DM-1801 DMR Microphone Level

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Fecskebeka
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Re: DM-1801 DMR Microphone Level

Post by Fecskebeka » Wed Aug 18, 2021 1:16 pm

Radios are often used in noisy environments. So you may not have the microphone overstretched. Then they speak up close, anyway.. :)
THX.

VK3KYY
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Re: DM-1801 DMR Microphone Level

Post by VK3KYY » Wed Aug 18, 2021 11:27 pm

We are aware of a bug when adjusting the DMR Mic gain, this doesnt work correctly, because one of the gain multipliers in the DMR chip is not being configured when the Mic gain option is changed on the options screen

But if you set the DMR Mic gain to the maximum and reboot the radio, that will set the DMR mic gain to the maximum, becuase the multiplier is being set correctly when the radio boots up

UA0LMC
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Re: DM-1801 DMR Microphone Level

Post by UA0LMC » Fri Aug 20, 2021 2:19 am

VK3KYY wrote:
Wed Aug 18, 2021 11:27 pm
We are aware of a bug when adjusting the DMR Mic gain, this doesnt work correctly, because one of the gain multipliers in the DMR chip is not being configured when the Mic gain option is changed on the options screen
As I've mentioned before, the low mic gain problem was on all of my Baofengs, even those without DMR at all. No wonder, considering copy-paste driven development, when schematic design flaws are literally migrating for years from one radio model to another. Software can compensate this to some extent - but IMO this particular problem is solely hardware-related.

Other DMR-capable radios I could test (Motorola, Anytone, Kydera, TYT) have no such mic gain issue.
Fecskebeka wrote:
Wed Aug 18, 2021 1:16 pm
Radios are often used in noisy environments. So you may not have the microphone overstretched. Then they speak up close, anyway.. :)
THX.
Agree with that, too much mic gain is just as bad as too low. However, you can play with resistor value to achieve the optimum gain for your needs, and then fine-tune it with menu options.

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R3FH
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Re: DM-1801 DMR Microphone Level

Post by R3FH » Sat Apr 30, 2022 5:51 pm

I am not an expert on SMD soldering. I solved this problem with the Bao-1801 by drilling a hole for a microphone in a larger case. So that it would not be obvious, I put a piece of black felt fabric into the hole. At the level of +9 dB in the DMR mode, the signal level was quite tolerable according to correspondents. This, about ten more walkie-talkies of my friends were finalized.
PS. Do this only by disassembling the radio station case, otherwise you will pierce the microphone.

yo3tco
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Re: DM-1801 DMR Microphone Level

Post by yo3tco » Fri Mar 31, 2023 7:35 pm

UA0LMC wrote:
Mon Aug 16, 2021 9:27 pm
DL2NEQ wrote:
Sat Jul 17, 2021 11:52 pm
It should not be a mechanical problem.

I even tried different electret microphones with some wires and open transceiver housing.
So the GD77 seems to be the better overall radio. Although I like the additional buttons of the DM-1801.

But performance on DMR seems to be limited then...unless somebody has an idea what needs to be changed hardware-wise.
There seem to be no schematics available for the DM-1801 (at least I couldn't find them yet).

73,

Daniel
All of the Baofengs I have or ever had (BF-T1, UV-5r, RD-5r, DM-1801 and DM-X) were suffering from the same problem of insufficient mic gain.

The solution is to replace a mic load resistor (the one between mic+ and power supply), this will increase a mic internal amplifier gain (more resistance means more gain to some extent). Original resistor values are from 0.82k to 1.2k depending on radio model, which IMO is very low. From my experience the optimal value is about 3.3k to 6.8k.

For dm1801 I've attached a (poor quality) photo, you need to replace the smd0402 resistor outlined in red. Much more common smd0603 just barely fits there.

I modded my dm1801 with 4k7 smd0603 resistor salvaged from an old PC motherboard, now DMR mic of -6dB (yep, that's minus 6dB) and FM mic of about 3 are just fine.
Hi,

any chance for a Rd-5r location for that resistor component? would love to make this mod.
Thx! 73!

Chris

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