Troubleshooting |
Limitations of the Signal Hound
8
3.1.2
Reducing Spurious and Residual Responses
Certain RF frequencies may produce small spurious and/or residual responses. To verify a displayed
signal, center it and step the span from 1 MHz down to 100 KHz. If it is not present in both spans, it was
likely a spurious mixing artifact or a harmonic from a system clock. To avoid known residual responses
at multiples of the primary system clocks, a secondary clock frequency is selected for some frequencies
when span is 200 KHz or less.
The mixers can typically operate with up to +0 dBm input, but keeping the input level –25 dBm or lower
will greatly improve linearity, reducing harmonic and spurious mixing products. You can accomplish this
in software by setting your reference level 15-20 dB above your actual input level.
3.1.3
IF-to-Bits Receiver
The IF-to-bits receiver has three gain ranges. The gain range will be automatically selected based on
attenuator settings and reference level to avoid IF ADC compression, which will greatly distort the data.
The software should warn you if compression is occurring. If this happens, increase your reference level.
3.1.4
IF and RBW Selection
The I/Q data comes in over USB and is processed using an FFT with a custom Flat Top window based on
the selected RBW. Software and firmware limitations only allow certain very low or very high RBWs for
certain spans, to keep sweep speed and trace size reasonable. For example, an RBW of less than 30 Hz is
only allowed for spans of 200 kHz or less, and the minimum RBW for spans of 100 MHz or more is 6.5
kHz. See the Spike
TM
manual for additional information. The available RBWs are a function of the span,
since very large RBWs with a small span would result in a trace with only a few data points and a blocky
appearance, and very small RBWs with a large span would result in a large data set that would be
difficult to manage and process.
4
Troubleshooting
If you experience a problem with your Signal Hound, please try these troubleshooting techniques before
contacting us:
1) Your Signal Hound Is Not Sweeping Properly
Try this first: Close the Spike
TM
software. Unplug the USB cable and any external 10 MHz
or trigger cables from the Signal Hound and wait 5 seconds. Plug the USB cable back in.
Check that both ends of the USB cable are firmly seated and the Signal Hound LED is green.
Launch the Spike
TM
Software. Try your sweep again.
Still not working? Contact technical support at
http://www.signalhound.com
2) Your Signal Hound LED is off