The Siglent SDG2042X Thread

[McBryce]

I'm going to build the Elenco AMFM108CK radio kit, and in the manual we can see several figures like this:



There is a capacitor between the function generator and the DUT.
So guess this is to block DC entering the generator when sending a signal into the middle of a circuit. Is this common, and a good way to protect the generator?

Full manual available here: https://www.elenco.com/wp-content/uploads/2017/10/AMFM-108CK_low-res-2.pdf

I think they just want show "best practice". As they don't know what sig-gen you are using or the quality thereof, they just want to ensure that you are not injecting DC into the circuit. If you are using a high-end sig-gen, where you are sure that the signal has no DC component you could leave the capacitor out.

McBryce.

[Performa01]

If you are using a high-end sig-gen, where you are sure that the signal has no DC component you could leave the capacitor out.

Signal-, Function- and Arbitrary Wave- Generators in general have DC-coupled 50 ohms outputs. High-end devices might have optical ports on top of that or exclusively.
Audio generators on the other hand, especially older ones, usually have 600 ohms outputs, still DC coupled, but often without the option to add an arbitrary DC offset.

That does not mean that some special (mostly DIY) signal sources with AC coupling cannot exist, but these are certainly not "high end".

So, having a DC blocking capacitor between generator output and circuit does two things:

• Protect the generator from high DC reverse voltages
• Prevent any effects on the circuit operation because of shunting DC bias voltages to ground through the internal 50 or 600 ohms generator source impedance

If fiddling with your own circuit, you might still use the DC offset feature of an AWG like the SDG2042X as a variable, remote controlable bias voltage for an amplifier stage. Especially handy for class B and C amplifiers, like they are common in narrowband HF applications.

[Johnny B Good]

 Attaching a 'scope probe to any part of an amplifier circuit is usually no problem (aside from the possibility of connecting to high voltage points in valved (tubed) kit), so the normal practice is to feed your test signal into its input socket where there are normally no pesky dc bias voltages to ruin your day.

 For the really paranoid (those of us all too familiar with "Sod's Law"), you might take the precaution of testing for the presence of day ruining dc voltages on the input before connecting your precious signal generator. You would then work backwards with the 'scope probe to look for the missing or an undistorted test signal rather than try working forwards injecting generator test signals.

 If you feel the need to work forwards with a test signal, that only makes sense if you're familiar with the (in this example) amplifier circuit and the various dc bias voltages you expect to encounter. For audio work in relatively lo-Z BJT based amplifier designs as per the example shown, that 1nF coupling cap seems a little on the low side imo. It seems to me that a 1uF cap with a 1K ESD limiting resistor in series would be a better choice here.

 In short, this working forward with a test signal requires some familiarity (experience, or else an actual circuit diagram to hand) of what you're working on to reduce the risk of damage to the signal generator and/or amplifier.

 Injecting test signals into a circuit should be the last resort to tracking down a fault. A better strategy would be to probe with a voltmeter and verify that the bias voltages are close to where they should be before blindly diving in with a sig generator. As with using a 'scope probe, you're merely measuring voltages rather than introducing a disturbing influence on the circuit's operation.

[blurpy]

Thanks for the feedback!

The reason for injecting a signal in this case is because the radio kit has very defined and somewhat isolated sections, like you can see from the image. First and second IF amplifier, AM detector, audio amplifier and several more. The sections are built starting at the "end", so you make the audio amplifier first. Need to inject a regular audio signal into that to test it. Then the AM detector. Need to inject some signal to test that as well, and so on. Finishing with the antenna, where you can finally test the complete circuit.

Looking forward to playing with modulation for a realistic use case on the SDG2042X.

Any best practice on how to hook onto a pcb with a cap on the generator probe? Looks a bit awkward.

[Johnny B Good]

@blurpy

 I was answering from a general usage case point of view, not having followed the link to the construction manual beforehand, hence my remark over the what seemed an unusually low capacitor value. When I did look at that instruction manual a day later, I realised that in this case, the choice had been entirely reasonable for the particular test in hand. However, for general fault finding on kit you're not actually constructing, the advice to use a larger cap value with a current limiting resistor (1 to 10K being a good starting value) still stands.

 Regarding probing around with a test signal, I'd be inclined to use a 'scope probe for this. You generally only need micro to milli volts of test signal anyway in most cases with audio and IF or RF stages so even if you have to set the probe's attenuation factor to x10 to inject vhf test signals, this will still prove effective, after all, it's not as if you don't have several volts peak to peak's worth of test signal available from that SDG2042X to play with. 

