DMR "Scanner" users B,ham Help

Scanning radio frequencies in the West Midlands
jhampton2000
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Re: DMR "Scanner" users B,ham Help

Post by jhampton2000 » 11 Dec 2016, 11:43

Glad you got sorted. Sorry we didn't spot the obvious error until late on. It was the LED with no audio that gave it away. It is always good practice not to program in the correct TX freq in case you accidentally TX on the channel: personally I would recommend using a default TX freq for which you do have a licence.

And just to clarify for others reading this thread perhaps at a later date:
- To receive a non-RAS enabled DMR Repeater channel you need the correct RX freq/CC/Gp/Slot combination, and the TX freq must be different to the RX freq: this tells the transceiver to expect Repeater Mode signalling
- To receive DMR simplex, TX and RX freqs are the same: this tells the transceiver to expect Direct Mode signalling
- You cannot use a transceiver to decode the input side of a DMR repeater transmission: the raw input transmission will 'sound' like the machine-gun simplex signal, but if you set up your transceiver to receive it in simplex mode, it won't decode: this in a way can help you discover if it's a repeater input or a genuine simplex signal.

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Metradio
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Re: DMR "Scanner" users B,ham Help

Post by Metradio » 11 Dec 2016, 12:20

Thanks for the update Scott, your kind comments are appreciated..

Mike
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600.
Raspberry Pi 2 and DV4Mini HotSpot.
AOR AR-DV1 Digital Voice Receiver / eSPY on ARD V1.

Whistler WS1088 / TRX-1 / Whistler Q / UBCD3600XLT / WTR Browser.

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welshevo
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Re: DMR "Scanner" users B,ham Help

Post by welshevo » 12 Dec 2016, 12:55

one major issue with retevis and TYT is if you have the same TX and RX in digital the radio goes "deaf" and confused... if you just want to listen and not TX then always put in a diff TX freq and tick the RX only check box ;) same happened to me when i first got my TYT and now it wont shut up! hahaha brilliant radios!
:thumbup: Tetra is a Lonely place! Get DMR instead! (163TM995) ...... :thumbup:

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Metradio
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Re: DMR "Scanner" users B,ham Help

Post by Metradio » 12 Dec 2016, 16:29

Not an issue with Retevis and TYT, nearly all DMR transceivers work like that.. I think the reasoning is so that "Talkaround" in the absence of a repeater works correctly.. Talkaround is selectable by the user to be able to use a repeater output frequency as a simplex one..

Mike
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600.
Raspberry Pi 2 and DV4Mini HotSpot.
AOR AR-DV1 Digital Voice Receiver / eSPY on ARD V1.

Whistler WS1088 / TRX-1 / Whistler Q / UBCD3600XLT / WTR Browser.

iscottybotty
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Re: DMR "Scanner" users B,ham Help

Post by iscottybotty » 13 Dec 2016, 12:01

Chaps, this may be a silly question but...

Does DMR have "open carrier waves"? See I'm scanning 440-450 on my UV5R. There is what sounds identical to New Street a DMR transmission but for the life of me I can't get it on the RT3?

I've tried all CC's and both slots, green light lol but no modulation. The frequency is 453.8250, I'm based in the midlands. I have a different frequency in the TX.

I've looked on the WTR and see Carillion operate on this frequency and as it happens, Carrillion are building a "Super Hospital" just over the road?

It's happened a few times on various frequencies, sounds like continuous DMR but stops and starts, when it starts the noise can be upto 20+ seconds long?

Thanks all.

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Metradio
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Re: DMR "Scanner" users B,ham Help

Post by Metradio » 13 Dec 2016, 13:34

Could be data rather than speech, some stations are set up for data only, sending equipment monitoring info.. Or it is encrypted or restricted (RAS)
The RT3 etc are designed to ignore encrypted, restricted or data signals..
Carillion also bugger about with the railway system...

Mike
Last edited by Metradio on 13 Dec 2016, 17:55, edited 1 time in total.
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600.
Raspberry Pi 2 and DV4Mini HotSpot.
AOR AR-DV1 Digital Voice Receiver / eSPY on ARD V1.

Whistler WS1088 / TRX-1 / Whistler Q / UBCD3600XLT / WTR Browser.

iscottybotty
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Re: DMR "Scanner" users B,ham Help

Post by iscottybotty » 13 Dec 2016, 14:17

Thanks Mike. Certainly a weird one. It happens on about 4 different frequencies between 440 & 454.000.

Also Mike, quickie, when the RT3 is loaded with CC 0-15 Slot 1 in Zone 1 and CC 0-15 in Slot 2 Zone 2, when I hit scan does the radio know to stop on the channel when a talk group activates as the green light will come on, on all channels whenever there's modulation.

