KerberosSDR & Aircraft Beacon Search

Discuss KerberosSDR - 4x Coherent RTL-SDR
Maginux
Posts: 6
Joined: Sun Apr 21, 2019 9:27 am

KerberosSDR & Aircraft Beacon Search

Post by Maginux » Sun Apr 21, 2019 9:47 am

Hello everyone,

I stumbled absolutely by chance on this project and I must admit that I was amazed by the quality of the idea, only, I would like to know KerberosSDR could be used to search for beacons of crashed planes (121.5 or 121.375 Mhz , the first being the frequency of beacons in real situation and the second one, especially used during exercises).
Working in an association dedicated to this kind of research, and having just missed the end of the crowdfunding campaign, I would have liked to have details about the use of this gem of technology.

If necessary, it would be entirely possible for me to invest in odroid and its screen (there must be a raspberry 2b in my drawers), but first of all, I would like to know if this is feasible (for use on battery). Regarding the configuration of antennas, I had in mind to use the circular, since they should be positioned on the roof of a car.

Thank you in advance for your answers ! :D

rtlsdrblog
Site Admin
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Re: KerberosSDR & Aircraft Beacon Search

Post by rtlsdrblog » Sun Apr 21, 2019 12:21 pm

Interesting idea, and I think it could be useful in some circumstances.

But at 121 MHz there is perhaps a physical limitation. For 121 MHz the frequency wavelength is going to be quite large at around 2.5m, so if you had a reasonably sized array at 0.3 spacing factor, (2.5 * 0.3), then you're still looking at an antenna array with a radius of 0.75m which could be quite difficult to drive around with.

Secondly I assume that aircraft beacons intermittently transmit? We haven't implemented any handling for intermittent signals at the moment, but we're working on a solution for that in future code updates. It's possible to implement this yourself now though via the open source code if you have a coder.

The device can be used on battery. You just need a high quality battery pack that can output a stable 3A for the Pi3, and at least 1.5A for the KerberosSDR simultaneously (or two separate battery packs).

Maginux
Posts: 6
Joined: Sun Apr 21, 2019 9:27 am

Re: KerberosSDR & Aircraft Beacon Search

Post by Maginux » Sun Apr 21, 2019 2:44 pm

rtlsdrblog wrote:
Sun Apr 21, 2019 12:21 pm
then you're still looking at an antenna array with a radius of 0.75m which could be quite difficult to drive around with.
For that, I do agree, in the rigor realize a removable installation would be the ideal, but it is "wasting time" during the search for the aircraft (in real situation) which is unfortunate. :?
rtlsdrblog wrote:
Sun Apr 21, 2019 12:21 pm
Secondly I assume that aircraft beacons intermittently transmit ?
They transmit a signal (normally on 2 frequencies: 121.5 and 406 Mhz) only when they are triggered (either manually or automatically, during an accident for example); here is for example what you can hear during a crash.

https://fr.wikipedia.org/wiki/Fichier:R ... ,5_MHz.ogg

rtlsdrblog
Site Admin
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Re: KerberosSDR & Aircraft Beacon Search

Post by rtlsdrblog » Mon Apr 22, 2019 1:45 am

Maginux wrote:
Sun Apr 21, 2019 2:44 pm
rtlsdrblog wrote:
Sun Apr 21, 2019 12:21 pm
then you're still looking at an antenna array with a radius of 0.75m which could be quite difficult to drive around with.
For that, I do agree, in the rigor realize a removable installation would be the ideal, but it is "wasting time" during the search for the aircraft (in real situation) which is unfortunate. :?
rtlsdrblog wrote:
Sun Apr 21, 2019 12:21 pm
Secondly I assume that aircraft beacons intermittently transmit ?
They transmit a signal (normally on 2 frequencies: 121.5 and 406 Mhz) only when they are triggered (either manually or automatically, during an accident for example); here is for example what you can hear during a crash.

https://fr.wikipedia.org/wiki/Fichier:R ... ,5_MHz.ogg
406 MHz would be more reasonable. And the signal is a continuous broadcast so that's good. Seems like it could work at 406 MHz.

