[ARC5] Square wave oscillators

[Ian Wilson]

Re: waveshape for local oscillators. A perfect square wave is composed of
odd
harmonics only. If the duty cycle is different from 50% then the harmonic
mix will
be different but the 3rd harmonic will probably still be dominant.

For an HF radio with some selectivity ahead of the mixer I don't see any
problem
with oscillator harmonics. For example, suppose you are mixing 7MHz down to
455kHz, so your LO is on 7.455MHz. The third harmonic of of this is
22.365MHz.
To cause problems, this has to beat with a signal that will result in a
difference
frequency of 455kHz or 7MHz. All these images are above 15MHz so the front
end really should be able to stop these before they reach the mixer.

Harmonics in the BFO are, in my limited experience, much more of a problem.
These can easily multiply up and cause trouble.

73, ian K3IMW


On Thu, Nov 21, 2013 at 6:46 PM, Robert Nickels <ranickel at comcast.net>wrote:

> On 11/21/2013 6:20 PM, Robert Eleazer wrote:
>
>> 1khz to 33MHZ Oscillator module
>>
>
> My experience in using similar square-wave oscillators (not this
> particular IC) has been exceptionally good - for example, I've used them as
> a crystal substitute in channelized commercial SSB radios. The output is as
> clean as with a crystal, and the frequency accuracy is dead-on.
>
> 73, Bob W9RAN
>
>
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