Jim and John,

This morning I want to physically move the PCB to the back of the enclosure, remount the CAN-Do module on the connector plate, and connect them with a short ribbon cable. I'll have that done in a few hours and post the results in my log.

Then I'd like to try to filter the switched 13 volts from the module so the receiver is spur-free and more or less configured the way I think it might need to go. Even if the receiver power bypasses the CAN-Do module it looks like it needs to be able to function with dirty DC power so a simple filter will probably be necessary in the next revision..

Assuming that this removes the spurs from the IF output, that still leaves us with passband ripple and microphonics to deal with. I'll remove the suspect capacitors that John suggests first to see what affect that has on microphonics. Then I can make John's suggested modifications to try to learn more about the ripple. The problem with these changes is that it will leave the receiver in a state where running the ATP might not be very useful. I think we might want to regroup after I make those changes and see what makes sense. We might want to order some film caps to replace the ceramic chips removed to chase the microphonics and see what John has in mind for the ripple before running the ATP. This will push the ATP to the right by a few weeks but would probably result in more meaningful test results. What do you and John think?

Juan

_____

From: Jim Sanford [mailto:wb4gcs@amsat.org] Sent: Friday, June 15, 2007 5:21 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] Preliminary CAN-Do EMI Findings and Suggestions to Mitigate in the 70 cm Receiver

Juan: As usual, good work, and well documented -- thanks!

What is your plan for proceeding to execution of the ATP?

After you've developed a test configuraton and executed/documented the ATP, I'd like to see a single document, titled "Recommended changes to design," which would be the single summary of all you've learned and would recommend we do different in this design. As always, I'm open to a better idea.

THanks & 73, Jim wb4gcs@amsat.org

Juan Rivera wrote:

All,

I've completed a preliminary evaluation of the CAN-Do RFI problem. Please see my log for details by clicking here http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo ting.htm .

Preliminary Findings...

The spurs seen in the receiver IF enter the receiver in two ways

As radiation from the CAN-Do inductor

Via CAN-Do module switched +14 VDC power on pins 39 and 40

I/O line filtering appears to be unnecessary

The switched power from the CAN-Do module pins 39 and 40 must be filtered

The CAN-Do module will either have to be kept physically separated from any sensitive components, redesigned, shielded or a combination of the three.

Moving the Can-Do module 2-1/4" forward of its normal location on the receiver PCB lowers the EMI level below the noise floor.

Suggestions...

Create a full size PCB for the next generation receiver and shift the RF components to the back of the board (away from the CAN-Do module.)

Add DC input filtering to the receiver

73,

Juan

WA6HTP

_____

_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle

Juan and Jim:

I've been up in Davis watching my niece graduate from high-school. I looked at the blog but my brother didn't feel comfortable with me sending personal email from a government-owned PC.

It's not worth the effort to implement the entire ATP now, testing the front end is useful. The new requirements allow some specifications to be relaxed so that the SAW filters can be kept warm enough to survive eclipses. The second mixer and the circuitry between it and the output will probably change.

73,

John KD6OZH ----- Original Message ----- From: Jim Sanford To: juan-rivera@sbcglobal.net Cc: 'David Smith' ; 'Dave Black (Work)' ; 'Dave Black (Home)' ; eagle@amsat.org ; 'Samsonoff@Mac. Com' ; 'Juan.Rivera (Work)' Sent: Friday, June 15, 2007 21:07 UTC Subject: [eagle] Re: Preliminary CAN-Do EMI Findings and Suggestions to Mitigate in the 70 cm Receiver

Juan: I think I concurr with our plan. Here's how I'd like to proceed: Fix the problems (microphonics, noise, passband ripple) Then execute the ATP.

I agree in the current condition, there's not much value in (yet) executing the ATP. We are, however, getting closer.

Thanks for all your efforts and excellent documentation.

