In this section, we are going to look at the tracking generator, reflection measurement,
and independent source capabilities that are available in spectrum analyzer mode. With
the tracking generator option installed, we can perform basic scalar network analysis
sweeps of 2-port devices such as cables, amplifiers, and filters such as this one I have here.
There is no phase information being measured in this mode, and hence, no vector error correction.
So instead, we have just performed a simple normalization of the trace to remove any basic
flatness errors from the measurement process. So we have turned on the generator by pressing
the Source Enable button and setting that to On. We have set the source mode to tracking.
We have normalized the trace by sweeping a straight through adapter first, and it is
now performing a simple trace 4 minus trace 1 normalization. We have the source power
set to 0 dBm, and you can see we can see down the skirts of the filter quite happily down
to about –90 or so dB. We could increase the dynamic range of the measurement, of course,
by pressing the Bandwidth button and narrowing the resolution bandwidth. But as you know,
that will also cause the trace to sweep slower. I will go back to 10 kHz. And as you would
expect if I press the Marker button, we have six markers available. There is marker 1.
Let us turn on another marker. And if I press More, we can display the marker table. This
shows us the values of all six markers, their frequency, and their – in this case – insertion
loss. And if you also have the reflection measurements option installed, we can easily
perform a basic reflection measurement too using the broadband direction bridge that
is built into every FieldFox. We can measure the return loss or VSWR of an antenna, a cable,
a filter, or an amplifier. Finally, and this is one of the most useful features on the
FieldFox, the RF source in the FieldFox spectrum analyzer can be used as an independent fixed
frequency signal generator. Obviously it is not as comprehensive as this benchtop signal
generator here, but if you are out in the field and quickly need to generate an RF or
microwave test signal or simulate a fixed frequency RF beacon, then it is a lot more
convenient than carrying a second instrument out onsite. So here we are monitoring a couple
of spread spectrum signals using this antenna here that is plugged into the FieldFox’s
spectrum analyzer input. But if I press the Measure key and Source, then we can generate
a signal out of the FieldFox’s second port here through this second antenna. Currently
it is turned off, so let me just press Source Enable to turn that on, and here you can see
the signal. The source mode is set to CW. The source power is adjustable. I have it
currently set to –45 dBm, but I can easily adjust that. In fact, I think we can go up
to 0 dBm and the output power is still leveled. Let us drop that back a bit, and we can set
the frequency as well…currently sits at 877 MHz, but we can adjust that with the knob
or just enter a numeric value. Hence, we have an extremely useful amplitude adjustable,
frequency variable CW signal generator built right into the FieldFox, which can be used
at the same time as we are sweeping the spectrum analyzer. And as with all the FieldFox measurements,
we can save the results as a PNG or trace file to the internal memory, an SD card, or
a USB memory stick along with the complete instrument state we have be using for future
recall. For further information on the FieldFox, please contact your local representative or
visit the website shown below.