Tracking

Discuss KerberosSDR - 4x Coherent RTL-SDR
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k2gc
Posts: 11
Joined: Sun Jan 19, 2020 5:58 am

Tracking

Post by k2gc » Mon Jan 27, 2020 4:02 am

Ok, so I purchased my Kerberos, because we are trying to track down a local jammer who keeps messing with our net on sunday nights.

I am having 'so-so' luck so far with tracking (been working with a fixed station) and i have a couple questions.
  • how does the gain setting work? please compare to a standard radio for me just to make it easy. I need to understand which way gives me a stronger/weaker signal overall. If I change the gain, do I need to re-sync??
  • Which algorithm would be the best? from what I can tell MUSIC makes it so I have to reverse the antenna, while when using Bartlett, I had more accurate results
  • While tracking (in the android app) what do the breadcrumb dot colors represent?
  • Where on the android device, can I find the log files (the csv) I would like to pull them off for potentially further manipulation

ckoval7
Posts: 21
Joined: Fri Sep 27, 2019 8:54 pm

Re: Tracking

Post by ckoval7 » Mon Jan 27, 2020 11:26 am

how does the gain setting work? please compare to a standard radio for me just to make it easy. I need to understand which way gives me a stronger/weaker signal overall. If I change the gain, do I need to re-sync??
This adjusts the sensitivity of the radio. Think of it as turning the RF Gain knob on an HF radio. I find 25.4 dB to be a good number. It strikes the right balance between sensitivity and managing the noise floor. Chances are, if you can't get the signal at a decent SNR at this gain setting, it's too weak to DF anyway.
Unfortunately, because of the way the RTL-SDR works, you'll have to re-sync every time you change gain or frequency. Honestly though, set it to 25.4 and leave it be.
Which algorithm would be the best? from what I can tell MUSIC makes it so I have to reverse the antenna, while when using Bartlett, I had more accurate results
I've always had the best luck with MUSIC. I've never had an issue with having to reverse the antenna. Try DFing a NOAA weather station or local repeater that you know the location of to double check your accuracy.
While tracking (in the android app) what do the breadcrumb dot colors represent?
Signal strength
Where on the android device, can I find the log files (the csv) I would like to pull them off for potentially further manipulation
Downloads/KerberosSDR if I remember correctly.

k2gc
Posts: 11
Joined: Sun Jan 19, 2020 5:58 am

Re: Tracking

Post by k2gc » Mon Jan 27, 2020 3:14 pm

ckoval7 wrote:
Mon Jan 27, 2020 11:26 am
how does the gain setting work? please compare to a standard radio for me just to make it easy. I need to understand which way gives me a stronger/weaker signal overall. If I change the gain, do I need to re-sync??
This adjusts the sensitivity of the radio. Think of it as turning the RF Gain knob on an HF radio. I find 25.4 dB to be a good number. It strikes the right balance between sensitivity and managing the noise floor. Chances are, if you can't get the signal at a decent SNR at this gain setting, it's too weak to DF anyway.
Unfortunately, because of the way the RTL-SDR works, you'll have to re-sync every time you change gain or frequency. Honestly though, set it to 25.4 and leave it be.
So to paraphrase - higher the db gain in this setting, will allow more signal in, lower gain lets less in?
ckoval7 wrote:
Mon Jan 27, 2020 11:26 am
Which algorithm would be the best? from what I can tell MUSIC makes it so I have to reverse the antenna, while when using Bartlett, I had more accurate results
I've always had the best luck with MUSIC. I've never had an issue with having to reverse the antenna. Try DFing a NOAA weather station or local repeater that you know the location of to double check your accuracy.
Knowing what I learned last night about the bandwidth, fir and decimation settings (missed the first time around) I am going to 'start all over' and try again. I did use a NOAA station for my initial attempt, and that is when we discovered everything backwards. Our result put us close to 1/2 mile away from the actual transmitter. I am going to try the same station again today with my new knowledge and hope for the best!

ckoval7 wrote:
Mon Jan 27, 2020 11:26 am
While tracking (in the android app) what do the breadcrumb dot colors represent?
Signal strength
I had figured this was the case, but wanted confirmation
ckoval7 wrote:
Mon Jan 27, 2020 11:26 am
Where on the android device, can I find the log files (the csv) I would like to pull them off for potentially further manipulation
Downloads/KerberosSDR if I remember correctly.
Found it! it was actually Download/KerberosSDR - but glad I have it now.

Because our jammer happens during a net where I may find others on the input freq, I have been starting/stopping the tracking software based on my opinion of the signals listening. (ie, is it only the jammer, or am I hearing 2 people). Because of that, we actually ran 2 android apps against the Kerberos, with 2 people operating the stop/start button. a difference of opinion means a bunch.

Nice thing is, now I can merge the files and see what it also looks like as a complete data set.

I also anticipate using that merged file on one device during the next session, as well as start a clean file on another.

This guy has been plaguing us for months now, and its getting quite old. We are much closer, and hopefully after I refine my skills more this week, next Sunday will go even better for us. Especially, as a second Kerberos will also be in the mix.

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