[eagle] Re: The DS4000 Digital Controlled TCXO

Juan Rivera juan-rivera at sbcglobal.net
Tue Jul 3 20:29:07 PDT 2007

Jim and group,


I can't either, but here's another area where we need requirements.  How
stable does this receiver need to be to satisfy the needs of the users?  Is
it driven by the human ear or the ability of a data decoder to stay locked
up?  - We need long term / short term requirements?


I'm getting set up to do a temperature run tomorrow.  I just ran the radio
from +26C to +50C to get an idea what to expect.  Here's what I found:



That missing chunk in the middle is me re-patching my test equipment.  When
I saw those saw-tooth's I wanted to hook the TS-2000 up so I could listen
again.  Sure enough they are jumps in frequency just as the chart shows.
Each "tooth" is made of multiple data points so this is not the +/- 1 digit
LSB frequency counter error I mentioned earlier.


For this preliminary test I didn't have a temperature probe inside the radio
so I don't know how close to +50 it actually got.  Tomorrow I'll do a much
more thorough job and take it down to about -30C.  I'm thinking -30C to
+50C.  Any other suggestions as to temp extremes?





From: Jim Sanford [mailto:wb4gcs at amsat.org] 
Sent: Tuesday, July 03, 2007 8:08 PM
To: juan-rivera at sbcglobal.net
Cc: 'Bill Ress'; eagle at amsat.org
Subject: Re: [eagle] Re: The DS4000 Digital Controlled TCXO


I can't imagine it NOT being a problem.

For the sake of completeness, let's assume that it IS, and solve it.

Thanks for all your hard work.

wb4gcs at amsat.org

Juan Rivera wrote:

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.
-----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:

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!
Juan - WA6HTP

Via the Eagle mailing list courtesy of AMSAT-NA
Eagle at amsat.org
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