RTCM Voting Configuration

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Voting allow us to have one repeater on a Premiere location while adding satellite receivers to improve Rx coverage.


Hardware needed

Main Site

The Main Site must be conformed by al least the following hardware:

  • 01 Duplexer and antenna or a double antenna set (Tx/Rx).
  • 01 Motorola Pro3100, Pro5100, Pro7100 or MTR2000(Rx).
  • 01 Motorola Pro3100, Pro5100, Pro7100 or MTR2000(Tx).
  • 01 Micro-Node RTCM board.
  • 01 Garmin GPS model GPS18x LVC, 5m.
  • 01 Raspberry Pi model 2A, 3A or 3B.
  • 01 Wired Internet connection with port forwarding capabilities.

Peer Sites

Each Peer Site must be conformed by al least the following hardware:

  • 01 Antenna (Rx).
  • 01 Motorola Pro3100, Pro5100, Pro7100 or MTR2000(Rx).
  • 01 Micro-Node RTCM board.
  • 01 Garmin GPS model GPS18x LVC, 5m.
  • 01 Wired Internet connection with port forwarding capabilities.

Tuning Hardware

  • Service monitor.

Configuration

Edit the voter.conf where 12345 should be your node number and each MainSite# / PeerSite# will define your sites. password# is the individual password for each site. It is important to notice that each site must have a different password.

nodeemp needed for Quantar and MTR2000 only.

[general]
port = 667
buflen = 500
password = BLAH
utos = y

[12345]
MainSite0 = password0,transmit,master
PeerSite1 = password1
PeerSite2 = password2
PeerSite3 = password3
PeerSite4 = password4,nodeemp

plfilter = n
txctcss = 100.0
txctcsslevel = 0
txtoctype = none

thresholds = 255,110=5
; linger=6
; streams = 12.34.56.78:1667

RTCM

Log in using the serial port (57600 baud) or telnet, the default user is admin and the default password is radios.


Firmware update

The VOTER/RTCM firmware is updated with a Windows program EBLEX C3 Programmer. Download from here. Put both the exe and the ini file in a folder.

If you are upgrading an RTCM be sure to use a .cry file that contains smt in the filename.

If you are upgrading a through-hole VOTER, do not use the smt files.

Save the .cry file in the folder with the .exe and .ini files.

Download the firmware here that is appropriate for your application.

Run the EBLEX Programmer:

  • Fill in the target bootloader IP address (or the public IP, if your RTCM is behind a firewall) of the device.
  • Click File and load the .cry file you are going to program.
  • Click the Capture Target button.
  • Reboot the VOTER/RTCM with TELNET (r option), power cycle, or use the reset button. In a moment you should see text come up on the programmer that it captured the target.
  • Click the Program button.
  • In a few minutes you will see some more messages including a program complete message.
  • Click the Reset LIA button. The VOTER/RTCM will restart with the new firmware.
  • TELNET into your VOTER/RTCM and verify the new version is loaded with menu 98:

GPS

The GPS should be connected thru the DB-15 port on the RTCM.

RTCM GPS pinout
RTCM Direction Garmin 18x LVC
6 GRX <-- Rx Data Green
7 GPPS <-- Pulse Output Yellow
8 GND Ground Black (2 cables)
13 +5V V in Red
14 GTX --> Tx Data White


Tuning

Don't disable COR in the RTCM/VOTER... it will cause it to disable the squelch and it will report an RSSI of 255 (full quieting) for all received signals.

RTCM Settings
Option Parameter Value
3 VOTER Server Port 667
4 Local Port 0
5 Client Password password#
6 Host Password 0
7 Tx Buffer Length 4000
8 GPS Data Protocol 0=NMEA
9 GPS Serial Polarity 0=Non-Inverted
10 GPS PPS Polarity 0=Non-Inverted
11 GPS Baud Rate 4800
11 External CTCSS 1=Non-Inverted
12 External CTCSS 1=Non-Inverted
13 COR Type 0=Normal

Level Settings

Setting the audio levels for the RTCM/VOTER is pretty straight forward. Just follow these steps:

Step 1 - Rx Level

  1. Ensure you have a connection to your host Asterisk server/chan_voter instance. Some internal settings on your RTCM are pooled from your PTTLink server.
  2. Send a 1 kHz @ 3 kHz on-channel, full-quieting signal in to the repeater's Rx.
  3. Set SW2-4 ON, LD5 will indicate (by brightness) if the Rx level is too low, and LD4 will indicate (by brightness) if the RX level is too high. So the idea is to tune R36 so that there is minimal brightness on both LD4 and LD5 (like a null, more or less). Alternatively, the "97" command from the console menu gives a more graphical method of setting the Rx input level.
  4. Now change the modulation from 1 kHz tone to 800 Hz followed by 1.8 kHz and verify that the deviation level doesn't change as the tone frequency changes. Changing levels indicates a pre/de-emphasis issue.

If you are using the built-in "offline repeat" functions, fail the connection to the host Asterisk server, and make sure your repeat audio performs the same as above.


Step 2 - Tx Level

  1. Now set the Tx Level pot to get 3 kHz out of the transmitter (No PL) measured on your service monitor.


Step 3 - Switches SW2-2 and SW2-3

  1. Calibrate Squelch and Diode. With the receiver connected and its antenna removed, turn ON switch SW2-3 and next switch SW2-2. In the next few seconds the "Receive Signal Indicator" (LED 3, Green) will flash On and off, then (hopefully) on steady. This indicates that the squelch calibration has occurred successfully.

If unsuccessful, the LED will flash either fast to indicate that the discriminator noise level is too high, or slowly to indicate that the discriminator noise level is too low.


Step 4 - Squelch Level

Squelch adjustment (R22) needs to be properly set. Make sure that:

  • 12 - External CTCSS is set to 0=Ignore
  • 13 - COR Type is set to 0=Normal
  1. Adjust R22 until the Receive Signal Indicator (LED 3) is On.
  2. Then advance R22 clockwise until LD3 is no longer On. That is the minimum squelch setting.
  3. You probably will want to crank it up at least another turn clockwise, because if you leave it there it will open on a REALLY low level signal.
  4. After proper setting has been achieved, return the "External CTCSS" configuration to its original setting.

RX/TX Buffers are NOT Both Millisecond Values

You might assume an RX buffer (in voter.conf) of 120ms would be equivalent of a TX buffer (in the RTCM) of 120ms. That is not the case.

The TX buffer is a number of 125 microsecond intervals, where the RX buffer is in milliseconds.

If you follow the buffer setting instructions, you should be fine, in most cases.



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RTCM Simulcasting

The RTCM/VOTER boards do support simulcasting, however, there are a bunch of quirks that one needs to be aware of.


Radio Hardware

9.6MHz Oscillator

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