Andy,

such a doubler will work but the flip-flop is not a guarantee for a
perfect 50/50 square wave in this case. The flip-flop will be clocked by
both edges of *one* of the XOR input signals, which one depends on the
clock polarity (rising or falling edge) at the flip-flop input so the
flip-flop output will have the same duty cycle as one of the XOR input
signals. The traditional C.T. transformer will work equally well (or bad).

73
Johan SM6LKM

----

Andy Talbot wrote:
> I was looking at driving push-pull transmitters from fundamental drive
> signals quite recently.
>
> How about a frequency doubler?    The output doesn't have to have 1:1
> mark-space ratio as it only clocks a flip-flop.   And simple doubler can
> consists of a delay line (CR network with around 0.5us time constant)
> followed by a squarer to give a resulting waveform shifted in phase from
> the 500kHz drive signal.  Then apply this one,  along with the original
> to a two input XOR gate whose output will then consists of a 1MHz train
> suitable for dividing by 2 for a perfect 1:1 squarewave drive.
>
>
> Andy

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