Re: 70 cm Receiver IF Spurs - Problem Solved
Chuck,
I don't want to tear into the CAN-Do module. I feel like it is a loaner and not mine to modify. It would be interesting to disconnect the switch and the current monitor from the CAN-Do power input and move it to those user pins as you suggest. That might just work, but I also know they don't want to have multiple versions of the module floating around and this would be one.
We also can't loose sight of the radiated noise from that inductor. I can see signs of EMI if it gets within 2 inches of the sensitive areas of the receiver.
73,
Juan
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Sunday, June 17, 2007 9:18 AM To: juan-rivera@sbcglobal.net Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
I am impressed with your testing and analysis.
I find it curious that you were unable to filter the power from the CAN-Do! . But switching noise is notorious for being difficult to filter. So maybe that is something to just forget. But in a total system (satellite) it may not be possible to forget. We may need to find a way to filter the power for sensitive modules even if not using power from the CAN-Do! ; in which case, such a filter may also filter the noise from the CAN-Do! .
If your analysis is correct, and it certainly seems to be, then it would also seem possible to remove the switch from the CAN-Do! (not just bypass it) and rout your clean power source through the CAN-Do! current measurement circuit thus saving having to do this in the module.
Great work! And thanks.
Chuck
Juan Rivera wrote:
Hi Chuck,
Bad news I'm afraid. See my report for details... I've sent out a link
to
the group.
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Saturday, June 16, 2007 8:57 AM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; David Smith; Dave Black (Work); Dave Black (Home); Samsonoff@Mac. Com; Juan.Rivera (Work) Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
This is fantastic!
Please try one more experiment. Pass the module current through the current measuring circuit on the CAN-Do! while bypassing the switch transistor (you could just short across the switch transistor) and see if the problem reappears.
If you end up having to use the user pins, you will need to add current measuring circuitry to your module. While this is no big deal, its one more thing you might not have to do.
Chuck
Juan Rivera wrote:
All,
The 70 cm Receiver spur problem has been solved. Click here
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
ting.htm>
for details.
73,
Juan
WA6HTP
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hi Juan,
One of the purposes of the CAN-Do! was to provide a standard interface so that a module couldn't do something nasty and take out the entire satellite. So custom mods to the CAN-Do! are not allowed. Having said that, we have always assumed that a jumper across the CAN-Do! power switch would be installed for those modules that needed to be powered up no-matter-what.
Chuck
Juan Rivera wrote:
Chuck,
I don't want to tear into the CAN-Do module. I feel like it is a loaner and not mine to modify. It would be interesting to disconnect the switch and the current monitor from the CAN-Do power input and move it to those user pins as you suggest. That might just work, but I also know they don't want to have multiple versions of the module floating around and this would be one.
We also can't loose sight of the radiated noise from that inductor. I can see signs of EMI if it gets within 2 inches of the sensitive areas of the receiver.
73,
Juan
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Sunday, June 17, 2007 9:18 AM To: juan-rivera@sbcglobal.net Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
I am impressed with your testing and analysis.
I find it curious that you were unable to filter the power from the CAN-Do! . But switching noise is notorious for being difficult to filter. So maybe that is something to just forget. But in a total system (satellite) it may not be possible to forget. We may need to find a way to filter the power for sensitive modules even if not using power from the CAN-Do! ; in which case, such a filter may also filter the noise from the CAN-Do! .
If your analysis is correct, and it certainly seems to be, then it would also seem possible to remove the switch from the CAN-Do! (not just bypass it) and rout your clean power source through the CAN-Do! current measurement circuit thus saving having to do this in the module.
Great work! And thanks.
Chuck
Juan Rivera wrote:
Hi Chuck,
Bad news I'm afraid. See my report for details... I've sent out a link
to
the group.
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Saturday, June 16, 2007 8:57 AM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; David Smith; Dave Black (Work); Dave Black (Home); Samsonoff@Mac. Com; Juan.Rivera (Work) Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
This is fantastic!
Please try one more experiment. Pass the module current through the current measuring circuit on the CAN-Do! while bypassing the switch transistor (you could just short across the switch transistor) and see if the problem reappears.
If you end up having to use the user pins, you will need to add current measuring circuitry to your module. While this is no big deal, its one more thing you might not have to do.
Chuck
Juan Rivera wrote:
All,
The 70 cm Receiver spur problem has been solved. Click here
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
ting.htm>
for details.
