An Introduction to Direction Finding

[@vasmor2887]

I am writing from 2024 from Ukraine from the war. Here we have to detect enemy (russian) quadrocopters - all knowledge from your webinar is extremely useful! Thank you!

[@chriscornelissen5075]

10:05 I know the problem from my history as a radar operator on a old system. In order to track a plane the radar needs to have a amount of target speed directed towards or away from the radar. If a plane flies parallel the radar couldn’t track it. Pilots learn this to evade air defense systems by flying in meandering patterns. We called it the zero Doppler tactic. That’s why modern radars for this purpose are almost always of the phased array type. The RDF methods you describe are following the same principles. Cool to see that after 20 I’m looking at a video to find inspiration for building a fun setup with my son and I almost hear my instructor basic radar and EOV from my initial training 20 years ago haha.😊 Love the explainer!👍

[@poissonpilote7777]

I am using extensively your videos in order to prepare my airline pilot licence, the quality is really good, vielen dank!

[@bigmac71201]

Great content. We use this DF system daily! Thank you, R&S.

[@pauldenisowski]

Thanks! Appreciate the feedback!

[@Barc0d3]

Me too, my wife and I love this product.

[@James_Bowie]

Excellent overview of the subject. Best I have seen to date. 👍

[@Barc0d3]

Insanely good information in this video, wow.

[@pauldenisowski]

Thank you!

[@josemariagomezsocola6246]

Amazing!!! Excellent summary about the DF's principles, pretty needed!

[@commonwombat-h6r]

very nice! Thank you

[@shellinblack1990]

Thank you so much You explained a topic which had been taught me with missing concepts..

[@bbnCRLB]

For the manual direction finding, the antenna can be mounted on a rotating platform and the signal measured so fast with the orientation of the antenna tagged to each measurement. The highest strength can be extracted by observation or by simple code.

[@pauldenisowski]

Yes, that's correct and some DF systems do exactly what you describe. However, there could be issues if significant multipath were present (highest received signal power may not occur at the azimuth closest to the source) and speed might be an issue (i.e. how quickly could you physically rotate the antenna and reliably measure the received level). But again, there are numerous systems, especially at higher (> several GHz) frequencies that operate based on the principle you described. Thanks!

[@erichungerboeck8344]

Ccoomm3366iooopöömmmmmmmmvvhhnmmm😋

[@talkinghat88]

Thanks for the well presented video; very concise and yet insightful.

[@pauldenisowski]

Thanks!

[@jmsjms296]

Great. Thanks!

[@pauldenisowski]

Thanks for watching!

[@SazzadHissain]

Great presentation on the subject-matter! Could you answer which methods modern mobile phone uses for finding inter-device directions within proximity of couple of centimeters?

[@adelarsen9776]

The Abhwer were specialists at this. Plenty of SOE agents were found by RDF. Cheers VK4SOE.

[@pauldenisowski]

Yes, a lot of DF originated in mil/gov applications and this is still a major application of direction finding. 73! Paul, KO4LZ

[@saurabhrawat1770]

interesting video ! can it be used to achieve the accuracy of 1cm or even less using Bluetooth LE direction-finding concepts?What challenge you see?

[@jayakumarsingaram8218]

Good presentation

[@chriscornelissen5075]

15:34 funny how receive only is different from a radar. The radar I worked with was a pulse/Doppler so the signal was not continuous wave (especially when you take the reflections that are being detected in account, fast manoeuvre aircraft and terrain produce a unstable signal)

[@lucasng3330]

lovely sound & webinar!

[@TKomoski]

Very informative on the concept of Where Am I ; )

[@g0fvt]

An excellent presentation, thank you very much R&S

[@pauldenisowski]

Thanks for the feedback! 73 DE KO4LZ

[@abdoroiss4594]

In this lesson, maps were displayed. Can I know what program is used to display these maps?

[@pauldenisowski]

Most of the maps are from Open Street Maps (OSM) and are displayed in our own software

[@shivanandchidri1735]

Sir ,What is formula for direction of arrival

[@SumaGouriPannala]

Can Bluetooth LE work in Non-LOS conditions (such as under rubble, filled with dust, stone, etc.).

[@pauldenisowski]

I think the biggest challenge would be the attenuation from the debris. If the intervening materials are non-uniform (e.g. a combination of concrete, steel, voids, etc.) that could also be an issue. Assuming this is a safety-of-life application, I would definitely want to perform field tests under different conditions before making any assumptions.

