the noise still there?
I think a mod that sense the audio, and keeps the speaker off until the audio level increases, would do a better job.
Certain older version of the radio may not have had the noise issue. Don;t know the cutown serial number.
The 22 ohm only reduces the noise to tolerable level in a vehicular environment. Of course, the desired audio level is reduced by an equal amount. If you have to have a loud setting, you must tolerate some distortion as well.
The Hytera external speaker on mine had the noise as well. That is why I purchased the external speaker (with the hope it would get resolved).
where can i find a 22ohm variable resistor i can only find standard 22ohm ones thanks
I just used a 22 Ohm resistor.