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Motorola Syntrx
Syntrx
The Motorola Syntrx has been a great radio, and it is easily modified and got running on the Amateur Radio Bands. With the use of an eprom, and tuning details you will find it easy to change.
Syntrx - Frequency Plan
The Eproms Board that have been designed by Ben VK5ABE allow the use of a single Eprom Image to cover both 2m and 70cm bands.
VK5 - 2M Syntrx Frequency Plan - Issued 22/11/2005 VK5 - 70cm Syntrx Frequency Plan - Issued 22/11/2005
Syntrx - VK5ABE Eprom Board Howto
For information on setting up the Syntrx using the VK5ABE Eprom Board, please download the PDF document below.
VK5ABE Syntrx Eprom Board Assembly - Issued 22/11/2005
TUNING UP A 70cm SYNTRX THE HAM WAY
This section of the page can be downloaded as a PDF file, SYNTRX_TUNING.PDF
Equipment needed,
Power lead
10amp power supply
Communications test set of some type.
Dummy load
Tuning tools.
BEFORE YOU START
CHECK ALL THE FOLLOWING LINKS AND COMPONENTS ARE IN!
Jumper
JU1
JU2
JU3
JU4
JU101
JU102
JU103
JU400
JU401
JU402
JU403
JU404
JU405
JU406
JU407
JU408
JU409
JU410
JU411
Q101Installed status
Q3 front end transistor
normal
Short if PL PCB not fitted
Short
Ref osc config
Ref osc config
Ref osc config
Short
Open
Open
Open
Short
Short
Open
Short
Short
Open
Open
Open
PNP transistor TX Audio gate
1 Insert AREG test prom with even test frequencies,
this just makes life easy. (normal channel plan is ok
if this is all you got)
2 TX VCO
While cycling the PTT on the microphone adjust the transmit VCO until the radio stops beeping on ptt. Find
the two limits and tune to the tuning slug to mid position.
Now measure the voltage at R230 nearest the deviation pot as below. Fine tune the TX VCO for approx 4 volts. Make sure the VCO locks on the lowest and highest.
3 TX Filter
You will be adjusting L206 and L205 on the center frequency. Transmit by pressing the PTT, adjust both filters until you read
maximun power output into the dummy load.
Now change channels between the upper and lower requencies trying to obtain a flat as possible response. Eg alanced for equal power.
4 Modulation Deviation
Using the deviation pot located near the refrence oscillator, adjust the level to obtain +- 5kHz with a whistle.
5 Reference Oscillator
Transmit by pressing the PTT, now adjust the
Reference Oscillator pot for +- 100Hz.
6 Receiver VCO
In receive mode (eg not pressing the PTT) adjust the VCO coil to obtain 4volts at the test point (R230 nearest Deviation pot, same at TX VCO).
The best way top obtain this is to generate a signal at the middle frequency, Tune the VCO coil to the upper and lower limit until the the VCO is out of lock. The middle position will be close.
7 Receiver Front End Pre Adjustment
Place the Communications test set to the middle generate frequency, Select the middle frequency channel on the radio. Inject a signal level enough to be heard on the receiver. Now
adjust L1,L2,L4 and L5 to obtain maximum sensitivity whilst reducing the input signal level.
8 Receiver VCO Filter
Adjust L7 and L6 for maximuin sensitivity on the middle channel frequency to start with. Now adjust for the lower and upper frequency channel to get a good balanance possible.Receiver Front End Final Adjustment
Follow procedure 6 over and over until you get the best sensitivity. You
should after a few runs of the above obtain a good signal at 0.5uV
9 Squelch Threshold
Adjust the squelch pot through the largest hole on the PL board if fitted. Adjust the pot so the squelch just mutes the audio with no signal to start with. If the PL PCB is not fitted refer to second figure. Now generate a carrier with enough level to be received on the speaker that has about 50% noise. The squelch should open letting the sound through to the speaker. This is a personal preference, basically adjust the pot so the minimum signal you like opens the squelch.
10 Ok you have finished!
Hopefully you have not smoked the radio up!
Remove the test prom and insert you AREG Eprom PCB in the same socket.
Insert the 70cm channel plan eprom and all should be good.
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Page updated on 9 May 2008 |
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