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Review: Hantek DDS 3X25. Anyone own one?
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saturation:
3 more 1052E grabs.

-3dB mark is likely for the Hantek, 32 MHz.  White is at 0dB for comparison, see photos below.  I think this is correct because the 1052E is rated to ~ 50 MHz, which is its -3dB mark, and this response is consistent with the tested rise times, blue is from a test signal from the Instek 1003, yellow is the rise time of the Hantek:



The slower Hantek gives ~ bandwidth of 0.35/15.5ns ~ 22.6 MHz.
The faster Instek gives ~ bandwidth of 0.35/4.8nS ~ 72.9 MHz.  

The above suggests the Rigol is much faster the Hantek, so the roll off is most likely caused by the Hantek.

Other 2 photos below are:

Sine output and sync output, in sync up to 2.5 MHz.

Unstable sync output at 2.8 MHz.  Using persistent view to show instability.



saturation:
dajones initially reported about the inability of the 3X25 to provide a suitable sync signal, that I confirmed.

The manual states the output port is capable of ~ 50mA, at 3.5v.  That suggests it was designed for an impedance of ~ 70 ohms.  I measured the sync output port at nearly 50mA too.  

Thus, all you need do is terminate the sync output at 50 ohms, and you have a usable sync signal good to 25 MHz.  I've confirmed this.

I have not solved the jitter issue, its still there.

Yellow is the signal output, blue is the sync signal.



At 25 MHz, there is at least a 45 marked phase shift.  But a stable image can be made by adjusting trigger level.



So fairly small excursions can be sync'd, here's 8mVpp, the limits of the 3x25 before severe pixelation begins.



alm:

--- Quote from: saturation on February 08, 2011, 04:52:55 pm ---The manual states the output port is capable of ~ 50mA, at 3.5v.  That suggests it was designed for an impedance of ~ 70 ohms.

--- End quote ---
My guess is that it's 50 ohm, like 95% of the generators. Should be easy to find out by measuring open circuit voltage and short-circuit current.


--- Quote from: saturation on February 08, 2011, 04:52:55 pm ---Thus, all you need do is terminate the sync output at 50 ohms, and you have a usable sync signal good to 25 MHz.  I've confirmed this.

--- End quote ---
Good find. Most generators are happier with a 50ohm load, unless otherwise specified. I expect the distortion and flatness spec were also specified for a terminated load. If you're unable to do this, back termination (termination at the generator's end) is usually preferable to none at all.
saturation:
Hi alm, yes absolutely, just an estimate but it confirms the 3x25 provides enough mW to drive a low impedance load [ 3.5Vp ~ 2.5V rms, @ 50mA gives 50 ohms].  The manual does not say the sync output was too, but why not?  And I presume now the trigger input is 50 ohms too, and duh, I've been using it already driving it from the 50 ohm Instek 1003.  And yes, did so measure the output current.  Yes, reconfirmed voltage output for flatnes but only on select frequencies before its roll off.

Here are some additional images regarding the sync and signal stability.  I think they show the phase shift better and the solid Lissajou image demonstrates the overall stability between the 2 signals.

Blue = sync output

Yellow = output signal


--- Quote from: alm on February 08, 2011, 07:35:50 pm ---
--- Quote from: saturation on February 08, 2011, 04:52:55 pm ---The manual states the output port is capable of ~ 50mA, at 3.5v.  That suggests it was designed for an impedance of ~ 70 ohms.

--- End quote ---
My guess is that it's 50 ohm, like 95% of the generators. Should be easy to find out by measuring open circuit voltage and short-circuit current.


--- Quote from: saturation on February 08, 2011, 04:52:55 pm ---Thus, all you need do is terminate the sync output at 50 ohms, and you have a usable sync signal good to 25 MHz.  I've confirmed this.

--- End quote ---
Good find. Most generators are happier with a 50ohm load, unless otherwise specified. I expect the distortion and flatness spec were also specified for a terminated load. If you're unable to do this, back termination (termination at the generator's end) is usually preferable to none at all.

--- End quote ---
Mechatrommer:
damned! i just hit it, buy it now from ebay chinese seller. wish me luck.
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