I have a RF attenuator with spec (Freq DC to3 Ghz, 30dB attenuation, 2W avg power rated, VSWR=1.2max. Imp= 50ohms , how can i test this attenuator without spectrum analyzer.
If you want to test its attenuation characteristics, you could use a signal generator and an rf power meter instead of a spectrum analyzer.
If you want to test its VSWR (impedance matching characteristic), you'll also need a directional coupler. Or else a slotted airline probe. At which point you're well on your way to trying to build your own network analyzer.
I have scope which has 1kHZ 5V output, can I use this signal to check the attenuator, and observe the atternuator output at scope.
Along with a 1 kHz signal generator, you could test the attenuator up to 1 kHz. But that won't tell you whether it works at 3 GHz as specified. Any deviations from specification are most likely to happen at the high end of the device's frequency range.
Will 5V is too high for this attenuator?
5 V into 50 50 ohms is 0.5 W, well below the rating for this attenuator.