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Supported hardware PDF Print E-mail
Written by Rick Kirchhof, NG5V   
Sunday, 06 February 2011 10:30

Save Time, Print this Hardware Guide

Hardware guide to print as you shop for used devices.

The original development was done on Linksys WRT54G hardware versions 1 through 4. Starting with hardware version 5, the firmware Flash and working RAM memory were reduced and the factory operating system was changed to VXworks. Version 5+ WRT54G and GS units don't have enough memory to run HSMM-MESH™. A repackaged version of a WRT54G is separately marketed as WRT54GL (for Linux) and is specifically advertised as supporting Linux. All hardware versions of the WRT54GL work fine.

Versions 1 through 4 of the WRT54GS are also supported. Versions 1-3 of WRT54GS have 32 Mb memory and 8 Mb of flash. They are very desirable. A few users have discovered that special versions of the WRT54GS were built under other model numbers and distributed by Internet Service Providers. You might find the conversion process to make existing firmware support those models by using the search feature at the top of each page. Just enter the model number to find discussions related that device.

The supported versions of the router all have a minimum of 4 Mb of Flash memory and 16 Mb of RAM.


Linksys Devices

Hardware versions are on the device label on the bottom but the font is very small and difficult to read. Keep in mind that the WRT54G v 1.0 uses only regulated 5.0v power. Higher voltage will let the smoke out. V 1.0 units are easy to spot since they have 3 status LEDs for each LAN jack and all others have one.The easiest way to determine hardware versions on Linksys devices is to read the serial number. The first few letters of the serial number decode the actual hardware version using the chart in the link above. These serial numbers are also printed on the outside of new hardware boxes near the UPC barcode and can be read without buying the product or opening the box.


Ubiquiti Devices

Ubiquiti firmware for the listed devices is available from the Software Download page, and properly interacts with BBHN devices of the same major version number. For example, a WRT54GL using 3.x.x will talk to a Bullet M2 if both are in the same band, in RF range of each other, and have 3.x.x firmware. You always have to match the SSID as some devices can create differing RF signals not compatible with other hardware.

    M2

    M5

    M9

    AirGrid

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    Bullet

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    Bullet Titanium

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    NanoBridge

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    NanoStation Loco

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    NanoStation

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    Rocket

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      Last Updated on Tuesday, 14 April 2015 10:17
       
      Packaging your Station PDF Print E-mail
      Written by David Rivenburg, AD5OO   
      Tuesday, 23 February 2010 17:52

      Coax loss is a problem at 2.4ghz. If you have a high gain antenna but need 30' of coax to get from your AP or Router to the antenna, you just lost a bunch of gain. The problem occurs in both directions. Loss of transmitted power means less to hear on the other end. Your unit also went partially deaf by the coax loss between the signals the antenna heard and what actually gets to the AP or router.

      You can eliminate this problem by using short jumpers and keeping the AP or router near the antenna. This requires two things. You have to power the network device (and any booster amp you might be using) and you need to get a CAT5 patch cord back to the computer. If the devices are put in a weatherproof box, POE (power over Ethernet) can be used to both talk to and power the remote box. This allows you to set the antenna out, have the box with the antenna and you up to 100 meters away. 328' is quite a bit and seldom proves to be a limiting factor.

      If you will be operating portable, consider the tripod or mount you will use. Ease of setup, size when folded for transport and resistance to shaking in the wind will all matter. If you can create an attachment method that lets you install the antenna on the mount without putting together lots of small parts, setup, takedown and transport will all be easier and less parts will get lost along the way.

      Wind loading must be considered. A flat panel antenna mounts close to the boom and isn't too much of a sail. A wire mesh reflector or solid dish mounts further away, sags more and catches more wind. Watch for deflection of your mount as you release the weight of the antenna. If it sags very much, the wind is also likely to move it around. Counterweights help a lot if deflection is a problem. You can limit some of the moving around with bungee cords or pre-stress wires/strings. Remember, the higher the gain on the antenna, the more critical the pointing accuracy and stability becomes.
       
      Coax loss measurements PDF Print E-mail
      Written by David Rivenburg, AD5OO   
      Tuesday, 23 February 2010 17:51

      Measurements of several coax jumpers

      We have been concerned about the loss in connecting antennas to routers and A/P units. Various cables, adapters and jumpers are available and no one seems to be making claims about signal loss as they are used.

      These measurements were done using a frequency counter, signal generator and microwave power meter. Signals are generated by a Polorad 1105 microwave signal generator. This unit covers 800-2400mhz and delivers a maximum of 0 dbm of output. This represents 1.0mw at 50 ohms. An EIP 535 microwave frequency counter measured the test frequency which was always held to 2400mhz. This is the upper limit of the signal source so it is not possible to test at mid-band. Power was measured by an HP-437B with an 8484A sensor head and required attenuators. The range on this head is 0.3 nanowatts to 10 microwatts so it is impossible to use directly.