 The only issue being the need to connect the ground fly lead to a grounding point as close to the injection point as is conveniently practicable. If required, you can even use the grounding spring attachment to minimise leakage to other parts of the circuit to minimise any confusing results that could arise. However, not bothering with a ground clip connection and just applying the probe tip to the injection point will usually suffice in most cases. You can save resorting to the ground wire clip or probe spring attachment to help reduce confusion between two or more test points that may be giving similar responses.

 If you're working with audio frequencies, you can just use a cheap BNC to croc clip ended cable and attach a cap with a small series resistor onto the hot end croc clip as a makeshift probe and connect the other croc clip to the DUT's ground.

[jhormilla]

Hi all, I'm considering buying a SDG2042X any way of getting a copy of 17R5? Any help would be appreciated.

[tautech]

Hi all, I'm considering buying a SDG2042X any way of getting a copy of 17R5? Any help would be appreciated.

Welcome to the forum.

All the old FW versions are available here:
https://int.siglent.com/download/firmwares/?ProId=5

[rf-loop]

Hi all, I'm considering buying a SDG2042X any way of getting a copy of 17R5? Any help would be appreciated.

Welcome to the forum.

All the old FW versions are available here:
https://int.siglent.com/download/firmwares/?ProId=5

source version  object version
2.01.01.35R3B1 2.01.01.35R3B2 Tested.
2.01.01.23R8 2.01.01.35R3B1 Tested.
2.01.01.23R7 2.01.01.35R3B1 Tested.
2.01.01.23R7 2.01.01.23R8 Tested.
2.01.01.23R5 2.01.01.23R8 Tested.
2.01.01.23R3 2.01.01.23R8 Tested.
2.01.01.22R5 2.01.01.23R8 Tested.
2.01.01.21R2 2.01.01.23R8 Tested.
2.01.01.17R5 2.01.01.23R8 Tested.
2.01.01.16R2 2.01.01.23R8 Not compatible. Please update to 2.01.01.17R5 at first
2.01.01.15R2 2.01.01.23R8 Not compatible. Please update to 2.01.01.17R5 at first
2.01.01.12R1 2.01.01.23R8 Not compatible. Please update to 2.01.01.17R5 at first

Available in Siglent web side 2.01.01.23R3 is most old.


I believe  it is so that if someone have SDG with version what is below 2.01.01.17R5 then he need first update to 2.01.01.17R5
2.01.01.16R2 
2.01.01.15R2 
2.01.01.12R1

And as we know, after  2.01.01.17R5 or later then can not anymore go back to older versions than 2.01.01.17R5.

I have some of these old versions. Btw, these older versions are not packaged to .ZIP, they are .RAR
(I will send  I have sent 2.01.01.17R5 to @tautech )

[jhormilla]

Hi all, I'm considering buying a SDG2042X any way of getting a copy of 17R5? Any help would be appreciated.

Welcome to the forum.

All the old FW versions are available here:
https://int.siglent.com/download/firmwares/?ProId=5

Thank you

source version  object version
2.01.01.35R3B1 2.01.01.35R3B2 Tested.
2.01.01.23R8 2.01.01.35R3B1 Tested.
2.01.01.23R7 2.01.01.35R3B1 Tested.
2.01.01.23R7 2.01.01.23R8 Tested.
2.01.01.23R5 2.01.01.23R8 Tested.
2.01.01.23R3 2.01.01.23R8 Tested.
2.01.01.22R5 2.01.01.23R8 Tested.
2.01.01.21R2 2.01.01.23R8 Tested.
2.01.01.17R5 2.01.01.23R8 Tested.
2.01.01.16R2 2.01.01.23R8 Not compatible. Please update to 2.01.01.17R5 at first
2.01.01.15R2 2.01.01.23R8 Not compatible. Please update to 2.01.01.17R5 at first
2.01.01.12R1 2.01.01.23R8 Not compatible. Please update to 2.01.01.17R5 at first

Available in Siglent web side 2.01.01.23R3 is most old.


I believe  it is so that if someone have SDG with version what is below 2.01.01.17R5 then he need first update to 2.01.01.17R5
2.01.01.16R2 
2.01.01.15R2 
2.01.01.12R1

And as we know, after  2.01.01.17R5 or later then can not anymore go back to older versions than 2.01.01.17R5.

