Juan:
From a practical aspect, the hanging of electronics on the outside
of an E05 20 module is rather implacable as there is no place to put them. The
thin metal cover is not a place as the heat would not be spread out for
dissipation, and the cover would not be “divorceable” from the rest
of the module. You would not want to place them on the front connector bracket
as you are already scrambling for space for connectors. Those are the only
areas that are open to the outside world.
We already have solutions for the mounting of these electronics on
the inside of the module, where they belong, so I do not see where you
otherwise plan to place these power conditioning electronics?
Dick Jansson, KD1K
From:
[email protected] [mailto:[email protected]] On Behalf Of Juan
Rivera
Sent: Saturday, 28 July, 2007 05.23
To: 'John B. Stephensen'
Cc: David Smith; Dave Black (Work); Dave Black (Home); [email protected];
Samsonoff@Mac. Com; Juan.Rivera (Work)
Subject: [eagle] Receiver Spec vs. ATP, a few Suggestions and a Question
or Two
John,
I took a few minutes to look over your new specs and
compare them against the Acceptance Test Procedure. I've got a number of
tests in the ATP for which there are no specs:
·
Image rejection
·
Internally generated spurs
·
Local oscillator leakage
·
Input and Output VSWR
Items that need to be addressed that aren’t in
either document:
·
EMI conducted susceptibility
·
EMI radiated susceptibility
·
Short and long-term frequency stability
I also take issue with the -60C minimum power-down
temperature. I think this is unrealistic just from a CTE mismatch
perspective. The reliability of anything subjected to that wide a
temperature spread is going to suffer. A way must be found to raise that
temperature.
I have a few thoughts... The CAN-Do switching
step-down converter is only supplying 11 milliamps. If we take a slight
efficiency hit we could just go to a simple linear regulator and completely
eliminate the radiated and conducted EMI emission problem from CAN-do.
That eases the EMI filtering and shielding requirements for every single
payload. That seems like a good trade-off to me.
Rather than worry about trying to conduct heat through a
PCB why not just go to externally mounted regulators for the CAN-Do and the
Receiver right on the case itself. We’re not that pressed for
space. That eases the heat sink and the associated thermal gap filler
issues. EMI will still be an issue, but only for external sources instead
of one that is inside the enclosure itself. That strikes me as a huge
bonus. Why not design a single-sided PCB with the regulators hanging over
the edge and the whole assembly, PCB and regulators, mounted directly to the
enclosure. Stick it in with the CAN-Do module in a separate cell.
Filter all the signal and power through the common bulkhead.
I’m also curious as to why you are specifying two
different types of SMA connectors.
73,
Juan – WA6HTP