[App_rpt-users] RTCM Simulcast question

[David McGough]

Hi Kevin,

Yes, I agree.  My first post (see my post about the Si5351B) mentioned the
spectral purity issues with the Si5351 family.  The post you referenced,
below, was in regard to using the Si5351 as a precision microprocessor
clock.

Anyhow, I'm tinkering with a solution for Mastr II radios right now, using
a Si5351 followed by a cleanup PLL/VCO. I think this method is going to
work nicely.

73, David KB4FXC



On Mon, 6 Jun 2016, Kevin Custer wrote:

> There is one thing everyone is missing in this discussion.  If the 
> intention of this oscillator is to be used in duplex service, be aware 
> that the Si series of products may not have the spectral purity for 
> duplex applications.  By spectral purity, I mean transmitter side band 
> noise.  Stability using GPS is likely easy, but making an oscillator 
> clean enough isn't always easy.
> 
> I say this because there has been a great deal of interest in making 
> programmable channel elements for older crystal radios using the Si 
> series.  These modules exist, but testing has shown that they don't have 
> the noise specification required for duplex operation.  This means it 
> may be more challenging or impossible to make them work in some duplex 
> applications.  Of course, this depends on how the OCXO/Si is used.  If 
> it were driving the loop reference of a free running on-frequency 
> oscillator, locked by PLL, then you'd have the best of all worlds  - 
> synthesized frequency reference, low transmitter side-band noise, and 
> the ability to modulate it.  Something similar to the GE MASTR II PLL 
> exciter and its operation could be considered.
> 
> Kevin Custer
> 
> 
> 
> 
> On 6/6/2016 12:06 PM, David McGough wrote:
> > If you GPS-discipline that OCXO, I think it would be more than adequate.
> > Since you've already got the 1 PPS GPS signal, all that should be needed
> > in addition to the OCXO/Si5351 is a little $3 Arduino board (like:
> > http://www.ebay.com/itm/131702108124 ) to program the desired output
> > frequency(s) and perform compensation.
> >
> > $16 for an OCXO ---NICE! ...The whole project maybe $25!
> >
> >
> >
> > On Mon, 6 Jun 2016, Joe Moskalski wrote:
> >
> >> I mentioned this to someone else, QRP Labs has a kit that creates a OCXO
> >> around the Si5351 chip. here is the link:
> >>
> >> http://www.qrp-labs.com/ocxokit.html
> >>
> >> If you couple this with another kit of theirs you can program it it any
> >> frequency you want. My only thought is would it be accurate/stable enough.
> >>
> >> http://www.qrp-labs.com/progrock.html
> >>
> >>
> >>
> >> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>
> >> Virus-free.
> >> www.avast.com
> >> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>
> >> <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> >>
> >> On Mon, Jun 6, 2016 at 11:36 AM, David McGough <kb4fxc at inttek.net> wrote:
> >>
> >>> Hi Joe,
> >>>
> >>> While on the subject of the Si5351 chips, the application of converting
> >>> one reference clock to a secondary frequency is what they were designed
> >>> for. So, since you've already got a GPS reference, this -might- be an
> >>> inexpensive starting point...For this application, you obviously won't
> >>> need all the bells and whistles presented in this article! See:
> >>>
> >>> http://www.knology.net/~gmarcus/Si5351/Si5351_VFO_QEX.pdf
> >>> http://www.knology.net/~gmarcus
> >>>
> >>> Note that I would replace the Si5351 25MHz reference with a decent TCXO
> >>> (available on ebay, etc.)....Note that I haven't used the Si5351 with an
> >>> RTCM, there may be simpler/better ways???
> >>>
> >>>
> >>> 73, David KB4FXC
> 
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