Preparation of Global Invacom OTx Installation
Preparation of Global Invacom OTx Installation
Lately, we've been receiving more inquiries regarding the setup of the GI OTx transmitter, which has become an integral part of most SMATV installations we design. Why is it increasingly finding its way into projects?
Simplification of Signal Adjustments
- It significantly simplifies the issue of calculating signal attenuation and correcting the inclination of radio, terrestrial TV, and satellite TV signals between the antenna field and distribution points.
- It requires fewer cables, making it quicker to install compared to traditional coaxial cable-based setups.
- The antenna field can be fully electrically separated from the multiswitch installation, leading to additional savings.
- The entire setup consumes less power due to the reduced number of main amplifiers.
- It's straightforward to set up :)
This text primarily revolves around the last point. But does it truly live up to that claim?
Common Issues in OTx Installation Setup
- Incorrect connection of optical connectors to devices (FC/PC connectors allow mounting in only one position).
- Contamination of optical connectors in devices and patch cords.
- Lack of appropriate signal meters for DVB-T2/DAB/FM and SAT.
- Absence of an optical power meter.
- Incorrect or excessively high RF input levels for the V, H, and TERR ports of the transmitter.
So, how to diagnose the problem? Just as with many installations, understanding the basic parameters of input signals is key to further measurements.
At the outset, measuring terrestrial antenna signals is crucial. Firstly, checking levels and MER (for digital transmissions). The OTx transmitter's specification notes a TERR input level range of 70-80 dBµV. The input is broadband (covering FM, VHF, and UHF signals from 45-694 MHz), hence input level values should be maintained for all incoming signals.
ATTENTION!
One of the most common reasons for faulty installation performance is excessively strong FM radio signals.
How to equalize signals?
The answer seems evident, yet it's not always that simple . Using a WWK Alpha+ or WWK 951+ channel amplifier allows signal alignment to meet the optical installation's requirements. These devices cut unwanted signals between VHF and UHF, eliminate high-powered LTE or 5G signals, and facilitate further signal distribution via multiswitches.
Another crucial step is connecting signals from the Wideband LNB converter (from the OTx kit). Here starts the part of the installation that's easily overlooked.
The WideBand converter has two RF outputs: V and H, transferring signals from the received satellite to the transmitter. The frequency range after conversion is 300-2350 MHz for each output. To recall, a universal Quatro LNB carries out additional division into upper and lower bands, with the output frequency range being 950-2150 MHz.
This is the key to conducting measurements. Most meters, even professional ones, can measure signals only within this narrower range, thus unable to measure frequencies from the upper and lower range of polarizations H and V when using a Wideband LNB.
To measure the signal before entering the transmitter, a meter with Wideband function (distinct from meters with LNB Wideband settings) covering the range from 300 MHz is required. Examples include the TAB 7 Ultra or HD TAB 900 Plus by the Italian manufacturer ROVER.
For satellite antennas with a diameter of 120cm (compliant with regulations), SAT signal input values may reach 75-85 dBµV, which, given densely populated transponder positions, is too high for OTx. The optimal value is around 70 dBµV +/- 2dB for the entire SAT band. How to lower the signal level? Employ an RF attenuator working within the 3GHz range capable of passing voltage or use an attenuating splitter—also operating within a broad frequency range with voltage passing capability.
Once TERR, H, and V input levels are adjusted, verifying the MER for these signals is crucial:
- For SAT signals, they should be above min. 15dB for tp. 10719V at 13E.
- For DVB-T2, they should ideally be around min. 29dB.
Another common observation is the drop in MER after implementing Global Invacom transmitters and receivers. A decrease of up to 2dB is acceptable in standard installation conditions, regardless of whether it concerns SAT or DVB-T2 signals. This is characteristic of any RF optical installation, irrespective of the equipment manufacturer.
What might cause a decrease in MER?
- Non-uniform signals at the OTx input—MER drops by several dBs or is immeasurable. Often reported is the absence of a signal at 10179V at 13E. Why does this happen? It's similar to overloading an RF amplifier (noise sharply rises, S/N drastically drops).
- Contaminated optical connectors. There's no solution other than ensuring cleanliness or using connector cleaners.
- Incorrectly connected FC/PC connectors.
- Poorly designed optical network—incorrect optical levels entering the GTU Quatro or GTU QUAD receiver.
The Global Invacom OTx, now a staple in many AIZ projects, simplifies signal attenuation calculations for radio, terrestrial, and satellite TV, requires fewer cables, electrically isolates the antenna field from the multiswitch installation, and reduces power consumption due to fewer amplifiers.
When diagnosing setup problems, remember points like incorrectly connected optical connectors, contamination, lack of appropriate RTV and SAT signal meters. Incorrect input levels on the transmitter require special attention. Basic parameters of input signals serve as a starting point for further measurements. Measuring signals from terrestrial antennas, checking levels, and MER are essential. Input level values should align with the transmitter specification, and excessively strong FM radio signals can disrupt the installation's performance.
Aligning signals necessitates using suitable channel amplifiers that eliminate unwanted signals and facilitate further distribution. Connecting signals from the Wideband LNB converter is pivotal for proper transmitter operation; however, most meters may not measure signals across the full frequency range. Consider purchasing meters capable of Wideband measurements throughout the range.
For satellite antennas with larger diameters (>100-110cm), SAT signal input values might be excessively high for OTx. Employing RF attenuators or splitters might be necessary to reduce signal levels.
Monitoring MER for SAT and DVB-T2 signals is crucial. A decrease in MER after installing Global Invacom transmitters and receivers is normal for optical systems but shouldn't be significant. Pay attention to factors like uneven signals at the OTx input, contaminated optical connectors, or improperly designed optical networks. Proper cleaning and network design are crucial to maintaining system efficiency.
This comprehensive approach to the Global Invacom OTx installation addresses common issues and provides insights into signal alignment, ensuring optimal performance and functionality.
Understanding the nuances of installation parameters, signal measurements, and potential issues ensures a smoother installation process and effective troubleshooting for any challenges that may arise.
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| TAB 900 Plus LNB WB V 10719 after optical division into 8 points and after conversion to RF1 | TAB 900 Plus LNB WB V 10719 measurement directly from OTx (OPT) 120cm antenna |
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| TAB 900 Plus LNB WB V 10719 measurement with LNB antenna 120cm | TAB 900 Plus LNB WB V spectrum antenna 120cm |
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