If all you need to measure is
the loss of the cable, then all you need is the spectrum
analyzer (SA)* and, if both ends of the cable cannot reach
the SA from the same place, a signal generator (SG).
* If the SA has a generator output built in.
both ends of the cable can reach the SA and it has a
built-in generator, then simply calibrate the SA and place
the two cable ends between the In/Out ports and measure
Otherwise, measure the output of the
signal generator and either se tthe S/A to give a relative
measurement from there, or note the power level to do the
math yourself. Then, connect one end of the cable to the
SA input and the other to the SG.
A good thing to
do is place an attenuator (at least 3 dB, preferably 10
dB) at the output of the SG both when taking a reference
reading and when connection the SG to the cable. Doing so
helps minimize any error that might be caused due to
impedance mismatch between the SG and the cable. When
measuring down to tenths of a dB, it can make a noticeable
difference in the measurement.
In both cases, be
sure that the SG is injecting enough power that the SA can
measure easily after passing through the attenuator and
- Kirt Blattenberger