I have these old versions. Btw, these older versions are not packaged to .ZIP, they are .RAR
(I will send 2.01.01.17R5 to @tautech )

[tautech]

Hi all, I'm considering buying a SDG2042X any way of getting a copy of 17R5? Any help would be appreciated.

PM sent.

[ebastler]

Hi all, I'm considering buying a SDG2042X any way of getting a copy of 17R5? Any help would be appreciated.

Just wondering -- why is that firmware version required? Are you buying an old SDG2042X with very old firmware on board, so you need 17R5 as an interim step to get to the current firmware?

[RoadRunner]

Hallo,

I own a SDG2042X from quite a few years, but some how today is the first time I needed to AM modulate with an external Signal. I just can't get it work. I have plugged External signal to Aux BNC with level of 12Vpp. But AM, FM or another modulation that may use analog external modulation signal does not work.

If i try to use FSK or ASK external modulation works, I suppose as for these modulation external modulation signal need to be a digital input?
But AM, FM, PWM modulation does not work with external modulation, I guess because they will an analog input?

Can anyone with SDG2000X please take your time for me and verify if external modulation work for AM or FM for them?
I have firmware version 2.01.01.35R3B2

Regards


Here is the solution

Found the issue to be U41 which is 3.0 Regulator AF7230M to be faulty. U41 supply 3.0V to external modulation ADC. Regulator has been replaced with alternative and issue is solved.

[Caliaxy]

I own a SDG2042X from quite a few years, but some how today is the first time I needed to AM modulate with an external Signal. I just can't get it work. I have plugged External signal to Aux BNC with level of 12Vpp.

Have you tried modulating with a lower amplitude? According to the manual, an external modulation of +/-6Vpp corresponds to a depth of modulation of 100% (the maximum 120%).

[RoadRunner]

I own a SDG2042X from quite a few years, but some how today is the first time I needed to AM modulate with an external Signal. I just can't get it work. I have plugged External signal to Aux BNC with level of 12Vpp.

Have you tried modulating with a lower amplitude? According to the manual, an external modulation of +/-6Vpp corresponds to a depth of modulation of 100% (the maximum 120%).

Thank you for pointing out, I think i misunderstood, but from datasheet "The output amplitude will be the maximum when the modulating signal is +6V and the minimum when the modulating signal is -6V" does this mean 6Vpp or 12Vpp?

I had started initially with really low voltage around 2Vpp (+1V to -1V) it didn't work, once manual was read then i set voltage to 12Vpp (+6v to -6V) but it still didn't work.

All the digital modulation works always though.

[thinkfat]

+6V to -6V is 12Vpp, but also specifies that the expected modulation signal must not have DC offset. Thats something else to check. 0V - 12V would also be 12Vpp but violate the given constraint.

[rf-loop]

+6V to -6V is 12Vpp, but also specifies that the expected modulation signal must not have DC offset. Thats something else to check. 0V - 12V would also be 12Vpp but violate the given constraint.

I can not now test using SDG2kX.
But this is how it is with SDS1kX and for Ext modulation specs are same if look both datasheets.

External modulation is DC coupled. Signal nominal/typical range is +6V to -6V and input impedance is 10k
These are typical values. (limits are min 11Vpp and max 13Vpp for full 100% mod depth)
Maximum modulation frequency is 50kHz
Modulation input is Aux In/Out BNC in rear panel,  later I use ExtMod name for it.




Modulated signal output voltage level is roughly 0 when ExtMod input is -6V
Modulated signal output voltage level is "full" when ExtMod input is +6V
When signal to ExtMod input is 0V  modulated signal level is half way from max.

If it works or not it can test just using suitable DC and oscilloscope.
SDG1000X: (apparently the SDG2000X works in the same way in this particular case - least I believe)

Very first set SDG for factory defaults.
Set SDG output for Hi-Z and connect it to iscilloscope 1Mohm input.
Set SDG for example 1MHz sinewave 1Vpp
Turn modulation ON, Type AM and Source External.



Adjust ExtMod DC voltage to 0V (BNC center to 0V or just do not connect anything to ExtMod so its level is around 0V)
Oscilloscope should now display around 1Vpp signal.

