Mototrbo 2 Timeslot in Simplex Mode

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moztas
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Mototrbo 2 Timeslot in Simplex Mode

Post by moztas »

Hi All,

I'm new on Mototrbo digital radios. I have a silly question I know but need to find a solution. Please advise me.

I had supposed that I could program Mototrbo digital radios as 2 timeslot in simplex mode also (two channels in 12.5kHz channel spacing) but realised that it was possible only using mototrbo repeater. This I understood very well.

One of my customer has one 12,5 KHz simplex frequency permission but they need two voice channels. I promised them that they would have 2 channels by using timeslots. It was my fault. They already purchased the radios. Is there any way to provide 2 voice channels in 12.5 Khz bandwidth? I can program frequencies by 6,25 Khz step but radios still interference each others.

Any idea or help will be appreciated. Thank you.
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mr.syntrx
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by mr.syntrx »

Nope. Short of giving each "channel" a different talkgroup so they can't hear each other. Depending on how busy they are on simplex, you can get away with it.

Otherwise you'll probably need to spring for license for a second frequency.
Pump3
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by Pump3 »

Yup agree with syntrx, two different talkgroups and set the admit criteria to channel free, worst case scenario they'll get a busy channel bonk and will have to retry in a few seconds
RFguy
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by RFguy »

If their requirement (or expectation) is that they will have 2 "simultaneous" voice channels to allow them to talk on two channels (or timeslots) at the same time, then you are out of luck on simplex with MOTOTRBO.

You only achieve that with a MOTOTRBO repeater.
moztas
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by moztas »

Thank you for the responses.

Yes, their expectation is that they will have 2 simultaneous voice channels in one 12,5 KHz bandwidth. So there is nothing to do.

What about if Mototrbo uses FDMA technology? Was it possible to have 2 simultaneous voice channels in one 12,5 KHz bandwidth?
moztas
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by moztas »

One of my friend who works in Motorola Distributor advise me that 2 simultaneous voice channels in simplex mode will be possible by next firmware upgrade (I guess firmware v1.8). Radios will syncronise the timeslots by themselfs. It is a good news if it is correct.
RFguy
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by RFguy »

moztas wrote:Thank you for the responses.

Yes, their expectation is that they will have 2 simultaneous voice channels in one 12,5 KHz bandwidth. So there is nothing to do.

What about if Mototrbo uses FDMA technology? Was it possible to have 2 simultaneous voice channels in one 12,5 KHz bandwidth?
Yes, that's possible, but only if the radios were in different RF zones (different cities for example). The 2 halves of a 12.5 khz channel in a FDMA solution have no seperation/selectivity and will interfere with each other (just the same as if you were to programm frequencies 5 khz apart from each other in 2 sets of radio's).

If they are to opperate in the same area (same city or site), then you are out of luck.
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Bill_G
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by Bill_G »

IIRC that's because Trbo is a 12.5k "equivalent" solution approved by the FCC, but is not truly 12.5k.

OOps! My bad. Trbo is 12.5 that is 6.25 equivalent.
Last edited by Bill_G on Thu Oct 27, 2011 5:28 am, edited 1 time in total.
RFguy
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by RFguy »

moztas wrote:One of my friend who works in Motorola Distributor advise me that 2 simultaneous voice channels in simplex mode will be possible by next firmware upgrade (I guess firmware v1.8). Radios will syncronise the timeslots by themselfs. It is a good news if it is correct.
I really don't see how that can work if all radios don't "see" each other.

Take the example of 2 radios (one on timeslot A and one on time slot B) on a hill. They are talking to 2 radios (one each on timeslot A and time slot B).

The time slot A radio is down one side of the hill and the other radio on timeslot B is on the other side of the hill. These 2 radios have no RF path between themselves. If one of those radios starts to transmit (time slot A radio), and them the other radio on the other side of the hill wants to transmit (timeslot B), he does not see any RF from the other radio, so how can he sync?

Would they use GPS timing to sync? What if the radios are inside a building without GPS signal?

If they do it, I will be interested in how they do it.
moztas
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by moztas »

RFguy wrote:
moztas wrote:Thank you for the responses.

Yes, their expectation is that they will have 2 simultaneous voice channels in one 12,5 KHz bandwidth. So there is nothing to do.

What about if Mototrbo uses FDMA technology? Was it possible to have 2 simultaneous voice channels in one 12,5 KHz bandwidth?
Yes, that's possible, but only if the radios were in different RF zones (different cities for example). The 2 halves of a 12.5 khz channel in a FDMA solution have no seperation/selectivity and will interfere with each other (just the same as if you were to programm frequencies 5 khz apart from each other in 2 sets of radio's).

If they are to opperate in the same area (same city or site), then you are out of luck.
Yes, they will operate in same area. thanks for your information.
moztas
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by moztas »

Hey all,

Motorola Solutions had announced that two timeslots will be used in simplex (direct mode) independently. Not sure if 1st generation models support or not.

Dual Capacity Direct Mode (DCDM) Feature Release R2.1 available September 2012:
- Two timeslots used independently without repeater
- Protocol adopted within ETSI DMR standard. Dual Capacity Direct Mode (direct mode 6.25e)
- Radios automatically synchronise themselves
- Robust synchronisation propagated across entire system
- Transparent to radio user
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wavetar
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Re: Mototrbo 2 Timeslot in Simplex Mode

Post by wavetar »

moztas wrote:Hey all,

Motorola Solutions had announced that two timeslots will be used in simplex (direct mode) independently. Not sure if 1st generation models support or not.
Only second gen radios will be capable of it (3000,5000,7000). At least, that's the official stance for now. Is it technically possible for the 1st gen radios to do it? Probably...but I believe all the R&D resources for new features from this point on will be going into 2nd gen stuff. Older radios will get minor features/bug fixes only.
No trees were harmed in the posting of this message...however an extraordinarily large number of electrons were horribly inconvenienced.

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