Interview: Wireless Bay Area Adventure with USRP B200 Software Defined Radio

Interview: Wireless Bay Area Adventure with USRP B200 Software Defined Radio

By Erik Luther | Thursday, September 12, 2013

Inspired by the capabilities of the new USRP B200 Software Defined Radio, our own Balint Seeber – Ettus Research Applications Engineer by day and SDR wizard by night, set
out to show what the new USRP is capable of with a broad frequency coverage from 70 MHz – 6 GHz, a bandwidth of 56 MHz, and entirely USB 3.0 bus powered, board-only design. We didn't see Balint for a week after we handed him the B200 device. I did have the
chance to interview him when he got back.

Here's his story:

Luther: What inspired your signal scavenger hunt with the USRP B200?

Seeber: Two and a half years ago I was lugging batteries up the side of the hill in Sydney, Australia to power my first USRP1. Now I can take the USRP B200 and my
laptop anywhere unbound by the shackles of wall power. With this newfound freedom I was ready to explore San Francisco's radio spectrum!

Luther: Where did you go on this wireless adventure?

Seeber: I was thinking about the postcard-style photos you see of San Francisco and all of the great RF signals you might find in those locations. I ended up climbing
mountains in the middle of the night, tracking ships in the early morning from above the Golden Gate Bridge, locating airplanes from hill tops near the airport, and listening to FM and TV signals from the center of the Bay. I even created a Google Map of my
trek.





Interactive Google Map of the Route

Luther: What motivated your first stop near Moffett Airfield?

Seeber: The USRP B200 has a lot of bandwidth and I intended to exercise it, so my first stop was a Primary Surveillance RADAR near Moffett Airfield that was rumored
to be visible from the road. Overall, I was curious how the USRP B200 performed with strong wideband signals and was interested in determining the type of RADAR system. Using the USRP B200 and my laptop I performed a frequency sweep in HDSDR and
found its transmission in the upper 2 GHz band. Curiously, the RADAR pulses were different from what I've seen in the past. With a little research I discovered that the signals I was seeing were from a RADAR running in Dual
PRF (Pulse Repetition Frequency) mode, which is actually used for simultaneous weather observation and aircraft approach tracking. It took a couple trips to the site, but ultimately I was able to analyze the pulse parameters in real time.



Moffett Airfield

Luther: How did you end up climbing a drainage ditch on San Bruno Mountain and crack
your cell phone screen?

Seeber: I was looking for a high vantage point to record Mode S Secondary
RADAR so that I could plot real-time plane location information. I ended up on the side of the San Bruno Mountain wearing four layers of clothing to fight the strong winds and blistering cold. From there I was able to see planes take off and land at San
Francisco Airport and create a live map their flight paths. The unfortunate part was when I lost my footing: I saved the USRP, but my cell phone wasn't so lucky!



Airplane flight path mapped using Mode S

Luther: The photos over the Golden Gate Bridge are impressive. What did you find there?

Seeber: The view from Battery Spencer Park was breathtaking. From that vantage
point I could see the entire city and ships around San Francisco. Pulling out my laptop and USRP, I ran an open-source AIS decoder and maritime mapping application (openCPN) to show the location
of both ships I could see and others further off in the distance. After scanning the spectrum and finding trunked radio networks and public safety channels, I decided to relax a bit and listen to FM radio coming from Sutro Tower with a GNU
Radio application that also decodes RDS station information and local traffic conditions.



Live AIS Boat Traffic from Battery Spencer Park

Luther: Did visiting Sutro Tower allow you to capture signals you couldn't from above the
bridge?

Seeber: Actually, I wanted to check out the USRP B200 performance with HAM and ISM band signals in the presence of strong out-of-band signals. What better place than
beneath Sutro Tower, a perch for San Francisco's many powerful radio and digital TV transmitters? Some SDR's really struggle with out-of-band signals and I was pleased that the B200 performed well. I was able to track the locations of Bay Area HAMs transmitting
their positions overAPRS, see FLEX pager messages being sent, and watch the bursty wireless traffic of the 900
MHz ISM band.



Sutro Tower

Luther: Where was your final stop in this week long adventure?

