Hans,
I just ordered one of Your 10 W PA kits and quickly read over the
assembly instruction.
Concerning the UBITX: the PA delivers 26 dB of gain, so for 10 W
output the input power for the PA is +40 dBm - 26 dB = +14 dBm
This power can be easily achieved with only one MMIC e.g. one of
the GALI amps--- or a discrete verions (BS170)?
As You also offer LPF kits, the problems of the uBITX can be
obsolete, but requires extra space for these extra boards.
One thing I m missing are the information about the P1dB pointz (
40 dBm)? and IMD performance.?
Henning Weddig
DK5LV
Am 09.10.2018 um 16:38 schrieb Hans
Summers:
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> Congrats for the amplifier. Surely
interesting for TX homebrewing?
> at a reasonable cost. Is there any evidence
that it would improve?
> the PA of the uBitx?
Evidence, no. I don't have a uBITX and the Linear kit has
only just become available this afternoon.?
Theoretically: yes, it would improve the PA on the uBITX -
a lot of care was spent on the board layout, keeping traces
symmetric and leads as short as possible (look at the 1mm or
so between the IRF510 body and the PCB, for example!). It has
very flat gain from 2-30MHz and can even produce 10W on 4m
band (70MHz) though gain is 8dB down by then... during testing
this amplifier could not be made to exhibit any instability
(oscillation). It also has a much larger heatsink than the
stock uBITX amp, and the heatsink is grounded which also
prevents feedback.?
BUT - the problems of the uBITX are not all in the driver
and final PA stages. Earlier stages are overdriven and don't
have flat gain with frequency. Spurs are generated but not
filtered. Simply replacing the final two stages of uBITX only
fixes some of the problems, not all.?
So yes, this amp would improve the PA... but at the end of
the day it can only amplify what you give it: if what you give
it is already unclean, it won't fix that.?
73 Hans G0UPL
