[amsat-bb] Re: Calculating link budgets with linear satellites

Anthony Monteiro aa2tx at comcast.net
Thu Jan 4 16:43:44 PST 2007

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.

Tony AA2TX


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
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