73,
Juan
WA6HTP
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Chuck,
At least in this particular case jumpering across the switch didn't work. (See my log for today on Eaglepedia.)
Since the CAN-Do module is such an imbedded and pervasive component in Eagle, I think it needs to be free of radiated and conducted EMI in both directions. It's a great little interface but I'm afraid it has some very serious shortcomings at the moment:
1. Conducts noise back towards the power source where it can impact other loads on the same power bus (one ohm of resistance out there was enough to screw up the receiver.)
2. Provides a noisy +14 to its load (the noise went right through the receiver like fat through a goose and ended up in the IF as spurs.)
3. Radiates EMI that can adversely affect sensitive circuitry at a distance of over two inches from the rear of the PCB
Attempting to mitigate those problems will put a huge burden on every payload and the adverse impact might not be fully known until integration and test, if then. Trying to go back and band-aid something like this after all the payloads come together would be a very bad corner to get backed into. You could do what I did and sacrifice 2 inches of space inside every module chassis, or you could try to build a two-section chassis and filter the lines passing through the bulkhead, adding complexity. But that doesn't address the potential impact to another payload from the spikes that are propagated back towards the common +14 bus.
I would expect that every receiver, block up or down converter, transmitter, or amplifier will be impacted by this noise in a similar way. In my opinion this is a global problem that needs a global solution. If the CAN-Do module can be made EMI-free, or meet a yet to be determined EMI spec, then all of the payloads teams can start their design with a known environment.
If the CAN-Do module is not modified then I think the only safe thing to do is to build each payload so it can function using CAN-Do switched +14 volt power (the receiver can't in the Rev-A configuration.) If your payload can function with that noisy +14, without any adverse impact, then it is probably a pretty well protected circuit and should be fairly immune to whatever noise is added to the source by conducted EMI from other loads on the power bus. It just seems simpler and cleaner to fix the problem at the source.
I have an idea for a noise generator that I will stick on my log... This could be the go/no go test for each payload. I'll go sketch it up and get it uploaded by about 2000 Pacific Time.
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Sunday, June 17, 2007 5:51 PM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; Bill Ress; Dave Black (Home); Dave Black (Work); Dave hartzell; David Smith; Don Ferguson; Juan.Rivera (Work); Samsonoff@Mac. Com Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
One of the purposes of the CAN-Do! was to provide a standard interface
so that a module couldn't do something nasty and take out the entire
satellite. So custom mods to the CAN-Do! are not allowed. Having said
that, we have always assumed that a jumper across the CAN-Do! power
switch would be installed for those modules that needed to be powered up
no-matter-what.
Chuck
Juan Rivera wrote:
Chuck,
I don't want to tear into the CAN-Do module. I feel like it is a loaner
and
not mine to modify. It would be interesting to disconnect the switch and
the current monitor from the CAN-Do power input and move it to those user
pins as you suggest. That might just work, but I also know they don't
want
to have multiple versions of the module floating around and this would be
one.
We also can't loose sight of the radiated noise from that inductor. I can
see signs of EMI if it gets within 2 inches of the sensitive areas of the
receiver.
73,
Juan
73,
Juan
-----Original Message-----
From: Chuck Green [mailto:greencl@mindspring.com]
Sent: Sunday, June 17, 2007 9:18 AM
To: juan-rivera@sbcglobal.net
Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
I am impressed with your testing and analysis.
I find it curious that you were unable to filter the power from the
CAN-Do! . But switching noise is notorious for being difficult to
filter. So maybe that is something to just forget. But in a total
system (satellite) it may not be possible to forget. We may need to
find a way to filter the power for sensitive modules even if not using
power from the CAN-Do! ; in which case, such a filter may also filter
the noise from the CAN-Do! .
If your analysis is correct, and it certainly seems to be, then it would
also seem possible to remove the switch from the CAN-Do! (not just
bypass it) and rout your clean power source through the CAN-Do! current
measurement circuit thus saving having to do this in the module.
Great work! And thanks.
Chuck
Juan Rivera wrote:
Hi Chuck,
Bad news I'm afraid. See my report for details... I've sent out a link
to
the group.
73,
Juan
-----Original Message-----
From: Chuck Green [mailto:greencl@mindspring.com]
Sent: Saturday, June 16, 2007 8:57 AM
To: juan-rivera@sbcglobal.net
Cc: eagle@amsat.org; David Smith; Dave Black (Work); Dave Black (Home);
Samsonoff@Mac. Com; Juan.Rivera (Work)
Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
This is fantastic!
