[eagle] Re: The DS4000 Digital Controlled TCXO

Juan Rivera juan-rivera at sbcglobal.net
Tue Jul 3 19:34:50 PDT 2007


Hi Bill,

Aren't all these tools neat?  I though you'd like the audio!

I'm thinking that the uplink guys are going to have to weigh in and tell us
if these jumps are a problem or not for data.  I'd think that they would be
for demodulating data and a major annoyance for SSB.  It's the sort if
subtle stuff that I didn't notice at first.  I'm sure there are a few more
surprises waiting to be discovered.

I'm curious about the beat since the two oscillators produced IF outputs
that were fairly far apart and yet the beat seems to be around 1 Hz.  I
guess I could try to sniff the internal oscillator to see exactly where it
really is.

73,

Juan

-----Original Message-----
From: Bill Ress [mailto:bill at hsmicrowave.com] 
Sent: Tuesday, July 03, 2007 6:49 PM
To: juan-rivera at sbcglobal.net
Cc: eagle at amsat.org
Subject: The DS4000 Digital Controlled TCXO

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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