[time-nuts] OT: Power level reference

Magnus Danielson magnus at rubidium.dyndns.org
Wed Dec 2 22:53:45 UTC 2009


Bob Camp wrote:
> Hi
> 
> I think that spending some time with a *good* reflection bridge at the specific frequencies of interest would be time well spent. 
> 
> Of course that heads us of to the subject "OT: 50 ohm Standard Reference". I have some nice HP cal kits running around, but none of them really agree with each other without going back to the calibration data. For low frequencies you can do pretty well with a set of precision thin film SMT resistors. They fall apart as frequency heads up past a few hundred MHZ. 

An even more hairpulling aspect is 75 Ohm BNC kits into several GHz. 
Doing networks analysis under those conditions isn't as safe ground as 
the 50 Ohm would be. Oh... yes, I do need to measure RL on BNC and over 
several GHz for 75 Ohm systems. Luckilly that isn't in my private lab.

Cheers,
Magnus




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