Re: uBitx Unfiltered

jim
 


On Saturday, September 1, 2018, 4:03:24 PM PDT, ajparent1/KB1GMX <kb1gmx@...> wrote:


What are you using for Q90 and all the other 3904s?

Words would make the posting informative.

Allison
_._,_._,_

Just changed only the one resistor ...Nothing else

consider ..Ft of 2n3904 is about 250 Mhz ...If beta rolls off at 6db/octave, then =at 250 Mhz, beta = 1..125 Mhz beta 6db betterĀ  (3db doubles =beta 2, 3db doubles beta 4)..60 Mhz 12 db better (4 doublesĀ  2,4,8,16)...30 Mhz 18 db better .(6 doubles 2,4,8,16,32,64)..

gain bandwidth product...gain of 1 to 250 Mhz,gain of 6db to 125 Mhz, gain of 12 db to 60 Mhz, gain of 18 db to 30 Mhz

18 db isn't great, but it'll do...besides when I dead-bug style bread-boarded Q90 I got 30 db gain rolling off at about 45 Mhz.

Thought the measurements would be of some use, maybe someone else will measure their power out across the bands and compare to see whats what

as I sed, q911;912 is next and looking at the biasing between q90 and 911/912 and q92/93/97/98 I don't see a nickels worth of difference between them

Jim


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