OFF topic... (or not)

User avatar
EB3AM
Posts: 204
Joined: Fri Jan 24, 2020 1:40 pm
Location: Catalonia, not Spain
Contact:

OFF topic... (or not)

Post by EB3AM » Fri Apr 16, 2021 10:29 am

https://www.instructables.com/Arduino-Walkie-Talkie/

A fully functional WT made with a chinese modules ...

Image

VK3KYY
Posts: 7478
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: OFF topic... (or not)

Post by VK3KYY » Fri Apr 16, 2021 9:39 pm

Interesting what can be built from modules.

But it would possibly cheaper and easier just to buy a cheap Baofeng dual band FM transceiver and replace the microcontroller with one that could be easily programmed.

The main limitation with the current generation of Chinese VHF / UHF radios is the use of the AT1846S RF chip , which is now quite an old design.

I think there may be a new variant of the chip in some Anytime radios, but AFIK its still just a FM triband chip and does not allow access to the internal SDR core if the core is SDR at all

What we need is a new generation IC with full SDR to allow AM and SSB etc, and radios where the CPU has direct access to the audio from the RF chip.

Umm. That's a thought , I could do some simple hardware modifications to one of my many GD77 radios to bypass the DTMF bandpass detector, then I could attempt to decode other digital modes

SP2ONG
Posts: 45
Joined: Sat Nov 16, 2019 9:47 am

Re: OFF topic... (or not)

Post by SP2ONG » Sat Apr 17, 2021 10:54 am

Yes, it's an interesting idea with GD77, in a similar way programmers were looking for a solution as for MD-380 using M17 (Codec2) they made modifications bypassing the HR_C5000 :

https://openrtx.org/#/m17_mods

Maybe in a similar way you can do it with the GD 77 / DM-1801?
VK3KYY wrote:
Fri Apr 16, 2021 9:39 pm
Umm. That's a thought , I could do some simple hardware modifications to one of my many GD77 radios to bypass the DTMF bandpass detector, then I could attempt to decode other digital modes

VK3KYY
Posts: 7478
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: OFF topic... (or not)

Post by VK3KYY » Sat Apr 17, 2021 11:09 am

Unforunately there is a not enough documentation for the C5000 or C6000.

Both chips have a FM mode and the chip may have a way to digitise the audio and feed to the MCU via I2S.

I don't think many people would be willing to modify their radio hardware to support other modes like M17.

Perhaps if the mode was another existing standard like P25, or YSF or DStar pople may be interested.

But overall these radios are not designed to operate on any other digital mode than DMR

SP2ONG
Posts: 45
Joined: Sat Nov 16, 2019 9:47 am

Re: OFF topic... (or not)

Post by SP2ONG » Sat Apr 17, 2021 3:53 pm

So it will turn out that people will not modify the radio, which they have, rather, if it is already, then you should consider buying a radio for the M17 to modify, so DM-1801 due to the price on Aliexpress $ 55 is such a compromise to try and find equipment to work an M17 where it is not hardware vocoder needed. But I realize that to get to work on the M17 DM-1801 it will probably require a lot of effort, but in my opinion, it is the only chance for the M17 to gain more popularity among radio amateurs. Create repeater on M17 is now easy because it is enough to do MMDVM and MMDMHost compilations in the version with M17 support and do, for example, MMDVM DMR + M17 compilations and such repeater already work only now access to radio equipment for the end-user and DM-1801 can be this way to achieve the goal.

Currently, many ham radio operators work on M17 reflectors using the USRP2M17 application to create route analog audio to M17 or DMR2M17

Anybody can try test M17 via Analog Reflector: https://allstar.dvswitch.org:8090/html/hUC-min.html
(info from https://dvswitch.groups.io/g/Analog-Ref ... essage/649 )

User avatar
EB3AM
Posts: 204
Joined: Fri Jan 24, 2020 1:40 pm
Location: Catalonia, not Spain
Contact:

Re: OFF topic... (or not)

Post by EB3AM » Fri Apr 23, 2021 10:04 pm

I also think that if you could find an economical walkie capable of processing codec2 it would be a shock.
Right now I think most radio amateurs are disappointed with the policy that the big companies in this world have. Some make D-stars, Fusion ... and, above all, do not let rivals use their technology. This far from selling equipment, ends up making no one buy any digital technology so there is no consensus.

