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.
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?
5. Perhaps with the two channels sync'ed you can then sweep two channels with a phase difference simultaneously?? One can only hope....
Again, thanks for your help in evaluating this generator and sharing.
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.
Quote from: KleinsteinAn FPGA and R2R ladder DAC is rather common for the low cost Fgens.Interesting, I've haven't torn down a cheapie Fgen like this before so that explains that.Quote from: KleinsteinI would consider 4 points for further tests:
Cheers for the suggestions!
what you test ? JDS6600 ?Quote from: Kleinstein1) Noise, e.g. from the SMPS or just from the DAC: So maybe use just a DC or low amplitude sine.
DC out at 1V, AC coupled, output OFF:
Same as above, output ON:Quote from: Kleinstein2) DAC linearity: This can usually be seen from a slow triangle / ramp.
Triangle wave, 1KHz, 1Vpp:Quote from: Kleinstein3) 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.
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: Kleinstein4) 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.
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;
what you test ? JDS6600 ?
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.
Quote from: gby4. 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?
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: gby5. Perhaps with the two channels sync'ed you can then sweep two channels with a phase difference simultaneously?? One can only hope....
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: gbyAgain, thanks for your help in evaluating this generator and sharing.
No worries at all!
Quote from: RD Techwhat you test ? JDS6600 ?Yes, all the waveforms I have posted are from the JDS6600.
Quote from: RD Techwhat you test ? JDS6600 ?Yes, all the waveforms I have posted are from the JDS6600.I just check all picture carefully, there is no problem, if you think there is some problem, please point it out, I will explain
I don't believe the 60Mhz claim. I'm sure there's something there, but I'll bet it winds up looking like a weak, wobbly triangle wave than a pure sine.
Yes! Finally! My JDS6600 has arrived!
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Speaking of the feeltech product, I came across a YouTube video in which a young engineer took it upon himself to improve on the old feeltech signal generator. With the addition of a few jumper wires and a couple of components, he improved it a great deal. The funny part was when he said," I don't know why they used XXXX part. This other part is a much better match for what they're doing, and it's cheaper!"
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The device has a very poor Electromagnetic compatibility,
Interference is caused by DC / DC motherboard converters.
This is noticeable immediately after switching on, if we put a probe next to it.
Sensitivity 500uV / div
Bandwidth 300MHz
The probes of the oscilloscope are connected to ground, there is no signal at the input, noise JDS6600 is very high.
Maybe it's because of your lousy way of connecting the probes to the signal generator.
First time that I see a Rigol DS2000A user (supposed to be professional player) without decent cables
If I am correct, the actual designer of this signal generator is in this thread. Maybe you can PM him with your suggestions to further improve the design.
I juste tested a JDS6600 60MHz model and it has a big problem, when set on certain frequency there is a phase shit