Re: DM-1801 DMR Microphone Level
Posted: 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.
THX.
Amateur radio firmware for the GD-77, GD-77S, DM-1801, DM-1801A, RD-5R, MD-9600/RT-90, MD-UV380/RT-3S, DM-1701/RT-84 and MD2017/RT-82 radios
https://www.opengd77.com/
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.
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.Fecskebeka wrote: ↑Wed Aug 18, 2021 1:16 pmRadios are often used in noisy environments. So you may not have the microphone overstretched. Then they speak up close, anyway..
THX.
Hi,UA0LMC wrote: ↑Mon Aug 16, 2021 9:27 pmAll 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.DL2NEQ wrote: ↑Sat Jul 17, 2021 11:52 pmIt 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
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.