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Identifying unknown frequency

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#1
Hi all,

I'm really curious to try and track down a particular frequency in my area. I live south of Santa Maria, CA and I'm picking up this frequency on my uniden bearcat scanner of 127.4750. For the life of me, via all sources I possibly have access to, I cannot locate who this frequency belongs to. I have used Radioreference as well as some local websites that list off frequencies, some quite in-depth but either because could be outdated, this frequency wasn't found on any of the sites.

I even tried this FCC database web page, License Search - Geographic Search

A friend of mine said it could possibly be a business 2-way especially if it is within the 450MHz range. Which it could very well be. I even asked them though that don't frequencies of the 450MHz range though need to be licensed by the FCC? They said yes. That said, how come it wouldn't show up on the FCC page I included above? Are there other sources on the web that can easily identify frequencies and who they're owned by?

Thanks
 
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#2
Confirm the frequency? You mention 127.475 then say it's in the 450mhz range??? That is not in that range.
 
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#3
My apologizes, I made a type-o. My Uniden scanner is actually 800MHz, not 450MHz. Yes, the scanner frequency is 127.4750
 
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#5
Since it's in the air band, you likely won't find a license for that specific frequency. Aircraft are not limited to a specific channel/frequency. Some airports, businesses using air band or other fixed services have licenses on a specific frequency.

Maybe if you can clarify what you are hearing? Where you are? What your setup is like?
 

TPC2075

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#7
127.475 KHZ Belongs to The United States Marine Corp,Helicopter Squad,Bomb Transportion by Air.
at Cherry Point. Northern California Area , that location is Classified !
the Other Frequency you might want to monitor is 244.875 Uhf ,this Frequency should repeat 127.475 Khz
Do you Remember ever seeing those very big military looking helicopters fly over you ? , those Ugly looking painted helicopters those are usually Airforce,USN,Marine,VAFB maybe doing something with them as well, have Fun "guy" ! ,i have been Monitoring this kind of stuff for years !
 

pro106import

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#8
127.475 KHZ Belongs to The United States Marine Corp,Helicopter Squad,Bomb Transportion by Air.
at Cherry Point. Northern California Area , that location is Classified !
the Other Frequency you might want to monitor is 244.875 Uhf ,this Frequency should repeat 127.475 Khz
Do you Remember ever seeing those very big military looking helicopters fly over you ? , those Ugly looking painted helicopters those are usually Airforce,USN,Marine,VAFB maybe doing something with them as well, have Fun "guy" ! ,i have been Monitoring this kind of stuff for years !
You must mean North Carolina, not Northern California??
AirNav: KNKT - Cherry Point Marine Corps Air Station (Cunningham Field)

[FONT=Verdana, Arial, Helvetica, sans-serif][SIZE=+1]Cherry Point Marine Corps Air Station (Cunningham Field)
Cherry Point, North Carolina, USA
[/SIZE][/FONT]
ATIS: 127.475 244.875

I doubt 'guy" is hearing this from California, however
 
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#9
Since it's in the air band, you likely won't find a license for that specific frequency. Aircraft are not limited to a specific channel/frequency. Some airports, businesses using air band or other fixed services have licenses on a specific frequency.

Maybe if you can clarify what you are hearing? Where you are? What your setup is like?
I live in a valley just south of Santa Maria, CA surrounded by a lot of hillsides. For example, what that does, I can hear pilot transmissions to Santa Maria Airport's ATC (KSMX) but I cannot hear the tower talk back to the pilots most likely due to the terrain challenges I face where I live. That also goes for a local CHP dispatch frequency too...42.560. I hear dispatchers, but not the CHP units respond to them.

Because I rent, and other unique circumstances, I am unable to mount an external antenna to help boost my reception so I only rely on the antenna that came with my Uniden Bearcat scanner.

As for the transmissions I heard, some of it was general small talk, something about a show earlier in the day and also I heard a few transmissions regarding weather radar. We do have a weather radar site a little more than 15 minutes north of where I live, it is the KVBX weather radar site.