Please try one more experiment. Pass the module current through the
current measuring circuit on the CAN-Do! while bypassing the switch
transistor (you could just short across the switch transistor) and see
if the problem reappears.
If you end up having to use the user pins, you will need to add current
measuring circuitry to your module. While this is no big deal, its one
more thing you might not have to do.
Chuck
Juan Rivera wrote:
All,
The 70 cm Receiver spur problem has been solved. Click here
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
ting.htm>
for details.
73,
Juan
WA6HTP
Via the Eagle mailing list courtesy of AMSAT-NA
Eagle@amsat.org
Team: I ABSOLUTELY agree with Juan's assertion that ... it needs to be free of radiated and conducted EMI in both directions.
We need to resolve these issues, and then issue such resolution as a requirement.
Size of incoming power conductor is a spacecraft issue, that we need to get into the Black Forest notes and subsequent requirements.
Eliminating the radiated noise is a CAN-Do! issue and should be solved -- especially if it is as simple as replacing a radiating inductor with a shielded inductor.
In my professional life, I've seen a similar situation, where such an inductor in a VERY sensitive instrumentation system was picking up noise, a fatal flaw. Replacing the one component with a shielded equivalent solved the problem.
We should at least TRY such an approach. .. . Juan, I'd like you to do the swap and then give us before and after plots and analysis. That will conclusively prove or disprove the issue.
Thanks & 73, Jim wb4gcs@amsat.org
Juan Rivera wrote:
Chuck,
At least in this particular case jumpering across the switch didn't work. (See my log for today on Eaglepedia.)
Since the CAN-Do module is such an imbedded and pervasive component in Eagle, I think it needs to be free of radiated and conducted EMI in both directions. It's a great little interface but I'm afraid it has some very serious shortcomings at the moment:
- Conducts noise back towards the power source where it can impact
other loads on the same power bus (one ohm of resistance out there was enough to screw up the receiver.)
- Provides a noisy +14 to its load (the noise went right through
the receiver like fat through a goose and ended up in the IF as spurs.)
- Radiates EMI that can adversely affect sensitive circuitry at a
distance of over two inches from the rear of the PCB
Attempting to mitigate those problems will put a huge burden on every payload and the adverse impact might not be fully known until integration and test, if then. Trying to go back and band-aid something like this after all the payloads come together would be a very bad corner to get backed into. You could do what I did and sacrifice 2 inches of space inside every module chassis, or you could try to build a two-section chassis and filter the lines passing through the bulkhead, adding complexity. But that doesn't address the potential impact to another payload from the spikes that are propagated back towards the common +14 bus.
I would expect that every receiver, block up or down converter, transmitter, or amplifier will be impacted by this noise in a similar way. In my opinion this is a global problem that needs a global solution. If the CAN-Do module can be made EMI-free, or meet a yet to be determined EMI spec, then all of the payloads teams can start their design with a known environment.
If the CAN-Do module is not modified then I think the only safe thing to do is to build each payload so it can function using CAN-Do switched +14 volt power (the receiver can't in the Rev-A configuration.) If your payload can function with that noisy +14, without any adverse impact, then it is probably a pretty well protected circuit and should be fairly immune to whatever noise is added to the source by conducted EMI from other loads on the power bus. It just seems simpler and cleaner to fix the problem at the source.
I have an idea for a noise generator that I will stick on my log... This could be the go/no go test for each payload. I'll go sketch it up and get it uploaded by about 2000 Pacific Time.
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Sunday, June 17, 2007 5:51 PM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; Bill Ress; Dave Black (Home); Dave Black (Work); Dave hartzell; David Smith; Don Ferguson; Juan.Rivera (Work); Samsonoff@Mac. Com Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
One of the purposes of the CAN-Do! was to provide a standard interface
so that a module couldn't do something nasty and take out the entire
satellite. So custom mods to the CAN-Do! are not allowed. Having said
that, we have always assumed that a jumper across the CAN-Do! power
switch would be installed for those modules that needed to be powered up
no-matter-what.
Chuck
Juan Rivera wrote:
Chuck,
I don't want to tear into the CAN-Do module. I feel like it is a
loaner and
not mine to modify. It would be interesting to disconnect the switch and
the current monitor from the CAN-Do power input and move it to those user
pins as you suggest. That might just work, but I also know they
don't want
to have multiple versions of the module floating around and this would be
one.
We also can't loose sight of the radiated noise from that inductor.
