George Hardesty

Mar 072015

Access Points & Bridges:  Definitions

Coaxial Antenna Cable Assemblies & Connectors: Definitions of types

Fresnel Zone:  An electromagnetic phenomenon, in which light waves or radio signals get diffracted or bent from solid objects near their path. The radio waves reflecting off the objects may arrive out of phase with the signals that traveled directly to the receiving antenna thus reducing the power of the received signal. Therefore you have to have more than visual line-of-sight:  You need for the fresnel zone to be clear or the obstructions will block part of your throughout – you will have lower rate of through-put.

Signal Strength:  RSSI: Received Signal Strength Indication:  Measured from 0 to -100, generally, though RSSI has no standard units for all vendors:  Generally the higher (closer to 0) the better, and the closer to -100 the worse.

SNR:  Signal-to-Noise Ratio and Noise Floor:  SNR is not actually a ratio but the difference in decibels between the received signal and the background noise level (noise floor). For example, if a radio (client device) receives a signal of -75 dBm and the noise floor is measured at -90 dBm, the SNR is 15 dB. Data corruption and therefore re-transmissions will occur if the received signal is too close to the noise floor. Re-transmissions adversely affect throughput and latency.

Noise Floor:  Use a spectrum analyzer to determine the noise floor: Ubiquiti’s AirView spectrum analyzer is built-in to all AirMax equipment:  Noise Floor is easily found by looking at the Waterfall View – the legend in the upper right corner:  The number to the far-left in this legend is always adjusted to the calculated noise floor (and the high end [right] is fixed at the highest detected power since the start of the session).

MCS:  Modulation and Coding Scheme: MCS Index Values:  Modulation and Coding Scheme (MCS) Index Values can be used in conjunction with channel width values to allow you to instantly calculate the available data rate of your wireless hardware.

  • The MCS index value list gives every combination of “number of spatial streams + modulation type + coding rate” that is possible.  In practice the achievable MCS value will depend on a large number of variables, and it may be prudent to run your hardware at a lower MCS value on purpose in order to allow for adequate fade margin in your link.
  • The MCS value will only tell you the ‘over the air’ data rate of a link and not tell you what the actual usable throughput will be. You will need to refer to the documentation of your hardware for this information.

PHY Rate (Link Rate) compared to Throughput (Transfer Speed):  Difference between wireless link rate, actual file transfer and web browsing speed:

  • The wireless link rate is sometimes called the physical layer (PHY) rate. It is the maximum speed that data can move across a wireless link between a wireless client and a wireless access point or bridge.
  • User activities like file transfer and web content browsing happen at the application layer. The rate obtained at the application layer is much lower than the physical layer rate. In fact, a link rate of “300 Mbps” usually corresponds to 50 to 90 Mbps speed on the TCP/UDP layer.
Mar 032015

If you use an antenna that is not 2×2 MIMO (if it only has one connector) you will not get 2×2 MIMO from the Rocket:

If the antenna only has one connector, you will only get one spacial stream rather than two (1×1 rather than 2×2) hence the throughout will be half of the throughput you would get with 2×2 MIMO.

The best antennas for the Ubiquiti Rockets are the 2×2 dual-polarity antennas from Ubiquiti – because:

  • the two connectors for 2×2 MIMO and
  • the rocket snaps right in to the back of the UBNT antennas.
Feb 262015

Six feet is not too long for the LMR-100-equivalent cable that we use for shorter antenna cables.  However, it is right at the threshold at which we would recommend that you consider the thicker cable.    This comparison shows that the expenditure for the thicker cable, which is about 25% higher cost, is proportional to the benefit of lesser signal loss (attenuation).  If you are using small antennas you may need as much gain as possible retained during passage through the cable and it would make good sense to pay the additional 25% for the 200-thickness cable:

CLF-100 coax (quality similar to LMR-100, but better):  Attenuation (signal loss) is 0.39dB per foot:  Over six feet, you would lose 2.34dB
CLF-200 (quality similar to LMR-200, but better):  Attenuation (signal loss) is 0.30dB per foot: Over six feet, you would lose       1.80dB
The difference is 0.54dB.  You may know that addition of an antenna multiplies the power of the WiFi device, such that even a difference of 0.54dB makes a big difference:
3.0dB net antenna gain (after cable loss) =  2.0X power increase for WiFi device
3.5dB net antenna gain (after cable loss) =  2.6X power increase for WiFi device   <- a 25% power increase coming from a 0.5dB net antenna gain in this example.
For a six foot cable VS. ten foot cable, the difference in your cost between using 100 thickness cable VS. 200-thickness would be $1.25.
Therefore your power increase would be roughly proportional to the difference in cost of the cable.
LMR-100 compared to RG316

