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@comcast.net]
Sent: Sunday, June 10, 2007 12:51
PM
To:
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