|
CAUTION:
STAY CLEAR OF PCS CELL PHONE SITE ANTENNAS |
Chances are those intermittent video flashes and crackling audio in microwave links near 2 GHz are caused by PCS Cell Phone packets. They can affect both Analog and Digital Systems.
The PCS Cell Phone Band for North and South America is shown above. It starts at 1850 Mhz, and meets the lower edge of 2 Gigahertz "Broadcast Auxiliary Band" (BAS), used by television broadcasters to relay signals from live news events ("Electronic News Gathering" or ENG), or as a "link" to bring TV signals from their Studio to their Transmitter Site ("Studio Transmitter Link" or STL)..
The American PCS Cell Phone Band is divided into
three distinct segments:
1). a 60 Mhz wide cell phone receive band (1850 to 1910 MHz),
2). a 20 MHz wide "unlicensed"
band, which also serves as a "guard band" (1910 to 1930 MHz), and
3). a 60 MHz wide cell phone base station transmit band (1930 to 1990
MHz).
Each transmit and receive band is further divided
into six additional segments: three 15 Mhz wide blocks: A, B, and C, and three
5 MHz wide blocks: D, E, and F.
The PCS cell phone tower site transmitters operate between 1930 and 1990 MHz. The PCS sites receive 80 Mhz below their transmit frequencies. The transmitters at the PCS towers are allowed to have an EIRP of 1,640 watts, but typically run ~500 watts EIRP for each loaded 1.23 MHz wide CDMA channel, and ~800 watts for the 200 KHz wide TDMA channels. Most sites break up power distribution into 120 degree sectors.
CDMA channels ideally handle no more than 25 simultaneously conversations in good practice. When traffic increases, additional transmitters, called "expansion" channels, handle the additional traffic, each handling an additional 25 conversations. The base station PCS transmitter output power for the "pilot" of a CDMA channel, with no conversations present, is normally ~1.2 watts. This is doubled to around 2.4 watts in difficult terrain. This low power, however, is going to a 17 db gain antenna that handles a 120 degree sector, so multiply the transmit power by 50.
But that isn't the maximum power! As more customers come on line, each PCS base station transmitter's power output increases. ONE typical PCS Channel will increase its transmitter output to around 16 watts per CDMA channel. Factor in about 2 db line loss, and multiply the remainder by 17 db (by 50), and you have around 600 watts EIRP for every loaded transmitter on an average PCS site. This higher EIRP from a loaded channels, accounts for the unpredictable interference to the ENG band. As more PCS Companies and subscribers, ENG interference potentially increases. Even in today's "state of the art" systems (except ours), the noise floor increases, and weaker and even moderate ENG signals and their audio subcarriers are masked or distorted.
TDMA is a different case. No matter the number of users, TDMA still has the same high power output per channel.. TDMA has lower channel capacities, so they need more channels. Each 200 KHz wide TDMA channel around here (South Florida) is running around 800 watts EIRP.
There are other types of modulation, but these seem to be the most popular so far.
PHILLIPS MICROTECHNOLOGY'S SuperFilter/LNA ELIMINATES VIRTUALLY ALL off-channel Interference, including PCS. You can be at the same height on the same tower, and still make your path.
ENG System Performance: Frequency vs. Rejection |
||||
Usage |
Frequency |
PHILLIPS MICROTEK SuperFilter/LNA-SP3 |
Microwave Radio-1996 Ultrascan |
Microwave Radio-latest Ultrascan |
|---|---|---|---|---|
| PCS Mobiles |
1800 Mhz | >140 db | 35 db | 87.1 db |
| 1900 Mhz | >140 db | 7 db | 71.2 db | |
| PCS "A" | 1930 Mhz | >140 db |
3 db |
55.6 db |
| PCS "B" | 1950 Mhz | >140 db |
1 db |
44.1 db |
| 1965 Mhz | >140 db | 1 db | 30.9 db | |
| PCS "C" | 1975 Mhz | >140 db | 1 db | 19.8 db |
| 1982.5 Mhz | >110 db |
1 db |
9.6 db |
|
| 1989.5 Mhz | 69.5 db |
1 db |
1.5 db |
|
You have the choice of "Living with PCS" or
ELIMINATING it.
We have an ENG receive system looking directly at a PCS Site
12 feet away!
Here are some PCS Companies and their RF Engineers:
IMPORTANT:
If you found this page using a search engine 
,
otherwise, please hit your Browser's BACK button.