[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

*Subject*: [amsat-bb] Re: Linear link budgets*From*: "OZ1MY" <oz1my@xxxxxxxxx>*Date*: Fri, 5 Jan 2007 18:47:58 +0100

Hi Grant and all, Yes you are right about the PEP - but it is not as bad as that if we take statistics into account. 10 stations are not likely to transmit at the same time. As far as I remember AMSAT-DL used the square root of the number of users as a good indication of how many users there can be on a linear transponder to calculate the power for each user. Have a nice weekend 73 OZ1MY Ib ----- Original Message ----- From: "Grant Hodgson" <grant@ghengineering.co.uk> To: <amsat-bb@amsat.org> Sent: Friday, January 05, 2007 11:35 AM Subject: [amsat-bb] Linear link budgets > Unfortunately, the calculations for dividing transponder power equally > amongst users are not as simple as have been suggested. > > For the 400mW case :- assume that 400mW is the maximum power that the > transmitter can produce. Then a single CW signal could in theory be > sent at a power of 400mW, assuming no AGC, beacons etc. > > However, if 2 equal level CW signals were being transmitted, then the > Peak Envelope Power of these 2 signals would be 6dB higher than each of > the signals individually. This is because the voltages of each of the 2 > CW signals have to be added together, giving a peak signal with double > the voltage of each signal, which is 4 times the power or a 6dB increase. > > Therefore, to keep within the 400mW limit, each CW signal would be > restricted to 100mW each. The same analysis can be done for 3 equal CW > signals, where each would be 9.5dB down; i.e. 44mW each etc. > > For SSB signals, the same analysis can be performed by simply taking the > PEP of each SSB signal; so one CW signal could co-exist with one SSB > signal, both of which would have a downlink power of 100mW. > > The above is actually a slight over-simplification, as it takes no > account for compression etc, but serves as a useful example. > > As Graham mentions, a beacon may be present at a much higher level than > the rest of the transponder, which makes the analysis slightly more > complex, but the principle remains :- > > It's the PEAK power that limits the RF performance of linear > transmitters, and that is valid for all linear transmitters. > > regards > > Grant G8UBN > _______________________________________________ > Sent via AMSAT-BB@amsat.org. 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 > _______________________________________________ Sent via AMSAT-BB@amsat.org. 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

**References**:**Linear link budgets***From:*Grant Hodgson

- Prev by Date:
**Linear link budgets** - Next by Date:
**SSTV/ISS** - Prev by thread:
**Linear link budgets** - Next by thread:
**Re: Linear link budgets** - Index(es):