MilAir - how to find frequencies faster?

flanker86

Member
Joined
Oct 22, 2015
Messages
35
Hello,
I am wondering if there are faster and more precise methods of finding milar frequencies than mine. I use two methods - one is rtl_power on my RTL-SDR and Raspberry Pi - it gives a waterfall of power vs time and frequency - it is precise but the output is some kind of "post factum" of action .
The second method is a cheap handled spectrum analyser RF Explorer - its limitations is limited to 112 points "on screen" resolution - so 225-380MHz band gives 155MHz span / 112 equals about 1.38 MHz resolution and we want 25kHz :) - finding a correct freq needs at least two measurements - wide one and a narrower.

Do you have any methods or hardware that can speed up the process of acquisition of new mil air frequencies?

BR
 

morfis

Member
Joined
Jan 24, 2004
Messages
1,049
At home -
1) Multiple scanners searching small segments of spectrum
2) sdrsharp with scanner plugin and airspy R2
3) multiple R2s searching smaller segments of spectrum ;)

Looking at FFT graphs is fine but the computers are quicker than my eyes and can be set to decode the signal for instant confirmation.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
5,019
Location
Stockholm, Sweden
I also use SDR# and rtl-sdr with a scanner plugin and a Omnirig plugin so it controls a Uniden BCD536 set to record. Set the scanner plugin to a lower threshold and first enter all known frequencies in the lockout list and then lockout the current interferencies and spikes and then raise the level a few notch.

In my area there seem to be a new frequency discovered with 2-3 years intervals and we keep track of them in forums. So we maybe have 30-40 frequencies that gets used and those are scanned in less than a second in a normal scanner that are monitoring them daily.

/Ubbe
 

morfis

Member
Joined
Jan 24, 2004
Messages
1,049
Does it have 10MHz span - so you need at least 15 of them?
You asked about faster rather than asking for something that could specifically look at 225-380MHz instantaneously (though that wouldn't cover the whole of your 'milair'?).

For hobby use I wonder how instantaneous is really required. I've seen people say they can search the whole milair allocation (though they generally mean the 230-400MHz part) in just over a second using a single R2 and sdrsharp with the scanner plugin. I'm not convinced that it is so simple or necessarily useful. A log of 'active' frequencies could be output but you'd still have to verify and identify each of those later. Fine for the commonly used stuff like (most) ATC, base allocations etc but maybe impractical for something used only on one day during an exercise or just a rarely used allocation?

As an experiment I did just try a single R2 searching 230-400MHz and was surprised to find that it almost flawlessly managed to cope with some HQ - let down because I don't have a lockout list for the common stuff in that part of the spectrum.
 

flanker86

Member
Joined
Oct 22, 2015
Messages
35
Thank you for you answers. I learned something new and I think that option 2 from morfis is the way I will go. Thanks once again.
 

batdude

Member
Database Admin
Joined
Jul 29, 2002
Messages
494
Location
East Central, Florida
Thank you for you answers. I learned something new and I think that option 2 from morfis is the way I will go. Thanks once again.
this is BY FAR the best/easiest way to find new and in-use MILAIR stuff.... when configured correctly, this setup will scan 225-380Mhz in <3 seconds - with very easy to use recording options for unattended operations.

i have been using this for over a year and the performance is just phenomenal. With my QTH here in Florida - I often see squadron after squadron of planes coming down to Key West / Homestead, Pinecastle and Avon Park for range time.... we have carriers off shore regularly conducting flight ops... and Florida still sees plenty of un-ENC fedCom stuff in the VHF and UHF bands..... therefore the Airspy + fastScanner plugin = an extremely versatile solution.... matter of fact, on VHF/UHF receive, the Airspy hears better than my R8600 for <10% of the cost.


doug
 

batdude

Member
Database Admin
Joined
Jul 29, 2002
Messages
494
Location
East Central, Florida
There's different noise floor levels and spikes and spuriouses like we all have with our SDR dongles. What's the lowerst signal level you can detect at that search speed?

/Ubbe
at the bottom of the screen you will see a red and yellow line. That's the detect / hold line for squelch. Red line to break the squelch, yellow line to hold the carrier. So the answer to your question is - it depends. I've not had any problems detecting signals hundreds of miles away on UHF with the settings shown. There is one box on the screen that isn't explained well but was mentioned above - the "DETECT" box. (The detect box is not shown below - it is on the left hand side of SDR# inside the scanner plugin area. This is a value in milliseconds that directly impacts your scan speed. The lower you go in that box, the faster you scan. Best I can figure is this setting is how long the scanner plug in must detect a signal to unmute. I keep mine on about 70.

1603193691927.png


doug
 
Top