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| RD JDS6600 25MHz 2-Channel DDS AW Function Signal Generator |
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| emocabras:
--- Quote from: vk2seb on June 24, 2017, 11:26:04 pm --- --- Quote from: gby on June 24, 2017, 01:27:56 pm ---The JDS6600 generator family has very similar functionality to the Feeltech FY3200 and the MHS-5200 generators. The JDS6600 even uses the exact same plastic case for the enclosure as the FY3200, MHS-5200. For a comparison of those other generators see: https://www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-2-channel-dds-aw-function-signal-generator/msg697718/#msg697718 --- End quote --- Huh, interesting. Thanks for the link! --- Quote from: gby ---From testing the FY3200 myself and reading on the MHS5200 they both are both limited in their output voltage range into 50 Ohm load without clipping or high distortion. So the first test I would suggest is: 1. Set 10 KHz sinewave with 20 Vpp/maximum amplitude on an oscilloscope with 1 Meg impedance. Then add the 50 Ohm termination and see if the output drops to 1/2 or if clipping or distortion starts happening. --- End quote --- 1 meg impedance, max amplitude @ 10KHz: 50 Ohm termination: --- Quote from: gby ---On these type generators the output buffer is often slew rate limited which in turn means the output amplitude at higher frequencies is limited. So, the second test I recommend is: 2. Set a 10 Vpp 100 kHz sinewave on the output into oscilloscope with 50 Ohm termination. Then increase the frequency until maximum frequency to see if or at what frequency it starts distorting horribly. --- End quote --- So I think there are 2 interesting points here, at 10MHz and at 25MHz. Because above 10MHz the amplitude is restricted down from 20Vpp to 10Vpp (probably for slew rate reasons). At the maximum frequency useable at 20Vpp (into 50 Ohms, so we should be seeing 10Vpp): Looks pretty distorted. Here's an FFT (didn't use specan because I couldn't find my big attenuator :P) So that second harmonic is at about -30dBc, which is out of spec (Spec says -40dBc). At 25MHz, it looks a bit cleaner (but the amplitude is now 10Vpp out, which should look like 5Vpp into 50 Ohms): And an FFT: Looks to be about -40dBc, so that's roughly in spec. --- Quote from: gby ---On the FY3200 generator when you change the frequency the output waveform glitches. Ideally one would expect a change in frequency with a sine wave to step change the slope at the frequency change with no step in the actual voltage. Unfortunately the FY3200 has steps in the output because the phase as well as the frequency changes when you change the frequency. So, the third test I would love to see is: 3. Set the generator to 5 Vpp, 10 kHz sine wave and then step change the frequency to 20 kHz. Try to capture on the oscilloscope the moment when the frequency changes. If you have advanced triggering I set trigger width must be < 20 uSec and then set to capture once. --- End quote --- Here's what that looks like: Slightly zoomed in: --- Quote from: gby ---When you use two channels both outputting the same frequency sine wave with the phase 90 Deg apart it would be great to repeat test 3 to insure that both channels change frequency at the same time and with no glitches. 4. Repeat test 3 but with two sine wave channels outputting sine waves with 90 Deg relative phase. --- End quote --- I couldn't find a way to change the frequency of both channels at once, so I'm not sure if that's possible. Here's what 2 channels at 90 deg phase shift look like when channel 1 is increased in frequency: --- Quote from: gby ---The last requested test is really just a question of functionality. This generator can do frequency sweeps. But, can it do frequency sweeps while outputting two wave forms? Last requested test is: 5. Can you set the generator to output 2 sine waves with 90 Deg relative phase and then sweep the frequency such that both channels sweep in frequency and stay in phase lock? In advance I thank you for any of the above tests that you could do and report back results. --- End quote --- As far as I can tell it's not possible to do sweeps on 2 channels at once. Cheers for your suggestions! --- End quote --- Hello sorry; for your measurements did you eliminate the 50 ohm load inside the generator ?. if you have not modified generator your measurements 1 Mohm be really load 50ohm. when you write 50 ohms if you entered the 50 ohm resistor to be real 25 ohm load. be, arrived one today to me, I have checked, the generator have an internal 50ohm load. sorry for bad english i write from italy |
| takfuji:
>1 Mohm be really load 50ohm. No. Generator has 50ohm output impedance, which means series resistance. vk2seb said "50 Ohm termination" and "into 50 Ohms", that means voltage get halved from the ogiginal DA output. Electoronics 101. Tak |
| emocabras:
--- Quote from: takfuji on February 28, 2018, 11:07:01 pm --->1 Mohm be really load 50ohm. No. Generator has 50ohm output impedance, which means series resistance. vk2seb said "50 Ohm termination" and "into 50 Ohms", that means voltage get halved from the ogiginal DA output. Electoronics 101. Tak --- End quote --- excuse me, I may have explained wrong, simply say that at the terminator the generator have 50ohm between output and gnd and create resistive divider. I checked pcb, 56ohm be interposed between output and gnd of channels, r38 channel 2 and r57 channel 1. with other generators do not have and to connect to my 1Mohm oscilloscope and I want to see correct amplitude I have to adjust to 50 ohm on oscilloscope input. I want to understand if eliminating 50 ohms it is possible to increase vpp of this generator. |
| takfuji:
>56ohm be interposed between output and gnd of channels Did you check it when singal is present? Those resisters are connected to BNC when signal is off, that means when the relay is turned OFF. I just probed it and found no signal at either end of R38, nor R57, when signal is present at BNC. Tak |
| 4x1md:
Does anybody know where can one find details about the communication protocol of this generator? |
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