BSugarberg <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Hello,
And if you have the Version 1 predriver board?
73, Bruce WA8TNC
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Jim Shorney wrote:
Looking at the schematic of the (version 2) predriver board, it looks like the R2203-RFC2202-C2204 network from collector to base of
buffer Q2201 is designed to flatten the gain of the predriver board across the HF range by providing increasing negative feedback as
frequency is decreased. I added a 1K resistor across R2203, which should reduce the net resistance to 338 Ohms. This did decrease
the gain somewhat, and I am now able to adjust the ALC for 150 watts CW output on 40 meters at the point where the ALC LED *just*
comes on. There is no longer any apparent instability or oscillation on 40 meters at this point. Power on 10 meters is now 105 wattts at
28.3, decreasing to 95 watts at 29.8, with ALC action across the entire band. The predriver gain pot was adjusted at 29.8 MHz, as I
previously described. This provides plenty of ALC at 28.3, and just enough at the high end of 10 meters. So far, the PA has been rock
stable on all bands after this modification.
73
-Jim
NU0C
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