73, Jim wb4gcs@amsat.org

Juan Rivera wrote: Jim and John,

This morning I want to physically move the PCB to the back of the enclosure, remount the CAN-Do module on the connector plate, and connect them with a short ribbon cable. I'll have that done in a few hours and post the results in my log.

Then I'd like to try to filter the switched 13 volts from the module so the receiver is spur-free and more or less configured the way I think it might need to go. Even if the receiver power bypasses the CAN-Do module it looks like it needs to be able to function with dirty DC power so a simple filter will probably be necessary in the next revision..

Assuming that this removes the spurs from the IF output, that still leaves us with passband ripple and microphonics to deal with. I'll remove the suspect capacitors that John suggests first to see what affect that has on microphonics. Then I can make John's suggested modifications to try to learn more about the ripple. The problem with these changes is that it will leave the receiver in a state where running the ATP might not be very useful. I think we might want to regroup after I make those changes and see what makes sense. We might want to order some film caps to replace the ceramic chips removed to chase the microphonics and see what John has in mind for the ripple before running the ATP. This will push the ATP to the right by a few weeks but would probably result in more meaningful test results. What do you and John think?

Juan

----------------------------------------------------------------------------

From: Jim Sanford [mailto:wb4gcs@amsat.org] Sent: Friday, June 15, 2007 5:21 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] Preliminary CAN-Do EMI Findings and Suggestions to Mitigate in the 70 cm Receiver

Juan: As usual, good work, and well documented -- thanks!

What is your plan for proceeding to execution of the ATP?

After you've developed a test configuraton and executed/documented the ATP, I'd like to see a single document, titled "Recommended changes to design," which would be the single summary of all you've learned and would recommend we do different in this design. As always, I'm open to a better idea.

THanks & 73, Jim wb4gcs@amsat.org

Juan Rivera wrote:

All,

I've completed a preliminary evaluation of the CAN-Do RFI problem. Please see my log for details by clicking here.

Preliminary Findings...

The spurs seen in the receiver IF enter the receiver in two ways

As radiation from the CAN-Do inductor

Via CAN-Do module switched +14 VDC power on pins 39 and 40

I/O line filtering appears to be unnecessary

The switched power from the CAN-Do module pins 39 and 40 must be filtered

The CAN-Do module will either have to be kept physically separated from any sensitive components, redesigned, shielded or a combination of the three.

Moving the Can-Do module 2-1/4" forward of its normal location on the receiver PCB lowers the EMI level below the noise floor.

Suggestions...

Create a full size PCB for the next generation receiver and shift the RF components to the back of the board (away from the CAN-Do module.)

Add DC input filtering to the receiver

73,

Juan

WA6HTP

----------------------------------------------------------------------------

_______________________________________________Via the Eagle mailing list courtesy of AMSAT-NAEagle@amsat.orghttp://amsat.org/mailman/listinfo/eagle

------------------------------------------------------------------------------

_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle

Chuck,

I actually think that the noisy power coming out of the CAN-Do module is perfect for these tests. The more I think about it the more delighted I am that its there. I have no other way to generate noisy power. This is great! I'll attempt to capture this noise with my oscilloscope and post it in my log if I can. My scope is not feeling well these days so I may need to dig up another one.

Even if the receiver eventually receives its power from another source, we need to assume that it will have switching noise on it from other payloads. That's the only reasonable assumption as far as I'm concerned. The receiver must be able to function in the presence of noisy power and the CAN-Do module is a perfect noise source.

Based on the above I think I'll leave the CAN-Do module alone for now and see if I can add some simple filtering to kill the spurs in the IF while running on the switched CAN-Do power. If it can do that then I think we will be on the right track.

Every other payload designer should take heed and plan to operate with noise on their DC inputs too. This is probably a topic that needs some high-level attention. Are there any power specs that describe maximum expected noise levels? Perhaps a standard DC input filer should be designed and incorporated in every power supply input. Why leave this up to each designer? Come up with a standard filter using SMD components. I would think that this filter would also work to reduce switching noise from the payloads and help prevent that noise from propagating back out to other payloads on the power bus. All this looks like an area that needs attention.

