Re: Transmitter Mods

Tom Christian
 

I made Howard's mods on both my uBITXs with great results in spite
of myself.....:) It was a comedy of errors....  On both rigs, I didn't
have any problems with the 220pf capacitors across R87 & R88, except
the 0805 size was like working with big grains of salt. The small size
gave these mid-60s eyes a good workout!.  The resistor/inductor was
another story.  I had issues with the 1K ohm R86 teepee attempt with
the 33uH inductor.

On the first rig, I destroyed the SMD resistor with too much heat while
trying to make the solder joint (went to infinity).  I didn't have SMD
replacements, so I used a descrete 1K since the inductor I had on hand
was also descrete.  Then on the 2nd rig, the 1K resistor flew out of
the tweezers and I never was able to find it....  So this rig also got
descrete components.  Enclosed is a humbling picture......:)  I obviously
need more SMD practice!

I don't have a precision power meter for measurements, but my cheapie
analog SWR/Power meter shows before and after readings as follows:

    Band    Before    After
    -------    ---------    ------
    80        5 watts    4 watts
    60        2             3
    40        4             4
    30        2             3
    20        2             4
    17        1.5          4
    15        1             2
    12        0.8          1.5
    10        0.3          1.2

Needless to say, I'm VERY pleased with the power increase!  My reports
when testing with other hams on FT8 have been good clean signals.  This
is going to make the uBITX even more fun!

Thank you so much, Howard, for the great recommendations! 
Much appreciated!

Tom
AB7WT

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