Cheap DDS boards - any good ones?

[smjcuk]

Are there any half respectable ones out there? Need something that will kick out a clean sine wave across the 100KHz-5MHz range. I've been bodging one off oscillators for a few months which is somewhat tedious. Don't really care if there is an output stage; I can build one

I've noticed a couple of designs ranging from a resistor ladder DAC off an AVR to an AD DDS IC so it looks like a minefield hence the request.

[tggzzz]

Consider something like http://www.ebay.co.uk/itm/1x-DDS-Function-Signal-Generator-AD9851-0-50MHz-DDS-signal-source-DDS-Module-/151254816780 It is essentially intended as a means of generating an accurate square wave clock, but which also gives a sine output 1Hz->50MHz.

The design is straight from the AD data sheet, and is essentially: 180MHz DDS clock, DAC -> 70MHz 7th Order LPF, and the LPF -> 50ohm output and comparator input. The comparator only works to ~5MHz. I found the comparator introduced glitches, so I disconnected the comparator's input from the LPF output.

I have no idea whether that would consititute a "clean" sine wave for your purposes.

[smjcuk]

Thanks - that looks like what I need. Plus it's only £25 so not the end of the world if it's a turd

Clean as in frequency stable, reasonable SNR, relatively low THD and preferably not too much EM noise although I can sort that with suitable shielding.

Seriously considering a Rigol with FFT now. 45 year old Tek isn't cutting it for this idea I had

[atferrari]

Just in case, google about a batch produced in China, not even sure if with that chip, which had an error in the components implementing the eliptic filter at the output. Maybe they are all sold already.

[Marco]

If you want to move up the frequency scale there's some decently priced AD9910 boards with GUI out there too now, but I have no idea about the quality and translation of the manual/GUI.

[smjcuk]

Just in case, google about a batch produced in China, not even sure if with that chip, which had an error in the components implementing the eliptic filter at the output. Maybe they are all sold already.

Ha I seeeee.

I might give that a miss then. Last thing I want to do is debug something new.

[smjcuk]

Have applied to the purchasing department (wife) for a new TTI generator...