Can outdoor antenna allow reception outside clear's wimax coverage area?
Would this antenna/modem combination allow me to receive Clear's Wimax signal from outside their current coverage area? If so, approximately how away from the nearest Clear Wimax transmitter can I be and still receive signal?
how then can I determine if these antennas will work for me?
If your received signal strength is currently -102dBm then you would not be picking up a sufficiently strong Clear 4G Wimax signal for a reliable link but by adding this antenna which has 16dBi of directional gain *** then even after cable/connector losses your received signal would be above the receiver sensitivity.
E.g for a 20ft LMR-400 cable with 1.4dB loss at 2.6GHz and 1dB connector losses including lightning surge device final RSSI would approach -88.4dBm (-102dBm + 16dBi - 1.4dB - 1dB)
Same goes for transmitted power (or more correctly the EIRP= Effective Isotropic Radiated Power). So even if you are currently connected but experiencing slow speed, improving your received signal could bring it above the receiver sensitivity required for a better modulation mode like 16QAM/ 64QAM which would improve speed!
So the surest way to determine if these antennas will work for you is to actually get your hands on a CPE/ USB modem and during the trial period measure the RSSI/CINR which is available from the communication manager software that comes with the modems. If the calculated original RSSI (negative dBm value) plus antenna gain minus cable/connector losses doesn't give you a strong enough signal then you are out of luck. Alternatively, if your outdoor signal at the location where you could mount an antenna is already very good and your speed is fantastic at this outdoor site then these antennas will clearly work for you and in fact you need not worry about RSSI/CINR readings (provided of course you get a strong enough antenna, keep cable lengths reasonabe & where necessary take advantage of MIMO by having two external antennas.
But as discussed extensively in our forums it's hard to predict precise RF radiation behavior especially for a MIMO multi-antenna protocol such as WiMax which is why we offer a 30-day return period with no restocking fees on these antennas.
Therefore in summary to determine if stronger external antenna could improve your performance you need to determine if:
(RSSI Before Adding Antenna) + (Antenna Gain) - (Cable Loss) - (Connector Loss) > (Receiver Sensitivity)
NOTE:
- RSSI before adding antenna is a negative number in units of dBM e.g -92dBm
- LMR-400 cable has a loss of about 6.9dB/100ft
- Assume about 0.1dB loss for each additional connector and 0.5dB loss for addition of lightning protection
- Receiver sensitivity depends on modems chipset used but typically for the fastest modulation mode (fasted speed) you needs to be in the -70's dBm or better.
- Note CINR (Carrier-to-Interference-Plus-Noise ratio) not mentioned above is also important. We have seen reliable communication with values lower than 10dB but generally needs to be above 10dB. A good RSSI and low CINR could point to too much co-channel or adjacent interference at the receiver site. One experiment to troubleshoot this would be to turn off 2.4GHz radios e.g 802.11b/g/n WiFi systems or to orient highly directional antennas differently. In fact this is one motivation for narrow bandwidth antennas (covering the ~2.5-2.7GHz Wimax band with sharp rolloff outside this band), narrow beamwidths (provided can pick up a sufficiently strong signal in oriented direction) and large front-to-back ratios (>20dB) since these keep interference power low.
- receiver sensitivity is the minimum signal that could be reliably received by the radio at a specified Bit error rate (the lower,i.e the more negative, the better)
- this receiver sensitivity figure is spec'd for QPSK which is the lowest modulation mode (lowest bit rate) so for 16QAM and 64QAM we expect a larger (worse) receiver sensitivity.