I'm open to advice here. All I was thinking of doing was adding about 10 uF across pins 39/40 to ground, an RF choke in series, and then another 10 uF cap and maybe a second smaller value to ground at the load end of that RF choke. I can cobble something like that together and stick it on the PCB in dead bug style. I can keep adding stages until I get rid of the noise.

73,

Juan WA6HTP

-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Friday, June 15, 2007 7:53 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] Preliminary CAN-Do EMI Findings and Suggestions to Mitigate in the 70 cm Receiver

Juan,

I have a couple of suggestions.

Based on previous messages I presume you will not want to use the switched power from the CAN-Do! regardless of the noise issue. I also see that the switch transistor in the CAN-Do! is in the same area of the PCB as the CAN-Do! power supply.

1) Put a jumper between pins 2 and 3 of the switch transistor (TO-220). This will bypass the switch and any noise it is picking up from the power supply. This will keep the 2 amp fuse in your power source and the current measurement circuit.

2) You might also eliminate the 2 amp fuse from your power source by placing a jumper from pins 1,9 of the DA15P to pin 2 of the switch transistor after removing the transistor (or just cutting it's leads). This will preserve the current measurement of the power going to your module.

3) You might also bypass everything by putting a jumper from pins 1,9 of the DA15P to any unused user pins on that same connector (pins 2,3,5,10,11,12) then picking up the power from the corresponding user pins on the 40 pin connector. If you do this, you should provide a current measurement circuit on your module and attach it's output to one of the analog input pins of the 40 pin connector.

The above may eliminate or reduce the noise in your power source while accomplishing other power source objectives.

Chuck

Juan Rivera wrote:

All,

I've completed a preliminary evaluation of the CAN-Do RFI problem. Please see my log for details by clicking here

http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo ting.htm.

Preliminary Findings...

1. The spurs seen in the receiver IF enter the receiver in two ways

o As radiation from the CAN-Do inductor

o Via CAN-Do module switched +14 VDC power on pins 39 and 40

2. I/O line filtering appears to be unnecessary

3. The switched power from the CAN-Do module pins 39 and 40 must be

filtered

4. The CAN-Do module will either have to be kept physically separated

from any sensitive components, redesigned, shielded or a combination of the three.

5. Moving the Can-Do module 2-1/4" forward of its normal location on

the receiver PCB lowers the EMI level below the noise floor.

Suggestions...

. Create a full size PCB for the next generation receiver and shift the RF components to the back of the board (away from the CAN-Do module.)

. Add DC input filtering to the receiver

73,

Juan

WA6HTP

---

---

Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle

If you can characterize the noise in the frequency domain you should be able to find a good off the shelf filter that will sufficiently remove the noise that you could buy and then recommend to the Eagle team for general use. The feed thru filters are the best since they don't let the noise enter the module at all. The best method given the requirement to use the Can-do module is to put up a barrier separating the can-do from the receiver. Thereby keepin the noise away from the receiver. That is why receiver modules and pre-amps usually come in little RF tight cans with the power coming in through a feed through. It's a lesson learned a long time ago.

Lou McFadin W5DID w5did@mac.com

On Jun 15, 2007, at 11:59 AM, Chuck Green wrote:

Hi Juan,

I don't know of any specifications but the idea that the power will be noisy has been the assumption all along. The CAN-Do! has some filtering at it's power input with this in mind. It starts out with an inductor (10 uH) followed by two capacitors (.1 uF and 33 uF). Unfortunately, the fuse precedes this filter so if you end up bypassing the fuse for your module power you won't be able to benefit from this filter.

We had a bad experience with using capacitors for the first element of power filters on P3D. So I'd suggest your first element be an inductor if you are going to bypass the CAN-Do! filter.