I can
see signs of EMI if it gets within 2 inches of the sensitive areas of the
receiver.
73,
Juan
73,
Juan
-----Original Message-----
From: Chuck Green [mailto:greencl@mindspring.com]
Sent: Sunday, June 17, 2007 9:18 AM
To: juan-rivera@sbcglobal.net
Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
I am impressed with your testing and analysis.
I find it curious that you were unable to filter the power from the
CAN-Do! . But switching noise is notorious for being difficult to
filter. So maybe that is something to just forget. But in a total
system (satellite) it may not be possible to forget. We may need to
find a way to filter the power for sensitive modules even if not using
power from the CAN-Do! ; in which case, such a filter may also filter
the noise from the CAN-Do! .
If your analysis is correct, and it certainly seems to be, then it would
also seem possible to remove the switch from the CAN-Do! (not just
bypass it) and rout your clean power source through the CAN-Do! current
measurement circuit thus saving having to do this in the module.
Great work! And thanks.
Chuck
Juan Rivera wrote:
Hi Chuck,
Bad news I'm afraid. See my report for details... I've sent out a link
to
the group.
73,
Juan
-----Original Message-----
From: Chuck Green [mailto:greencl@mindspring.com]
Sent: Saturday, June 16, 2007 8:57 AM
To: juan-rivera@sbcglobal.net
Cc: eagle@amsat.org; David Smith; Dave Black (Work); Dave Black (Home);
Samsonoff@Mac. Com; Juan.Rivera (Work)
Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
This is fantastic!
Please try one more experiment. Pass the module current through the
current measuring circuit on the CAN-Do! while bypassing the switch
transistor (you could just short across the switch transistor) and see
if the problem reappears.
If you end up having to use the user pins, you will need to add current
measuring circuitry to your module. While this is no big deal, its one
more thing you might not have to do.
Chuck
Juan Rivera wrote:
All,
The 70 cm Receiver spur problem has been solved. Click here
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
ting.htm>
for details.
73,
Juan
WA6HTP
Via the Eagle mailing list courtesy of AMSAT-NA
Eagle@amsat.org
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
CAN-Do guys,
Can someone supply me with a suitable shielded replacement for the L3 inductor? I'll be happy to swap it out and report back.
Juan
_____
From: Jim Sanford [mailto:wb4gcs@amsat.org] Sent: Sunday, June 17, 2007 7:35 PM To: juan-rivera@sbcglobal.net Cc: 'Chuck Green'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black (Home)'; eagle@amsat.org; 'Samsonoff@Mac. Com'; 'Juan.Rivera (Work)' Subject: Re: [eagle] Re: 70 cm Receiver IF Spurs - Problem Solved
Team: I ABSOLUTELY agree with Juan's assertion that ... it needs to be free of radiated and conducted EMI in both directions.
We need to resolve these issues, and then issue such resolution as a requirement.
Size of incoming power conductor is a spacecraft issue, that we need to get into the Black Forest notes and subsequent requirements.
Eliminating the radiated noise is a CAN-Do! issue and should be solved -- especially if it is as simple as replacing a radiating inductor with a shielded inductor.
In my professional life, I've seen a similar situation, where such an inductor in a VERY sensitive instrumentation system was picking up noise, a fatal flaw. Replacing the one component with a shielded equivalent solved the problem.
We should at least TRY such an approach. .. . Juan, I'd like you to do the swap and then give us before and after plots and analysis. That will conclusively prove or disprove the issue.
Thanks & 73, Jim wb4gcs@amsat.org
Juan Rivera wrote:
Chuck,
At least in this particular case jumpering across the switch didn't work. (See my log for today on Eaglepedia.)
Since the CAN-Do module is such an imbedded and pervasive component in Eagle, I think it needs to be free of radiated and conducted EMI in both directions. It's a great little interface but I'm afraid it has some very serious shortcomings at the moment:
Conducts noise back towards the power source where it can impact other loads on the same power bus (one ohm of resistance out there was enough to screw up the receiver.)
Provides a noisy +14 to its load (the noise went right through the receiver like fat through a goose and ended up in the IF as spurs.)
Radiates EMI that can adversely affect sensitive circuitry at a distance of over two inches from the rear of the PCB
Attempting to mitigate those problems will put a huge burden on every payload and the adverse impact might not be fully known until integration and test, if then. Trying to go back and band-aid something like this after all the payloads come together would be a very bad corner to get backed into. You could do what I did and sacrifice 2 inches of space inside every module chassis, or you could try to build a two-section chassis and filter the lines passing through the bulkhead, adding complexity. But that doesn't address the potential impact to another payload from the spikes that are propagated back towards the common +14 bus.
