DMR max distance record ?

[1enry1]

DMR RECORD DISTANCE ...

On September 7, 2014 ZL2KG, who was situated at the Stratford Plateau car park on the slopes of Mt. Taranaki, an active stratovolcano located in Egmont National Park, worked John, ZL4JY at his home in Waikanae – a distance of over 191.7 km ,in simplex.

KC1HBM and KC1XT on Mt. Washington Mt. Greylock, MA to Mt. Washington, NH: 234.2 km (both VHF and UHF) in simplex.

June 17, 2018, WSSM members set out on a coordinated mountain topping expedition in order to learn more about the range limits of DMR simplex. The longest distance contact achieved was between Mt. Equinox, VT and Saint-Jean-Sur-Richelieu, QC – a distance of: 243.2 km (UHF) in simplex.


Now last day ( 21 october 2019 ) the collegue SV3EXP in Greece with an PLUTO SDR receiver have heard in qso on a DMR BM Network located in Ragusa , Sicily distance is over 640 Km !

I think that is a RECORD of distance using the DMR digital sytem comunication (not in simplex ) on UHF 430.850 Mhz .


73

 

[ko6jw_2]

OK, great. DMR is still FM and relatively wide band. SSB or CW would easily top those distances on UHF.

 

[chief21]

If the QSO was heard on a BM talkgroup, the signal most likely rode on the internet and would NOT be a record. Amateur DMR talkgroups can easily accommodate QSO's all over the world.

 

[vagrant]

The Sierra Nevada range here in California allows myself and others to make long distance contacts. I remember talking with another operator using FM on 1.25 meters. We were both using handhelds. Our signals to each other were quite clear. I turned down the power to 2.5W and still fine. I was using a Kenwood TH-F6A with a Diamond 320A handheld antenna. He was using some off brand radio out of China with its stock antenna. We were over 150 miles (250 km) away from each other. I think I even tested by turning down my power further to 0.05W and there was white noise and my signal would drop in and out. We were both above 8000' (2440 m) elevation and mostly nothing was between us.

I have made other contacts on VHF and UHF using a handheld on FM to a location over 160 miles (260+ km) away and they were around 3300' (1006 m) elevation. I was above and below 8000' on those other occasions. I am unsure if they were using a handheld though on those instances.

An 8000 foot antenna is fantastic. I recommend it for everyone! With over 100 miles LOS (Line Of Sight) at that elevation one way, one can do a lot with a little.

I encourage people to participate in the ARRL VHF contest. It occurs three times a year. It can be educational.

 

[prcguy]

DMR on amateur bands has been heard passing through a satellite, so that would probably be the furthest distance.

 

[bill4long]

OK, great. DMR is still FM and relatively wide band. SSB or CW would easily top those distances on UHF.

My cell phone tops them all. So what. This thread is about DMR not SSB or CW.

 

[bill4long]

If the QSO was heard on a BM talkgroup, the signal most likely rode on the internet and would NOT be a record. Amateur DMR talkgroups can easily accommodate QSO's all over the world.

And if pigs fly, poop will drop from the sky. Whatever.
He explicitly said "in simplex." Why would you think that he meant a "BM talkgroup" ?

 

[chief21]

"Now last day ( 21 october 2019 ) the collegue SV3EXP in Greece with an PLUTO SDR receiver have heard in qso on a DMR BM Network located in Ragusa , Sicily distance is over 640 Km !"

Because that's what the OP wrote to justify the claim of a record contact.

 

[n2nov]

The limitation for the DMR contact was the two-way trip for the timing of the alternating datastreams. Data is sent through a short timeslot and looks for an ACK in the same timeslot and not overwritten by the second timeslot. Data propagation timing is the limiting factor. The further away, the longer the round trip.

 

[bill4long]

The limitation for the DMR contact was the two-way trip for the timing of the alternating datastreams. Data is sent through a short timeslot and looks for an ACK in the same timeslot and not overwritten by the second timeslot. Data propagation timing is the limiting factor. The further away, the longer the round trip.

DMR simplex does not send ACKs back. There is no "round trip."

 

[ParanoidAndroid]

OK, great. DMR is still FM and relatively wide band. SSB or CW would easily top those distances on UHF.

DMR in simplex single slot mode is only 6.25 khz wide. And %95 of all user radios ignore the timeslot when in simplex, so the max distance is only limited by the decoder, which I saw someone do the math for once, and UHF can travel over 65,000 km in the time between the on/off slot.

To stay on topic, I have done 70cm DMR simplex text msging over 100 miles in SoCal regoin (lots of hills and bldgs), on flat ground, not on the hill tops.

From San Diego to Long Beach did voice DMR at 5 watts, and text msg'ing (100 miles) Used beams on both sides, both horizontal.
From San Diego to Santa Monica did voice DMR at 40 watts into a home made folded dipole. Other station was running a dual band vertical. (120 miles).

