Searching for unknown frequencies . . .

[KB2GOM]

Okay, first off, I know so little about this topic that I'm not even sure I am asking the right questions.

Alright, so I already own several pretty good scanners: SDS200, Uniden 436, Icom R6, Uniden 125, and I use them frequently to scan services and frequencies that I have found on Radio Reference.

But suppose I want to search for "unknown frequencies,," to find voice communications that are not listed on RR . . . just to see who is doing what on the airwaves. . .

What radio would you use (feel free to suggest ones I don't own)?

What strategy would you use to do the searching?

I'm genuinely interested, and I know that some of you folks are really good at this.

 

[Whiskey3JMC]

What radio would you use (feel free to suggest ones I don't own)?

I use every radio & SDR in my arsenal. For me it depends on what band & modes I'm searching. If I'm seeking out new DMR or NXDN then my Unidens do the job with their custom search & discovery functions. If I want to get a visual of a chunk of spectrum to seek out elusive unknowns then that's where my SDRs shine. For aviation, my goto is my Icom IC-R20. Invest in Proscan for your Unidens so you can upload your logs and filter out your findings history for future review. Your Unidens have a built in recorder so you can log & record findings when you're "out in the wild" without a computer and software. Universal Scanner Audio Player also allows you to review, filter & play back your findings

What strategy would you use to do the searching?

Know what services typically operate on what band(s) in your area. This frequency allocation chart gives you an in depth picture of what service typically live on what bands. What is (are) your target service(s): Businesses, rail, aviation, others? Utilize custom searches and the applicable step size corresponding to the band you're searching so you can sweep portions of the radio spectrum within seconds/minutes. Get a Radioreference premium subscription so you can utilize the database query search to search your state, surrounding states or the entire RRDB & compare your findings with what is already listed in the RRDB. Finally once you've completed your research, ID'ed unknown frequencies, their TGID(s), tone(s) if applicable, license(s) and usage and verified they're unlisted in the RRDB, then submit your findings so you and others can benefit.

 

[UTE-GE]

As Whiskey3JMC said, "that's where my SDRs shine"

 

[nd5y]

A good places to start learning which services are on which bands and frequencies is:

Radio Spectrum Management and Allocations - The RadioReference Wiki

wiki.radioreference.com

 

[u2brent]

Your Uniden 200 & 436 have the Close Call feature for finding local signals as well as what others have suggested.

 

[IC-R20]

I do general band scans based on what I'm looking for and often in sequel to previous bandscans to help hunt. Uniden is good about having a bunch of programmable search ranges instead of being limited to 1 like GRE/RS/Whistler. I have have the programmable search ranges set for 30-50 LoBand, 70 MHz LMR, 150-160, 450-460, 700, 850/860, and 935 commercial in addition to a few others for unrelated weird uses.

The 436HP has discovery mode which works on conventional and is super helpful as it will group recordings from a single frequency and PL/DPL tone (useful for itinerant scanning which has multiple users on the same frequency) and I can just listen back to them later. 462, 464, 467, 469 are great 1MHz search ranges to start off with in more busy urban areas for UHF-Lo. Pick a range of interest and cast a wide net to see what's out there then start narrowing down when you find things. If you don't want to use the discovery mode or want to use a scanner that doesn't have it then as you start finding active UNID frequencies start adding them to a SIGINT favorites/scanlist for more effective scanning.

I gotta say though having the record ability with metadata is a huge game changer when the scanner can essentially monitor for you nonstop all day. I've caught things I missed just stepping out of the room for a minute, plus being able to have it in a log makes it easier to correlate as sometimes I'll find something I forgot I had already spotted weeks earlier.

Also do this before you start:

 

[kc2asb]

Unidens also have pre-programmed service search ranges. I've often utilized it with my Uniden 996T/780XLT/536HP to find active aircraft, marine, railroad, etc frequencies. I also do custom/limit searches (ex 155.000 - 156.000 MHz) on narrow portions of various bands.