I would expect that every receiver, block up or down converter, transmitter, or amplifier will be impacted by this noise in a similar way. In my opinion this is a global problem that needs a global solution. If the CAN-Do module can be made EMI-free, or meet a yet to be determined EMI spec, then all of the payloads teams can start their design with a known environment.
If the CAN-Do module is not modified then I think the only safe thing to do is to build each payload so it can function using CAN-Do switched +14 volt power (the receiver can't in the Rev-A configuration.) If your payload can function with that noisy +14, without any adverse impact, then it is probably a pretty well protected circuit and should be fairly immune to whatever noise is added to the source by conducted EMI from other loads on the power bus. It just seems simpler and cleaner to fix the problem at the source.
I have an idea for a noise generator that I will stick on my log... This could be the go/no go test for each payload. I'll go sketch it up and get it uploaded by about 2000 Pacific Time.
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Sunday, June 17, 2007 5:51 PM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; Bill Ress; Dave Black (Home); Dave Black (Work); Dave hartzell; David Smith; Don Ferguson; Juan.Rivera (Work); Samsonoff@Mac. Com Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
One of the purposes of the CAN-Do! was to provide a standard interface
so that a module couldn't do something nasty and take out the entire
satellite. So custom mods to the CAN-Do! are not allowed. Having said
that, we have always assumed that a jumper across the CAN-Do! power
switch would be installed for those modules that needed to be powered up
no-matter-what.
Chuck
Juan Rivera wrote:
Chuck,
I don't want to tear into the CAN-Do module. I feel like it is a loaner
and
not mine to modify. It would be interesting to disconnect the switch and
the current monitor from the CAN-Do power input and move it to those user
pins as you suggest. That might just work, but I also know they don't
want
to have multiple versions of the module floating around and this would be
one.
We also can't loose sight of the radiated noise from that inductor. I can
see signs of EMI if it gets within 2 inches of the sensitive areas of the
receiver.
73,
Juan
73,
Juan
-----Original Message-----
From: Chuck Green [mailto:greencl@mindspring.com]
Sent: Sunday, June 17, 2007 9:18 AM
To: juan-rivera@sbcglobal.net
Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
I am impressed with your testing and analysis.
I find it curious that you were unable to filter the power from the
CAN-Do! . But switching noise is notorious for being difficult to
filter. So maybe that is something to just forget. But in a total
system (satellite) it may not be possible to forget. We may need to
find a way to filter the power for sensitive modules even if not using
power from the CAN-Do! ; in which case, such a filter may also filter
the noise from the CAN-Do! .
If your analysis is correct, and it certainly seems to be, then it would
also seem possible to remove the switch from the CAN-Do! (not just
bypass it) and rout your clean power source through the CAN-Do! current
measurement circuit thus saving having to do this in the module.
Great work! And thanks.
Chuck
Juan Rivera wrote:
Hi Chuck,
Bad news I'm afraid. See my report for details... I've sent out a link
to
the group.
73,
Juan
-----Original Message-----
From: Chuck Green [mailto:greencl@mindspring.com]
Sent: Saturday, June 16, 2007 8:57 AM
To: juan-rivera@sbcglobal.net
Cc: eagle@amsat.org; David Smith; Dave Black (Work); Dave Black (Home);
Samsonoff@Mac. Com; Juan.Rivera (Work)
Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
This is fantastic!
Please try one more experiment. Pass the module current through the
current measuring circuit on the CAN-Do! while bypassing the switch
transistor (you could just short across the switch transistor) and see
if the problem reappears.
If you end up having to use the user pins, you will need to add current
measuring circuitry to your module. While this is no big deal, its one
more thing you might not have to do.
Chuck
Juan Rivera wrote:
All,
The 70 cm Receiver spur problem has been solved. Click here
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
ting.htm>
for details.
73,
Juan
WA6HTP
Via the Eagle mailing list courtesy of AMSAT-NA
Eagle@amsat.org
_____
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Hello Juan!
I have been watching all of this pretty much in the background for a variety of reasons. IN addition to the CAN-Do! noise that you've noted, we are also faced with a few power system unknowns that are likely to dwarf the CAN-Do! conducted noise:
1) The spacecraft power will probably be coming from a distributed set of sources that will be switching themselves on and off bus, with hysteresis in their switching logic.