[@zynthos9]

Two questions: 1. Why is Wattson-Watt better for HF (low frequency) than Doppler? I understand antennas have to be larger for lower frequencies, which for a scenario that involves physically moving the antenna with Doppler would make it more difficult, but that wouldn't seem to be in play for electronically switched Doppler. Is it because the magnitude of the frequency difference of the Doppler effect is dependent upon the wavelength of the signal, and lower frequencies have a smaller magnitude frequency shift due to Doppler effect and thus it's harder to resolve the frequency shift due to Doppler at lower frequencies? 2. Not understanding how an omnidirectional antenna helps resolve 180 degree directional ambiguity with Wattson-Watt. An omnidirectional antenna has a theoretically equal gain in all directions, correct? Then how can it resolve one direction from another? How would an antenna that sees all directions equally be able to differentiate a signal coming from the north from a signal coming from the south?

[@zynthos9]

Regarding question 2 on the omni antenna for the Wattson-Watt technique, I believe I understand now that it's not the amplitude of the signal received by the omni that's involved, it's the phase of the signal received by the omni to the phase of the signal received by the 4 antenna elements. I.E. Comparing the phase of the signal received by the omni to the phase of the signal received by the 'North" antenna and the "South" antenna, one can determine if the signal is hitting the "North" antenna or the "South" antenna first to resolve the 180 degree ambiguity.

[@pauldenisowski]

There are a few reasons why Doppler isn't used much at HF, the biggest one probably being the size of the antennas: you would need a very large antenna array (or multiple arrays to cover all of HF) and even 1/4 wave verticals would become unmanageably large. In Watson-Watt the signal from the omnidirectional antenna is usually combined with the signal from one or more other antennas in the array. As you point out, without this it wouldn't be much use :)

[@zynthos9]

​@@pauldenisowski Ok that makes sense, thank you.

[@paulp1204]

I don't believe hyperbolae intersect because the sharpest curvature occurs in a direct line between the focii. For example if only R1 and R2 are considered, the 'points' in the hyperbolae curves (and they come in pairs!) will 'point' at the R1 and R2 stations. i.e These two curves are closest in the direct line between R1 and R2. The example shown seems to confuse range rings except uses hyperbolae instead of circles.

[@pauldenisowski]

I've only heard the term "range rings" used in the context of radar PPI displays. The hyperbolic method is pretty well established (TDOA used to be called "hypebolic direction finding"). I think that what you're referring to is the fact that you could draw circles around each station with the radio representing the distance to the source (direction is unknown). The intersection of these circles would then be the location of the emitter. In most cases, though, the literature refers to them as "hyperbolae" Sorry if I'm misunderstanding your comment - it's really hard for me to discuss these things in text only comments :)

[@stargazer7644]

The curves don't point at the transmitter. The lines are constant difference of delay lines. Given the time delay reported between each pair of stations, the transmitter can lie anywhere along each line. With multiple lines, the possible position narrows to where the lines cross. Depending on the number and geometry of the receiving station positions there can be multiple intersection points. For disambiguation you need 3 stations that are arranged in a triangle.

[@alessandrolima4266]

Amazing

[@petercarlson2680]

what is the symbol inside the C(a) at time stamp 23:58? the x axis is the symbol and y is C(symbol). I must be brain farting on it.

[@pauldenisowski]

It's the Greek letter alpha. Nothing special about that letter, just the one I chose for the graphic. Next time I'll stick to Roman letters :)

[@bbnCRLB]

Non static source, multiple sources, near field, etc.

[@pauldenisowski]

Yes, these are all interesting topics that we are planning to address in future videos. :)

[@AliHassan-tb7pm]

can u plzz upload your slides and documents for more help?

[@pauldenisowski]

HI Ali - We have a special website for direction finding with whitepapers, videos, etc. : www.rohde-schwarz.com/us/campaigns/direction-finding_252649.html

[@AliHassan-tb7pm]

it was a very informative video.i have some questions regarding TDOA if u could plzz answer.

[@AliHassan-tb7pm]

my email is [e-mail]

[@pauldenisowski]

Hi Ali - Please feel free to post your questions here and I'd be happy to address them in the comments section if I can. Thanks!

[@AliHassan-tb7pm]

@@pauldenisowski can u plzz upload your documents and slides for more help?? It would be kind of u sir

[@douglasmcmahon6852]

Mid

[@kanchachina1515]

you need to clarify the content

[@yadavhemant5359]

you need to clarify the content