The output level is also frequency dependent. I already knew this but
needed some more concrete numbers so I did some testing last nite. At 7.5
MHz I was getting approx 2VRMS with the current set at 2ma (I was using
your library, Jerry). At 35.5 MHz that level dropped to less than
0.25VRMS.
In at attempt to minimize this, at various points added some code to
increase the output at certain frequencies. The best I was able to get at
35.5 MHz was a little over 0.5VRMS with 8ma selected.
Vince.
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Yes, but the si5351 gives a square wave.
And the root-mean-square voltage of a square wave is half of the
peak-to-peak voltage.
From ?? ?? (
)??
" RMS is equal to the value of the??direct current (
)??that would produce the
same average power dissipation in a??resistive load" (
)
Another thought: asking the si5351 to drive a 50 ohm load is asking a lot.
There is only one pin going in for the 3.3v rail, so this would certainly
aggravate any crosstalk between the three output buffers.
The diode ring mixer wants to see a 50 ohm source impedance at the local
oscllator input to avoid reflections there.
Might be better off with an asymmetric resistor network there.
Or an mmic buffer amp.
And/or use multiple si5351 chips.
Jerry
On Mon, Oct 23, 2017 at 09:47 am, Gordon Gibby wrote:
Hi, I didn't follow all of that, but RMS for a sine wave is .707 times
peak
??
--
Michigan VHF Corp.