Chuck

Juan Rivera wrote:

...

Chuck,

I actually think that the noisy power coming out of the CAN-Do module is perfect for these tests. The more I think about it the more delighted I am that its there. I have no other way to generate noisy power. This is great! I'll attempt to capture this noise with my oscilloscope and post it in my log if I can. My scope is not feeling well these days so I may need to dig up another one.

Even if the receiver eventually receives its power from another source, we need to assume that it will have switching noise on it from other payloads. That's the only reasonable assumption as far as I'm concerned. The receiver must be able to function in the presence of noisy power and the CAN-Do module is a perfect noise source.

Based on the above I think I'll leave the CAN-Do module alone for now and see if I can add some simple filtering to kill the spurs in the IF while running on the switched CAN-Do power. If it can do that then I think we will be on the right track.

Every other payload designer should take heed and plan to operate with noise on their DC inputs too. This is probably a topic that needs some high-level attention. Are there any power specs that describe maximum expected noise levels? Perhaps a standard DC input filer should be designed and incorporated in every power supply input. Why leave this up to each designer? Come up with a standard filter using SMD components. I would think that this filter would also work to reduce switching noise from the payloads and help prevent that noise from propagating back out to other payloads on the power bus. All this looks like an area that needs attention.

I'm open to advice here. All I was thinking of doing was adding about 10 uF across pins 39/40 to ground, an RF choke in series, and then another 10 uF cap and maybe a second smaller value to ground at the load end of that RF choke. I can cobble something like that together and stick it on the PCB in dead bug style. I can keep adding stages until I get rid of the noise.

73,

Juan WA6HTP

-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Friday, June 15, 2007 7:53 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] Preliminary CAN-Do EMI Findings and Suggestions to Mitigate in the 70 cm Receiver

Juan,

I have a couple of suggestions.

Based on previous messages I presume you will not want to use the switched power from the CAN-Do! regardless of the noise issue. I also see that the switch transistor in the CAN-Do! is in the same area of the PCB as the CAN-Do! power supply.

1. Put a jumper between pins 2 and 3 of the switch transistor

(TO-220). This will bypass the switch and any noise it is picking up from the power supply. This will keep the 2 amp fuse in your power source and the current measurement circuit.

2. You might also eliminate the 2 amp fuse from your power source by

placing a jumper from pins 1,9 of the DA15P to pin 2 of the switch transistor after removing the transistor (or just cutting it's leads). This will preserve the current measurement of the power going to your module.

3. You might also bypass everything by putting a jumper from pins

1,9 of the DA15P to any unused user pins on that same connector (pins 2,3,5,10,11,12) then picking up the power from the corresponding user pins on the 40 pin connector. If you do this, you should provide a current measurement circuit on your module and attach it's output to one of the analog input pins of the 40 pin connector.

The above may eliminate or reduce the noise in your power source while accomplishing other power source objectives.

Chuck

Juan Rivera wrote:

...

All,

I've completed a preliminary evaluation of the CAN-Do RFI problem. Please see my log for details by clicking here

<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN- Do_Noise_Troubleshoo ting.htm>.

...

Preliminary Findings...

1. The spurs seen in the receiver IF enter the receiver in two ways

o As radiation from the CAN-Do inductor

o Via CAN-Do module switched +14 VDC power on pins 39 and 40

2. I/O line filtering appears to be unnecessary

3. The switched power from the CAN-Do module pins 39 and 40 must be

filtered

4. The CAN-Do module will either have to be kept physically

separated from any sensitive components, redesigned, shielded or a combination of the three.

5. Moving the Can-Do module 2-1/4" forward of its normal location on

the receiver PCB lowers the EMI level below the noise floor.

Suggestions...

. Create a full size PCB for the next generation receiver and shift the RF components to the back of the board (away from the CAN-Do module.)

. Add DC input filtering to the receiver

73,

Juan

WA6HTP

---

---

---

Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle

---

Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle