Re: ubitx - stop press
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i have measurer the input impedance of these stages to be appox 50 ohms when terminated in the 220 resistor in the output. i made these measurements with a homemade return loss bridge and the sweeperino.
the original wes/kopski amps uses separate resistors for bias and feeback, i used just one. if you want to experiment with different feedback resistors while keeping the bias the same, you could use the original block.
the noise figure should be 14 db. i say that because i havent measured it. i do not have calibrated noise source. this figure is based on the accumulated (measured) losses of the lpf, first mixer and the first if amps figure of 6 db.
connecting the antenna brings up the noise on all bands at my qth. i must, though admit that i havent had any contacts in 28 mhz at all.
On 8 Apr 2017 7:52 p.m., <selfy.dtp@...> wrote: