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Re: Increase uBitx to 25 watts internal or external amp with 12v supply for portable use

 

Thanks! I was looking for information on how to separate the PA from the +12v input I will check that out? (I was having trouble tracing that down - I guess worth taking a look under the connector that shouldn't be too bad to desolder).? Thanks for the other DIY idea as well.? ? I like all these ideas.? I was thinking about trying something that seemed super simple... which makes me wonder if it's just not going to work..... a ready made step up transformer from 12 to 24v, cut that PA trace to separate that line and just feed the step up right from P1 connector and feed the 12v input to the step up transformer from the P1 connector and the 24v output to the center pin.? If it worked I could even throw in a simple DPDT switch that can switch between using standard 12v for low power and engaging the step up for high power.

I figure there is probably some reason folks aren't doing this..noise from the transformer maybe or doesn't work... I thought I've heard of someone on here trying it and it worked though.? Also I was trying to consider the safest board surgery options to avoid damaging the board and the most stable for portable operations that might survive getting banged around a bit.??

For that DIY amplifier does it need some sort of control line to detect when transmitting or just detects the power input on transmit to enable?



On Mon, Oct 25, 2021 at 06:00 AM, Evan Hand wrote:
Dave,

Here is a link to the author's implementation of a DIY Kit that produces 50 watts with a 13.8volt power supply and 5 watts input:


You could try to modify the uBitx PA section to match this (as far as I can tell the DIY kit uses IRF520 MOSFETs).? The issue would be that the driver does not put out 5watts, so an intermediate drive would need to be added.? This was verified in a number of trials by others more skilled in RF design than am I.? If you just add the DIY amp after the uBitx amp, then you will need to reduce the output of the uBitx power amp to less than 5 watts.? This can be done with RV1.? You could do surgery on the board to use the built-in LPF, though I would add a second LPF assembly that is rated for greater than 50watts.? There are DIY kits on eBay for those filters.

As to separating the v6 PA supply from the rest of the radio, the 3 pin power connector is still provided, but you will need to cut a trace on the board to separate the supplies.? I HAVE NOT DONE THIS, so please verify for yourself!!? Tracing the runs on the PC board point to the jumper trace between the two power pins on P1 being on the top side of the board under the connector.? You would need to remove the connector, cut the trace, and then solder the connector back on the board.? Again, this is visual only, I have not removed the connector to verify.

Hope this is helpful.
73
Evan
AC9TU
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