Ron
Power with and without the PA3BWI mods should not be different by more
than 1 or 2 percent. If more than that I would suspect that your IRF510's
may have been oscillating on signal peaks and that the PA3BWI mods have
eliminated that spurious oscillation.
Not sure how much power you are getting, or how much you are trying to
get. The BITXxxA transceiver output impedance matching is designed for
10 to 12 watts output. It is usually possible to get 16 watts out with
a 13.6
volt power supply but that causes RF peak compression due to impedance
mismatch if the final is driven to that level.
Yes, you can add the 0.1 mfd cap across R7 in BITX20A, BITX17A, and
other band versions as well. In prototype testing we did not need it in the
BITX20A version, and definitely did not need it in the BITX40A build.
Adding
this capacitor to the BITX17A was thought necessary because some IRF510
devices needed a little more drive at 18 MHz.
Arv K7HKL
_._
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On 06/29/2013 12:00 PM, ronbaechle wrote:
After adding 1K resistor between drains Q18 and Q19 and 220 ohm across
pri t3 noticed lower pwr. Will adding .1 mf increase drive like stated
for Bitx17a? Before experimenting will this same value work on
Bitx20a? Thanks Ron
