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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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Brats plunges head on into 2014!

For those that missed the January board meeting and don’t get the minutes, here’s our list of projects for 2014:

APRS Weather Station
ATV Amplifier upgrade and Internet Stream of Repeater
High Altitude Balloon project with ATV/telemetry
Further repeater/data network upgrades
Jamboree on the Air (expecting over 100 scouts for Oct ’14!)

Be sure to attend the meeting Monday, Feb 10, at 7 pm at the Pikesville library to learn how you can be a part of these activities!

Kevin
KB3PLX

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BRATS 5GHz Links and WB3DZO Fully online!

K0RYX, N3GXH, and KB3PLX spent a few hours on a chilly, icy roof adjusting the aim of one of the dishes, and a few more hours inside tweaking settings, before finally getting everything set just right.

Our 9.4 mile wifi link now has ping times of 1.1-1.4 ms, and sustained bidirectional transfer rates of 80 Mbps! With a little more tweaking we hope to boost that even more.

This should eliminate the occasional pop/digitization that occurred when voting between sites, and give us a strong, solid signal through the worst weather we can expect.

WB3DZO now has modern, reliable links, battery backups and emergency power, and multiple control points – standing by for the snowy season ahead!

Here’s N3GXH holding up the 30dB dish as we mount the radome/shield around it:
5 GHz  Dish with RF Armor

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Holiday Party!

The BRATS Holiday Party will be this Monday, December 9th, at 7 pm at the Pikesville Library. Dinner and beverages will be available, and elections will be held for 2014.

Attendance is open to all!

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Meeting update!

Be sure to attend the Monday, Nov 11, 2013 meeting at 7:00 PM at the Pikesville Library for a demonstration of the new 147.030 repeater network!

Learn what the new messages mean!
See how we’ll be cutting down interference/noise!
See how we’ll be expanding our receive coverage!

A complete receive package (before we finished cleaning the wires up):

Repeater controller cabinet. Note, the hardware voter, hardware controller, and two link receivers are dark. Repeater controller and voter are running on an HP ThinClient.

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SK – John Wingert K3TAY

John, K3TAY, passed away last month after a long illness.

There will be a short memorial service for John on
November 7 at 1300EST at the Garrison Forest Veteran
Cemetery. John’s amateur radio friends are invited.

John is survived by his ex-wife, Iris, and their son, Aaron.
Please contact us for the contact information for Iris Wingert and Aaron Wingert.

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BRATS Host Successful Jamboree on the Air

On Saturday, October 19th, the BRATS and the Arrowhead district of the Baltimore Area Council/Boy Scouts of America worked to introduce over 50 Scouts and their families Amateur Radio. There were smiles all around from the Scouts, their parents, and the volunteers as demonstrations were held on VHF, fox hunting, and HF communications.

The BRATS made over 60 contacts in 26 states and 8 countries, with several QSOs lasting nearly an hour. The Scouts had plenty of opportunities to talk to other current and former Scouts across the country and across the planet.

JOTA US Contacts

These pins represent radio contacts made during the Jamboree. The world map includes both radio and Internet contacts.

JOTA/JOTI Contacts

The BRATS set up 5 Jamboree on the Internet workstations inside K0RYX’s HQ truck, a 50′ tower trailer, 30′ self supporting tower on the other side, and three HF stations under tents.

The BRATS 2013 Jamboree on the Air facilities

The BRATS 2013 Jamboree on the Air facilities

A special thanks to Chris Gutberlet of Pack 307 for spearheading the event, K0RYX for his assistance in planning and working with the Scouts, and his vehicle, N3GXH for his time, RV command post, and generator, and WA3AER, K9FXY, K2AGR, and K2GZL for their work with the Scouts ensuring we had a successful event.

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