UNI-T UTG932/UTG962 200MSa/s Function Arbitrary Waveform Generator

[rifkum]

The problem with the UTG962E is that the output is reduced for all output levels, whether they are near to maximum or not. OK, I can live with that, but the amplitude reading on the front panel should reflect this reduced level. You shouldn't have to remember to take 6dB off the reading when switching on AM.

Agree!  I guess I will make a label to stick on the top saying "With AM modulation enabled, level out is 6 dB below setpoint" or something like that.

I think Uni-T firmware could/should be updated to simply boost the output by 6dB and flash warning saying "with AM Mod the max output is reduced"

This seems like what Dave Jones would call a "trap for young players".

regards
dm

[807]

Idealy this generator should be programmed to do what the "big boys" do, & only reduce the carrier when it's set to within 6dB of it's maximum output level.

At the very least the firmware should have been written to show this reduced level on the Amplitude display. Surely that wouln't have taken much coding?

[rifkum]

@807,
Yes!! and I believe your second option is best since the normal workflow is to turn on Wave output level first and choose your desired level then second is to go to Mod and choose your modulation type.  And the assumption is that you will get your chosen modulated level out.

Still going to try to "hound" Uni-T tech support to correct the firmware but not holding my breath on that possibility.

Cheers
dm

Note: see my "fix" in below image

[rifkum]

Well, I got an initial response from Uni-T on my tech support question about the signal dropping 6 dB when Mod is enabled...

Message I sent:

There is a problem with the UTG962 signal generator.
When AM modulation is turned on the signal level drops by 6 dB
This happens even if the "depth" of modulation is 0%
Please confirm that this is a problem

Test conditions... 
Wave: Sine, Freq 14 MHz
Mod Sine, Freq 1 KHz

Turning Mod off/on causes the output signal to drop by 6 dB

Their Reply...

Hi
Thanks for asking the question!

AM modulation is different from FM modulation , the signal was transmitted as side band ,and the side band level will be suppressed. With 100% point of modulation , the primary side band signal will be compressed 6dB .

At the point of 100% modulation, the spectrum appears identical to a normal double-sideband AM transmission, with the center carrier at 0 dB reference level, and both side bands on either side of the primary carrier at -6 dB.

Please  refer to the link to get more theoretical explanations :
https://en.wikipedia.org/wiki/Single-sideband_modulation

 

And here is my reply back to them...

Thank you for the reply.
I agree that the side bands may be 6 dB down but in the case of the UTG962 it is the MAIN Carrier that is dropping by 6 dB when MOD is enabled no matter what the % modulation.
The center carrier SHOULD NOT DROP!!  And the level out should match what the display shows.

Please do a check on your end with a sample unit and you will see that the Center carrier drops by 6 dB when Mod is enabled.
This should not happen!!

The display on the UTG962 still shows the initial set value even though the actual level out has dropped.
This is a firmware bug!  The MAIN carrier should still show the correct value of the WAVE as displayed on the SINE output screen.

Please let me know how your test performs.

Thank you for looking into this.

Hopefully they will actually do some testing.
I'll report if I hear anything else.

Someone please speak up if I am in error here about this being a firmware issue!! 

[807]

Be interesting to see how they reply to your follow up.

Out of interest, I looked at a similar AWG, the Owon DGE2070. It appears that range of generators also behave the same as the UTG962. Here's what their manual says about AM modulation...

"In 0% modulation, the output amplitude is half of the specified value. In 100% modulation, the output amplitude is equal to the specified value."

Owon have got it wrong too IMO.

[TheoB]

I received my UTG962 and noticed that the DC offset voltage is out of spec by a lot.
I wanted to use the device as a 25 Ohm power source. A power source that can be programmed to any DC, ramp or noise voltage.
The specification says +/-3% of offset value +/-6% of amplitude value +/-2mV
I interpret this as +/-3% of the DC value +/-2mV if I set the amplitude to a small value as is the case with a DC "wave" output setting. Anyhow I get up to 12% error at +/-600mV.
I can send the device back as being not properly calibrated, but wanted to know first what others see. Simply put it in HiZ mode and measure the DC output voltage at some DC values. See my error plot.

[wasedadoc]

Notwithstanding the offset observations, the output impedance is always 50 Ohms regardless of the setting. Changing that setting only makes the display show what will (or should) be found across such an external load.

If you truly want 25 Ohms, connect a 50 Ohm resistor from output to ground and set the dial to 50 Ohm.

[TheoB]

I know, I have a 50 Ohm load connected to lower the impedance to 25 Ohm. My dut is a lower power tranceiver capable of running on a CR2032 battery. So 25 Ohm is ok.
The offset error however, is not the same for HiZ and when terminated with 50 Ohm. For DC the generator source is clearly not a voltage source with 50 Ohm output impedance only.

[Skyguard]

Hello!
I want to make a query.
I have a UTG962e that is slightly frequency shifted.
Approximately 30 hz when it is emitting 10,000,000 hz.-
Does anyone know of a hidden menu command or other way to correct this small difference?
Thank you so much

[Mechatrommer]

how about typing 9999970 Hz? or check the clock?

[electr_peter]

IIRC, there was a post (and video) how to add 10MHz reference input to UTG962.

[Skyguard]

how about typing 9999970 Hz? or check the clock?