Maginux
Posts: 6
Joined: Sun Apr 21, 2019 9:27 am

Re: KerberosSDR & Aircraft Beacon Search

Post by Maginux » Mon Apr 22, 2019 7:46 am

If in any case, it would be possible to work as well in 121.5, as in 406 Mhz; in a pinch with a ground installation and not on the car, I am strongly interested to have the opportunity to try this device in exercise situation, it is the civil protection that may be impressed ! 8-)

gzcp31
Posts: 8
Joined: Mon Mar 18, 2019 8:22 pm

Re: KerberosSDR & Aircraft Beacon Search

Post by gzcp31 » Fri May 17, 2019 11:51 am

I am interested in the same capability. This is the main reason I purchased the KSDR. We are using the original RTL-SDR for DFing ELTs on 121.5, 121.775, 243, and 406. It works better that the commercial equipment we have been using for years.

Maginux. I would like to keep in touch on this and work together on making this system a reality. I have a Practice beacon on 121.775 to test with and we usually train with the 406 at least once a month. I can get special authorization for 406 testing if needed at my location here in the US. You can reach me at gzcp31 at yahoo dot com. I am not a coder but I would like to get this to a reality. Current commercial 406 capable equipment with 121.xx equipment is running over $10,000 each.

Maginux
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Joined: Sun Apr 21, 2019 9:27 am

Re: KerberosSDR & Aircraft Beacon Search

Post by Maginux » Fri May 17, 2019 12:24 pm

gzcp31 wrote:
Fri May 17, 2019 11:51 am
I am interested in the same capability. This is the main reason I purchased the KSDR. We are using the original RTL-SDR for DFing ELTs on 121.5, 121.775, 243, and 406. It works better that the commercial equipment we have been using for years.
If it can guide you, I work with the French civil security, I'm not radio amateur (for now :P ) but the association in which I am, mainly gathering OM who work in direction finding to find this kind of tags (the ADRASEC); and Kerberos could, I think, greatly assist us in this kind of research and above all could avoid doing kilometers in cars and walking with an HB9CV in hand and a compass around the neck. :lol:

Regarding your proposal to stay in touch, I have absolutely nothing against, I do not know how I could help you, but leaving on the basis of Kerberos or Montreal 3V2 could be a good idea!

gzcp31
Posts: 8
Joined: Mon Mar 18, 2019 8:22 pm

Re: KerberosSDR & Aircraft Beacon Search

Post by gzcp31 » Fri May 17, 2019 1:16 pm

I work with Civil Air Patrol here in the States. I am also an Amateur Extra. The main project I want to use the KSDR for is for vehicle mounted Doppler. I would like to have it show direction to the current and previous 10 directions plotted. As you know the 406 only sends out a 10-20msec signal every 50-70 seconds. the 121.5 signal is 0.1 watt on the same ELT/EPIRB. Older 121.5 beacons were 5 watts. We have had one elt that the 121.5 failed and was not transmitting. we had to track on the 406 ping.

We have also had a 406 that was not sending out the correct GPS coordinates.
Having the historical data on the screen would help tremendously. Also having a unit that is resonably priced is helpful.

rtlsdrblog
Site Admin
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Re: KerberosSDR & Aircraft Beacon Search

Post by rtlsdrblog » Tue May 21, 2019 6:05 am

I'd like to revise my statement about 121 MHz and antenna sizing. My experiments with spacing factors below 0.33 seem to work out okay. So I think an interlement spacing factor of about 0.2 - 0.25 might be sufficient. And see the revised calculations for a circular array on the guide which results in a smaller radius www.rtl-sdr.com/ksdr.

So for the 2.5m wavelength of 121 MHz:

Interelement Spacing = 2.5 * 0.25 = 0.625m

Converted to Radius Spacing = 0.625m / sqrt(2) = 0.44m.

So an antenna array with a radius of only 0.44m, or even 0.35m @ a spacing factor of 0.2 might work out.

Maginux
Posts: 6
Joined: Sun Apr 21, 2019 9:27 am

Re: KerberosSDR & Aircraft Beacon Search

Post by Maginux » Tue May 21, 2019 9:55 am

rtlsdrblog wrote:
Tue May 21, 2019 6:05 am
Interelement Spacing = 2.5 * 0.25 = 0.625m
Converted to Radius Spacing = 0.625m / sqrt(2) = 0.44m.
So, if I understand correctly; something of that order ? I'm not sure it would work on the roof of a car.
Image
Anyway, I do not already see where to buy Kerberos and if by chance, considering my project of use, the designer of the project, would be inclined to make me a small reduction. :oops:

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