Let's start with the FM transponder mode Down Link. Echo will produce a minimum power of 1 Watt (+30dBm) on 70CM. The transmit antenna is 2dBic. The path loss at maximum range (3000 km) is 155 dB. We should allow an extra 3dB loss for polarisation mismatch and another 1dB from travelling through the ionosphere.
A typical 70CM hand held transceiver is rated at -120 dBm for 12dB SINAD, considered the minimum useable signal. So we have:
Satellite Tx (minimum) +30 dBm
Antenna Gain +2 dB
Path Loss -155 dB
Polarisation -3 dB
Ionosphere -1 dB
Hand held yagi gain +10 dB
-117 dBm
This is just above the minimum for a useable signal.
At minimum range (800 km) the path loss reduces to 143 dB so we have:
Satellite Tx (minimum) +30 dBm
Antenna Gain +2 dB
Path Loss -143 dB
Polarisation -3 dB
Ionosphere -1 dB
Hand held yagi gain +10 dB
-105 dBm
So Echo in FM mode will be able to be received on a dual band handheld with a handheld yagi antenna.
For the 2M Up Link we have a path loss of 145 dB at maximum range and a receiver on Echo that is specified at -125 dBm for 12dB SINAD. So with a hand held yagi antenna we have:
Ground Station Tx (5 Watts) +37 dBm
Path Loss (maximum) -145 dB
Polarisation -3 dB
Ionosphere -1 dB
Hand held yagi gain +6 dB
-106 dBm
And at minimum range we have:
Ground Station Tx (5 Watts) +37 dBm
Path Loss (maximum) -134 dB
Polarisation -3 dB
Ionosphere -1 dB
Hand held yagi gain +6 dB
-95 dBm
So Echo in FM mode will be easily workable on a dual band handheld with a handheld yagi antenna. If the transmitters can be run at increased power levels then the Echo could be worked with "rubber duck" antennas.
樓主: VR2GY
發表於 3-6-2010 00:22:24