Bill: As usual, thanks for your cogent comments and suggestions. 73, Jim
Bill Ress wrote:
Hi Juan,
The audio is a fantastic addition to your super analysis regime. Just really fine work!!
I've already addressed the issue of the two 10 MHz oscillators beating as heard in clip #1.
Now what you hear in the second audio clip doesn't surprise me. Just another reason why I remain digitally challenged and analog biased.
The DS4000 is a "digitally" corrected voltage controlled oscillator. I believe what you are hearing is the frequency being corrected in finite digital steps. An analog temperature corrected VCO will not do this. The correction will be continuous and smooth. The key advantage of the "digitally" corrected VCO is the ability to "remotely" correct the frequency with a digital input. I would submit, that feature is not needed for our application.
The "analog" TCVCXO used in the S2 concept converter uses a low cost device (available from several suppliers) and offers +/- 1 PPM stability over temperature (-40 to 85 C).
Regards...Bill - N6GHz
Juan Rivera wrote:
All,
I should have gone to work today but I ended up working on the 70 cm Receiver all day instead. Today marks a milestone for me -- my first use of audio files. You'll find two in my write up if you click HERE http://www.juanr.com/pages/hobbies/ham_radio/Eagle/Stability.htm. I think they work much better than descriptions and graphs. Now you can hear what I’m talking about...
Have a great 4th! I plan to do a temperature run on the receiver tomorrow to celebrate! Let’s see what that internal oscillator does when it’s not at room temperature!
P.S. to OSCAR guys... If you have time come on over and help me run this test. I’ll probably start early to beat the heat. If you’ve never been gassed by CO2 before, now is your chance!
73,
Juan – WA6HTP
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