G8JNJ

Hi Glen,

I was able to enter these commands directly via the KiWi admin console page.

I don't know if this is possible, but the responses I got back seem to indicate that it worked OK.

Regards,

Martin - G8JNJ

Hi All,

I've had some issues with radiated noise from a KiWi that I installed on a shared site. The main issues were that it was interfering with of VHF satellite reception and degrading the GPS performance of another system in the same room.

The KiWi was installed in the Seeed metal case, and I had fitted ferrites to the cables.



As I'm currently building up a KiWi for installation at another site, I thought that it would be a good idea to see if I could further reduce the level of emissions from a KiWi fitted in the Seeed case.

In order to do this I used an EMC H-Probe consisting of a 1"diameter screened loop connected to a spectrum analyser, in order to see what the level of emissions looked like and where they were escaping from the case.

The majority of the noise was leaking out through the holes in the ends of the case and also via the additional interconnecting cables I had fitted to bring out the GPIO ports for antenna switching.

This shows the general level of radiation from a KiWi without a case, with the Seeed metal case and with the Seeed case and additional modifications. Note that the measurements were made without the external GPIO cable connected.



The next shot shows the difference between the Seeed metal case and with the Seeed case and additional modifications in more detail.



As you can see the biggest difference is achieved by fitting the metal case, and I would definitely recommend doing this if you are still using the plastic frame supplied with the KiWi.

However there is still a fairly significant amount of radiated noise throughout the whole spectrum, especially in the VHF / UHF / Microwave range, and the only way to cure this is to close up the holes in the box.

As I didn't want to restrict airflow and ventilation I used some very fine woven brass mesh that I previously bought for antenna construction.

I added a section of mesh at each end of the box and sandwiched it between the end plates and the box sides, having first cutout suitable holes for the connectors I still wished to use.



Note that I had to solder short brass sheet straps between the Ethernet port metal socket surround and the mesh and also the -ve of the DC input connector where it enters the board (prior to the common mode choke on the board) in order to reduce the level of radiated noise from the external screened CAT5 Ethernet cable and DC power cable. There already was physical / electrical contact between the mesh and Ethernet connector, but I noticed that the screening effectiveness varied as I flexed the cable, and I didn't want to risk problems on-site at a later date if the mesh tarnished or developed an oxide layer.




Here are a couple of external views, showing the wire mesh with the case closed.




Once I had done this work I still had some noise from the GPIO port, so I added some 0.1uF decoupling capacitors and some 1/8th watt 1K Ohm resistors in series with the wires from the KiWI GPIO pins (not the 0v ground return) and the decoupled pins of the output connector. This also provided some short circuit protection, as previously suggested as best practice earlier in this thread.




After doing all of this work, the level of emissions are now minimal, and the ambient level of noise in my workshop is higher than the majority of noise produced by the KiWi, even though the close field probe is right next to the case. There is still a bit of radiation along the seams between the top and bottom case halves, but this is very low level, and if necessary can be further reduced by running self adhesive aluminium (ducting) tape over the seams.

One other interesting observation is that before fitting the mesh and additional earth bonding strap, I didn't find that using screened Ethernet cable made much difference to the level of noise radiated around 20MHz. However after performing the modification it's really noticeable that using screened cable makes a big difference.

Overall I think the additional mods are worth doing, especially if you are bringing the GPIO pins out of the box. But if you are already housing your KiWi in a diecast box with suitable cable bonding, then you are probably already experiencing most of the benefits I have observed.

Regards,

Martin - G8JNJ

Hi All,

I've had some issues with radiated noise from a KiWi that I installed on a shared site. The main issues were that it was interfering with of VHF satellite reception and degrading the GPS performance of another system in the same room.

The KiWi was installed in the Seeed metal case, and I had fitted ferrites to the cables.



As I'm currently building up a KiWi for installation at another site, I thought that it would be a good idea to see if I could further reduce the level of emissions from a KiWi fitted in the Seeed case.

In order to do this I used an EMC H-Probe consisting of a 1"diameter screened loop connected to a spectrum analyser, in order to see what the level of emissions looked like and where they were escaping from the case.

The majority of the noise was leaking out through the holes in the ends of the case and also via the additional interconnecting cables I had fitted to bring out the GPIO ports for antenna switching.

This shows the general level of radiation from a KiWi without a case, with the Seeed metal case and with the Seeed case and additional modifications. Note that the measurements were made without the external GPIO cable connected.



The next shot shows the difference between the Seeed metal case and with the Seeed case and additional modifications in more detail.



As you can see the biggest difference is achieved by fitting the metal case, and I would definitely recommend doing this if you are still using the plastic frame supplied with the KiWi.

However there is still a fairly significant amount of radiated noise throughout the whole spectrum, especially in the VHF / UHF / Microwave range, and the only way to cure this is to close up the holes in the box.

As I didn't want to restrict airflow and ventilation I used some very fine woven brass mesh that I previously bought for antenna construction.

I added a section of mesh at each end of the box and sandwiched it between the end plates and the box sides, having first cutout suitable holes for the connectors I still wished to use.