Seeber: I found a new-and-improved airport overlook in a cul-de-sac on the side of a hill. Although it was night time, I managed to capture some nice footage of parallel
landings and takeoffs, and record video of the very same planes being mapped in real time on my laptop. This brought back memories of my nights in Sydney where my friend and I camped out on a hill with a USRP1 near the local Airport following air traffic and
experimenting with the Mode S decoder.



Two Airplanes landing at night at SFO with real-time position plotted on the map

Luther: Did anything unexpected happen on the journey? I heard something about police!?

Seeber: At one point I did manage to slip and fall, breaking my B200 in the process but at least I caught my laptop. Also on that last neighborhood stop a resident
must have told the police that a crazy Australian with binoculars and a video camera was spying on them. However it was all cleared up amicably when local law enforcement stopped by: the police officer seemed to be entertained by my "airplane research".



The moment Balint Seeber realized the B200 was broken

Luther: So what's next in your adventures with Software Defined Radio?

Seeber: MIMO for sure. I've been using the USRP B200, but the USRP B210 features
two channels of coherent MIMO. I haven't done any MIMO implementation before, so I look forward to diving into the field and creating some compelling GNU Radio demos that use this MIMO capability of the USRP B210.





USRP B210 (2x2 MIMO, 70 MHz – 6 GHz)

Luther: Alright, last question. Where could someone get all of these great examples if they wanted to go on their own B200 adventure?

Seeber: Once you have a B200 and a computer, the rest is easy. I would start on GNURadio.org and CGRAN.org. There you can find tutorials and examples, respectively,
which cover a broad range of applications (many of which can be set up easily using PyBOMBs). Also I use free apps, such as HDSDR, for spectrum scanning and listening to new signals.

GNURadio	GNURadio.org	Open source software development toolkit that provides signal processing blocks to implement software radios.
CGRAN	CGRAN.org	Open source repository for 3rd party GNU Radio applications
PyBOMBs	github.com/pybombs/pybombs	GNU Radio install management system for resolving dependencies
HDSDR	HDSDR.de	Freeware interactive spectrum analysis and radio listening
openCPN	opencpn.org	Open source concise chart plotter and navigation software, for use underway or as a planning tool.

Luther: Thanks for sharing your adventures and documenting them so well with photos and video. We look forward to the next one!

Seeber: My pleasure. I was thinking the radio spectrum in Hawaii needs exploring if you'd let me have a go at it for another week.



The interview: Balint Seeber (Left), Erik Luther (Right)

Comments

Mine has arrived at last - but I am lacking any documentation, how to select antennas, what the gain settings should be - that sort of thing. Hopefully this will appear.

What they don't yet tell you but you may need to know is the board in 100x155mm and looks designed to fit a standard 103x163mmx30mm Hammond 1455L case

Mike at 6:40 am on November 1, 2013

Nice adventure with an SDR receiver. I'm about to start developing with B200. Would you share the laptop model that has worked well for you? Does it have one of the faster USB3.0 chipsets you've tested? Thank you.

Dave at 7:53 pm on November 4, 2013

I am just using a Dell E4310 with a USB3 expansion card. Its not up to doing much processing at maximum bandwidth but fine for lower rates.

On the Box above, I found the USRP list this evening and found others asking the same question. The Hammond case is 5mm too long so will need cutting down but the width is right.

I have a mill so that should not be a problem but I am not sure what the normal punter is expected to do.

I am hopeful Ettus will provide a mechanical drawing and some documentation - one has to discover the 89.5dB TX gain settings from the RF chip datasheet and the antenna settings via the UHD examples. Its hardly the documentation you expect from NI!

Mike at 12:41 pm on November 5, 2013

Hey all, Does anyone know the P1dBm for the AD9361 on the B200? I want to use it for a backscatter RFID system, but I'm afraid that the RF input will get saturated by the transmitter from cross-talk.

Albert at 7:19 pm on November 7, 2013

Hi all, I am trying to contact somebody in the sales department there. I sent an order to buy some E100 and B210 cards but nobody reply. Can someone please help me. Thanks!

Manuel Perez at 12:06 pm on May 7, 2014