|- SYNTOR X PACKET HOOKUP|
|- "VBJ" and "VXJ" Radio Model Differences|
|- Tx Modulation Controls|
|- Trouble Shooting Signal Location Table|
|- Packet Modifications|
|- Improved Receiver Squelch Recovery Modification|
|- Syntor X Home|
The information here needs to be checked. If anyone out there has any experience using these radios for packet and wants to share it, please contact me.
Because the Syntor X was designed to work with DVP it is already a data capable radio. Basically all you have to do is get control of this built in data mode, wire up the packet modem and set the deviation. Why buy a special data radio when the Syntor X already has the capability? On frequencies where it is legal, these radios should be able to do 9600 baud or higher. Again the important part is, I'm not yet really sure of the compatibility between the radio and packet modem audio levels. I did hookup an old PAC-RAT modem and found it was barely able to drive the Data input (J1-7 Securenet Modulation) at its full output. However, it did work.
High speed 9600 baud modems need to get their audio directly from J1-2 Detected Audio (through a squelch gate if needed). They also need to use J1-7 Securenet Modulation to bypass the microphone, pre-emphasis, deviation limiter and filter. This allows for undistorted modulation of the transmitter. Slower 2400/1200 baud modems may or may not be so picky about their installation connections.
Unless your modem does not need any received signal audio muting or a control signal to mute the received audio, there is no ready made simple packet hookup. Unfortunately the current examples all expect you to have just such a modem. I will get around to complete functional examples for all the other modems in the future. For now there is enough information for you to probably come up with your own packet interface. If you are familiar with basic electronics, none of the modifications are very difficult because everything except a fast squelch gated received audio signal is already inside the radio. This fast squelch gate should only take one transistor or possibly two transistors if the Channel Activity signal needs to be inverted. Even though the interfaces are not complex, building, testing, documenting and posting them to the web site is very time consuming.
There are 3 different Syntor X transmitter audio modulation paths. They are the Microphone, PL/DPL and Data audio paths. Each one of these audio paths has its own on/off Control Gate. All of the Control Gate Enable lines allow their associated audio to pass when they are not connected or pulled up and block their associated audio path when they are grounded. When an audio path is enabled it allows its audio source to modulate the transmitter. The radio model ("VBJ" or "VXJ") determines how each of these paths are controlled.
"VBJ" and "VXJ" radio model differences:
An important consideration for packet connections is understanding the difference between the "VBJ" model radios and the "VXJ" model radios. This is because the "VXJ" model radios have a HLN4270A, HLN4270B, HLN4425A or HLN5008A DVP Interface Board installed. These boards control the transmitter voice / data configuration. This causes packet hookups to be very different for these two types of radios. Just to make things even more fun there are four different versions of the "VXJ" DVP Interface Boards (see below). Another consideration is for radios that have the actual external System 90*s DVP hardware hooked up. This DVP hardware is wired into the radio resources you need to hookup your packet to, so you will need to figure out how to switch between the two. If you do not need to use DVP you can remove the external System 90*s DVP hardware and setup the radio for packet. "VBJ" radios should be checked to see if they are really "VXJ" models.
Since the external System 90*s DVP hardware already switches the radio into data mode, you could just use it and switch the modem transmit audio on J1-7 (Securenet Modulation). This will only work if the DVP has a valid key loaded. If it does not have a valid key it will not switch into DVP mode.
There is another variation on the DVP control head setup. It is a DVP Bypass Board that allows a "VXJ" model that is still jumpered as a DVP radio to be used without a DVP control head (i.e. the DVP Bypass Board is used instead of the DVP Board in the control head stack). There are no controls or external switches on the DVP Bypass Board. I do not have any schematics or information on the DVP Bypass Board so I can not say exactly how to hook it up for packet, but you should be able to remove the Bypass Board and hookup your own packet controls.
