[ARC5] Programmable Oscillators

[mstangelo at comcast.net]

Ian,

The Si570 is also a good candidate but it generates a squarewave so additional filtering would be required.

I've used K5BCQ's kit:

<http://www.qsl.net/k/k5bcq/Kits/Kits.html>

The K3 uses a DDS/PLL combination while the KX3 uses the SI-570.

The AD9951 spurs are prettly low and I don't believe they would be a factor in a surplus radio. I believe the spur issue is overblown. ICOM uses a DDS based oscillator in their IC7000 and I haven't heard any complaints about spurious responses. Note the K3 has spurious responses but I believe that is because of the downconversion architecture, not the choice of oscillator.

In any case, I'd invest on one of these digital oscillators when replacing crystals.

Mike N2MS



----- Original Message -----
From: Ian Wilson <ianmwilson73 at gmail.com>
To: ARC-5 Maillist <arc5 at mailman.qth.net>
Sent: Wed, 13 Feb 2013 17:10:02 -0000 (UTC)
Subject: Re: [ARC5] Programmable Oscillators

Thought I'd put in my customary plug for the Si570 - good phase noise
performance and doesn't have those ugly DDS spurs. I believe that
one (or more) of these are used in the Elecraft K3, which has pretty
impressive specs for a glowless radio :)

73, ian K3IMW

On Wed, Feb 13, 2013 at 9:01 AM, <mstangelo at comcast.net> wrote:

> If your experimenting with oscillators or replacing crystals in
> oscillators you may want use in a DDS oscillator such as WA1FFL's Direct
> Digital VFO based on the Analog Devices AD9951:
>
> <http://www.wa1ffl.com/index.html>
>
> The phase noise is much better than those microprocessor clock oscillators
> and they are tuneable.
>
> I'd invest in one of these instead of purchasing crystals or single
> frequency crystal oscillators.
>
> Mike N2MS
>
> ----- Original Message -----
> From: Dennis Monticelli <dennis.monticelli at gmail.com>
> To: David Stinson <arc5 at ix.netcom.com>
> Cc: ARC-5 Maillist <arc5 at mailman.qth.net>
> Sent: Wed, 13 Feb 2013 16:15:03 -0000 (UTC)
> Subject: Re: [ARC5] Programmable Oscillators
>
> Dave,
>
> Keep in mind that these digital oscillators often have high phase noise in
> addition to rich odd harmonics.  For harmonic filtering I would suggest a
> simple two section LC low pass.  The output section of these oscillators
> has a low Z so you can design the low pass for low Z terminations.
> Unfortunately, there is nothing you can do about the phase except try to
> buy those oscillators that have this noise specified or you know were
> intended for a noise critical application.  For some of our uses the phase
> noise won't be a big deal.  But if the oscillator is going to multiplied up
> to VHF then the phase noise is going to rear its ugly head.
>
> <snip>
>
> Dennis AE6C
>
>
> On Sun, Feb 10, 2013 at 7:50 AM, David Stinson <arc5 at ix.netcom.com> wrote:
>
> > Here is a page from Digikey.  Lowest-price for through-hole
> > oscillator, programmed to order by them is $4.10 in quantites of 1.
> >
> > <snip>
> >
> > 73 Dave AB5S.
> >
> >
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