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XPR7550 - transmit restriction if not in range?

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g8tzl2004
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XPR7550 - transmit restriction if not in range?

Postby g8tzl2004 » Sun Sep 07, 2014 2:55 pm

I have just acquired an XPR7550 but I have not yet programmed the radio.

The XPR7550 is programmed on a simplex TRBO frequency with no analog channels.

I have briefly tested the TRBO radio using an analog radio. On receive, the XPR7550's LED will flash green - so its receiving OK - albeit an analog carrier so nothing is heard.

However, when I press the XPR7550's PTT , the radio just emits a low level tone after about 1/2 second - no signal is transmitted.

Is the XPR7550 listening for a constant TRBO carrier from the base and if nothing is heard the TX is disabled? I am well out of range of the base.

I'm certain the XPR7550 is not transmitting any quick burst of RF when I press the PTT - so all I can assume is that the receive side must always have to detect a constant carrier from the base otherwise the XPR7550's TX is disabled?

Any ideas?

Thanks

g8tzl2004
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Re: XPR7550 - transmit restriction if not in range?

Postby g8tzl2004 » Sun Sep 07, 2014 3:16 pm

Panic over - the XPR7550 is TXing a very fast data burst. It was too fast for my freq counter until I changed the gate setting.

I assume the base will need to automatically reply with a corresponding fast data burst before the XPR7550 is allowed to TX?

I guess its a good way to check range with no help - if the XPR7550 does not TX, it's out of range of the other radio?

tvsjr
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Re: XPR7550 - transmit restriction if not in range?

Postby tvsjr » Sun Sep 07, 2014 7:56 pm

Simplex, you say? It sounds like you have the radio in the Dual Capacity Direct Mode, which allows TDMA on simplex. Previous radios didn't support this, and fell back to FDMA on simplex due to the smarts required to do time sync. When you get up in DCDM, some magic goes on to elect one radio as the timing master... I've never tried it, but if there isn't another radio out there to talk to, I wouldn't be surprised to see this behavior.

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borisf
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Re: XPR7550 - transmit restriction if not in range?

Postby borisf » Fri Dec 05, 2014 12:56 am

Search the CPS help for "Private Call Confirmed".

RFguy
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Re: XPR7550 - transmit restriction if not in range?

Postby RFguy » Fri Dec 05, 2014 9:06 am

tvsjr wrote:Simplex, you say? It sounds like you have the radio in the Dual Capacity Direct Mode, which allows TDMA on simplex. Previous radios didn't support this, and fell back to FDMA on simplex due to the smarts required to do time sync.


This is not correct. Every MOTOTRBO radio that I've ever worked on transmits TDMA on simplex digital. Previous to 2.0, there was no way to sync on simplex to use both time slots in direct mode, so only one timeslot was used.

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Bill_G
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Re: XPR7550 - transmit restriction if not in range?

Postby Bill_G » Fri Dec 05, 2014 7:05 pm

And they definitely need a target radio to transmit to before it will continue to xmit. They have to handshake.

RFguy
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Re: XPR7550 - transmit restriction if not in range?

Postby RFguy » Sun Dec 07, 2014 9:57 am

Bill_G wrote:And they definitely need a target radio to transmit to before it will continue to xmit. They have to handshake.


In what mode? This is not the case with digital simplex. A simplex radio will transmit regardless of any other radios in range. Are you talking about Capacity Plus, or Connect Plus trunking?

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tdats
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Re: XPR7550 - transmit restriction if not in range?

Postby tdats » Mon Dec 08, 2014 6:31 am

Not sure if this is your issue, but I have noticed the Admit Criteria on digital and analog channels is defaulted to Channel Free. Might have to be the the expert view to see that setting. If there is an analog signal (or any signal) on the frequency and you try to transmit, it will do the low beep not allowing you to transmit until the channel is free. Set that to Color Code Free (or correct PL on analog), or always admit. We ran into that using trbo radios on analog, any noise being picked up by the radio keeps it from transmitting.

g8tzl2004
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Re: XPR7550 - transmit restriction if not in range?

Postby g8tzl2004 » Fri Dec 12, 2014 9:41 am

Thanks - but the Admit criteria is already set to Color Code Free.

Maybe the problem may be due to the ARS (Automatic Registration Service) being set to On System Change rather than disabled?

Maybe the radio is attempting to register at power up and when this is unsuccessful, TX is disabled?

com501
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Re: XPR7550 - transmit restriction if not in range?

Postby com501 » Wed Jan 07, 2015 11:23 pm

RFguy wrote:
Bill_G wrote:And they definitely need a target radio to transmit to before it will continue to xmit. They have to handshake.


In what mode? This is not the case with digital simplex. A simplex radio will transmit regardless of any other radios in range. Are you talking about Capacity Plus, or Connect Plus trunking?


Incorrect for Gen II radios.

In a Gen II radio, you can have 2-slot simplex, but for slot 2, there MUST be another radio within range, and one of the two radios on simplex must be a master which sets the timing parameters for slot 2, otherwise the radio will NOT transmit when selected for slot 2 simplex. You will get an out of range indication.

Slot 2 simplex is also not receivable by a Gen I radio. It does not know what to do with the signal.


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