Calculating link budgets with linear satellites
I've recently been toying with spreadsheets to estimate antenna requirements for some of the upcoming satellites. I'm not sure, however, how I should integrate the downlink power of a linear bird over its bandpass.
Take for instance Delfi C3. It is said to have a 400mW downlink in a 40kHz bandpass. Does this mean that a solitary CW signal would be 400mW, two such signals (both with equal uplink power) would produce a 200mW downlink, etc.? In calculating power and pathloss using the simple addition and subtraction of dBm, what starting value is it recommended that I use in this case?
73, Bruce VE9QRP
Hi Bruce,
Most linear satellites have some sort of AGC that results in dividing the downlink power among the users based on the total uplink power which is why LEILA was useful on AO-40.
A reasonable assumption is 1 QSO per 5KHz of passband so a 40KHz passband could support 8 simultaneous QSOs and a 400mW downlink would give you about 50mW per QSO on average. This is fairly conservative except on field day.
73, Tony AA2TX
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At 03:07 PM 1/4/2007, Bruce Robertson wrote:
I've recently been toying with spreadsheets to estimate antenna requirements for some of the upcoming satellites. I'm not sure, however, how I should integrate the downlink power of a linear bird over its bandpass.
Take for instance Delfi C3. It is said to have a 400mW downlink in a 40kHz bandpass. Does this mean that a solitary CW signal would be 400mW, two such signals (both with equal uplink power) would produce a 200mW downlink, etc.? In calculating power and pathloss using the simple addition and subtraction of dBm, what starting value is it recommended that I use in this case?
73, Bruce VE9QRP _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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participants (2)
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Anthony Monteiro -
Bruce Robertson