-Jordan
 

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SCPD

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#11
I live in a valley just south of Santa Maria, CA surrounded by a lot of hillsides. For example, what that does, I can hear pilot transmissions to Santa Maria Airport's ATC (KSMX) but I cannot hear the tower talk back to the pilots most likely due to the terrain challenges I face where I live. That also goes for a local CHP dispatch frequency too...42.560. I hear dispatchers, but not the CHP units respond to them.

Because I rent, and other unique circumstances, I am unable to mount an external antenna to help boost my reception so I only rely on the antenna that came with my Uniden Bearcat scanner.

As for the transmissions I heard, some of it was general small talk, something about a show earlier in the day and also I heard a few transmissions regarding weather radar. We do have a weather radar site a little more than 15 minutes north of where I live, it is the KVBX weather radar site.

-Jordan
The reason you are not hearing the tower, but are hearing the aircraft is topography is blocking the signal from a ground station. The aircraft are high in the air and their transmissions see over all the hills, valleys and ridges The reason you are hearing the CHP dispatcher is that you are hearing a remote base station installed on a high peak that sees over much of the topography between you and that base station. The cars are at ground level, transmit at lower power so topography blocks their signals unless they are fairly close to you. In addition low band (30-50 MHz) signals have the ability to bend over and around topography.

You can hear the mobile side of the SLO sheriff's department because they utilize repeaters where the weaker signal of the mobiles is transmitted over the higher powered repeater output frequency at a high mountain location. The CHP does patch the frequency of the lower powered mobiles out onto the remote base station frequency, but usually does this only in large metro areas.

You are obviously a beginner and I suggest you utilize the Radio Reference wiki pages where a lot of basics are explained. There is a good article on CHP radio that you can access by clicking on the wiki tab in the upper right corner of the CHP database page.
 

ko6jw_2

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#12
Another reason why you can't hear CHP mobile units is that they are on 42.48Mhz. You will only hear mobiles on 42.56Mhz for car-to-car traffic. SLO CHP tried using a "repeater" at one time, but just on Santa Ynez Peak. They have problems with phase distortion if they try to simulcast on multiple mountain tops.

As for the aircraft frequency, I am a 15-20 miles south of you and have tried to listen on 127. 475Mhz, but have not heard anything yet. Many private pilots have air band HT's. You may be hearing some being used as a bootleg two-way system. These HT's can transmit anywhere in the band.
 
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#13
You are probably hearing the Marine Air units transitioning between an offshore platform and Fort Hunter Liggett or another training base in that area.
 

kruser

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#15
Anything is possible with low band signals getting into other bands, especially with receivers that are not triple conversion.
A 1 watt low band signal can travel thousands of miles when conditions are correct and can also show up all over the place on a double or single conversion receiver.

As far as the civil air band goes, nobody really owns a frequency. There are some frequencies licensed by some airlines or manufacturers but most of those are in the upper few MHz of the civil air band.
Then the lower part of the civil air band is mostly used by navigational aids.
The FAA does have some rules in place for certain frequencies that only allow them to be used for specific type traffic as well. The same goes for Marine band frequencies where the Coast Guard regulates what some frequencies can be used for.
So 127.475 could possibly be used by many operators across the country or even the world or it could simply be an image not even in the air band.
Several have suggested a low band image which is very possible as low band signals can travel thousands of miles.
Even an FM modulated signal could create an image heard in AM mode depending on how well the emission mode is filtered in your radio model.
Some will pass it just like it's an AM signal while some will pass an FM signal but with distortion making it harder to understand.

If you can ever catch and record a call sign heard in voice or morse code on 127.475, someone could probably figure it out pretty easy for you.
If it is an image, you may hear the actual call sign said by voice or sent via morse code and if it is an actual aviation band signal, you may get lucky and hear the users tail or registration number of the aircraft or who they are talking with.
I've heard the Boeing company here actually use a call sign before in the air band but generally they use the tail or registration number of the aircraft they are talking with. Boeing also uses a lot of test flight numbers but you get used to those that do the talking.
Air band signals can be heard for hundreds of miles or more due to their altitude if actually in an aircraft.

