Ahhh, I actually have one of these under a different name, but the 15MHz variant.
With regards to using it, it's an analog generator as opposed to DDS so there's some frequency variation at the top and bottom end, but you can always change ranges. I'd certainly say it's no worse than most other cheap generators.
It has quite a few features like the DC offset and VCF which are normally quite a bit more on other generators, the VCF in particular is useful for generating basic FM signals and sweeping. I did measure the THD when I first got it but I can't remember the exact numbers-was fairly typical though.
Right, as you're interested, I finally got around to opening it up and having a poke around. My impressions...
It's a through hole, very discrete parts heavy design. It uses lots of through hole resistors, caps and to-92 transistors.
The resistors are all metal film 1% accuracy aside from some (look like they're in the signal path) which are 0.5%-nice to see, and should translate to much better performance over temp than carbon resistors.
Some of the resistors haven't been pulled flush to the board-not perfect, but shouldn't be too much impact on something like this.
The caps look decent quality ceramic, although some are the wrong spacing on the board and have been bent over a bit.
There are quite a lot of variable capacitors around for tuning which probably partially explains the frequency instability. Definitely a compromise compared to a top quality generator
There are some integrated circuits around in DIP packages, lots of standard op-amps and some matched transistors pairs. There's some 7400 chips as well, oddly enough only the 7400 chips are socketed.
The power supply is a standard linear jobby, seems designed well enough and should be nice and clean. However some of the TO-220 packages are heatsinked, with only the chip holding the heatsink down. Glob of RTV on there before reassembly methinks... On the bright side, a proper mains power switch mounted on the front.
The frequency counter, unusually, is on the same board as the rest of the circuit. Controlled by an Atmel MCU (AT89C52 24), and has a proper xtal oscillator on there so the accuracy & stability should be fine.
There are some signal wires run alongside power rails to the panel, not great but should be a steady load from the display so not too much dI/dT to affect the signal
The frequency is controlled by a proper 10 turn pot-impressive! Has a smooth feel to it as well, as well as fine frequency controls
Pictures,
Sorry about the quality of the pictures, using a little sport camera. Bottom line, a good generator for the money if you need the bandwidth or functions. If you need rock steady frequency accuracy get a DDS generator. If you want any better pictures/details just say
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