Reducing RFI From Our QTH

Fiber Wall Outlet

Fiber Wall Outlet

Many Hams (including this one) have problems with RF Interference (RFI) at their stations. Many RFI sources typically come from inside our own homes. Symptoms include birdies at single frequencies, interference that moves around across the Amateur Radio Bands, and high noise floors. We have had all of these problems here.

We recently built an improved EME station for the 2m Band. We noticed a higher than ideal noise floor when operating 2m EME during initial testing of the new station. We decided to do some additional testing to see if we could isolate the source of the noise levels. One test we did was to shut down much of the ethernet network and associated devices here at our QTH. To our surprise, this lowered our noise floor on 2m some 6 dB, and eliminated many birdies in the EME section of the 2m Band!

Our network mostly uses wired Ethernet running throughout our home on Cat 5e and Cat 6 unshielded ethernet cable. Many of the devices in our home use Power Over Ethernet (PoE) connections to power them through the ethernet cables.

NAS Drives with 10 GbE Optical Interfaces

NAS Drives for Video Storage and Backups

We also do quite a bit of video editing work and often transfer large files from our computers to several large Network Attached Storage (NAS) drives for file storage and backup. We also use an extensive IP Camera System to monitor our towers and for general security purposes.

Core Network Rack Enclosure

Core Network Rack Enclosure

We decided to solve our noise problems via a pretty major upgrade to our home network. The upgrade included:

  • Installing OM4 multimode fiber optic cables to replace all of the non-PoE wired Ethernet connections to the rooms in our home. The fiber cables were chosen to support 1 GbE and 10 GbE connections now and to be upgradable to 100 GbE connections in the future.
  • Installing a shielded rack enclosure to house the switches and management devices for our upgraded Network
  • Installing new Cat 6A Shielded Ethernet cables to PoE devices that we wanted to remotely shut down when we are operating using weak-signal modes on 6m and above
  • Upgrading portions of our network to 10 Gbs Ethernet speeds to improve the efficiency of Video Editing and Backups

The project began with the installation of a Shielded Rack Enclosure in our basement. The Rack is wall-mounted and is fully shielded and grounded. It also includes cooling fans that move air vertically through the Rack to keep the gear inside cool.

Core Network in Rack

Core Network in Rack

Next, we mounted all of the gear for our upgraded core network in the Rack. The main components include (from bottom to top):

PDU Web Interface for Network Control and Management

PDU Web Interface for Network Control and Management

We are going to power down most of our IP Cameras and the WiFi AP devices around our home when we are operating on 6m and above. We implemented this capability using an IP-Controlled Power Distribution Unit (PDU) that allows us to remotely turn network devices in our network on and off via a web browser from anywhere in our home.

IP Camera PoE Switches

IP Camera PoE Switches

The PDU controls a pair of Netgear PoE Edge Switches that power most of the IP Cameras in our home via PoE connections. Shutting down these switches via the PDU removes power from the associated IP Cameras which eliminates a great deal of noise and other RFI.

WiFi AP Control via PoE Edge Switch

WiFi Acess Point Control via PoE Edge Switch

We also installed a VLAN-capable Netgear PoE Edge Switch and connected it to the PDU. This switch enables us to shut down other devices on our network such as WiFi Access Points which are also significant sources of RFI. This switch uses a pair of optical interfaces that connect it to our core network

OM4 Fiber Cable with LC Connectors Installed

OM4 Fiber Cable with LC Connectors Installed

A large part of the work associated with our network upgrade project involved running OM4 Multi-mode Fiber Optic cables to all of the rooms in our home. We ran 12-fiber cables to locations that would likely benefit from upgrades to 100 GbE in the future (ex. our shack, home offices, media equipped rooms, and servers/NAS devices) and 6-fiber cables were used elsewhere. All of our fiber cables use LC connectors with two fibers for each Ethernet connection (one for Tx and one for Rx). We used a mix of pre-terminated cable assemblies and unterminated cables to complete the room installations.

Fiber Prep using Fiber Cleaver

Fiber Prep using a Fiber Cleaver

Field terminating fiber optic cables is not difficult but it does require some special tools and careful attention to detail. The ends of each fiber must be prepared to precise specifications and be very clean before the LC connectors can be installed. The image above shows a Fiber Cleaver which is used to “cleave” the end of each fiber to form a square, low-reflection/low-loss connection to a field-installable LC connector. Proper use of a high-quality Fiber Cleaver is important if you are to achieve low-loss, low-dispersion field terminations.