One thing you could try is get an air band bandpass filter. If the mystery signal goes away, you can pretty much figure that the unknown signal was just an image getting into your radio. If the signal remains, then you can assume it really is an air band signal.

If you are really into air band monitoring, I'd get yourself an air band bandpass filter. They can make a world of difference in monitoring aircraft as they filter out everything above and below the civil air band.
I use one on one of my radios when monitoring the air band and it helps greatly. I can hear the low power frequencies at some of the local airports that otherwise cannot even be detected when the filter is not inline.
Several make these filters for the civil air band. Mine were made by AOR back in the day.
I've never invested in a bandpass filter for the military range of aeronautical frequencies but I know they are made, just not as common as those made for the civil air band.
Good quality filters can open up your receiver like you purchased a high quality receiver and air band antenna!

If you are setup for mobile operation, you could also drive around and try and narrow down if the source of the signal is local or not. That could be hard though if the signal is not on the air very often.

I live in the Kansas City ARTCC region and have logged many hits on the frequency but I never recorded them so can't say what the conversations were about.
Lie you, I also rent (apartment) but they let me put up several antennas on the roof plus give me 24 hour access to them. Not wanting to push my luck, I invested in several multicouplers so I can keep the antenna count down. I feed around 30 radios from the few antennas I have up and use various bandpass filters on some radios that I dedicate to a band. I'm not really into aircraft much so I only have one radio dedicated for that. I do use the bandpass filter on that radio and it can hear signals from the ground stations near me that cannot even be detected by much higher quality receivers.
If you are seriously into air band monitoring, you can't go wrong with an air band bandpass filter made by someone like AOR or PAR Electronics.
Even with an indoor antenna only, the filters can help a lot especially if you can locate an antenna in say a window or attic space. Try and get the antenna away from other electronic equipment and play with its placement and you may be very surprised in its performance over a back of radio mounted antenna.

I'm monitoring 127.475 while typing and all of the traffic I'm hearing tonight is Southwest Airlines so they may be licensed to use that frequency for business ops with their planes flying in and out of Lambert Field which is just a few miles away from me.
I can actually hear the ground station very well and right now it is a female talking with Southwest's fleet of aircraft in the area. It appears to be more business based talk and she is not giving any clearance for departure or arrival. The tower should be handling that part if the airport is even open. It sounds like she may be coordinating aircraft with the correct terminal for baggage handling ops. I also hear some de-icing talk as we have an ice storm going on most of the weekend. The aircraft she is talking with appear to all be on the ground as I do not usually hear them but identifiers I hear from the female are local and specific to Lambert.

Good luck in your hunt!

edit: The specs for your model do not say if it is a triple conversion radio or not so most likely it is just a double conversion type.
That does not make it bad! It just makes it more susceptible to images from out of band (or in band) sources.
What that means is that it may display 127.475 MHz but could be picking up an image from another frequency.
I don't think the specs listed the IF frequencies used but if those were known, one could make a reasonable assumption of what the image frequency may be. If the image freq falls within one of the radios bands, you could program the image directly and see if you still hear the unknown signal. But... without knowing the IF frequencies used, it's anyone's guess as to what the image frequency is.
Triple conversion models cost more usually but they offer better image reduction as they put the images outside the IF passband ranges. Triple conversion models are also still susceptible to images but not as bad as double conversion models can be especially if you are located in an RF rich environment like a large city but it sounds like you are in an area not bad for these problems plus the indoor radio mounted antenna can also really help in reducing images.
I wish Uniden published more specs on all their models but they keep that info hush. Probably so people cannot use it to try and circumvent picking up non-existent analog cell phone frequencies! That's a stupid law still on the books that should be removed as there is no reason to even have that law today with no analog cell signals used anywhere in the country for many years now.
 
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Oakland_Tower

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#16
I think I found it: USFS Orange County (air ops). This may explain the casual chatter- probably air to air. They may have been using the frequency while transitioning back to home base after fire season. It should light up again this summer.


127.475
USFS / Orange County
Backup Frequency / Air OPS
127.925
USFS / Orange County
Backup Frequency / Air OPS

source: http://www.vistacert.org/resources/local_frequencies.pdf
 
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