Next
Adjust ExtMod DC voltage to +6.0V  (BNC center to +6V  BNC GND is GND aka 0)
Now oscilloscope should display around 2Vpp signal.  (with 3V around 1.5pp)

Adjust ExtMod DC voltage to -6.0V  (BNC center to -6V  BNC GND is GND aka 0)
Now oscilloscope should display around 0Vpp signal. (with -3V around 0.5V)

Most simple  "go/no go" style test can do using just onew battery.

Also of course SDG other output can use as adjustable voltage source also for playing this...just connect it using coaxial to rear panel ExtMod only remember adjust this channel for HiZ Load (or 10kohm load) because ExtMod impedance is 10k. If adjust it for HiZ level error is irrelevant in this case.

If you have now example -6V to +6V 1kHz sinewave signal you have then 1MHz signal AM modulated with 1kHz and modulation depth 100%.

Note that ExtMod input true levels/mod depths may have some differeences between individual units and manufacturing lots.

If it do not at all works like this, then there is some problem on your cables or other things OR  SDG  ExtMod is broken.

[RoadRunner]

Just tried one more time. Reset everything setup once again. All digital modulations works so cable and setup works, but no analog modulation works regardless of input or level.

It would be really great help if anyone could try with instrument with current firmware.

Regards

[RoadRunner]

Found the issue to be U41 which is 3.0 Regulator AF7230M to be faulty. U41 supply 3.0V to external modulation ADC. Regulator has been replaced with alternative and issue is solved.

[tautech]

Found the issue to be U41 which is 3.0 Regulator AF7230M to be faulty. U41 supply 3.0V to external modulation ADC. Regulator has been replaced with alternative and issue is solved.

Wow, good detective work. 

Would you mind going back to your first post and adding: Solved, it was a HW fault.

Do you have any idea why U41 may have failed ?

[RoadRunner]

Found the issue to be U41 which is 3.0 Regulator AF7230M to be faulty. U41 supply 3.0V to external modulation ADC. Regulator has been replaced with alternative and issue is solved.

Wow, good detective work. 

Would you mind going back to your first post and adding: Solved, it was a HW fault.

Do you have any idea why U41 may have failed ?

I really have no idea, I have been looking for quit some time. Scratching my head, is it a software issue or hardware issue.

[tautech]

Found the issue to be U41 which is 3.0 Regulator AF7230M to be faulty. U41 supply 3.0V to external modulation ADC. Regulator has been replaced with alternative and issue is solved.

Wow, good detective work. 

Would you mind going back to your first post and adding: Solved, it was a HW fault.

Do you have any idea why U41 may have failed ?

I really have no idea, I have been looking for quit some time. Scratching my head, is it a software issue or hardware issue ?

Faults in these are pretty rare other than output stage damage from reverse voltages so it would seem your U41 failure is very unusual.
I've never had one apart but the more info you can give us can maybe help others that have a similar problem.
Even some pictures and external tests of U41 showing it faulty would be great to have so to help anyone else.

[RoadRunner]

I tried to follow modulation signal path through relay,  than into ADC found that U41 not generating 3.0 needed. I removed U41 and first supplied power with my power supply,  only consumed 1mA and everything just worked.

Somewhat strange is that marking suggest with part is AF7230M  also matches in voltage and function being regulator. but AF7230M  datasheet shows input and output pins swapped.

Input on U41 is around 6.4V with that there are not many regulators in the market that are in same pinout and accept >6V at input.

[RoadRunner]

I would highly appreciate, If anyone could suggest a regulator with 3.0V out 100mA >6V Vin with SOT-23-3 package and pin 1 being input ,2 output and 3 GND.
I have tried looking around found none that meets all expectation. AP7313 meets all but not max input voltage.

[jeraymond]

Anyone come across an issue where the frequency drifts when burst is enabled?

I have my SDG2042X connected to an external 10MHz reference. I set a 10 MHz sine wave on CH1 and enabled the output. Feeding both the reference and SDG CH1 output to my oscilloscope I see the signal phases are stable relative to each other. Next, I switch to CH2 and enable burst (output not yet enabled on CH2). On the oscilloscope I see CH1 now drifting from the input reference. The CH1 keeps drifting until I disable burst on CH2 and toggle the output of CH1 on/off (or change freq on CH1).

I'm running the latest firmware I see v 2.01.01.35R3B2.

[Hexley]

Anyone come across an issue where the frequency drifts when burst is enabled?

That behavior can be reproduced on an SDG1000X box. Drift starts when the other channel's burst is engaged, just as you reported.