Neil Smith G4DBN
I bought one to see how it works. You need small fingers, but the thing does what is says on the tin. One output port is fixed frequency, selected on the top line, it has a seven-digit entry box and on-screen keypad for entry. The second output port is for the sweep function, there you set start, stop, step size and step period. You can start and stop the sweep using two on-screen buttons. It defaults to 100kHz step once a millisecond. Top end frequency is 4.4GHz as it says. After a decent warmup, it was about 4.4kHz LF at 4.000000 GHz.
Not looked closely, but there is a setting for crystal frequency set at 30MHz, so it might be possible to inject a locking reference. There is an unpopulated SMA socket location that could be for an external ref or maybe a VCO. No sign of any documentation at all.
Looking at the noise, it seems to have rather noisy sidebands at -60dBc out to 100kHz, then it falls away fast to the noise floor of my 8562 at -80-ish. Could be because I am using a USB power lead inverter thingy. I'll get it on to a clean supply via the power socket instead and see how it compares. It looks like it has a programming header, and there are four push buttons which do nothing obvious.
The harmonics at sub-GHz frequencies are terrible, it looks like it might be a square wave, with odd harmonics falling away only slowly, so it would need a serious LPF for anything requiring a pure tone. Above 2GHz, it is much cleaner, and at 3.9GHz, the second harmonic was 60dB down and the third better than 80dB down.
Output is about 0.5dBm at 200MHz and 2.4dBm at 2GHz, back down to 1.4dBm at 3.9GHz.
Spurs are about -70dBc
I only bought it to use as a signal source for 3.4GHz because my Agilent runs out of puff at 3GHz. Might find a few more uses for it, but it isn't going to replace the E4421B. I might put it into a box, it is very convenient to use if it is running from a battery.