Next test is going to be 200+ miles flat land. (not mountain to mountain)

My assumtion is, a DMR text msg could easily propagate as far as UHF SSB. DMR voice will likely carry as far as SSB as well. You'll need more power to get there, but in the end, it's RF just the same. You got line of sight, or refraction, or ducting, you're not going to ever reach the upper limit of the time slotting, and even if you did, it probably wouldn't matter in simplex, only in a dual slot repeater.

A satellite running a transponder designed to take DMR in, and return it down on another frequency should work just fine. It's when you try to squeeze both slots into the same frequency that distance becomes a problem, and it's due to the time sync, not the signals themselves.

 

[prcguy]

I believe the 70cm DMR that was heard through a satellite was the output of some amateur repeaters and they could have had dual slots going. I'll ask the person who reported it to me if they know the answer.

A satellite running a transponder designed to take DMR in, and return it down on another frequency should work just fine. It's when you try to squeeze both slots into the same frequency that distance becomes a problem, and it's due to the time sync, not the signals themselves.

 

[ParanoidAndroid]

I don't doubt a dual slot transmission could make it to a satellite and back, but decoding properly on both slots, not going to work out well.

I do know for a fact, that unless you are using a dual slot simplex radio (only motorola and couple others make these), there are no time slots when doing simplex. Setting the slot only tells the transmitting radio to start sending data after the preamble on the first or 2nd slot, but the receive radio can be set to either slot 1 or slot 2, and it will still receive the other radio's transmission, because without both slots being filled with data, the RX radio cannot determine which is which.

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) and if there are delays due to refraction, ducting, etc... The RX radio will still receive and decode everything, because it doesn't care. I have tested this at low power levels with multiple radio types.

Motorola makes a dual direct mode radio that actually fills both slots while doing simplex to allow it to send/communicate with simplex users privately on the single frequency, but again, this is actually going to make the simplex max distance shorter. Theoretically light can travel really freakin far inbetween the two slots, so you would think it wouldn't matter, but because of the sensitivity the radios have to time sync, dual slot transmissions with sync (like a repeater) cannot travel as far as direct simplex radio to radio with the same circumstances. I'll be on 441.000 in san diego around 6pm tonight to about 7pm if anyone wants to try and hear me. I'll be running 40-45 watts on a 12 el beam.

 

[prcguy]

I'm in Texas at the moment but if your available for a simplex DMR test from San Diego to LA next week, I'd like to try it. I can get into many parts of San Diego from my LA QTH.

I'll be on 441.000 in san diego around 6pm tonight to about 7pm if anyone wants to try and hear me. I'll be running 40-45 watts on a 12 el beam.

 

[ParanoidAndroid]

I'm usually playing radio on Monday nights from 5pm to 730pm. Other than that, msg me private, and I'll give you my email, and we can coordinate something. I also have been experimenting with LoRa msg'ing using the hamshield, on 70 cm. Planning on comparing it to DMR text msg'ing soon. I'm pretty sure LoRa is going to beat the pants off DMR text msg'ing, but we'll see.

 

[slicerwizard]

DMR in simplex single slot mode is only 6.25 khz wide.

It definitely is not. Lots of other errors in your posts in this thread, starting with your claims about Motorola's DCDM...

 

[bill4long]

I do know for a fact, that unless you are using a dual slot simplex radio (only motorola and couple others make these), there are no time slots when doing simplex.

Partially true. In simplex, the slot value still matters to the receiving radios (at least on my chi-com radios.) E.g., a receiver listening for slot 1 will not pass audio for slot 2 in simplex. But in simplex the transmitter doesn't sync it's timing with anything external as it does for a repeater.

 

[ParanoidAndroid]

It definitely is not. Lots of other errors in your posts in this thread, starting with your claims about Motorola's DCDM...

Well then correct the errors. That's what a forum is all about.

And yes bill, I explained that the TX radio still picks a slot. I was trying to explain that the RX radio will receive the TX radio's transmission whether it's set to slot 1 or slot 2. Unless the transmitting radio is a dual direct type. Maybe slicing wizard can enlighten us all.

 

[slicerwizard]

I explained that the TX radio still picks a slot. I was trying to explain that the RX radio will receive the TX radio's transmission whether it's set to slot 1 or slot 2. Unless the transmitting radio is a dual direct type. Maybe slicing wizard can enlighten us all.

No, RXing radios do not pick up both slots. They decode the slot they're programmed to monitor. Now you're enlightened. Maybe you should take up weather forecasting, where wild guesses are more the norm.

 

[ParanoidAndroid]

No, RXing radios do not pick up both slots. They decode the slot they're programmed to monitor. Now you're enlightened. Maybe you should take up weather forecasting, where wild guesses are more the norm.

You’re an idiot. Go take (2) md-380’s, or any other cheap chinese DMR radio, and program a simplex frequency into them. Set one to slot 1, and the other to slot 2. Now talk from one to the other and back, then come back here and tell us how you should refrain from typing **** into a msg board without knowing what the hell you’re talking about. Radios decode a single slot (1 or 2) no matter which slot the transmitting radio is set to, unless the transmitting radio fills the empty slot with sync and blank data. If you don’t believe me, it doesn’t matter, because it’s a hardcore fact. Go try it yourself.