On 10/7/2014 11:29 PM, Ralph Mowery wrote:
"rickman" wrote in message
...
You say the filter removes "all" of the harmonics... that is obviously not
correct. The filter may reduce them, but it does not and can not
completely remove them. The nearest tones (which are also the largest
amplitude tones) will only be reduced a small amount really. Or maybe you
are planning to use a brick wall filter?

My question intended to ask *WHY* would anyone design a circuit to produce
a square wave and then spend the time and trouble to filter it? Earlier
you mention that filters are easier now, but in reality analog filters are
still much more difficult than just generating a tone in the first place.

I can use a single chip and a DAC to produce tones up to many MHz with
very high accuracy and purity.

I don't get it...

When I said all harmonics, that should have been taken as to reduce them to
a very low value as not to cause any problems. If the third harmonic is 40
or 50 db down or more , it probably won't cause a problem.

Big "IF"... That's my point. Knocking the third harmonic down to where
it is tolerable can be hard.


My whole thoughts was that someone already had a device that was on the
corrrect frequency but it put out square waves. I just thought that if it
could be ran through a low pass filter it would knock the harmonics down
enough not to cause problems in a mixer circuit.

If starting from the start, then there are beter ways to do it just as you
are stating.

No one *has* a device. Someone suggested using a device to make a
circuit and I didn't notice it had a square wave output at first. So we
are starting from the start...

--

Rick