The DMR is a patch that has caused many people to get into digital systems because the price is very economical.
That doesn’t take away from the fact that we’re talking about a technology that’s not meant for us. Slots, colors, TDMA ... All this is designed for business environments.
The equipment that comes into our hands is cheap, with very fair firmware and not at all effective for how we want to use them.
We were lucky (are we?) That a bunch of crazy people have made fabulous firmware that would turn mediocre radios into the best ever seen.
Thanks for that. I would never have used a DMR radio if this firmware had not appeared.

Now, another group of people is fighting for a brand-free digital standard, which ideally can run on economical hardware. An sdr is a good choice. It may be some current equipment can run on M17, I don't know. But I know that if they get the right hard it can work. The MChf is working, an economic equipment that works in any analog system and also in FreeDV (codec2) in HF.
There is the idea of ​​making a version with VHF and even UHF ... Nothing is impossible. Although unscrupulous manufacturers copy the hardware and lower the quality of the original, more and more we choose free software, and, if possible, free hardware.
A VHF / UHF radio with a processor capable of decoding codec2 is not a chimera, it already exists. In Open Hardware, and probably also in some model walkie for sale, as long as we can change the firmware.
The M17 should lead the unification of digital systems. I don’t think it will happen tomorrow, it will depend on how many people sign up for this mode.
I, at the moment, am reconfiguring the MMDVM nodes that we have in our country to be able to work this modality ... Let's see when we can listen to M17 transmissions ...

VK3KYY
Posts: 7478
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: OFF topic... (or not)

Post by VK3KYY » Fri Apr 23, 2021 10:48 pm

It would be possible to make the OpenGD77 use codec2 for DMR instead of the ambe codec.

The DMR specification does not define what codec must be used. ambe is used because Motorola etc chose it.

Last year I contacted David Rowe about how to use codec2 in the OpenGD77, however he was too busy to help and explain how to do this, but he did think it would be compatible.

AFIK the DMR audio data has to include a specific type of Forward Error Correction. I don't know if codec2 uses the same FEC or whether it any FEC or anothe type of FEC.

Without FEC it may be possible to transmit to other radios directly via simplex, but the data would get mangled by MMDVMHost as it applies FEC correction to the signal received by hotspots etc.

The other thing I don't know, is the compile size of codec2. There is not much space remaining in the MCU ROM. Perhaps 100k max, perhaps less.

If codec2 is quite small, e.g. 50k - 100k, it would be possible to include both the ambe and codec2 in the firmware, and switch via a menu option.

But if codec2 is bigger, either some features would need to be removed, e.g. hotspot mode, power saving, voice prompts etc.
So make more space available

Or have a version which is only codec2.

However a codec2 only version would only be of interest to experimenters, and not the wider ham community, as the OpenGD77 would be the only radio to offer codec2 over DMR.

Also, probably DMR MARC and BM may not allow use of codec2 on their networks, as all other users don't have this functionality.

Probably FreeDMR allow it, but I would need to check with the admins for FreeDMR

SP2ONG
Posts: 45
Joined: Sat Nov 16, 2019 9:47 am

Re: OFF topic... (or not)

Post by SP2ONG » Sat Apr 24, 2021 7:33 am

I agree with what Jordi wrote.
Roger I think that at the present moment it should not be considered to use Codec2 in DMR instead of AMBE because of the reasons you wrote about the network BM they will not allow it. But concentrating the forces on M17 and providing the firmware for DM-1801 / GD77 with M17 Codec2 support would give a chance that this standard will take over among hamradio and then there is a chance that maybe large networks BM etc states that it is worth allowing the use of Codec2 in their networks.
If it was possible to make the M17 with Codec2 usable without modifying the hardware radio, the M17 Codec2 on the DM-1801 / GD77 would be such a big jump in DV as it happened with OpenGD77, which made the DMR hamradio friendly for many. Rather, you should expect people to buy as a local M17 radio and not modify the current one. Most will be using OpenGD77 and if the M17Codec2 firmware is available on the DM-1801 a lot of people will buy a 55$ radio and when the M17 becomes popular it will be an easier way to switch from DV Hamradio to Codec2 in DV.
We also locally try to upload MMDVM software to local repeaters with DMR / M17 support, because it can be done when MMDVM and MMDVMHost versions are available, so if there is HT radios with M17 support, we will be able to use it on RF. We are currently using the DMR to M17 transition through available tools like USRP2M17 DMR2M17 and therefore we are popularizing M17 among local hamradio

