builing a DPMR relais with chinese devices

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f1iwq

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Hello...

I've built a DPMR relais with 2 zastone zt9908. Here is a pic of the rack inside. I've also built a little electronic interface to process the "Squelch rx signal" and drive the TX.

I don't know if this is a standard, but I found that the RX mod has a continuous +3V component when a signal is received and valid (both in analogue or digital modes) :) this is nice and means it's very easy to drive a microcontroller logic to process the RX/TX, using temporisations... etc

at the time of tesing, the pic shows a non-connected power amplifier. Now it's done and works fine

73
 

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arctic

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Are the repeater meant to relay any dPMR compatible radios?
I have two of this radios, but in digital mode i can not just transmit at a frequency, instead i have to
go to meny -> Contacts and choose a group or radio, how do you solve that?
 

f1iwq

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Hello..
This experimental repeater decodes all the zaston zt9908 compatible "dpmr" signal or other compatible brands. BUT i've never seen an icom IDAS nor a kenwood NXDN (4K version) decoding the zt9908 signal.

Right now, this repeater works with all zt9908 users. The contact group is as is was a simplex way ulink and downlink and use the ID=1 without any color code.

So all users have the same config and use the ID=1 without any colour code.

This is a deviant system of course, but the cheaper one indeed.
 

arctic

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It's a fantastic idea, and the setup looks very pro. Please update us with you're progress.

I don't have a programming cable, so i can't test this but there is a setting at the software called

"Allow all call", so perhaps this setting might help you to avoid the need for all the transceivers have an id=1
 

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902

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Hello F1IWQ,

Very nice! And nice technique!

Does your interface simply retransmit the demodulated signal as received, drop it to baseband audio and re-modulate a transmitter, or take the demodulated signal, re-clock it, perform corrections if needed and then modulate the transmitter?

I am curious how you approached this. I would like to do something similar with "Project 25 phase 1" FDMA signals.

VY 73!
 

f1iwq

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hello

Well I checked the "allow all call" parameter, it's set to "OFF" and it should be set to "ON" of course !
thks for the tip artic.

For 902: The interface uses a pic16f675 to process signals between the RX and the TX. the SQUELCH signal is read from direct RX audio, as a continuous voltage is set to 3V as soon as the RX reads a valid HF signal. If not, there is no continuous information. This could be interpreted as a squech sgnal and be use to drive the TX. The processor drives RX sq to TX PTT using temporisations etc...

The input audio is simply redirected to the output TX audio with a capacitor, then through a 100K poti.
 

arctic

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Not sure if it's relevant but Zastone has a anoying BCLO function. If there is traffic or noise on the channel (or the squelch is set to low), it blocks the PTT and beeps and the led is green. I then have to push the PTT twice (fast). Very anoying, it could cause problems for the repeater if it's high up and pickups noise.
 

f1iwq

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I think the BLCO function is called "OACSU" on the zatson program and it can be disabled. :)
 
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How do you stop the Zastone from turning itself off after 4 Hours of standby as all mine do?

I'm also curious how you are powering the units, did you solder into the battery contacts?

Nice work by the way!

Cheers Nigel
 

f1iwq

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Hello!
the only way I find out to prevent Zastone from turing off was to set the SQL at 0. When using the zastone in digital mode, when no stream is received it looks like it's in standby mode. Then, it won't never power off.

The power pinouts has been wired-solded to a 7,5 volts generator using an ajustable voltage regulator.

here is the final pic of the repeater
 

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makhmutova

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Hello....

My name is Franck, and I am amateur radio since 1997 and I live in south of France.I wish to congratulate for your dpmr repeater. Nice job!
I have a question please, I would like to make also a dpmr repeater in my area with these zastone zt9908.
Could you give me the shema connecting the connector to the microphone jack?
I've already a uhf duplexer.
Franck.
 

f1iwq

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I remember this duplexor has 70 dB isolation from RX to TX. The space chanel between RX & TX is 7,6 MHz. I have also insert 3 High-Q pass band cavities directly after the PA (TX). Here is how the elements are interconnected.
For non french : Ampli = PA - Récepteur = Receiver - Emetteur = Transmitter. All other items are easily translatable :D
 

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