On Mon, Feb 16, 2015 at 10:03 AM, Bruce Perens <br...@perens.com> wrote:
> Hi Daniel,
>
> I think Chris has been working for 3 years with his CMX991 based radio
> design and we hope we'll be able to sell the board turn we're about to
> send in. I concur with Glen's assessment that the data sheets are only
> half of the information you need and not even accurate in that half.
>
>
Yes it's taken me a long time, but I was learning a lot of the RF from
scratch; I got my license 3 years ago too.
My experience with the CMX991's PLL was that it was noisy enough to hear it
in CW. That wasn't acceptable for me. I'm not sure how good the CMX994's
PLL is in comparison, but I'm using an ADF4360-7 as my IF PLL instead.
For DC offsets: The modulator is spec'ed for carrier and sideband
supression of 40-50 dBc, if I'm reading it correctly. That's because
there's 0 dBm fundamental output, and carrier and sideband are anywhere
between -40 and -50 dBm. That's okay for SSB @ <25W, but if you want to
amplify higher you'll want that at 60 dBc.
Bruce just posted slides on his Hamcation talk, with some annotations on my
latest schematic to the list; you may find some of it useful.
> Also, good test equipment proved essential. I spent a lot on an RF lab.
>
>
I think this was the main issue I had at the start. If you can't see what
you're making or what's happening, you don't have a very good shot of
getting it done. A spectrum analyzer & rf signal generator are a must.
The more tools you have, the easier it is to set up the appropriate tests
to answer those questions that aren't in the datasheet.
> Ours is a more ambitious project, but I think it would be fair to say
> you could work on this for a year. You'll learn a lot during that time.
> I hope you stick with it.
>
>
The direct conversion option from CML sounds really interesting. Good luck!
Testa KD2BMH
> Thanks
>
> Bruce
>
>
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