LMR-100 has lower signal-loss than RG316

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Jan 232015

To whom it may concern,

In my world, I only seem to hear when someone on our team doesn’t live up to our expectations.  I believe it’s important when people go above and beyond that they should be recognized.  Simon Kingsley has done just that.  Our company is in the middle of a development project and at the critical junction.  On this Friday afternoon at 4:00PM EST we needed a very unusual adapter.  When searching online, what we found was 15 to 30 days to deliver from China.  My colleague went to google and your company caught our attention.  We were fortunate enough to get Simon on the phone and he was a tremendous help.  He configured the adapter set to meet our requirements and was able to get your shipping department to run to UPS and drop it off for Saturday delivery.  We were thrilled; the project would not come to a halt.
After the adrenaline and settled we reviewed the order and realized our configuration was wrong.  We immediately called Simon knowing we were at the UPS cut off time.  He went into action and identified the right parts, got the warehouse and shipping people on the phone and was able to get the correct parts out for delivery on Saturday.  A remarkable feat.
He was calm, courteous, patient and projected this “can do” attitude.  Please note, I’m talking about an $8.00 part.  In both cases, the cost of freight was immaterial, we were happy to pay the Saturday delivery premium.  The fact that Simon refused to give in and found a way to make this happen was wonderful.
We congratulate your company for having him as a representative.
I can’t thank everyone enough and you have certainly found a new customer.
Sep 202014
Use a cluster mount which enables you to cluster 3 or 4 Ubiquiti sectoral antennas in an array:  There is an array mount for three (3-Gang Mount) and a 4-gang mount.
We recommend that when you use a cluster mount for sectors, that you use the RF Armor shields to prevent the antennas’ leakage from the back, from interfering with each other – and reduce the noise in general.

To connect multiple antennas to the same Rocket: You can if you use a “power divider” or antenna-combiner (not a coax-splitter):  Please see this page on this subject.

The other solution would be to connect one rocket per antenna:   Feedback from customers indicates that this is configuration is noisy – maybe too noisy, even with the RF Armor shields (which are sold separately from the  array mounts).  Of course, the purpose of the shields is to isolate each antenna and reduce the noise among the antennas.

Ubiquiti Sectoral Antenna Array

Sectoral antenna array on 3-Gang Mount

RF Armor Radome Shield Kit for Ubiquiti 120-degree Sector Antennas

RF Armor Radome Shield Kit for Ubiquiti 120-degree Sector Antennas

RF Armor Radome Shield Kit for Ubiquiti 90-degree Sector Antennas

RF Armor Radome Shield Kit for Ubiquiti 90-degree Sector Antennas

May 202014
  • NanoStation M5 has a 60-degree beam and a 10dBi antenna. MSRP is $89.95
  • NanoBeam M5 has a 30-degree beam:
    • NBE-M5-300 has a 23dBi antenna: MSRP: $84.95
    • NBE-M5-400 has a 25dBi antenna. MSRP: $94.95
    • NBE-M516 has a 16dBi antenna: MSRP: $67.95
    • NBE-M519 has a 19dBi antenna: MSRP: $89.95
  • When Nanobeam is connecting to AP there is very little difference in signal at client side. On AP side it is usually better by about 3db, and usually results in a better connection. With a long distance you will see improvement; very short distance that you will not see much improvement.
  • In ideal conditions on a long link:  You might get 30mb more throughput with the NanoBeam vs. NanoBridge.
Mar 292014

You have one person on the tower and a second person(s) on the ground. The Rohn pulley attaches to a pole (could be a Gin Pole) near the (current) top of the tower.

The person on the ground hoists the next tower section by pulling a rope through the pulley, until the tower section is all the way at the top, and then the person on the tower, fits that section of tower into place.

Mar 132014

Ubiquiti Aircam and Aircam Dome run on 24-volt POE.

Higher-end cameras including Pan Tilt Zoom (PTZ) cameras, use 48-volt POE.

If you are using Ubiquiti POE switches, you will need a TS-PRO-8 for 48-volt: That is the 8-port version.  The smaller version of Tough Switch with 5-ports only has 24-volt POE.

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