Why does QO100 use a TWT?

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Basil
Posts: 297
Joined: Tue Sep 10, 2013 7:28 pm

Why does QO100 use a TWT?

Post by Basil » Tue Jul 13, 2021 7:09 am

I believe QO100 uses a travelling wave tube PA for the down link, certainly the NB one? Why does it not use a semiconductor PA, I am wondering if it's because generating high voltage at low current is easier in space than a lower voltage at a much higher current as needed for most power semiconductors?

Just curious, thanks for any insight.
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g0mjw
Posts: 2346
Joined: Sat Sep 20, 2014 9:15 am

Re: Why does QO100 use a TWT?

Post by g0mjw » Tue Jul 13, 2021 5:08 pm

TWTs have been used in satellites for years. Known reliable tech. Satellites tend to be slow to adopt new devices as it's not easy to send out a servicing mission should things fail. SSPAs are also used but TWTs are still common. They can be quite efficient and are linear.

Mike
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Basil
Posts: 297
Joined: Tue Sep 10, 2013 7:28 pm

Re: Why does QO100 use a TWT?

Post by Basil » Tue Jul 13, 2021 5:56 pm

Thanks Mike, I must admit, having seen the spectacular demise of many FET's when getting a handle on building 1kW level Class D amps for my passion on LF 136kHz, I can see the attraction of robust thermionic devices :) Is anyone here using a TWT to generate amplification for their uplink? I know we have one fan of a pair of 817's ;) Regards, 2E0ILY
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