2) The various power sources may not be synchronized in terms of their switching frequencies.
3) As a result, well have both switching regulator noise from the regulators themselves, as well as varying source impedance as the various power sources attach and remove themselves from the power bus (due to spacecraft spin, varying power demand from transmitters, ...).
4) The power system is not designed, so it is very hard to characterize it.
From all of this, I think that all modules need to have excellent on-board regulation and assume dirty power in terms of both switching noise and source impedance. I don't have numbers for this, but perhaps a source impedance of 0.05 to 1 ohm is not unrealistic. Similarly, switching noise amplitudes on the order of 1 volt are likely.
If we can shield the CAN-Do! inductor to reduce its radiation, we should. This will be a retrofit, of course. The dynamic magnetic environment is not known at this time, and I think we've been assuming that most radiated energy would be from the antennas, along with "leakage" from the power supply switching system.
***
In a previous life, I had to deal with systems that included radios with VCOs that were susceptible to external fields. In the end, we had to the VCOs had to be shielded to make them essentially immune to such fields.
Since we don;t yet know what the power system will be like in terms of conducted or radiated energy, we have to assume a pretty dismal picture for both of these components and try to design our modules to be insensitive to them to the extent practical.
Lou, any ideas on the power system and how it might look/behave/targets for noise, load regulation, etc? Any measurements available on the cap/cell charge/discharge distributed power system modules?
73,
Lyle KK7P
Hello Lyle, Jim, and folks,
The uglier this gets the more interesting I find it! I hope no one is getting disheartened. After all, this is why we all got involved in the first place, isn't it? If it was easy it would be boring.
I just cooked up an idea for a noisy power source that could be used during payload development and test. I stuck my write up and a block diagram at the end of my current log.
Here's the link: http://www.juanr.com/pages/hobbies/ham_radio/Eagle/Spur_Suppression.htm
What do you think?
Shielding the CAN-Do inductor obviously won't solve all these problems but it might buy back 2 inches of space and that's worth the effort.
Lyle,
My suspicion is that the two VCOs on this receiver are also the most susceptible to radiated EMI from CAN-Do. I can't say for sure but it looks that way to me. Both are in metal cans soldered to ground. The closest one was about 2 inches away from the CAN-Do inductor. I've more than doubled that distance to 4-1/4 inches to get away from it. That's a lot of EMI!
73,
Juan WA6HTP
-----Original Message----- From: Lyle Johnson [mailto:kk7p@wavecable.com] Sent: Sunday, June 17, 2007 7:44 PM To: juan-rivera@sbcglobal.net Cc: Chuck Green; David Smith; Dave Black (Work); Dave Black (Home); eagle@amsat.org; Samsonoff@Mac. Com; Juan.Rivera (Work) Subject: Re: [eagle] Re: 70 cm Receiver IF Spurs - Problem Solved
Hello Juan!
I have been watching all of this pretty much in the background for a variety of reasons. IN addition to the CAN-Do! noise that you've noted, we are also faced with a few power system unknowns that are likely to dwarf the CAN-Do! conducted noise:
1) The spacecraft power will probably be coming from a distributed set of sources that will be switching themselves on and off bus, with hysteresis in their switching logic.
2) The various power sources may not be synchronized in terms of their switching frequencies.
3) As a result, well have both switching regulator noise from the regulators themselves, as well as varying source impedance as the various power sources attach and remove themselves from the power bus (due to spacecraft spin, varying power demand from transmitters, ...).
4) The power system is not designed, so it is very hard to characterize it.
From all of this, I think that all modules need to have excellent on-board regulation and assume dirty power in terms of both switching noise and source impedance. I don't have numbers for this, but perhaps a source impedance of 0.05 to 1 ohm is not unrealistic. Similarly, switching noise amplitudes on the order of 1 volt are likely.
If we can shield the CAN-Do! inductor to reduce its radiation, we should. This will be a retrofit, of course. The dynamic magnetic environment is not known at this time, and I think we've been assuming that most radiated energy would be from the antennas, along with "leakage" from the power supply switching system.
***
In a previous life, I had to deal with systems that included radios with VCOs that were susceptible to external fields. In the end, we had to the VCOs had to be shielded to make them essentially immune to such fields.
Since we don;t yet know what the power system will be like in terms of conducted or radiated energy, we have to assume a pretty dismal picture for both of these components and try to design our modules to be insensitive to them to the extent practical.
