Re: uBITX Increasing 28 Mhz output by changing C81 #ubitx-help


Allison :

I am running off of a 12v SLA so I am seeing an input voltage of maybe 12.3 V DC.

I get about 7+ Watts out on 80m, around 5 watts out on 40m and about 1 watt out on 10m with this DC voltage in and the stock components.

I made the mods twice, the first time without changing R83 and the second time with both R83 and C81 using the V4 board values.
In both cases I doubled checked the component values (and measured them) before installation and the soldering looked fine.
What I saw was  < 1 W out on 40m through 10m (didn't check 80m). Increasing RV1 improves that but I only have a few 
degrees of rotation before I hit max so it tops out at a little above one watt. 

Everything is back to normal when I restored the original components at C81 and R83, so Q90 is fine. 
I am seeing the original power out values but I am at a loss to explain why this didn't work if this is stock
on the V4 boards ? 

I don't see any other related changes in the V4 schematic, which is why I asked if anyone else has done this mod
to a V3 board. 


Michael VE3WMB

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