Below is a description of the four "VXJ" DVP Interface Boards (HLN4270A, HLN4270B, HLN4225A and HLN5008A) and their connections. It shows the differences between these "VBJ" and "VXJ" radios. It also shows the differences between the DVP Interface Boards:
|Syntor X "VXJ" DVP Interface Board Comparison|
|JU2||JU2||JU2||J1-21||J1-21||Transmit Mode (reverse burst)|
|-||-||-||P301-8||P303-2||Tx Control Eanble|
|-||J1-35||J1-35||J1-35||-||EMS Mute (mute)|
|-||-||-||-||J1-35||EMS Mute (priority sample mute)|
||Transmit DVP (data path)|
|-||Transmit DVP (PL/DPL path)|
|-||-||special||-||special||Detector Mute Control (MVS-20)|
|-||J443-2||J443-2||J443-2||JU451-in||Audio PA Mute Disable|
|-||special||special||special||-||VHF 110/10 Watt Power Control|
The following is a description of the packet control signals for the "VXJ" model radios:
If J1-36 Transmit DVP is grounded, the radio is in normal voice mode (the Tx PL/DPL is enabled and the Tx Data input is disabled). If J1-36 Transmit DVP is a high impedance (disconnected) or pulled high the radio is in DVP mode (the Tx PL/DPL is disabled and the Tx Data input is enabled).
The external System 90*s DVP hardware shorts J1-27 Mic. Hi (input) to ground when the radio is in DVP mode. This disables the unused microphone audio input. The IDC Enable control line can also be wired with a diode to provide the same function.
If J1-21 Transmit Mode is grounded the PL/DPL Reverse Burst is turned on. If J1-21 (Transmit Mode) is not connected or pulled high (above about +2.2 volts), the PL/DPL Reverse Burst is turned off. The HLN4270A or HLN4270B DVP Interface Boards do not support the PL/DPL Reverse Burst control and JU2 must be used instead.
Because the J1 control leads travel through a long cable to the radio, the DVP control head uses 13 volt Zener Diodes across J1-21 and J1-36, presumably to help control possible high voltage switching transients on these cable lines.
Tx modulation controls:
|Transmit Audio Modulator Controls|
|SIGNAL DESCRIPTION||"VBJ" Location||"VXJ" Location|
|Microphone Audio||J1-27 (Mic. HI)||J1-27 (Mic. HI)|
|IDC Enable||J401 pin 6||J401 pin 6|
|PL/DPL Enable||J401-4||J1-36 (Transmit DVP-inverted)|
|Data Audio||J401-2||J1-7 (Securenet Modulation)|
|Data Enable||J401-1||J1-36 (Transmit DVP)|
Trouble shooting signal location table:
The table below describes the radio's internal controls and audio signals for voice and data mode operation. Use this table as a reference or to help trouble shoot packet control connections. Check the approiate DVP interface board drawings (HLN4270A, HLN4270B, HLN4425A or HLN5008A) for additional location pin number information on "VXJ" model radios. J401 is the ribbon cable that connects the Personality and Common Circuits Boards.
|Packet Interface Internal Radio Connections|
|Microphone Audio||J401-5||Active during Transmit||do not care @||-|
|Microphone IDC Enable||J401-6||Enabled (N.C. or high)||Disabled (gnd)||#|
|PL/DPL Audio||J401-3||Programmed||do not care||-|
|PL/DPL Enable||J401-4||Enabled (N.C. or high)||Disabled (gnd)||x|
|Data Audio||J401-2||do not care||Active during Transmit||x|
|Data Enable||J401-1||Disabled (gnd)||Enabled (N.C. or high)||x|
|PL/DPL Reverse Burst||U3-9||Enabled (gnd)||Disabled (N.C. or high)||x|
|R31 Data Deviation Control||-||do not care||Set for deviation||*|
|PTT||J1-4||Mic. PTT Button||Modem control||x|
|Receiver Audio||J1-2||Active during Receive||Active during Receive||-|
The above conditions are what you need to make happen for a packet interface using the Data audio input for the transmit audio from the packet modem. How you make this happen is different for "VBJ", "VXJ", external System 90*s DVP hardware, HLN4257 and TRN8861 Personality Board radios. The deviation must be set correctly. Because there is no 3000 Hz Splatter Filter on the Data Audio it can reach the maximum deviation and frequency response the radio is capable of (way beyond the normal 5 KHz deviation) so care must be exercised to meet F.C.C rules and to avoid causing adjacent channel interference.
