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A trick for the spectrum analyzer in TV Signal analyzer: The spectrum footprint

In this short article, we are going to explain you a trick for the spectrum analyzer to apply on HD RANGER and RANGER Neo field strength meters. It is about capturing a trace or "footprint" of the spectrum, saving it in memory and using it as a template for later.

Get the most out of the Spectrum Analyzer function!

How to quickly check the attenuation for an operating SMATV installation

The spectrum footprint can be used to visually verify the attenuation levels of an already working SMATV installation.

This can be done in those cases in which, due to lack of time or resources (or because the head-end equipment cannot be disconnected), it is impossible to use more appropriate methods such as calibrated pilot generators.

Follow this procedure:

1. Connect the field strength meter to the user socket closest to the head-end amplifier output.
2. Capture the spectrum in full span.
3. Recover and maintain on screen that spectrum footprint.
4. Check the rest of sockets, comparing each spectrum with the footprint saved in step 2.

In this way, it is possible to assess if attenuation induced to signal is tolerable as sockets are farther away from the head-end. Quality of wiring, shunts and other elements of installation affect attenuation levels.

How to save a spectrum footprint?

First of all, you should check that your field strength meter is properly configured (HD RANGER or RANGER Neo):

• Open the PREFERENCES menu (long press on the folder key).
• Go to TOOLS.
• For the option Export button set value to Screen + Data (or Screen Only if you want to capture only the trace line and skip full screen).

Now, go to spectrum analyzer mode and when you have the spectrum you want on screen, press and hold the Screenshot key. Write a name and it is ready.

Set value to Screen + Data (or Screen Only if you want to capture only the trace line and skip full screen).

How is the spectrum footprint recovered?

The trace is saved along with the files of the current installation, so you have to use the field strength meter installation manager to recover it:

• Open the Installation List (short press on the folder key).
• Scroll to current installation, which should be highlighted, and press F2 (Manage).
• Press F1 and filter list by Capture Data.
• Highlight and select (by moving and pressing the joystick or touch screen) the file you saved previously and press F4 (Open file).
• The field strength meter returns to spectrum analyzer mode and overlaps the trace you just recovered from memory.

The trace or footprint of the spectrum that was in memory overlaps the current spectrum.

Other ways to take advantage of this resource

Usefulness of this function goes far beyond aligning antennas. For example, it can be used to:

• Align satellite antennas. After having captured the spectrum of a well-pointed satellite, it can be used as a very approximate guide to align other antennas to the same satellite.
• Verify the correct functioning of single-channel amplifiers. You can capture the spectrum of a channel that is well amplified, and then overlap it on the spectrum of a channel that we suspect is bad amplified. In this way we can discover harmonics or distortions outside the band (shoulders). If you do not know what shoulders are, we recommend you to read this article.
• Check filtering of LTE band. Compare how much 4G channels are attenuated by comparing the spectrum before and after enabling the LTE reject filter.
• In general, to check the correct operation of any filter.

PROMAX is a leading manufacturer of test and measurement systems, broadcast and TV signal distribution equipment. Our product lines include measuring instruments for cable TV, satellite TV, broadcast, wireless and fibre optics networks, FTTH and GPON analyzers. DVB-T modulators, IP streamers or IP converters (ASI, DVB-T) are among the company’s latest developments.