Re: Are these output watt rating crazy?

 

Hi,

I used the AADE filter simulation/design program.  I posted because I had seem some comments on the power outputs and was curious to simulate the low filter to see if that might impact some of the power levels.  I simulated the lowest filter I saw on the ubitx v3 schematic.  Did I miss a lower one?  This one seems to be the lowest and used for both 40m and 80m with a cutoff very close to 7MHz (actually showed -2dB at 7.3MHz).

Yes the design environment is 50 ohms.  That does not mean the filter will show that for all frequencies.  At the design frequency, they should show that (as this one does for 40m).  At other frequencies they can present higher or lower impedances which will affect power output.  This one does also show around 50 ohms at 80m.  However at 60m it shows to be about 20 ohms and at 160m about 10 ohms.  Even using another filter on the output, with this filter inline it may cause trouble.  So it would be best to have a designed 160m filter linked directly to the output of the PA if one wants to use that band.  My thoughts anyway.

Of course it would be good to see an actual measurement of the filter with a VNA etc.  My equipment is packed away from a move at the moment so I have to rely on software at the moment.

I just thought people may be interested in what I had found.   I can work on my own no problem.




Cheero,


Mark.

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