Experimental version with option to disable CC filtering

F6GVE
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Re: Experimental version with option to disable CC filtering

Post by F6GVE » Sat Feb 22, 2020 11:14 am

Disabling CC often gives me a weak DMR decoding (needs a strong signal to be clear) BUT is very usefull even like that

I can scan some UHF segment with no filtering in order to discover some new DMR frequencies. When I ear something, even if not good, I can pick up the frequency and focuse on it to determine the CC with CC scan or do it manually.

I find this option very interresting.

Luc
73

IZ2EIB
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Re: Experimental version with option to disable CC filtering

Post by IZ2EIB » Sat Feb 22, 2020 12:08 pm

VK3KYY wrote:
Sat Feb 22, 2020 1:01 am
Thanks to some research from Colin G4EML, we have been able to disable the Colour Code filtering inside the HR-C6000 DMR chip
Colin, Roger, great catch!
VK3KYY wrote:
Sat Feb 22, 2020 1:01 am
I've modified the DMR filtering in the options, so that the list is now

NONE
CC
CC,TS
CC,TS,TG
CC,TG,Ct

when CC filtering is disabled, the Colour Code display e.g C1 is shown in inverse video
Thank you Roger!
In my opinion it might help to identify repeaters and hotspots and in case of interference.
VK3KYY wrote:
Sat Feb 22, 2020 1:01 am

There is no shortcut to change the radio to the Rx signal CC.

So if CC filtering is disabled, you may transmit on a different CC to the Rx CC, even though you can clearly hear the signal
Would not it be possible to stem the thing by simply removing the ability to transmit when the CC filter is enabled (only RX)?

VK3KYY wrote:
Sat Feb 22, 2020 1:01 am
I think possibly we may be able to speed up the CC scan function, by briefly disabling the CC filtering and then checking the received CC over several frames and then calculate which is the most likely CC for the Rx signal to be using.
I don't think we can simply use the first CC on the Rx signal in this case, as the received CC value may not be 100% accurate when the CC filtering is disabled.
Excellent thought Roger!
Although honestly I do not often use that function and in any case I do not consider it lacking in terms of speed.
As I have already written before in other occasion, from my side every added feature is welcome, as well as any improvement.

Thanks for everything Roger!

73 best regards de Fabio IZ2EIB

VK3KYY
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Re: Experimental version with option to disable CC filtering

Post by VK3KYY » Sat Feb 22, 2020 9:03 pm

Colin has sent me some updated code which may help fix the noise problem

I have also had some ideas about how this system can be improved.

I am not a statistician, so I don’t know the best algorithm for this, but the firmware can still read the CC of the signal.

The CC value may contain noise, and hence not always be the same number, but if for example, I store a list of the CC code that is received, and how many times each code number is received, I could search the list and find the value with the highest number, and this would be the CC of the signal.

Obviously, if the signal was extremely noisy then he same number of each CC code could be received for several adjacent CC numbers, but it’s probably better than just turning on the audio for all received CC codes

Because I have a debugger soldered to the inside I the radio, I can send these statistics to the PC screen terminal and plot them in a spreadsheet to see the spread of CC numbers.

Actually we could draw this as a graph on the screen of the GD77 but it’s not necessary

TA2ISO
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Re: Experimental version with option to disable CC filtering

Post by TA2ISO » Sat Feb 22, 2020 9:46 pm

I just tried this version of the firmware and noticed that it displays some private calls on the screen and there is a garbled noise. Before there was no audio. Haven`t had the chance to try this with a group call but so far it decodes the dmr signal, even i set the color code deliberately wrong (I have set CC to 10 while the correct one was 11 and it still worked just as expected).

VK3KYY
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Re: Experimental version with option to disable CC filtering

Post by VK3KYY » Sat Feb 22, 2020 9:51 pm

TA2ISO wrote:
Sat Feb 22, 2020 9:46 pm
I just tried this version of the firmware and noticed that it displays some private calls on the screen and there is a garbled noise. Before there was no audio. Haven`t had the chance to try this with a group call but so far it decodes the dmr signal, even i set the color code deliberately wrong (I have set CC to 10 while the correct one was 11 and it still worked just as expected).
I think that disabling the CC filer should not actually disable the filter.

What this feature should do is analyse the Rx CC and decide what the code the signal is being transmitted on, and then just set the normal filtering to that code.

The user just thinks that the CC is open, but thats not technically how it really works.

TA2ISO
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Re: Experimental version with option to disable CC filtering

Post by TA2ISO » Sat Feb 22, 2020 9:59 pm

VK3KYY wrote:
Sat Feb 22, 2020 9:51 pm
TA2ISO wrote:
Sat Feb 22, 2020 9:46 pm
I just tried this version of the firmware and noticed that it displays some private calls on the screen and there is a garbled noise. Before there was no audio. Haven`t had the chance to try this with a group call but so far it decodes the dmr signal, even i set the color code deliberately wrong (I have set CC to 10 while the correct one was 11 and it still worked just as expected).
I think that disabling the CC filer should not actually disable the filter.

What this feature should do is analyse the Rx CC and decide what the code the signal is being transmitted on, and then just set the normal filtering to that code.

The user just thinks that the CC is open, but thats not technically how it really works.
I think i understand, so it is just detecting the RX CC and setting the filter to use that to monitor the DMR signal.(DMR chip limitation, no way to totally disable the filter ?) I will be testing it on more DMR frequencies by Monday, hopefully.

VK3KYY
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Re: Experimental version with option to disable CC filtering

Post by VK3KYY » Sat Feb 22, 2020 10:23 pm

The filter can be totally disabled, but it now lets too much noise into the DMR system.

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KV0A
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Re: Experimental version with option to disable CC filtering

Post by KV0A » Sun Feb 23, 2020 2:43 am

I'm still a little unsure how the Ct filtering works. Does this make it so that if you're on a private call then everything except the private call is filtered?

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Ik0nwg
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Re: Experimental version with option to disable CC filtering

Post by Ik0nwg » Sun Feb 23, 2020 2:56 am

VK3KYY wrote:
Sat Feb 22, 2020 5:25 am
Doing some more testing, I think TA is not always working if the CC does not match.

I'm not sure why this is happening at the moment.

Edit.
It looks like the ID is OK, but its the TA that is not being decoded.
ciao Roger
drove around with the vfo scan activated and the CC filter disabled for several hours, everything seems to work fairly well:
- small noises
- on low signals there is some uncertainty in decoding and the audio is not always perfect.
But his work of decoding all CCs does it and therefore goal achieved.
You're right it is only the TA that is not displayed, id dmr appears (sometimes late) but is displayed. It would be useful to view the decoded information (CC number) but obviously this is not a priority. I read that you are working to solve these small problems and thank you.
Sal

VK3KYY
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Re: Experimental version with option to disable CC filtering

Post by VK3KYY » Sun Feb 23, 2020 3:23 am

KV0A wrote:
Sun Feb 23, 2020 2:43 am
I'm still a little unsure how the Ct filtering works. Does this make it so that if you're on a private call then everything except the private call is filtered?
Colour Code on DMR is a bit like CTCSS on FM.

It does not make the call private, but if you radio is not set to the same Colour Code as the other station, the radio may not even put on the green LED to indicate that there is a signal at all.

Most Ham radio stations and repeaters seem to use CC 1, however there are some repeaters which use other CC numbers - and this has confused quite a few people, who presumed that everything was on CC1.


Apparently repeaters in close proximity to each other which are on the same frequency, are supposed to use different CC, but I'm a bit sceptical about how effective this would actually be.

CC has a special use for DCS but I don't know the technicalities of this.

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