Verifying an LC Connector Installation using Visual Fault Locator

Verifying an LC Connector Installation using a Visual Fault Locator

A Visual Fault Locator (VFL) with an LC Connector Adapter is used to confirm the proper installation of each LC connector. The tool shines a bright red laser light through the LC connector and fiber cable. The field installable LC connectors include a window that indicates laser dispersion at the fiber/connector junction. Too much light in the window due to dispersion indicates a poor connection. The VFL tool is also very useful for checking end-to-end optical transmission and continuity of the completed fiber cable installations.

Fiber Wall Outlet

Fiber Wall Outlet and Patch Cables

The fibers were terminated in wall outlets in the rooms of our home. The outlet plates accept standard keystone jacks. We used LC Keystone Couplers with our wall jack plates. This approach ensures that the ends of fragile fiber optic cables running to the rooms will not be damaged or broken when connecting the fibers to ethernet switches and other devices.

Fiber Interconnect Tray

Fiber LC Interconnect Enclosure

The other end of each fiber cable is terminated in a Fiber LC Patch Enclosure Trays in our Rack. The enclosures provide a test point and LC patch cable interconnect point for the fiber cables. The advantage of using enclosures such as these is that they protect the ends of the fiber cables running to the rooms from damage. A total of three trays terminate a total of 72 OM4 fiber pairs that we installed in our home.

Optical Fiber Connector Cleaner

Optical Fiber Connector Cleaner

It is very important to keep all of the fiber connections clean. Standard practice should be to ALWAYS clean the ends of each LC connector with an Optical Fiber Connector Cleaner each time before an LC connector is installed in a jack. It is also important to keep the supplied caps that come with LC connectors installed when they are not connected to a jack or optical SFP.

10GBase-SR SFP+ Transceiver

10GBase-SR SFP+ Transceiver

The fibers in the core rack and in the rooms are connected to switches, computers, and NAS devices via SFP or SFP+ Transceivers. An example of an SFP+ Transceiver is shown above. These devices convert the laser signals carried on the multimode OM4 fibers to a standard electrical format that can be handled by the core and edge switches in our network.

Core Network Components

Core Network Components

The connections between the Fiber Termination and Patch Enclosures and the SFPs and SFP+s in the Core Switches in our rack are made using OM4 LC Patch Cables (the aqua cables shown in the image above).

Fiber Wall Outlet

Fiber Wall Outlet and Patch Cables

Similar patch cables are run from the Wall Jacks to the Ethernet Edge switches in each room to complete the connections to the core network. Most of our Edge Switches in the rooms in our home use two pairs of fibers in a LAG configuration. This increases the bandwidth capacity of the connections and also increases reliability. Should one of the fiber pairs experience a failure, the other pair continues to carry the traffic until the problem can be repaired.

Reducting RFI - Shielded CAT6A Ethernet Terminations

Shielded CAT6A Ethernet Terminations

Some devices in our network such as the PoE IP Cameras on our Towers and a portion of our WiFi Access Points cannot be shut down without significantly compromising the operation and functionality of our Network. We controlled the noise and RFI contribution from these devices by installing new, Cat 6A Shield Ethernet cabling to connect them. The Cat 6A cables must be terminated using a grounded, fully shielded ethernet panel. This device is 10 Gbps Ethernet capable and properly terminates that the shielded Cat 6A cables in our Rack.

Cat 6A Shielded Keystone Jack

Cat 6A Shielded Keystone Jack

Shielded Cat 6A Keystone Jacks and Shielded Ethernet Patch Cables are used in the rooms to connect to the edge devices.

10 GbE Connected Computer

10 Gbps Ethernet Connected Computer

So how did all of this work out? We are seeing 6 – 7 dB improvement in the noise floor on 2m. This is a huge improvement for our EME station! We are also seeing about 1 dB in noise floor improvement on 6m. We are also seeing a significant reduction in birdies on all the bands. Finally, many of our computers and most of our NAS drives have been upgraded to 10 Gbps Ethernet which enables us to move large files around our network much more quickly. We are also seeing some improvement in the actual measured throughput of our 1 Gbs/400 Mbps Fiber Internet connection.

I hope that our readers find our Fiber Optic and 10 Gbps Networking project interesting.

Fred, AB1OC

 

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