73 Waldek

SP2ONG
Posts: 45
Joined: Sat Nov 16, 2019 9:47 am

Re: OFF topic... (or not)

Post by SP2ONG » Sat Apr 24, 2021 7:55 am

But I agree with Roger that under FreeDMR (I have my local DMR server running on the basis of HBlink ) where people like to experiment if OpenGD77 were able to switch codec from AMBE to CODEC2 I think a lot of people would start using CODEC2 as part of DMR as well. It could be considered 2 ways to add (if possible CODEC2 to OpenDG77) or write separate M17 Codec2 firmware GD77 / DM-1801 for M17 network

73 Waldek

VK3KYY
Posts: 7478
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: OFF topic... (or not)

Post by VK3KYY » Sat Apr 24, 2021 9:15 am

SP2ONG wrote:
Sat Apr 24, 2021 7:33 am
I agree with what Jordi wrote.
Roger I think that at the present moment it should not be considered to use Codec2 in DMR instead of AMBE because of the reasons you wrote about the network BM they will not allow it. But concentrating the forces on M17 and providing the firmware for DM-1801 / GD77 with M17 Codec2 support would give a chance that this standard will take over among hamradio and then there is a chance that maybe large networks BM etc states that it is worth allowing the use of Codec2 in their networks.
If it was possible to make the M17 with Codec2 usable without modifying the hardware radio, the M17 Codec2 on the DM-1801 / GD77 would be such a big jump in DV as it happened with OpenGD77, which made the DMR hamradio friendly for many. Rather, you should expect people to buy as a local M17 radio and not modify the current one. Most will be using OpenGD77 and if the M17Codec2 firmware is available on the DM-1801 a lot of people will buy a 55$ radio and when the M17 becomes popular it will be an easier way to switch from DV Hamradio to Codec2 in DV.
We also locally try to upload MMDVM software to local repeaters with DMR / M17 support, because it can be done when MMDVM and MMDVMHost versions are available, so if there is HT radios with M17 support, we will be able to use it on RF. We are currently using the DMR to M17 transition through available tools like USRP2M17 DMR2M17 and therefore we are popularizing M17 among local hamradio

73 Waldek
I think the OpenRTX are already trying to do this, but they have to modify the hardware of the radio to connect the FM speaker and mic connections to the MCU chip.

I know the audio signal paths in the GD-77, and there is no direct connection of the mic or speaker audio to the MCU.

The only input from the mic is via the vox input, and this has a low pass filter.
The only connection from the received audio to the MCU is via the DTMF detector circuit, which is a band pass filter, so it would not be usable
There is no connection from the MCU to the mic input of the TRX RF chip.

There is only a path from the MCU to the speaker via the DMR chip, which can send normal audio, becuase its used for the beep

The C6000 DMR chip has a FM mode, which may have the paths required for other modes, but there is very little in the data sheet which explains how to configure the C6000 for FM and I don't know what audio connections are required for FM in the C6000

It is connected to the Rx audio but not the Tx. Possibly the C6000 normally modules the Tx signal in the same way as it does for DMR, by modulating the control signal to the master VCTCXO, but I don't know if thats how it operates.

It may be possible to generate modulation by using the RF freq calibration register in the C6000, but sending data to the calibration register is very ineffecient, and it may not be possible to vary the calibration signal fast enough, because of either the SPI data transfer rate, or the C6000 may also not respond quickly to changes in calibration value.

Overall, you could spend months working on this, and then find its impossible becuase the C6000 does not support it.


It is probably better if anyone wants to access the M17 network, is for MMDVMHost to be modified to convert the DMR protocol to M17 (and vice vera) .

Then if the radio transmits DMR using codec2 then MMDVMHost does not need to transcode to and from AMBE.
It would not be possible to transcode in MMDVMHost, but if the signal is already AMBE then it would not be difficult for MMDVMHost to change the protocol.

But the problem is actually just BM and DMR + / DMR MARC, so why not use the FreeDMR network.

Post Reply