RCAG Sites

[zla_datm]

I've been doing some research and compiling data from the FAA AFF file for RCAG sites. They are listed like this, here, and RR appears to have mostly scraped from the AFF file. However, I can't for the life of my figure out how it's determining a "range" for the antenna. Anyone have insight here?

Additionally, looking to see if there's a database of RTR sites out there like there are for RCOs. My best guess is that RTR antennas are just on the airports they are supposed to service.

Thanks!

 

[majoco]

It's probably not a 'range' where the signal fades out, it's an area where you are guaranteed to get a minimum signal at a certain altitude, probably the published MSA (minimum safe altitude) for the area. It's the same for navigation beacons - they have a published MRA - minimum reception altitude - on a route to and from the beacon - very dependant upon the terrain. We had to fly these routes with a calibrated signal strength receiver and record the results once a year - if the signal fell below a certain minimum then we had to loop back, go up a thousand feet and check again - if we had good reception there then a NOTAM (Notices to Airmen) was published raising the MRA for that route and then the new altitude was published in the next chart update.

 

[zla_datm]

It's probably not a 'range' where the signal fades out, it's an area where you are guaranteed to get a minimum signal at a certain altitude, probably the published MSA (minimum safe altitude) for the area. It's the same for navigation beacons - they have a published MRA - minimum reception altitude - on a route to and from the beacon - very dependant upon the terrain. We had to fly these routes with a calibrated signal strength receiver and record the results once a year - if the signal fell below a certain minimum then we had to loop back, go up a thousand feet and check again - if we had good reception there then a NOTAM (Notices to Airmen) was published raising the MRA for that route and then the new altitude was published in the next chart update.

View attachment 74656

Cool info about the MRA, thanks! I didn't realize you had to test them yearly. So you're saying it's an assumption made by cross referencing local Low IFR charts?

 

[alcahuete]

I don't know where RR got that info, and I don't know what you clicked on to get that map, so I can't see the others. I know that generally speaking, tech ops./comms. "guarantees" a 90NM coverage for the RCAG sites at ZLA. Of course, many of them will cover a couple hundred miles, but if there coverage issues outside of the 90NM, they generally just chalk it up to the distance and won't attempt to fix the radios.

I don't know if that 90NM is actually written somewhere in stone, or if it even applies to other facilities, but that is the rule of thumb at ZLA.

 

[nd5y]

As far as I know the range circles in the RRDB are created by the admins (or sometimes submitted by users) to try to cover the geographical area of the DB entry. It's mainly for GPS location based scanners and has no relationship to real life radio coverage.

 

[zla_datm]

I don't know where RR got that info, and I don't know what you clicked on to get that map, so I can't see the others. I know that generally speaking, tech ops./comms. "guarantees" a 90NM coverage for the RCAG sites at ZLA. Of course, many of them will cover a couple hundred miles, but if there coverage issues outside of the 90NM, they generally just chalk it up to the distance and won't attempt to fix the radios.

I don't know if that 90NM is actually written somewhere in stone, or if it even applies to other facilities, but that is the rule of thumb at ZLA.

Thanks! Not sure how to get there either, generally just google "ARTCC RCAG" and got there: Los Angeles (ZLA) Air Route Traffic Control Center Scanner Frequencies and Radio Frequency Reference

My understanding of VHF is that it's Line of Site, so the RACG height + the height of an aircraft would determine range. Suppose the rings on the database are roughly for the ground. At this point I'm trying to reconcile the database I have from faa.gov with RR. The FAA Database includes RCAG sites and also airports, so I'm trying to determine if RCAG sites are also colocated with ATCT RTRs.

As far as I know the range circles in the RRDB are created by the admins (or sometimes submitted by users) to try to cover the geographical area of the DB entry. It's mainly for GPS location based scanners and has no relationship to real life radio coverage.

Thanks! Makes sense.

 

[alcahuete]

My understanding of VHF is that it's Line of Site, so the RACG height + the height of an aircraft would determine range.

That is 100% accurate. Aircraft at altitude can very easily be reached for a couple hundred miles.

The FAA Database includes RCAG sites and also airports, so I'm trying to determine if RCAG sites are also colocated with ATCT RTRs.

As far as ZLA is concerned, I can't think of a single RCAG that is colocated at an airport. Generally speaking, the RCAGs are located on mountaintops to provide the most coverage possible.

 

[zla_datm]

That is 100% accurate. Aircraft at altitude can very easily be reached for a couple hundred miles.



As far as ZLA is concerned, I can't think of a single RCAG that is colocated at an airport. Generally speaking, the RCAGs are located on mountaintops to provide the most coverage possible.

Thank you for your replies! I'm working on a project that is mapping some of this and am really trying to reconcile the FAA AFF.txt file, the RadioReference Database, and the ZLA SOP I have access to. The Grand Canyon site is throwing me off, it's not in the FAA database but is on RR and in the SOP. It got me wondering if there were similar discrepancies, which then got me thinking about how TRACONS do this (I assume piggyback on an RCAG or just on the airport(s)).

