Sunday, 18 November 2018

Es'hail 2 and my Spectrian amp

2 MS/s @ 2.4 GHz 80 watts

Spectrian bare bones amplifier

Thermal image of Spectrian

Now that Es'hail 2 is launched I thought it might be time to see how much
power I will be able to generate when it comes time to use the asset.

It didn't go as well as I had planned. I can generate about 80 watts of DVB-S2
at 2.405 GHz that looks reasonable but it requires almost 800 watts of input power.
The amplifier is the working parts of a Spectrian unit minus the original heatsinks
(because of shipping costs from the U.S). It is not obvious from the thermal image
as to why the efficiency is so low. The MRF286 devices have a claimed efficiency
of 28 - 32% at 2 GHz obviously they will have less efficiency at 2.4 GHz and there
will be losses in the PCB and the combiners but 10% is pretty low.

So it looks like I will have to try a different approach to saving us all from
global warming. Currently I am looking at the MRF7S24250 device which has
250 watt output at 2.4 GHz a gain of 14.5 dB and an efficiency of about 55%.


5 comments:

  1. Looks interesting. The efficiency is certainly very frequency dependent. I must have a look at Es'hail 2, I read that it had been deployed.

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  2. Class A amp so runs warm driven or not.

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    Replies
    1. Wrong, the driver on the left is Class A but the main amplifier modules are Class AB. With no drive the main amplifier draws about 2 amps driven to 80 watts output it draws around 38 amps.

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  3. Why do you need 80watt? When 20 will be enough? Are you going to use 60cm dish?

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  4. Well I hope I need a lot less than that but that 80 watts was at the output of the amplifier. What actually gets radiated will be considerably less than that due to feeder losses and poor dish illumination. Until we have some actual figures in February rather than estimates we won't know. Someone in the industry told me that the estimates satellite manufacturers give are usually optimistic.

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