Re: Maximum Power using FR4 board ?

John Quarmby

I found 50W of 1296MHz through a 50 ohm stripline on FR4 cooked the board and discoloured it over time. Why not use suspended microstrip with air dielectric, that would avoid the problem entirely at any reasonable power level.


John G3XDY 

Sent from my Samsung Galaxy smartphone.

-------- Original message --------
From: John Worsnop <johnworsnop@...>
Date: 15/06/2019 08:28 (GMT+00:00)
Subject: Re: [UKMicrowaves] Maximum Power using FR4 board ?

So much depends on where the line is in the circuit, the dielectric thickness and the type of FR4. At RF, not all FR4 is the same! The thing is the the power density in the dielectric. The reason I used low loss RF35 in my 45W pa was the original FR4 version cooked the output line. In contrast, designs by  Goran AD6IW I've seen work perfectly well at similar powers. That may of course just be a reflection on Goran's design skills compared to mine!

Stick to proper microwave materials for power if you can.

73 John

On Sat, 15 Jun 2019, 01:01 Gordon REASON via Groups.Io, <> wrote:

If .............. you have a good load , 100 W should be ok .............

Some years back I made and  testee , low power , a 2,7 Ghz coupler .

The customer put 400 watts through it , and it melted ...............!

On 14 June 2019 at 17:56 simonchettle <simon@...> wrote:

This is  a simple question what is the maximum power anyone would risk using a 1/4 length strip line on FR4 on 23cms ? 
Why because my metal working tools and skills are close zero and I am thinking of building a Wilkinson divider. 
I am thinking of combining two power amplifiers each of circa 100 W  O/P. 



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