It's also got me thinking about the sheer amount of cable that must have been run, but that's just an extra though hah.

 

[zz0468]

As far as ZLA is concerned, I can't think of a single RCAG that is colocated at an airport.

Blythe, maybe? There's several FAA radio sites on or adjacent to the airport, and the terrain is such that, sitting at ground level, LOS range would be a long, long way. I've always thought there was both RCO and RCAG sites there.

 

[zla_datm]

Blythe, maybe? There's several FAA radio sites on or adjacent to the airport, and the terrain is such that, sitting at ground level, LOS range would be a long, long way. I've always thought there was both RCO and RCAG sites there.

In the AFF database, the coordinates are 33.603911,-114.632733 off in a farm field. Makes more sense it's right by the admin building there. I have a feeling it's a typo someplace or converting to decimal got weird. No other radio out at Blythe though, just CTAF. RCO might still work, but those are being sunsetted pretty much everywhere except Alaska.

A shame the FAA isn't keeping this RCAG/AFF database more current and clean. Still curious about RTRs and if they just use antennas at the major airports.

 

[alcahuete]

Blythe, maybe? There's several FAA radio sites on or adjacent to the airport, and the terrain is such that, sitting at ground level, LOS range would be a long, long way. I've always thought there was both RCO and RCAG sites there.

It's not co-located. It's about 10 miles east of the airport or so if I recall.

Thank you for your replies! I'm working on a project that is mapping some of this and am really trying to reconcile the FAA AFF.txt file, the RadioReference Database, and the ZLA SOP I have access to. The Grand Canyon site is throwing me off, it's not in the FAA database but is on RR and in the SOP. It got me wondering if there were similar discrepancies, which then got me thinking about how TRACONS do this (I assume piggyback on an RCAG or just on the airport(s)).

It's also got me thinking about the sheer amount of cable that must have been run, but that's just an extra though hah.

The TRACONs have their own sites usually. As far as the cable, it used to be microwave links, but now it's either fiber or TELCO copper already run by the various companies. But yeah...it's a bunch! ha ha!

 

[zla_datm]

It's not co-located. It's about 10 miles east of the airport or so if I recall.



The TRACONs have their own sites usually. As far as the cable, it used to be microwave links, but now it's either fiber or TELCO copper already run by the various companies. But yeah...it's a bunch! ha ha!

My other reply is awaiting moderation but yeah, the AFF database has Blythe's out in a field. Google sat imagery isn't high enough resolution to tell if it's accurate, but street view shows two antennas on the airport. For sure one is the RCO.

For TRACON Sites, is there an FAA Database? Best I could find was the TWR database which has every frequency but only lists airports. Makes me assume all the TRACON sites are on the airports.

 

[spanky15805]

There really isn't one uniform answer. You have to start back in the 1958-62 time frame, think like an engineer trained in tube radios, when almost ALL the RCAG/RCO/VOR/RTR sites were platted. Now, add that almost all the RCAG/(C)ASR were manned 8-16 hours a day and could tweak any radio at will. RCO/RCOA sites are usually the RCO being VHF(122.***)/UHF(363.***), the RCOA side is almost always VHF(121.500)/UHF(243.000). They try and follow a plan but with so many VHF RCAG sites transmitting 10 watts, AM you can only do so much, especially when they are fighting a commercial FM broadcaster with an ERP of 150,000-250,000 watts from an 8 bay JamPro and no filtering for 108-136mhz. I've seen on paper, were the RCAG is suppose to have a 150nm range. Not with all the rf floating around today, 100nm is doing good. Like alcahuete said, they are accustomed to 90nm. Most RCAG's are elevated but not mountain top(hill top,yes), by any means. And lots of T1 copper, it's crazy how much T1 copper is out there.

As for "line of sight", growing up in the ham world, that was all you could think of when placing an antenna. Not in their world(FAA), they have there RCAG site which is the bottom of the cone(narrowest) to the top(widest), that is the simplest why to explain it. They mount their antennas on fibercast poles so that the top of the cone is filled in by a lobe. They want a specific area of space covered and thats it.

Questions? Spam? Show me pictures...

 

[zla_datm]

There really isn't one uniform answer. You have to start back in the 1958-62 time frame, think like an engineer trained in tube radios, when almost ALL the RCAG/RCO/VOR/RTR sites were platted. Now, add that almost all the RCAG/(C)ASR were manned 8-16 hours a day and could tweak any radio at will. RCO/RCOA sites are usually the RCO being VHF(122.***)/UHF(363.***), the RCOA side is almost always VHF(121.500)/UHF(243.000). They try and follow a plan but with so many VHF RCAG sites transmitting 10 watts, AM you can only do so much, especially when they are fighting a commercial FM broadcaster with an ERP of 150,000-250,000 watts from an 8 bay JamPro and no filtering for 108-136mhz. I've seen on paper, were the RCAG is suppose to have a 150nm range. Not with all the rf floating around today, 100nm is doing good. Like alcahuete said, they are accustomed to 90nm. Most RCAG's are elevated but not mountain top(hill top,yes), by any means. And lots of T1 copper, it's crazy how much T1 copper is out there.