      The procedure is to warm up all equipment for an hour. Next, these steps are used:

      • Set reference power on the generator output dial to 0dbm
      • Adjust output frequency to 2400mhz via the frequency counter
      • Measure the output power at the signal generator using attenuators
        • This includes back to back adapters for coax connectors to be tested
      • Make minor adjustments to frequency or power attenuator to get it steady
      • Turn on "Relative" display on the power meter (sets display to 0.00 db)
      • Remove the sensor head from the generator and insert cable to be tested
      • Record direct loss reading (example: -4.09db)
      • Gently flex and move cable especially near ends to watch for dropouts
      • Remove cable and replace sensor head with adapters on source
      • Verify reading is very near 0.00 relative reading set before
      • Connect frequency counter and verify near 2400mhz


      Testing done in this way is a direct reading of loss in db at the frequency of use and includes the coax connectors and adapters. Adapters can be lossy if poorly made. Below are our findings.

      Cable Measurements
      		 Total Loss   Unit Loss 

      50' Andrew 1/4" Heliax-Superflex with N connectors   4.87 dB 0.10 dB/ft

      15' length of RG8 style with N connectors   5.95 dB 0.40 dB/ft

      Hawking HAC7SS 7' HPP-100 R-SMA extension cable   3.43 dB 0.49 dB/ft

      Linksys AS2TNC 6' R-TNC antenna stand   3.45 dB 0.57 dB/ft

       

      Adapter Measurements
      		  Total Loss 

      Pan Pacific RFA-8892P RJ-SMA/RP-TNC
      Pan Pacific RFA-8893P RP-SMA/RJ-TNC      		 0.45 dB/pair


      Connector notes:

      • Brass SMA connectors require 4-5 in/lb torque to provide the design impedance
       
      Fiber Links PDF Print E-mail
      Written by David Rivenburg, AD5OO   
      Tuesday, 23 February 2010 17:48
      What are they?

      Fiber links are optical ethernet (100base-FX) connections that port to/from CAT5 ethernet (100base-TX/RJ45) connections. Recently, a number of the D-Link DFE-855 transducers became available used. D-Link list price is just under $180 (two required to work). Here is the blurb:

      The D-Link DFE-855 is a Fast Ethernet media converter that translates transmission signals from a twisted-pair 100BASE-TX cable to 100BASE-FX fiber optic cable. It expands network data transmission distances beyond the 100 meter limitation of copper wire to a maximum of two kilometers by using fiber optic cable in full duplex.

      The DFE-855 provides auto-sensing detection of full duplex or half duplex signaling. It has easy-to-read diagnostic LED´s for continuous status reports on network speed, duplex media access control connection, and network traffic. The DFE-855 uses standard RJ-45 UTP/STP and SC fiber optic connectors and is IEEE 802.3u 100BASE-TX/FX compliant and operates with all devices that adhere to this standard.


      These come with a 5vdc, 1.5a brick that uses a standard 120v IEC computer wall cord. They need an SC/SC 62.5/125 dual mode Duplex optical cable set between them.

      They don't do MDIX so you have to connect one to either the crossover port of a hub, an autosensing switch or use a true crossover cable to connect one directly to a computer. This is because both devices are MDI when one should be either auto-sensing or MDIX. You can join two routers directly since nearly all do autosensing.

      Testing

      Testing them is simple. Connect a CAT5 jumper from your router to one transducer/power brick set. Connect your laptop to either a crossover cable or a switch-then to the other device pair. You must connect the TX port of one device to the RX port of the other. Example: Red in TX, Black in RX on the sending end, Black in TX, Red in RX on the receiving end.

      Open a cmd or shell window and ping your gateway. I was able to leave the router end connected and cycle through all of the other devices w/o relinking the DHCP address. This is because the router "saw" the first optical device and gave it an address during the first test. Between tests, there is no link but the DHCP remained. I ran a dfw.speakeasy.net speed test on the pair and saw exactly the same speed as hard wired to the router.

      What are they good for?

      In high RF environments and where there is risk of lightning, ground loops or power surges, optical is the industry standard for separating one network from another. The optical run can also be up to 2km so they are frequently used for long distance links. You can run a CAT5 jumper to a transducer, a number of feet of fiber and another CAT5 jumper on the other end to totally isolate RF and electrical interaction between two lan segments.

      We are currently investigating alternate (read cheap) sources of fiber that will work with these devices. Weed trimmer stock has been mentioned by some.
       
      About Antennas PDF Print E-mail
      Written by David Rivenburg, AD5OO   
      Tuesday, 23 February 2010 17:43
      Antennas have 3 main operating features of interest. Gain, directivity, and polarization. Size also matters but usually isn't the biggest factor. Stock antennas for the AP or Router have very low gain and are omnidirectional. Polarization is variable depending on what direction the shaft is pointing.

      You can get double duty by adding gain in a forward direction while excluding signals to the side of or behind your antenna. This gets better still when you set the antenna up for horizontal polarization. Most existing WiFi signals are vertical. The industrial noise in the band is also more vertical than horizontal.

      Directivity is measured lots of ways but one of the most common is the 3dB beamwidth. Another is front to back or front to side gain ratios. With a 12-15 dBi flat panel, you will knock off almost everything behind you and most of what is to the side. However, anything within 30-40 degrees or so of the aim point is in the hot spot. Going up to 24dBi of gain takes the beamwidth and shrinks it to only a few degrees. This is a superior way to exclude other signals by not looking at them. The weak, distant signal you receive can still be used just fine if you make all of the others near the same frequency MUCH weaker.

      Both stations need to use the same polarization or the signals really dip in strength.

      Some possible antennas include:

      This site lists some interesting home brew antenna measurement test equipment. Unfortunately, some of the articles are in Dutch.
       
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