Products > Test Equipment
RD JDS6600 25MHz 2-Channel DDS AW Function Signal Generator
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RD Tech:

--- Quote from: Kleinstein on June 25, 2017, 02:07:32 pm ---The parts used seem to be a little more expensive (e.g. AD835 instead of lower cost AD603)  than those in the super cheap versions. The amplifiers also look rather fast. Still strange that there are additional AD8017.

I finally found the higher resolution pictures. So I got a look at the DAC: they seem to use 15 lines in a thermometer style to get the upper about 4 Bits with less errors / glitches. So the DAC is not just an R2R ladder.

--- End quote ---
you should know quality decide the price ...
acastlenut:
I received my JDS6600/25Mhz about a week ago and I am suitably impressed with its functionality. I have put it through some tests on a Siglent SDS 2204X 200Mhz DSO and it performs rather well. The two exceptions are a)  the power pack leaks 78 V AC measured from mains earth to the DC ground of the power pack. Leakage current is 14µA. Not life threatening and can be fixed by replacing it with a transformer based PS. b) Both BNC connector cables have a very intermittent and tenuous connection when plugged into the generator. Sometimes I cannot get a solid signal without putting side tension on the leads.
To vk2seb, I enjoyed your presentation video and noted the relay click noise was masked by the incessant transducer beep. There is a way to turn of the beep and save that setting so it never sounds unless you turn it on again. Also QBY's question regarding both channels syncing. As far as can see the SYS button lets you set the frequency, waveform, amplitude, offset and duty to track (sync) chan 1 and chan 2. This is also true in the software which drives the JDS6600 through the USB port. Altogether a nice piece of kit.
vk2seb:

--- Quote from: gby ---  4.  For changing the frequency when both channels are running the same frequency you say:
    "I couldn't find a way to change the frequency of both channels at once, so I'm not sure if that's possible"
These generators usually have a channel synchronization mode where you lock them such than changing one channel parameter changes both channels.  In the JDS66000 manual I found on line it says under the system setting menu:

4.4.2 Sync: When sync, CH1 is the object of operation. CH2 parameter will be changed with the changes of CH1 parameter. When the sync item is selected, you can press  or knob to select the sync item needed, press ON softkey to select and press OFF softkey to cancel.

Could you check for the system setting sync function and try changing the frequency of two channels locked at 90 Deg phase again?

--- End quote ---

You're dead right, a case of 'RTFM, vk2seb' ;).

Here's what that looks like 10KHz->20KHz, 90 deg phase lock, 5Vpp:



So yeah, channel 2 is definitely not behaving there.


--- Quote from: gby ---  5.  Perhaps with the two channels sync'ed you can then sweep two channels with a phase difference simultaneously??  One can only hope....

--- End quote ---

Good news: You can indeed sweep the 2 channels simultaneously.
Bad news: They don't stay in phase lock.

With a 0 deg phase set (sweeping 10KHz->20KHz):


With a 90 deg phase set (sweeping 10KHz->20KHz):


Difficult to get a capture of the whole sweep without nothing meaningful being visible.


--- Quote from: gby ---Again, thanks for your help in evaluating this generator and sharing.

--- End quote ---

No worries at all!
vk2seb:

--- Quote from: acastlenut ---The two exceptions are a)  the power pack leaks 78 V AC measured from mains earth to the DC ground of the power pack. Leakage current is 14µA. Not life threatening and can be fixed by replacing it with a transformer based PS. b) Both BNC connector cables have a very intermittent and tenuous connection when plugged into the generator. Sometimes I cannot get a solid signal without putting side tension on the leads.

--- End quote ---

Ooft, nice find on the mains leakage. I haven't been able to break my BNC connection by wobbling it around a fair bit (just tried), maybe luck of the draw? :/


--- Quote from: acastlenut ---To vk2seb, I enjoyed your presentation video and noted the relay click noise was masked by the incessant transducer beep. There is a way to turn of the beep and save that setting so it never sounds unless you turn it on again. Also QBY's question regarding both channels syncing. As far as can see the SYS button lets you set the frequency, waveform, amplitude, offset and duty to track (sync) chan 1 and chan 2. This is also true in the software which drives the JDS6600 through the USB port. Altogether a nice piece of kit.

--- End quote ---

Glad you enjoyed it! Good point on the annoying transducer beep, I'm definitely going to try that. You're right about the channel synchronization, I didn't RTFM ;)
RD Tech:

--- Quote from: vk2seb on June 24, 2017, 09:26:40 am ---
--- Quote from: Kleinstein ---An FPGA and R2R ladder DAC is rather common for the low cost Fgens.

--- End quote ---
Interesting, I've haven't torn down a cheapie Fgen like this before so that explains that.

--- Quote from: Kleinstein ---I would consider 4 points for further tests:

--- End quote ---

Cheers for the suggestions!
what you test ? JDS6600 ?


--- Quote from: Kleinstein ---1) Noise, e.g. from the SMPS or just from the DAC: So maybe use just a DC or low amplitude sine.

--- End quote ---

DC out at 1V, AC coupled, output OFF:



Same as above, output ON:




--- Quote from: Kleinstein ---2) DAC linearity: This can usually be seen from a slow triangle / ramp.

--- End quote ---

Triangle wave, 1KHz, 1Vpp:




--- Quote from: Kleinstein ---3) Output amplifier slew rate: Many similar low cost generator run in to a slew rate limit with full amplitude and high frequency. So usually the maximum amplitude is reduces at the highers frequency.

--- End quote ---

Here's a sine wave, 25MHz, set to 1Vpp (but into a 50 Ohm load so what we 'should' see is 500mVpp)



Same as above, but a square wave:




--- Quote from: Kleinstein ---4) There are 2 relays per output channel. So this could be an output attenuator. This has good sides, but might also limit the Offset range, when using low amplitudes.

--- End quote ---

Looks like you were right about the output attenuators, at 100mVpp setting (into 50 Ohms again), the maximum offset I can set is 0.25V;



--- End quote ---
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