Flat audio (9600baud G3RUH) data port from SP/MIC?

[yu4tet]

Hi all,

I have a question and/or suggestion on how to make the UV380/UV390 the go-to radio for the digitally oriented Amateur Radio operators.

I’m curious, would it be feasible to make “flat audio” analogue mode available on the UV380/390 models?

From my understanding, high-cut filter, low-cut filter and emphasis/deemphasis is done via DSP in the chip, and can be switched off. This info comes from talking in Matrix with one of the developers from the OpenRTX.

There was only one handheld radio that I am aware of that had this ability, the Kenwood TH-F6A in US and the TH-F7E for European markets. It had the ability to set the SP/MIC connection to Data, and then to select the 1200buad, or the 9600 baud (which was the flat audio setting). This made it a very versatile radio. It is no longer in production, unobtanium, and prohibitively expensive when you do find it.

If this is to be implemented in the MD UV380/390, it would make it the only one to have this ability, and make it very versatile. A ham operator can use one device for DMR, AX.25 at 9600 baud (G3RUH), Vara FM WIDE, 4FSK AX.25 (like MMDVM-TNC and NinoTNC are developing), M17, etc.

I’m a cash strapped ham, and I can’t afford a radio for each functionality. This would be very useful and I’d go and buy the UV380 in a heart beat. Any chance this is possible and would be done?

73 de YU4TET

[G4EML]

In theory it would be possible to have flat audio option for the radio, at least as far as the actual RF chip is concerned. However there is no control over the additional audio components in the microphone and speaker paths. So the end result may not have a flat response, especially at the low frequency end.

True flat audio as required by the G3RUH Modem really needs direct connection to the modulator and discriminator which we do not have on any of the supported radios.

So, in answer to your final question, it may be possible but I doubt that any of the current developers have the time to investigate it.

Colin G4EML

[yu4tet]

With external SP/Mic connection, the audio path shouldn't be an issue. One can just make a cable with the connector for speaker microphone. Also, there are ways to adjust frequency response without any additional hw on the audio source in Linux, and Mac, possibly Windows.

This "Flat audio" mode would really be an awesome addition.

[VK3KYY]

With the UV380 the audio would need to have it's electronic routing changed, so that it does not go via the C6000 DMR/FM chip, but there is no volume control in this path.
The TRx chip has limited audio output gain control which is the reason this path is not used.

I also agree with Colin about the other audio components like the audio amplifier chip and it's analogue filtering because of the various capacitors and resistors between the TRx chip and the amp and the jack sockets, all of which will effect the audio envelope

It may work, but it's not something any of the developers have an interest in , or time to persue

We released the source code at the end of last year, so that people with special interests can work on their own modifications, but no one has time to support people working on their own versions


BTW.

There is no clean TX audio path. DMR modulation is generated by the DMR/FM directly varying the master clock oscillator, not via the TRx chip, hence why on all these radios , modes like M17 require people to make hardware modifications to the radio

[VK3KYY]

BTW

The radio can generate 1200 baud using the TRx chip, but I never found a way to route clear Rx audio to the CPU input ADC