Help. I can see RF coming out of teh board and it's at teh right frequency but nothing being decoded. Are there jumpers that should be on JP1 to make it go?
LEd flashing and software seems to be working. Anything else I can test?
Andrew
Digilite Jumpers
Re: Digilite Jumpers
JP1 is for expansion. There are no jumpers to set.
The LED should be flashing on/off at 1Hz. DigiLite Transmit should show the packet counters increasing, Avail 100k or less, PCR Lag Now not negative, Pad% about 5, Serialiser Reboots and Resyncs not occurring.
Have you adjusted the pots? In the absence of a spectrum analyser (like myself) I have set the DC bias on the I and Q inputs to the modulator to 1.2v and peak-peak level on each to 500mV. The peak-peak level should be 1v in theory, but try that for the moment. Selecting the In Phase test mode on DigiLite Config gives a sine wave on I and Q. DigiLite Transmit needs to be running to use the test modes.
There are 2 handy vias for a scope probe: I is between R12 and pin 1 of the modulator and Q is in line with and near R14.
Brian
The LED should be flashing on/off at 1Hz. DigiLite Transmit should show the packet counters increasing, Avail 100k or less, PCR Lag Now not negative, Pad% about 5, Serialiser Reboots and Resyncs not occurring.
Have you adjusted the pots? In the absence of a spectrum analyser (like myself) I have set the DC bias on the I and Q inputs to the modulator to 1.2v and peak-peak level on each to 500mV. The peak-peak level should be 1v in theory, but try that for the moment. Selecting the In Phase test mode on DigiLite Config gives a sine wave on I and Q. DigiLite Transmit needs to be running to use the test modes.
There are 2 handy vias for a scope probe: I is between R12 and pin 1 of the modulator and Q is in line with and near R14.
Brian
Re: Digilite Jumpers
Thanks Brian,
I found a bad connection under R31 so the bias volts were sitting at 5 v. I can't find anything saying what the bias V should be? Also I don't seem to be getting 500mv at you test points but that's maybe another dodgy joint. This soldering is at the limits of my eyesight!! Any other info from any other members on the line up and testing would be gratefully recieved, I'm using a freesat receiver to attempt to decode and think I've got the parameters correct. I'm seeing signal strength at the right frequency but no demod happening.
Andrew
I found a bad connection under R31 so the bias volts were sitting at 5 v. I can't find anything saying what the bias V should be? Also I don't seem to be getting 500mv at you test points but that's maybe another dodgy joint. This soldering is at the limits of my eyesight!! Any other info from any other members on the line up and testing would be gratefully recieved, I'm using a freesat receiver to attempt to decode and think I've got the parameters correct. I'm seeing signal strength at the right frequency but no demod happening.
Andrew
Re: Digilite Jumpers
You need to get the levels set roughly as above first. Can you trace I and Q from the 74AC574 using the circuit diagram and see if they get to the modulator.
Which VCO are you using and is it well shielded? I would separate the receiver and the DigiLite as far as possible to minimise problems with direct LO pickup on the receiver.
You could check the 8 data lines in between the FT2232H and the PIC. Have a look on the PIC on pins 2, 3, 4, 6, 7, 11, 12, 26.
You should see lots of square wave activity when running normally (not test mode) on the PC. Some of the positive going edges will look a bit slow due to the tri-stating on the bus.
Brian
Which VCO are you using and is it well shielded? I would separate the receiver and the DigiLite as far as possible to minimise problems with direct LO pickup on the receiver.
You could check the 8 data lines in between the FT2232H and the PIC. Have a look on the PIC on pins 2, 3, 4, 6, 7, 11, 12, 26.
You should see lots of square wave activity when running normally (not test mode) on the PC. Some of the positive going edges will look a bit slow due to the tri-stating on the bus.
Brian
Re: Digilite Jumpers
If you have V5.6 board then check the digilite website main page for the correction/mod to the uderside of the board, this effects the I/Q bias levels to the modulator.