Here are the various drawings to accomplish the above controls for packet operation.
|Syntor X Packet Modifications Chart|
|Model||External DVP Hardware||Personality Board Mods.||J1 Connection Mods.|
|"VXJ"||Yes||none||Drawings to follow|
|"VXJ"||Bypass Board||HLN4760 A / B / C||Drawings to follow|
|"VXJ"||none||HLN4760 A / B / C||Instructions|
|"VBJ"||none||HLN4760 A / B / C||Instructions|
For dedicated packet radios, a packet interface can be built directly on the radio's J1 connector body, without any control head or normal radio cable. A Syntor X trunking cable will provide the necessary parts and the pins will already be in the connector (you just cut the wires to a usable length).
Make sure JU2 is not installed as the reverse burst will add about 180 milliseconds delay after the PTT is released (which is detrimental to packet operation).
For the external DVP board, J2 light green 22 pin connector pin 19 (CH MIC BLK-YEL), not J1-4 (PTT) should be switched to ground for modem PTT switching. All other modifications use J1-4.
Improved Receiver Squelch Recovery Modification:
Most data modems require squelch muted audio to feed the receiver audio to the modem. Some modems have an external input control line to perform their own internal receive audio muting. Some modems do not care or have to use any gated receiver audio. If you modem falls into the first two categories then you will need to come up with a circuit and/or interface to mute the received audio.
The Syntor X squelch circuit has the potential to respond very quickly when the radio switches from transmit to receive. Whenever the synthesizer changes frequency, a signal called Adapt is sent to the squelch circuit to prepare it to respond to the frequency change (this adapt circuit is used for switching from Tx to Rx and also used for Rx scanning). Since there is a frequency change every time the radio is switched from transmit to receive, the squelch circuit is prepared ahead of time for this change. This Adapt signal also causes a Squelch Tail delay signal which has its own output from the squelch circuit. This squelch tail delay prevents the Syntor X receiver speaker from making a noise burst after a Tx to Rx frequency change. Capacitor C411 (2.2 uf) is responsible for the squelch tail timing. This means the squelch circuit puts out a separate Channel Activity signal (with no delay) and a Squelch Tail signal (with a hang time delay). The Personality Board microprocessor combines both of these signals to create the audio Mute and Priority Sample Mute control signals. So if you use the audio Mute or Priority Sample Mute (both of which already control the audio amplifier mute and one of them goes to the optional J1-35 EMS mute) to gate audio to a modem, the Tx to Rx turn around time will be delayed by the squelch tail delay. This squelch tail delay will cause very poor packet performance. Ideally, you want to use the Channel Activity signal (Personality Board J401-19, J8-1 or U3-4) directly from the squelch circuit to control or gate the receiver J1-2 Detected Audio to a modem.
If your radio is only going to be used for data, you can try replacing C411 (2.2 uf) on the Common Circuits Board with a much smaller value capacitor (maybe a .1 uf). Reducing C411 should make the radio's squelch circuit have a much faster Tx to Rx turn around time. Since the microprocessor still has to process the Channel Activity and Squelch Tail signals, there will still be very small delay before the audio Mute or Priority Sample Mute (i.e. J1-35 EMS mute) is changed. Even though it is a step in the right direction and might simplify your interface, leaving C411 alone and using the Channel Activity instead is still the best option. This capacitor change should cause the radio's audio to make unwanted noise bursts so is not compatible with voice communications.
If your radio is going to be used for both voice and data, what you will need to do is make a custom modification. The Channel Activity should be used to gate the modem audio. You can install the entire circuit inside the radio and feed the gated received audio signal to the modem on an unused J1 pin (i.e. J1-18 or J1-20). Or if your modem only needs a squelch control signal, you can simply connect the Channel Activity line to one of these J1 pins. You could short pin 9 to pin 19 on the Common Circuits Board J401 connector solder side to make J1-20 become Channel Activity (remove Q909 (VHF) or Q955 (800 MHz) if present on the Common Circuits Board - I have never found an installed Q909 even on the boards that have a place for it).
In the future I will provide a simple receiver Detected Audio mute circuit schematic driven by the Channel Activity line (I know, still UNDER CONSTRUCTION after all this time).
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