850 Sligo Ave. Suite 600
Silver Spring, MD 20910
1-888-322-6728
fahnen/12.jpg AO-51 Link Budget Calculations
Launch Pad Return

Calculating Link Budget for AMSAT-OSCAR 51 (Echo) 

Download

Download the Link Budget Calculator (Excel Spreadsheet 15kb)

Instructions

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.


Contributed by Terry Osborne (ZL2BAC)
AMSAT-ZL Committee Member

  Copyright©The Radio Amateur Satellite Corporation 2004 ,2014 - All Rights Reserved
  Report a bug on this page