As for "line of sight", growing up in the ham world, that was all you could think of when placing an antenna. Not in their world(FAA), they have there RCAG site which is the bottom of the cone(narrowest) to the top(widest), that is the simplest why to explain it. They mount their antennas on fibercast poles so that the top of the cone is filled in by a lobe. They want a specific area of space covered and thats it.

Questions? Spam? Show me pictures...

Thank you! I understand, I am a pilot as well and the FAA in entirety can be summed with the metaphor of just building new buildings directly on top of old buildings. Trying to understand the FAA's data on what they have, and filling in the gaps where things are referenced in some documents but not others.

From a user's perspective, I hardly run into issues talking to ATC. Now I'm trying to understand the infrastructure that supports that.

 

[alcahuete]

For TRACON Sites, is there an FAA Database? Best I could find was the TWR database which has every frequency but only lists airports. Makes me assume all the TRACON sites are on the airports.

I'm sure there is somewhere, but I sure couldn't tell you where. Generally speaking, that is a safe assumption to make...except in ZLA and some of the other larger approach controls. With the small ones, yes, the radio site is usually at the airport itself. But with SCT, there are radio sites scattered all over...some at airports, some not.

 

[nd5y]

Google sat imagery isn't high enough resolution to tell if it's accurate, but street view shows two antennas on the airport. For sure one is the RCO.

In case you haven't noticed, the FAA's location data can be way off or it can just be the "official" latitude/lonigitude location of an airport.

There is a Google Earth .kml map of FAA sites with most of the RCAG and RCO locations corrected under the Maps section of this wiki article:

Aircraft - The RadioReference Wiki

wiki.radioreference.com

 

[dlwtrunked]

In the AFF database, the coordinates are 33.603911,-114.632733 off in a farm field. Makes more sense it's right by the admin building there. I have a feeling it's a typo someplace or converting to decimal got weird. No other radio out at Blythe though, just CTAF. RCO might still work, but those are being sunsetted pretty much everywhere except Alaska.

A shame the FAA isn't keeping this RCAG/AFF database more current and clean. Still curious about RTRs and if they just use antennas at the major airports.

I am sure what you are saying. In satellite view, at those coordinated, I see the FAA antenna towers.

 

[dlwtrunked]

...
My understanding of VHF is that it's Line of Site, so the RACG height + the height of an aircraft would determine range. ...

Not quite accurate. One does not add the two heights to predict range. It is calculated as
1.23*( square_root(antenna height) +square_root(height of aircraft) )
where the height is in feet and the range (ground distance) is in miles
from using the curvature of a round earth (excluding hills, building etc.). This adds the horizon range for the two towers (adding the heights does not do the right thing). The aircraft height dominates the calculation which is why the FAA does not bother putting the ground antennas on taller towers as they use ones tall enough to get over local obstructions.

 

[nd5y]

Thank you for your replies! I'm working on a project that is mapping some of this and am really trying to reconcile the FAA AFF.txt file, the RadioReference Database, and the ZLA SOP I have access to. The Grand Canyon site is throwing me off, it's not in the FAA database but is on RR and in the SOP. It got me wondering if there were similar discrepancies, which then got me thinking about how TRACONS do this (I assume piggyback on an RCAG or just on the airport(s)).

I don't think TRACON radio site location data is available. At least I can't find it in the 28 day subscrition files.
I have noticed that most larger airports have two or more sites that look just like a RCAG with the 4 or so short towers. DFW for example has 6 sites like this and none are listed anywhere as ARTCC RCAGs or AFSS RCOs.

 

[dlwtrunked]

I don't think TRACON radio site location data is available. At least I can't find it in the 28 day subscrition files.
I have noticed that most larger airports have two or more sites that look just like a RCAG with the 4 or so short towers. DFW for example has 6 sites like this and none are listed anywhere as ARTCC RCAGs or AFSS RCOs.

Generally, one should consider ARTCC entirely a separate operation from airport ATC and not likely to be at an airport. For example, in the DC area, even with Dulles with lots of land nearby, nearest ARTCC transmitters are at Leesburg (at the ARTCC) and Falls Church. I have visited around 100 large airports. Most had two transmitter sites (a few had more). None of those were ARTCC RCAG or RCO. I have noted TRACONs being associated with airport ASR radars (not FAA/USAF ARSR radars) to have their transmitters at the airport relative to the coverage of that frequency. That makes since since it is the radar serving that airport also.