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How to increase the power output of a 300 w broadcast amplifier ?

Alexander Soto

Oct 10, 2018
1
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Oct 10, 2018
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The link below is the schematic for the design of a 300 watt broadcast amplifier.

http://www.electroschematics.com/19/300w-fm-88-108-mhz-amplifier-tp9383

This amplifier uses two tp9383 transistors. The individual output power of each individual transistor is 150 watts. A link to the specification sheet of this transistor is provided below:

https://www.mouser.com/datasheet/2/453/tp9383-15678.pdf

As you can see from the schematic, there is a simple pattern of repeating the same basic circuit with another of the same transistor to double the output wattage, then combining their individual output power wattages together in the final stage, resulting in a doubling of the output power.

Hypothetically, if a person were to continue this pattern six more times for a total of eight transistors, would they get an output wattage of approximately 1.2 Kw ?

If yes, can this be done indefinetely, or rather, what is the limit ?
 

kellys_eye

Jun 25, 2010
4,876
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Jun 25, 2010
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4,876
The schematic shown uses two anti-phase signals (via Q1 and Q2) that are 'added' through the 'combiner L10/L11.

You can take the output of two complete amplifiers and combine them (again in anti-phase) to boost the power - this is a common method to build high-output power stages but requires very capable design of the output transformer (combiner) to minimise losses. The combiner is a 'passive' device but requires critical design to work.

This can be scaled up in a 2, 4, 8, 16 etc step but each 'combination' results in power loss as the combiners (being passive devices) consume power rather than 'create'.

You also need output stage monitoring to shut down the system in case of failure of one (or more) power stages as the mismatch this causes will feed back to the other stages and may damage them.

You do realise that you're discussing commercial radio frequencies and that you require the appropriate licenses and permissions to use them? Even at the power levels of a single stage you're looking at a 'night time knock on the door' if you operate without authority and they WILL find you.
 
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