[eagle] Re: Latest 70 cm Receiver Test Results

Juan Rivera juan-rivera at sbcglobal.net
Sun Jun 10 15:17:16 PDT 2007


John and group,

 

Questions:

 

1)       What about the phase noise?  I'm assuming that that big hump is
phase noise.  Do you consider that to be excessive?

2)      What about the passband ripple?  That needs to get fixed.

3)      If the next generation of the radio is going to be autonomous, fixed
tuned, and have continuous power, what exactly is the CAN-Do module doing
except returning a few parameters to the IHU?  It makes sense to me to get
it away from the radio completely.  You can feed it whatever it needs such
as loop lock status and temperature.  That also fixes our lack of front
panel space problem.

 

Until question 3 is resolved it doesn't make any sense to me to spend the
time necessary to desolder the CAN-Do module and relocate it.  For now we
can initialize the receiver and then kill the CAN-DO module (RFC10 id
removed and the receiver is powered separately.)  That will create the same
conditions as perfect CAN-Do module isolation would without the work.

 

I'd like to get back to the ATP testing but until we have items 1 and 2
resolved and correct the microphonics, there isn't too much sense in
starting the ATP now.  I'll focus on the microphonics while you folks digest
this latest information.

 

By the say, are there new specs for the receiver yet?  Is it still expected
to cold soak to -70C?  That's close to the temperature of liquid CO2 and
well below the storage temperature of most components and way below the
operating temperature limits.

 

73,

 

Juan

WA6HTP

 

  _____  

From: John B. Stephensen [mailto:kd6ozh at comcast.net] 
Sent: Sunday, June 10, 2007 12:51 PM
To: juan-rivera at sbcglobal.net
Cc: 'AMSAT Eagle'
Subject: Re: [eagle] Latest 70 cm Receiver Test Results

 

The time that I spent optimizing the layout of the U17 switching regulator
appears to be worth it if it isn't polluting the VCOs. What would be ideal
is a module case where the CAN bus can exit from one side and the RF and IF
from the other.  

 

For now, the RF and IF can be run back to the connector bracket with SMA
jumper cables. What is needed is a CAN-Do widget without the header
connector so that wire leads can carry power and signals to the receiver
PCB. 18-22 guage wire should work for power and 22-26 guage for signals. The
wires need to be wound around a torroidal ferrite core to kill any
common-mode noise. It may also be necessary to run the coax through ferrite
beads. Do you have any beads or torroids made of material 75 or 77?

 

73,

 

John

KD6OZH

----- Original Message ----- 

From: Juan <mailto:juan-rivera at sbcglobal.net>  Rivera 

To: eagle at amsat.org 

Sent: Sunday, June 10, 2007 17:59 UTC

Subject: [eagle] Latest 70 cm Receiver Test Results

 

All,

 

As I troubleshoot the 70 cm receiver I stop and add to my logs every few
minutes.  I won't bother to announce every step I take (I just made an
addition) because it takes too long.  If you are interested please check the
latest log at the top of the list or go to my web site.  If you have a
comment or suggestion just drop me an email via this Eagle/AMSAT mailer and
everyone can participate.  I'll check email often when I'm working on this
project.

 

Here's the link to the AMSAT/Eagle receiver page -->
http://www.amsat.org/amsat-new/eagle/EaglePedia/index.php/U-Band_Receiver

>From there find the latest log at the top of the list under Project Status.
At the moment it's 'Spur Troubleshooting'

 

Or...

 

Go to my web at http://www.juanr.com/

Select Amateur Radio, select AMSAT/Eagle, and select the log you want to see
from the menu.

 

73,

 

Juan

WA6HTP

 

 

 


  _____  


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