Satellite Communications/Satellite Transponders

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Question
Why do  satellites have 36 MHz, 54 MHz and 72 MHz transponders. Why are they not uniform. What parameters drive the decision on transponder bandwidth. If 72 MHz transponders are not ideal for DTH why not have 2 X 36 MHz instead.

Answer
Hi Ramesh,

Apologies for the delay, I was on holiday.

Typically, the limiting factor is the power of the TWTA of a transponder.
In case of a 36 MHz transponder, all the power resides in that single 36 MHz bandwidth.
That is an optimal combination for DTH.

Some carriers don't need that much power but rather more bandwidth (Vsat or data networks), in that case a wider 72 MHz transponder is created allowing more carriers but on the downside, the power of the TWTA is now spread out over double the bandwidth.

So it is basically a balancing act between needed bandwidth and achievable power density.

I hope this clarifies,

Kind regards, Dave

Satellite Communications

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Dave Suffys

Expertise

Questions related to design of satellite communication links.

Experience

Satellite communication, link budgets, DVB-S2, ACM

Organizations
Newtec

Education/Credentials
Telecommunications engineer, Sales Support Manager at Newtec

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