Lou, any ideas on the power system and how it might look/behave/targets for noise, load regulation, etc? Any measurements available on the cap/cell charge/discharge distributed power system modules?
73,
Lyle KK7P
Hello Juan!
The uglier this gets the more interesting I find it! I hope no one is getting disheartened. After all, this is why we all got involved in the first place, isn't it? If it was easy it would be boring.
No one is bored... :-)
I just cooked up an idea for a noisy power source that could be used during payload development and test. I stuck my write up and a block diagram at the end of my current log.
Here's the link: http://www.juanr.com/pages/hobbies/ham_radio/Eagle/Spur_Suppression.htm
What do you think?
It would be nice to be able to add to the bench supply output a noise source capable of a volt or more at whatever current the D.U.T. might require. Maybe an amplifier we can feed with a function generator to simulate a sawtooth or ??? waveform from a few kHz to a few tens of kHz to better simulate the assumed dirty power source?
We really need to get an idea what to expect worst case from the S/C power system.
Shielding the CAN-Do inductor obviously won't solve all these problems but it might buy back 2 inches of space and that's worth the effort.
Yes, we need to shield this if we can.
Lyle,
My suspicion is that the two VCOs on this receiver are also the most susceptible to radiated EMI from CAN-Do. I can't say for sure but it looks that way to me. Both are in metal cans soldered to ground. The closest one was about 2 inches away from the CAN-Do inductor. I've more than doubled that distance to 4-1/4 inches to get away from it. That's a lot of EMI!
Indeed it is. We should try and find a toroidal inductor to minimize radiation, then put a magnetic shield around it to suppress what the toroid radiates.
73,
Lyle KK7P
Lyle,
Did you even receive a reply from Lou?
Juan
-----Original Message----- From: Lyle Johnson [mailto:kk7p@wavecable.com] Sent: Sunday, June 17, 2007 7:44 PM To: juan-rivera@sbcglobal.net Cc: Chuck Green; David Smith; Dave Black (Work); Dave Black (Home); eagle@amsat.org; Samsonoff@Mac. Com; Juan.Rivera (Work) Subject: Re: [eagle] Re: 70 cm Receiver IF Spurs - Problem Solved
Hello Juan!
I have been watching all of this pretty much in the background for a variety of reasons. IN addition to the CAN-Do! noise that you've noted, we are also faced with a few power system unknowns that are likely to dwarf the CAN-Do! conducted noise:
1) The spacecraft power will probably be coming from a distributed set of sources that will be switching themselves on and off bus, with hysteresis in their switching logic.
2) The various power sources may not be synchronized in terms of their switching frequencies.
3) As a result, well have both switching regulator noise from the regulators themselves, as well as varying source impedance as the various power sources attach and remove themselves from the power bus (due to spacecraft spin, varying power demand from transmitters, ...).
4) The power system is not designed, so it is very hard to characterize it.
From all of this, I think that all modules need to have excellent on-board regulation and assume dirty power in terms of both switching noise and source impedance. I don't have numbers for this, but perhaps a source impedance of 0.05 to 1 ohm is not unrealistic. Similarly, switching noise amplitudes on the order of 1 volt are likely.
If we can shield the CAN-Do! inductor to reduce its radiation, we should. This will be a retrofit, of course. The dynamic magnetic environment is not known at this time, and I think we've been assuming that most radiated energy would be from the antennas, along with "leakage" from the power supply switching system.
***
In a previous life, I had to deal with systems that included radios with VCOs that were susceptible to external fields. In the end, we had to the VCOs had to be shielded to make them essentially immune to such fields.
Since we don;t yet know what the power system will be like in terms of conducted or radiated energy, we have to assume a pretty dismal picture for both of these components and try to design our modules to be insensitive to them to the extent practical.
Lou, any ideas on the power system and how it might look/behave/targets for noise, load regulation, etc? Any measurements available on the cap/cell charge/discharge distributed power system modules?
73,
Lyle KK7P
Hello Juan!
Did you receive a reply from Lou?
Not that I noticed, but when I was on the road the last several weeks it's possible something fell through the cracks. I would have expected it to come to the group, though.
Lyle
I mistyped that last one. I meant, "Did you EVER receive a reply" not, "Did you EVEN receive a reply."
