DMR max distance record ?

[kayn1n32008]

This is actually a good thing, because it means you can do DMR simplex at 6.25 khz (the other 6.25khz of your transmission, your radio will be off)

No. DMR is 6.25KHz equivalent. All DMR transmissions occupies the 12.5KHz channel, even when operating simplex. You divide the carrier in time, not frequency. Each timeslot occupies the same bandwidth, just not at the same time.

 

[bill4long]

I was trying to explain that the RX radio [in simplex[] will receive the TX radio's transmission whether it's set to slot 1 or slot 2.

Not on my chi-com radios, as I said above. Other brands may differ, although I would guess some radios have an "admit both slots" option.

 

[ParanoidAndroid]

No. DMR is 6.25KHz equivalent. All DMR transmissions occupies the 12.5KHz channel, even when operating simplex. You divide the carrier in time, not frequency. Each timeslot occupies the same bandwidth, just not at the same time.

The bandwidth is 12.5khz, I was wrong on that, but what I am saying about the sync and slotting is true. That’s why they make “dual direct” radios. If the transmitting radio is off for half the slots, and provides no sync, the RX radio has no way to differentiate between slot 1 or slot 2. So it decodes it either way.

Point being a dual direct radio providing sync data and actually filling the other slot with empty data packets, will not travel as far as a cheaper radio that does not. Point no 2, you will never achieve a distance record going through or communicating with a dual slot TX repeater, for the same reason. Single slot/no sync simplex will travel further.

 

[prcguy]

Could somebody with a spectrum analyzer please verify DMR single slot simplex occupied BW? I would but am away from my shop this week.

 

[ParanoidAndroid]

Could somebody with a spectrum analyzer verify DMR single slot simplex occupied BW? I would but am away from my shop this week.

I confirmed it just now. My md-380 in simplex occupies 12.5 khz +/-. Also confirmed that a 2nd md-380 and a cs800 receive the simplex radio, both set to slot 2, while the TX radio is set to slot 1

 

[bill4long]

but what I am saying about the sync and slotting is true. That’s why they make “dual direct” radios. If the transmitting radio is off for half the slots, and provides no sync, the RX radio has no way to differentiate between slot 1 or slot 2. So it decodes it either way.

It's up to the radio manufacturer how to deal with "promiscuous" reception of alternate slots. But slot recognition is not determined by mere timing. The data packets have a slot field that indicates what slot number a packet belongs to and what the kind of data it is. If it didn't, radios would never be able to sync with a repeater. (They don't sync with other simplex radios.) Your understanding of this is faulty. You can find the specs here. Digital Mobile Radio Association | The DMR Standards, developed by ETSI

"Every data and control burst contains a 20-bit Slot Type PDU (SLOT) that defines the meaning of the 196 information bits."
--ETSI TS 102 361-1

 

[slicerwizard]

Hey genius, you said nothing about toy radios. Nice attempt to move the goalposts.

If the transmitting radio is off for half the slots, and provides no sync, the RX radio has no way to differentiate between slot 1 or slot 2. So it decodes it either way.

Meanwhile, real DMR radios (Motorola, etc.) have no issue determining simplex slots 1 or 2.

 

[ParanoidAndroid]

It's up to the radio manufacturer how to deal with "promiscuous" reception of alternate slots. But slot recognition is not determined by mere timing. The slot number has a bit in the packet that indicates what the slot is. If it didn't, radios would never be able to sync with a repeater. And they don't need to sync with other simplex radios at all. Your understanding of this is faulty. You can find the specs here. Digital Mobile Radio Association | The DMR Standards, developed by ETSI

Nope. Your understanding is faulty. After a preamble, the data packets start on either slot 1, and the radio un-keys during slot 2, or the radio sends the preamble, and unkeys, then begins on slot 2.

The RX radio has no way to know if it lost a packet, and is receiving slot 1 or slot 2, unless the empty slot is filled with blank data, aka a time sync.

This is what the repeater does. It fills the un-used slot with sync data so that as soon as traffic starts on that other slot, the RX radios know where it is in time, and ignore it.

Why do you think they make “dual direct radios”!? And how are you even arguing this? Get a couple radios that are not capable of dual direct TX, and set them to different time slots, and see if you can have a conversation on a slot without the other radios RX it. You’ll quickly discover it has nothing to do with manufacturers. It IS the standard. The transmitting radio, repeater, sets the clock, sets the sync. If it doesn’t, the RX radio has no way to determine if it just missed a packet in time, or if it is on slot 1 or slot 2. You go try it and tell me what you find out. I’ve tried it with dozens of radios and it always comes out the same.

