Direction finding with directional antennas. Is it possible?

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dfer
Posts: 2
Joined: Mon Sep 14, 2020 5:55 am

Direction finding with directional antennas. Is it possible?

Post by dfer » Mon Sep 14, 2020 6:11 am

Hi all,
How does KerberosSDR function in DF mode with directional antennas? In hardware setup instructions there is stated that you should use omni antennas for DF'ing. In my case I need to determine the directions of signal sources in a fixed 150 degrees sector. Would it make sense to use let's say 4 log-periodic antennas per set (50 degrees horizontal beam width)? I would probably need 3 sets of KerberosSDR's to cover the sector. The reasoning behind this setup is to gain more detection range (up to 400 km needed) vs omni antennas.

Thanks

rtlsdrblog
Site Admin
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Joined: Mon Nov 19, 2012 11:54 pm

Re: Direction finding with directional antennas. Is it possible?

Post by rtlsdrblog » Thu Sep 17, 2020 5:05 am

It should work fine with directional antennas. Just use a linear array setup.

The guides assume use on a vehicle, where omni antennas are needed.

SIGINT
Posts: 13
Joined: Wed Oct 19, 2016 10:19 pm

Re: Direction finding with directional antennas. Is it possible?

Post by SIGINT » Thu Sep 17, 2020 11:37 am

Interesting question.

I would expect interferrence on the higher frequencies - if you need to keep a a distance between multi element yagis at 1/3 wavelength. that would be just over 20 cm at 460 Mhz.

Keep us posted with results - I see the need, as my SDR's appear to be much less sensitive than my Uniden SDS-200 scanner.

Regards

dfer
Posts: 2
Joined: Mon Sep 14, 2020 5:55 am

Re: Direction finding with directional antennas. Is it possible?

Post by dfer » Thu Sep 17, 2020 1:48 pm

Thanks for your replies,

As you may have already guessed the signal sources are not land based. The final goal is to have a solution which triangulates the position of the signal source. This however requires at least two geographically dislocated KSDR receiver sets and custom software.

My current solution with 3 sets of TV dongles turned into SDR receivers with custom software (one antenna per dongle, each looking to different bearing) is working fine but I want to move one step further and to experiment with KSDR for approximate location detection and possibly track creation. Will let you know how this experiment will work out.

As "SIGINT" rightly pointed out the issue may arise with linearly positioning the yagis at 1/3 wavelength. Will see.

SIGINT
Posts: 13
Joined: Wed Oct 19, 2016 10:19 pm

Re: Direction finding with directional antennas. Is it possible?

Post by SIGINT » Thu Sep 17, 2020 7:42 pm

This may not work for KSDR triangulation - with the .33 wavelength optimal distance, but I am considering attempting to construct a vertical parabolic reflector with a half wavelength dipole in the center. Parabolic in the horizontal plane only - like a metal drum split vertically in two - and reshaped to focus on the dipole at my most common frequency around 460 Mhz.

That should give a very high gain with high attenuation of side and rear lobes - and it can be turned to direction find a signal -and hopefully increase reception of of weak signals

I then wonder - if you create three of these - angled slightly differently like 320, 360, 20 degrees - would someone be able to write a piece of software that will control a servo, making the antennas track a slowly moving target like a ship at distance.

.. or just auto adjust to the best signal path/direction for a stationary transmitter.

At 800 mhz these can be made at a decent size.

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