Antenna Systems: Upgrade the Antenna System First
This is the distorted output of a widely used ENG antenna system, with only two -42 dbm signals hitting the antenna. YOU NEED PLENTY OF HEADROOM, LINEAR LNAs, AND FILTERING IN TODAY'S CROWDED SPECTRUM.
Your present antenna system could be masking weak COFDM signals, and freezing digital video when you are too close in, or have strong signals from other stations!
Until the 1980's, few receivers had built-in preamps. Today's receivers are very sensitive, but have wideband front-ends, and require EXTERNAL FILTERING in high RF areas.
Because of the migration of many services, including WLAN, PCS Cell Phones, Sirius and XM-Radio, Wireless Cable, et., the terrestrial microwave spectrum has become quite crowded. Modern receive equipment may work well at weak to medium signal levels, but because of the many high-power services migrating higher and higher, some receive sites need a little extra filtering and linearity to do their job.
High power signals, and even distant lightning discharges hitting your antenna's low power handling LNA can cause a digital COFDM signal to momentarily "freeze" the video. Our LNAs have an IP3 approaching +50 dbm, and do not saturate.
If you have a state of the art analog or digital receiver, it does not want to see MULTIPLE SIGNALS HIGHER THAN - 36 dbm, Modern receivers usually have a 20 db or higher LNA gain built in.
Here is a typical ENG installation:
- Multiple -40 dbm signals from PCS, XM Radio, and other ENG users arrive at your antenna
- Your 20 db gain antenna increases these signals up to -20 dbm.
- Your antenna system's 30 db LNA attempts to linearly increase RF output to +10 dbm, which saturates most LNAs, causing intermod.
- The typical - 20 db transmission line loss between the antenna system on your tower, and your receiver on the ground, reduces signal levels to -10 dbm at your receiver.
- Your receiver's 20 db built-in LNA tries to increase the -10 dbm signals to +10 dbm each, saturating your receiver's LNA, mixer, IF Stages, et.,.
- Video and audio are degraded or unusable, and digital streams are corrupted.
- Non-Gaussian Filters cause group delay as selectivity increases. This corrupts the soft decision data stream, causing digital signals to "freeze."
We provide Consulting and Equipment to allow both analog and digital equipment to meet or exceed specifications.
Mr. LLoyd W. Phillips
C.E.O., Phillips Microtechnology, Inc.
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