Rob
Rob
Re: Digilite Jumpers
Ok found a couple of dodgy joints and now got signals, square waves around the board. Still not getting anything to demos with receiver. I've done the mods as detailed and have vco and rx well screened and distanced as suggested.I'll keep tring. I can't see the difference the bias pots make to i&q at the modulator chip though?
Sorry if I'm asking stupid questions.
Sorry if I'm asking stupid questions.
Re: Digilite Jumpers
I have made some voltage readings around the pots etc and that is part of the CQTV article.Here is a paragraph that might help you.....
Ensure the regulators are working properly. With a dc supply of 12v the DigiLite board should draw about 150mA. The local oscillator described here draws 60mA.
Sliders of I & Q Bias presets R29/R30 should be set to mid-way initially.(2.1v on sliders)
Set I & Q Level presets R16/R23 to mid-way. ( 4v on sliders)
Check IC4 pin 11 (output) for between 3.5 and 4v.
Check for approx. 4v on output leg of MMIC.
Also mentioned in the article is the importance of getting the correct local oscillator level. Too much or too little you will not get results.
This may help you pin down the problem. To assist others please report back here when you discover the problem or let us know if you are still in trouble and we will go into more detail.
Dave G8AJN
Ensure the regulators are working properly. With a dc supply of 12v the DigiLite board should draw about 150mA. The local oscillator described here draws 60mA.
Sliders of I & Q Bias presets R29/R30 should be set to mid-way initially.(2.1v on sliders)
Set I & Q Level presets R16/R23 to mid-way. ( 4v on sliders)
Check IC4 pin 11 (output) for between 3.5 and 4v.
Check for approx. 4v on output leg of MMIC.
Also mentioned in the article is the importance of getting the correct local oscillator level. Too much or too little you will not get results.
This may help you pin down the problem. To assist others please report back here when you discover the problem or let us know if you are still in trouble and we will go into more detail.
Dave G8AJN
Re: Digilite Jumpers
Thanks, I'm getting somewhere slowly.
With the voltage checks I've set R29 and 30 to give 2.1V bias
On I & A level presets is this with signal input from the PC present? with just the board I get a range of between 1.65 and 1.95V? not 4V so something seems amiss in this area unless I should be passing signal when measuring
Ic4 does have 3.7V on output and I assume MMIC is the MAR6? Again with no signal this sits at 1.64V. ( I changed the IC as when I first checked I had 7.5V on output and input so asumed this was not good!)
Unit draws 150mA again without the PC connected.
Can you confirm if your readings were with on without the PC connected. I'll try another run with the sat receiver again later, after dark as XYL wants garden sorted and non compliance not allowed!!!
A
With the voltage checks I've set R29 and 30 to give 2.1V bias
On I & A level presets is this with signal input from the PC present? with just the board I get a range of between 1.65 and 1.95V? not 4V so something seems amiss in this area unless I should be passing signal when measuring
Ic4 does have 3.7V on output and I assume MMIC is the MAR6? Again with no signal this sits at 1.64V. ( I changed the IC as when I first checked I had 7.5V on output and input so asumed this was not good!)
Unit draws 150mA again without the PC connected.
Can you confirm if your readings were with on without the PC connected. I'll try another run with the sat receiver again later, after dark as XYL wants garden sorted and non compliance not allowed!!!
A
Re: Digilite Jumpers
ok padded down the LO and now the sat RX shows green 80% signal bar but nothing demoded? Still no 4V at the I & A level pots?
We'll get there eventually!
A
We'll get there eventually!
A
Re: Digilite Jumpers
It's best to always have the USB connected to the PC.
If data is not being sent from the PC, there will be a pseudo random pattern being sent to the modulator by the PIC. The best way of setting levels is to have DigiLite Transmit running and select 'In Phase' test mode on DigiLite Config. This give a sine wave on I and Q at the modulator.
Are you making measurements with a meter or scope?
Brian
If data is not being sent from the PC, there will be a pseudo random pattern being sent to the modulator by the PIC. The best way of setting levels is to have DigiLite Transmit running and select 'In Phase' test mode on DigiLite Config. This give a sine wave on I and Q at the modulator.
Are you making measurements with a meter or scope?
Brian