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Review: Hantek DDS 3X25. Anyone own one?

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torch:
I know Mechatrommer built an amplifier to get 10v out of his, but does anyone know the minimum voltage the Hantek can reliably produce?

I'm restoring an old (1939) tube powered floor model BC and SW radio. To align the tuner, the manufacturer's instructions say to connect a signal generator to the antenna input. Required frequencies range from 655KHz to 17MHz. I figure the AM waveform on the Hantek is perfect. However, I'm concerned about the output voltage. Near as I can figure it, a weak signal would produce around 0.2uV and a strong signal around 50uV at the antenna connection (I believe it's approximately 50 ohm impedance). The lowest setting on my Rigol scope is 2mV/div, so I can't verify if the Hantek can operate at that level. It does seem to still be working at 1mV, but even that is hard to see.

Option B would seem to be installing a 10K resistor inline. If this was a DC (or at least, low frequency) circuit and if the input impedance was resistive, I think the load and resistor would form a voltage divider so 1mV from the Hantek would produce 5uV (a reasonably strong, but not overwhelming signal) at the antenna. But I have no idea if that would really work at 17MHz.

Option C would be to install a short piece of wire as an antenna on each and let the Hantek broadcast to the radio by laying the wires next to each other. But that seems even more random.

Any other options?

SeanB:
Normally you couple by using a single turn of wire draped over the IF transformer, with it twisted pair to the signal generator. This normally couples enough in to use for alignment. This works to align the IF stages, for the RF side just hold the loop over the antenna input.

Mechatrommer:
i havent done this but if its me i'll set the signal magnitude to max (6Vpp or 20Vpp doesnt matter) and attenuate it at the output end accordingly using simple voltage divider or other better mean. the rational is so you can get minimal stairsteps effect. my 10x25 amplifier is not suitable for this application imho as it may introduces more distortion to the original output in opamp stage. use the original output as is. since its iirc 12bit @ 6Vpp you may expect 1.46mV stairsteps out of it. attenuating the signal should attenuates the stairsteps as well. but be careful with your attenuator design as it is near dark region (20MHz) this thing has made me crazy and probably brain shorted for a while now. a resistor is not a resistor, it also an inductor and capacitor, add pcb ground somemore? they will dance make you nuts.

zibadun:
Yes I agree the lower the output the higher is harmonics content (relative to main carrier). At 0.1 V the sine wave is hardly a sine anymore. An attenuator or loose coupling is the way to go :)

jahonen:
Why not just get a coaxial attenuator, fixed ones should not be too expensive? You can also cascade them to get desired attenuation if one is not enough.

Regards,
Janne

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