 

[kayn1n32008]

oint no 2, you will never achieve a distance record going through or communicating with a dual slot TX repeater, for the same reason. Single slot/no sync simplex will travel further.

This makes zero sense...

 

[slicerwizard]

Why do you think they make “dual direct radios”!?

Because it's efficient and it's part of the DMR standard.

And how are you even arguing this? Get a couple radios that are not capable of dual direct TX, and set them to different time slots, and see if you can have a conversation on a slot without the other radios RX it. You’ll quickly discover it has nothing to do with manufacturers. It IS the standard.

If your toy radios don't support TDMA direct mode, they're not compliant with the DMR specs. Why do you keep getting everything backwards?

 

[AK9R]

Folks, I think we have deviated from the intent of the original post which was some sort of distance record claimed with some sort of DMR transmission.

If you want to debate DMR bandwidth, promiscuous mode, "toy" radios, please start a new thread in a more appropriate forum.

If you want to verbally abuse each other, please don't do it anywhere at RadioReference.

 

[nanZor]

Wait - I was under the impression that if you worked simplex, and transmitted on slot 1, that over VERY great differences, due to the relatively long length of time to travel, that the receiving end could possibly pick you up on slot 2 and not slot 1.

Or am I missing something ...

 

[ParanoidAndroid]

Wait - I was under the impression that if you worked simplex, and transmitted on slot 1, that over VERY great differences, due to the relatively long length of time to travel, that the receiving end could possibly pick you up on slot 2 and not slot 1.

Or am I missing something ...

Unless the transmitting radio is filling both slots and negotiating the time sync, the RX radio will receive a simplex transmission on either slot 1 or slot 2. It doesn’t matter if it’s 2 feet away.

Anyone who says otherwise needs to prove it. I’ve yet to see any radio “toy” or not, do otherwise.

If what I’m saying is not true, then why do “toy” radios RX only on a single slot when listening to a repeater, or when a fancy dual direct radio is transmitting?

Answer: because the time sync is being negotiated/managed by the TX side. %100 fact of life. Anyone with brains can go try for themselves and realize by monitoring the two different types of transmissions with DSD’s decode software, that this is what’s happening.

 

[kayn1n32008]

Unless the transmitting radio is filling both slots and negotiating the time sync, the RX radio will receive a simplex transmission on either slot 1 or slot 2. It doesn’t matter if it’s 2 feet away.

Anyone who says otherwise needs to prove it. I’ve yet to see any radio “toy” or not, do otherwise.

If what I’m saying is not true, then why do “toy” radios RX only on a single slot when listening to a repeater, or when a fancy dual direct radio is transmitting?

Answer: because the time sync is being negotiated/managed by the TX side. %100 fact of life. Anyone with brains can go try for themselves and realize by monitoring the two different types of transmissions with DSD’s decode software, that this is what’s happening.

I can confirm this using an XPR-7550 and a CS-700. I just programmed the XPR-7550 to be the opposite of the CS-700 on simplex.

CS-700:
TX/RX-446.075, CC-1, TS-1, TG-99

XPR-7550:
TX/RX-446.075, CC-1, TS-2, TG-99. This radio is NOT set up for DCDM or what ever Motorola call it.
Transmitting from either radio results in the other unmuting.

 

[ParanoidAndroid]

I can confirm this using an XPR-7550 and a CS-700. I just programmed the XPR-7550 to be the opposite of the CS-700 on simplex.

CS-700:
TX/RX-446.075, CC-1, TS-1, TG-99

XPR-7550:
TX/RX-446.075, CC-1, TS-2, TG-99. This radio is NOT set up for DCDM or what ever Motorola call it.
Transmitting from either radio results in the other unmuting.

Thank you. The whole point of me bringing this up, is we have found doing actual testing, not reading DMR standards online, that when the TX radio is not negotiating sync, and the RX radio is hearing it on either slot, that there is more leeway once you start approaching the edge of communication. Radios or repeaters negotiating the sync, start to fall off earlier.

So wether it’s a standard or not, if you want to do DMR simplex far distances, use a TX radio that does not negotiate the time slot sync.