DSO aliasing and the AD9850

[Karl W4KRL]

I've been getting some strange outputs from my $7 eBay AD9850 direct digital
synthesis board in that the output seems to include both the desired RF
frequency, say 10 MHz, and an unexpected low frequency, say 300 Hz. Terry F.
pointed out that it could be an aliasing artifact of my digital storage
scope. Here is a well illustrated article that supports his suggestion:

 

http://koti.mbnet.fi/jahonen/Electronics/Scope%20Sampling/aliasing.html

 

The article gives an example where a Tektronix TDS3034A shows a 10 MHz
signal as both 10 MHz and 60 Hz - almost exactly the same as what I have
observed on my Rigol DS1052E.

 

I will be looking for a good used analog scope this Sunday at the OVH
Hamfest. Meanwhile, I am open to offers.

 

73 Karl W4KRL

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