I'm trying my best to calibrate an old HP spectrum analzer but ill be honest, I get a bit baffled when I start playing with signal level attenuation and impedance matching .

Here's what I need;
Take a 10k hzhz sign from my generator, attenuate it to -80dbV (.1 mv) and deliver it to the spectrum analyzer

Here's my equipment,
50 ohm function generator with -20db button
600 ohm HP attenuator (variable down to -100)
1 Meg input spectrum analyzer

When I attenuate the signal to -80 db, the signal is destroyed by the noise at that level

Any tips?
Thanks in advance

 

Connect a 600 ohm resistor to ground at the attenuator output when connected to the 1 megohm analyzer input.
That should give you the correct attenuation as shown by the attenuator setting.

If the signal is below the noise level than that's the noise of your spectrum analyzer.

 

At the end he shows some cute techniques to build your own high-bandwidth attenuators, probably at a fraction of the cost of commercial units of similar ratings.

 

Connect a 600 ohm resistor to ground at the attenuator output when connected to the 1 megohm analyzer input.
That should give you the correct attenuation as shown by the attenuator setting.

If the signal is below the noise level than that's the noise of your spectrum analyzer.

Thanks, that did the trick . I found the signal was cleaned up even more when I removed the 50 ohm termination on the input side of the attenuator, does this make sense?

 

I found the signal was cleaned up even more when I removed the 50 ohm termination on the input side of the attenuator, does this make sense?

What do you mean "cleaned up"?
If the signal generator has a 50Ω output then an added 50Ω load will reduce the output signal by 1/2.