Note that I had to solder short brass sheet straps between the Ethernet port metal socket surround and the mesh and also the -ve of the DC input connector where it enters the board (prior to the common mode choke on the board) in order to reduce the level of radiated noise from the external screened CAT5 Ethernet cable and DC power cable. There already was physical / electrical contact between the mesh and Ethernet connector, but I noticed that the screening effectiveness varied as I flexed the cable, and I didn't want to risk problems on-site at a later date if the mesh tarnished or developed an oxide layer.




Here are a couple of external views, showing the wire mesh with the case closed.




Once I had done this work I still had some noise from the GPIO port, so I added some 0.1uF decoupling capacitors and some 1/8th watt 1K Ohm resistors in series with the wires from the KiWI GPIO pins (not the 0v ground return) and the decoupled pins of the output connector. This also provided some short circuit protection, as previously suggested as best practice earlier in this thread.




After doing all of this work, the level of emissions are now minimal, and the ambient level of noise in my workshop is higher than the majority of noise produced by the KiWi, even though the close field probe is right next to the case. There is still a bit of radiation along the seams between the top and bottom case halves, but this is very low level, and if necessary can be further reduced by running self adhesive aluminium (ducting) tape over the seams.

One other interesting observation is that before fitting the mesh and additional earth bonding strap, I didn't find that using screened Ethernet cable made much difference to the level of noise radiated around 20MHz. However after performing the modification it's really noticeable that using screened cable makes a big difference.

Overall I think the additional mods are worth doing, especially if you are bringing the GPIO pins out of the box. But if you are already housing your KiWi in a diecast box with suitable cable bonding, then you are probably already experiencing most of the benefits I have observed.

Regards,

Martin - G8JNJ

Hi All,

Just some brief notes regarding the installation of a 15 way D connector on the Seeed metal case in order to bring out the GPIO port for use with an antenna switch.

The ventilation slot cuts out very easily and only required a small amount of filing in order to make the connector shell fit.

First the pinout I used



End view of case



Top view of connector



Wiring to GPIO ports



Side view



Hope this is of some use to others.

Regards,

Martin - G8JNJ

Hi All,

I've had some issues with radiated noise from a KiWi that I installed on a shared site. The main issues were that it was interfering with of VHF satellite reception and degrading the GPS performance of another system in the same room.

The KiWi was installed in the Seeed metal case, and I had fitted ferrites to the cables.



As I'm currently building up a KiWi for installation at another site, I thought that it would be a good idea to see if I could further reduce the level of emissions from a KiWi fitted in the Seeed case.

In order to do this I used an EMC H-Probe consisting of a 1"diameter screened loop connected to a spectrum analyser, in order to see what the level of emissions looked like and where they were escaping from the case.

The majority of the noise was leaking out through the holes in the ends of the case and also via the additional interconnecting cables I had fitted to bring out the GPIO ports for antenna switching.

This shows the general level of radiation from a KiWi without a case, with the Seeed metal case and with the Seeed case and additional modifications. Note that the measurements were made without the external GPIO cable connected.



The next shot shows the difference between the Seeed metal case and with the Seeed case and additional modifications in more detail.



As you can see the biggest difference is achieved by fitting the metal case, and I would definitely recommend doing this if you are still using the plastic frame supplied with the KiWi.

However there is still a fairly significant amount of radiated noise throughout the whole spectrum, especially in the VHF / UHF / Microwave range, and the only way to cure this is to close up the holes in the box.

As I didn't want to restrict airflow and ventilation I used some very fine woven brass mesh that I previously bought for antenna construction.

I added a section of mesh at each end of the box and sandwiched it between the end plates and the box sides, having first cutout suitable holes for the connectors I still wished to use.



Note that I had to solder short brass sheet straps between the Ethernet port metal socket surround and the mesh and also the -ve of the DC input connector where it enters the board (prior to the common mode choke on the board) in order to reduce the level of radiated noise from the external screened CAT5 Ethernet cable and DC power cable. There already was physical / electrical contact between the mesh and Ethernet connector, but I noticed that the screening effectiveness varied as I flexed the cable, and I didn't want to risk problems on-site at a later date if the mesh tarnished or developed an oxide layer.




Here are a couple of external views, showing the wire mesh with the case closed.




Once I had done this work I still had some noise from the GPIO port, so I added some 0.1uF decoupling capacitors and some 1/8th watt 1K Ohm resistors in series with the wires from the KiWI GPIO pins (not the 0v ground return) and the decoupled pins of the output connector. This also provided some short circuit protection, as previously suggested as best practice earlier in this thread.




After doing all of this work, the level of emissions are now minimal, and the ambient level of noise in my workshop is higher than the majority of noise produced by the KiWi, even though the close field probe is right next to the case. There is still a bit of radiation along the seams between the top and bottom case halves, but this is very low level, and if necessary can be further reduced by running self adhesive aluminium (ducting) tape over the seams.

One other interesting observation is that before fitting the mesh and additional earth bonding strap, I didn't find that using screened Ethernet cable made much difference to the level of noise radiated around 20MHz. However after performing the modification it's really noticeable that using screened cable makes a big difference.

Overall I think the additional mods are worth doing, especially if you are bringing the GPIO pins out of the box. But if you are already housing your KiWi in a diecast box with suitable cable bonding, then you are probably already experiencing most of the benefits I have observed.

Regards,

Martin - G8JNJ