Juan
-----Original Message----- From: Lyle Johnson [mailto:kk7p@wavecable.com] Sent: Friday, June 29, 2007 3:15 PM To: juan-rivera@sbcglobal.net Cc: 'Chuck Green'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black (Home)'; eagle@amsat.org; 'Samsonoff@Mac. Com'; 'Juan.Rivera (Work)'; Lyle Johnson Subject: Re: [eagle] Re: 70 cm Receiver IF Spurs - Problem Solved
Hello Juan!
Did you receive a reply from Lou?
Not that I noticed, but when I was on the road the last several weeks it's possible something fell through the cracks. I would have expected it to come to the group, though.
Lyle
Juan,Lyle, I have been watching the correspondence about noise on the power buss with great interest. I am waiting to see if a noise specification comes out of this. I can tell you that the power buss will probably be noisy at least to your standards. The latest plan would have lot's of capacitance on the buss (many Farads) but of course that would not help with the high frequency noise. I have been noting the discussion about noise from the inductors and that will be taken into account in the design. In other words we will probably shield all the inductors as best we can and have EMI shielded Power converters. The plan calls for a distributed system where there will be many small converters and not just one or two big ones.
We plan to have many max power point converters mounted near the solar panels and then many cell voltage to buss converters located where the battery and super capacitors are placed. They are not planed to be synchronized so the frequencies will vary based on load. In other words modules should build in as much noise immunity as possible.
Lou McFadin W5DID w5did@mac.com
On Jun 29, 2007, at 6:27 PM, Juan Rivera wrote:
I mistyped that last one. I meant, "Did you EVER receive a reply" not, "Did you EVEN receive a reply."
Juan
-----Original Message----- From: Lyle Johnson [mailto:kk7p@wavecable.com] Sent: Friday, June 29, 2007 3:15 PM To: juan-rivera@sbcglobal.net Cc: 'Chuck Green'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black (Home)'; eagle@amsat.org; 'Samsonoff@Mac. Com'; 'Juan.Rivera (Work)'; Lyle Johnson Subject: Re: [eagle] Re: 70 cm Receiver IF Spurs - Problem Solved
Hello Juan!
Did you receive a reply from Lou?
Not that I noticed, but when I was on the road the last several weeks it's possible something fell through the cracks. I would have expected it to come to the group, though.
Lyle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Lou,
Is there a sketch or block diagram of this proposed architecture that you can share?
Juan
_____
From: Louis McFadin [mailto:w5did@amsat.org] Sent: Friday, June 29, 2007 7:31 PM To: juan-rivera@sbcglobal.net Cc: AMSAT Eagle Subject: Re: [eagle] Re: 70 cm Receiver IF Spurs - Problem Solved
Juan,Lyle,
I have been watching the correspondence about noise on the power buss with great interest. I am waiting to see if a noise specification comes out of this. I can tell you that the power buss will probably be noisy at least to your standards. The latest plan would have lot's of capacitance on the buss (many Farads) but of course that would not help with the high frequency noise. I have been noting the discussion about noise from the inductors and that will be taken into account in the design. In other words we will probably shield all the inductors as best we can and have EMI shielded Power converters. The plan calls for a distributed system where there will be many small converters and not just one or two big ones.
We plan to have many max power point converters mounted near the solar panels and then many cell voltage to buss converters located where the battery and super capacitors are placed. They are not planed to be synchronized so the frequencies will vary based on load.
In other words modules should build in as much noise immunity as possible.
Lou McFadin
W5DID
w5did@mac.com
On Jun 29, 2007, at 6:27 PM, Juan Rivera wrote:
I mistyped that last one. I meant, "Did you EVER receive a reply" not, "Did
you EVEN receive a reply."
Juan
-----Original Message-----
From: Lyle Johnson [mailto:kk7p@wavecable.com]
Sent: Friday, June 29, 2007 3:15 PM
To: juan-rivera@sbcglobal.net
Cc: 'Chuck Green'; 'David Smith'; 'Dave Black (Work)'; 'Dave Black (Home)';
eagle@amsat.org; 'Samsonoff@Mac. Com'; 'Juan.Rivera (Work)'; Lyle Johnson
Subject: Re: [eagle] Re: 70 cm Receiver IF Spurs - Problem Solved
Hello Juan!
Did you receive a reply from Lou?
Not that I noticed, but when I was on the road the last several weeks
it's possible something fell through the cracks. I would have expected
it to come to the group, though.
Lyle
_______________________________________________
Via the Eagle mailing list courtesy of AMSAT-NA
Eagle@amsat.org
participants (5)
-
Chuck Green -
Jim Sanford -
Juan Rivera -
Louis McFadin -
Lyle Johnson