Re: ubitx - stop press

Ashhar Farhan
 

One could push it that high, but not on the same PCB as the rest of the circuitry. I would say that 30 watts should be the tops. the RF ground loops on the board can make the entire TX chain wobbly. that said, i haven't tried anything of the sort. I'm curious to know what happens, i havent transmitted more than 25 watts for two decades.

- f

On Mon, Dec 11, 2017 at 12:16 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Hfsignals.com write-up also mentions that power out is 10 Watts up to 10mhz, falls off to 2 Watts at 30mhz.
It is tough to drive IRF510's at 30mhz, but the WA2EBY amplifier uses two IRF510's in push-pull
like this to give 40 Watts up through 30mhz from a 28v supply.  Perhaps we can borrow some of the
WA2EBY design to approach that kind of performance.  May require beefier caps and coils.
And maybe an additional driver stage. 
    http://www.golddredgervideo.com/kc0wox/wa2ebyamp/amppart1.pdf
    http://www.golddredgervideo.com/kc0wox/wa2ebyamp/amppart2.pdf

Also in the hfsignals uBitx write-up:  "TIA".
Not found in most dictionaries.
Means "Termination Insensitive Amplifier"
    http://w7zoi.net/bidirectional_matched_amplifier.pdf

Jerry, KE7ER


On Sun, Dec 10, 2017 at 10:18 pm, AndyH wrote:
Just the close the circle, so to speak.  Farhan has additional comments in the sales write-up for the µBITX:
The power chain uses four common plastic 2N3904s in push-pull as drivers. The 2N3904s have enough gain at 30 MHz. The 2N2219s tried  earlier were found to have low gain at higher frequencies.


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