WB3DZO/MM Repeater!

Sailing Vessel Bay Retriever with a dual band 2m/440 antenna atop her mast

Sailing Vessel Bay Retriever with a dual band 2m/440 antenna atop her mast

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WB3DZO/MM Repeater!?

For this weekend’s public service event, the BRATS hope to use an alternative to the trailer tower and operate a portable repeater “mobile maritime’ from the S/V Bay Retriever. The top of her mast sits 44′ above the water, providing a great platform for a repeater for the 18 mile walk around Kent Island.

Stand by for pictures of the setup and reports after the event!

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Next meeting 9/8 at the Pikesville Library!

It’s time to buckle down as we wind down JOTA preparations, and the BRATS will be returning to the Pikesville Library for the September meeting.

Monday, 9/8/14, at 7 pm at the Pikesville Library.

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Special Location for August Meeting

The Aug 11, 2014 meeting of the BRATS will be held at The Greene Turtle Owings Mills, Restaurant Park Drive South, Owings Mills, MD, United States.

Be sure to attend as we plan our September MS event and the October Jamboree on the Air!

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MS Society Thanks the BRATS

MS Society Thank you letter

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Coming soon: Internet stream of W3WCQ

w3wcq

Still in development, but it works!

w3rcj

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WB3DZO Data Repeater

The WB3DZO data repeater is now online and ready for normal amateur use. Come to the next meeting on Monday, May 12, at 7 pm at the Pikesville library to vote on a new name!

Channels are 5 MHz, with frequencies on 5870 on northern sectors, 5890 to the southeast, and 5910 to the southwest.

Until then, here’s where we expect coverage from a Nanobridge NB5-G25 ($90 dish) to our network:

House coverage

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BRATS Presents High Speed Data Network Design for Amateur Radio

The Baltimore Radio ATV Society invites all hams and technology enthusiasts to our next meeting on Monday, April 14, at 7 pm at the Pikesville Library in Reisterstown, MD.

The Brats have built a high speed digital backbone connecting 5 sites across 20 miles of Baltimore, replacing our aging analog repeater links with modern commercial wireless gear and in the process joining the forefront of a technological revolution.

Learn about our early trials, how we planned our network, how we selected our gear, why we spent hours a hundred feet above the ground on a frigid winter night – and why we can send 3 gigabytes of data in 300 seconds with wind gusts over 50.

Get an overview of the regulatory environment and concerns. What frequencies can we use? Is encryption allowed? How do we secure the network, and how do we ensure priority traffic gets through?

See how the Brats are currently using our network today, where we’re going tomorrow, and how the amateur radio community can leverage this technology in both everyday amateur use and emergency situations.

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What about during a windstorm?

Tonight’s high winds provided a good opportunity to see how the network holds up. Result: the dishes definitely sway enough to affect signal (from +3 dB better than normal to -3 dB worse), but data rates have been consistent.

The following tests are end to end across two hops:

100,000 x 1024 byte pings in 329 seconds:
— ping statistics —
100000 packets transmitted, 99999 received, 0% packet loss, time 329014ms
rtt min/avg/max/mdev = 2.511/3.252/14.082/3.625 ms, pipe 18, ipg/ewma 3.290/2.847 ms

And iperf results:
[SUM] 0.0-300.1 sec 3.19 GBytes 91.3 Mbits/sec

Moving 3 gigaBYTES across two wireless hops a total of 13 miles in winds gusting to 50 in 300 seconds isn’t too shabby!

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5 GHz and Directional Antennas

Here’s the part 15 wifi spectrum as seen from a directional antenna at one of our sites. The strong signal at 5800 is some part of Towson University’s wifi network, about a mile away, directly in the path of this dish:
Wide spectrum

Operating in Part 15 under the Unlicensed National Information Infrastructure (U-NII) allows for outdoor use and user-installable antennas in much of the spectrum above. Operating under amateur rules allows for greater power, and some unlocked/international gear can be used above 5825 MHz.

We have two dishes very close to each other, pointing 120 degrees apart. One is a 25dB ~18″ dish:
Site Survey Towson 25 dB dish

And the other is a 30dB ~30″ dish:
Site Survey Towson Directional

The 25dB dish has one small cluster of trees and a 2.4 mile run, but you can see one building from the other. That’s why its signal is -65 with a noise floor of -90. The link is 240 mbps bi-directional, but with 100 mbps ethernet as the limiting factor we can get sustained transfers of 9 megaBYTES per second.

The 30dB dish is aimed at a site 9.4 miles away, with a ridge and a cluster of trees in the middle. We’re pretty sure we can aim them better to get the signal into the low 70s, but through the recent snow and ice storms the signal remained constant, and the bandwidth remained above 100 Mbps. Sustained transfers through this link are 8 megaBYTES per second.

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