See my logic is, when a scanner detects signal it stops scanning. Now, what if the RT3 stops on say CC3 because that's the first channel getting modulation confirmed by the green led, but what if the correct CC is 5? Does the scanner stop on CC3 and then move on after the modulation stops or does it continue scanning all channels until it confirms a hit with the correct CC and TalkGroup?

I hope that makes sense.

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Metradio
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Re: DMR "Scanner" users B,ham Help

Post by Metradio » 13 Dec 2016, 17:51

iscottybotty wrote:....Also Mike, quickie, when the RT3 is loaded with CC 0-15 Slot 1 in Zone 1 and CC 0-15 in Slot 2 Zone 2, when I hit scan does the radio know to stop on the channel when a talk group activates as the green light will come on, on all channels whenever there's modulation...
Although the Green RX comes on, all this shows is that there is activity on the channel, the radio looks for the matching Time Slot and Colour Code of each channel scanned and in an un-modified firmware radio it looks for a matching Talkgroup as well..
..See my logic is, when a scanner detects signal it stops scanning. Now, what if the RT3 stops on say CC3 because that's the first channel getting modulation confirmed by the green led, but what if the correct CC is 5? Does the scanner stop on CC3 and then move on after the modulation stops or does it continue scanning all channels until it confirms a hit with the correct CC and TalkGroup?..
It will carry on scanning until it finds a matching CC and Slot, on an un-modified firmware radio it will also look for a matching Talkgroup.

All this is conjecture as I do not have a MD-380 or RT3 so have never played with the modified firmware, but I understand how it SHOULD work..

To be honest a digital scanner is the way to go, I know they are expensive but they are worth it..

Mike
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600.
Raspberry Pi 2 and DV4Mini HotSpot.
AOR AR-DV1 Digital Voice Receiver / eSPY on ARD V1.

Whistler WS1088 / TRX-1 / Whistler Q / UBCD3600XLT / WTR Browser.

iscottybotty
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Re: DMR "Scanner" users B,ham Help

Post by iscottybotty » 13 Dec 2016, 18:25

Thanks Mike. All is slowly starting to make sense! :crazy:

jhampton2000
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Re: DMR "Scanner" users B,ham Help

Post by jhampton2000 » 13 Dec 2016, 21:14

>sounds like continuous DMR but stops and starts
In very crude terms, when the channel is just carrying signalling data it will sound like a long burst of constant buzzing noise.
When there is user data or voice transmitted on the channel, you will hear it 'warble' before returning to the constant buzzing noise at the end of the transmission.

As mentioned above, you're really much better off with a SDR dongle or tapped-scanner/DSD+ decoder, or a scanner that's DMR capable, and leave the DMR transceiver for decoding channels with known parameters. DMR transceivers really aren't that good for discovering new channels with so many unknown parameters that can easily defeat them.

iscottybotty
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Re: DMR "Scanner" users B,ham Help

Post by iscottybotty » 13 Dec 2016, 21:32

Yes, I'm starting to agree with a capable scanner, Whistler, or the Dongle. I'm only running XP though? I hear this can be set up for as little as £60 but I was put off that specialist cabling was required?

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Re: DMR "Scanner" users B,ham Help

Post by bigbloke » 13 Dec 2016, 21:38

welshevo wrote:one major issue with retevis and TYT is if you have the same TX and RX in digital the radio goes "deaf" and confused...
no it doesnt! it simply knows whether to select tier 2 repeater mode or simplex (tier 1-even-its-not-on-446) format.

if you tried to monitor simplex dmr with a tx offset freq you wouldnt get far.

the radio is completely au fait - the problem is the loose nut behind the programming lead :D :D :D

seasons greetz

BB

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welshevo
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Re: DMR "Scanner" users B,ham Help

Post by welshevo » 14 Dec 2016, 10:14

bigbloke ... somewhat contradicting considering this is what you told me when i bought mine and was trying to listen to a local CAP+ system?
:thumbup: Tetra is a Lonely place! Get DMR instead! (163TM995) ...... :thumbup:

iscottybotty
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Re: DMR "Scanner" users B,ham Help

Post by iscottybotty » 14 Dec 2016, 17:52

Guys, if a channel is encrypted, (not sure if it's just a weak signal at the moment) is that it, move on or will selecting a privacy mode in the Programming Software get round it? I'm guessing it's dependent on the make, i.e if it's Motorola then the answers no as I'm using a RT3?

Thank you.

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Metradio
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Re: DMR "Scanner" users B,ham Help

Post by Metradio » 14 Dec 2016, 19:56

Think you will find the RT3 will ignore an encrypted channel, some scanners can be programmed to: ignore, play a tone or pass encrypted audio when they find encryption.

Mike
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600.
Raspberry Pi 2 and DV4Mini HotSpot.
AOR AR-DV1 Digital Voice Receiver / eSPY on ARD V1.

Whistler WS1088 / TRX-1 / Whistler Q / UBCD3600XLT / WTR Browser.

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