ARTCC Microwave Towers

Status
Not open for further replies.

Lynch_Christopher

Member
Database Admin
Joined
May 28, 2006
Messages
820
Location
Bethpage, NY
Over the past few years I have noticed that the FAA has started to take down the large microwave towers at various en-route centers across the country. With everything going over fiber optic lines these days any idea what these microwave towers were used for. After looking at google street views seems like not all the microwave towers were removed at all the centers for example Miami, Atlanta, Washington, as of July 2018 New York still had their 3 towers. Wouldn't it make sense to have some sort of microwave backup just in case the fiber lines get cut by mistake?


Kansas City Center July 2014

87100

Kansas City Center July 2019
87099


Boston Center October 2012
87102





Boston Center Nov 2019
87101

Chicago Center April 2012.
87103


Chicago Center July 2019 Looks like the one smaller radio tower is remaining.
87104


Indianapolis Center December 2017
87105

Indianapolis Center June 2019
87106
 

alcahuete

Member
Premium Subscriber
Joined
Jul 24, 2015
Messages
1,444
Location
Antelope Acres, California
With everything going over fiber optic lines these days any idea what these microwave towers were used for.
They were used for communications to the RCAG sites through various relay stations and such. All fiber now.


Wouldn't it make sense to have some sort of microwave backup just in case the fiber lines get cut by mistake?
You're using common sense. Can't be doing that when you think about why the government does the things they do. At the end of the day, it comes down to cost, and the effort associated with maintaining two completely separate systems and equipment. The costs are truly astronomical. As technology improves, you're going to see a lot of systems go away.
 

AI7PM

Member
Premium Subscriber
Joined
Sep 6, 2015
Messages
563
Location
The Intermountain West
The original system was called "RML", the RADAR Microwave Link. It's how RADAR data from remote RADAR sites was brought back to the Center. It was analog, and as I recall had 25 channels on a given link. The additional channels were used for back up radios, usually located at a RADAR site, on the RML towers, or by phone lines from an RML tower. Normal (RCAG) radio site linking was via phone lines, not the RML In the late 80s, the RML system was updated to digital and renamed RCL, Radio Control Link. It now had 900 channels. Some paths to RCAGs were then added to reduce longline costs. To create (NADIN) the National Data Interchange Network, FAA had additional links built to connect the 20 separate ARTCC RCL systems into one network. Along came IP, and moving data through other means became more cost effective. Many elements of the RCL system have been decommissioned. What remains is in use for various reasons, some having to do with the location of RADAR and RCAGs. Many are in areas or remote locations where fibre isn't available.
 

ATCTech

Active Member
Joined
Aug 13, 2002
Messages
1,492
AI7PM, that's an excellent summary and closely resembles what we did here in Canada over a couple of decades. And you're spot-on, rural farmer's fields, mountain tops and in our case Arctic tundra aren't particularly fiber-friendly or even reliable copper-pair places. We're using satellite in and out of some truly remote sites.
 

xms3200

Member
Joined
Jul 18, 2018
Messages
56
Location
Cleveland, Ohio
Using these microwave links to communicate with RCAG sites, isn't there a slight delay from when the controller transmits at one location to the RCAG site at another location actually transmitting....as compared to like a tower where the antenna is right up there on the roof.
 

evilbrad

My head makes a bad antenna
Joined
Aug 11, 2004
Messages
217
Chicago Center(Aurora) used to have a beautiful log periodic hf antenna. :( it probally ended up in scrap very sad.....I had never caught anything on close call vhf or uhf Govt freqs for FAA other then reg close call hits on VHF air

A ham and former employee told me the hf lp was mainly backup at one time or another.
 

nd5y

Member
Joined
Dec 19, 2002
Messages
9,447
Location
Wichita Falls, TX
Using these microwave links to communicate with RCAG sites, isn't there a slight delay from when the controller transmits at one location to the RCAG site at another location actually transmitting....as compared to like a tower where the antenna is right up there on the roof.
Yes. It takes 6.34 microseconds for a radio signal to travel 1 nautical mile (in air).
For voice communications that is totally meaningless and not noticeable even on HF paths of thousands of miles.
Optical fiber is slower than RF through air but still the delay makes no difference for voice communications.
 

alcahuete

Member
Premium Subscriber
Joined
Jul 24, 2015
Messages
1,444
Location
Antelope Acres, California
Using these microwave links to communicate with RCAG sites, isn't there a slight delay from when the controller transmits at one location to the RCAG site at another location actually transmitting....as compared to like a tower where the antenna is right up there on the roof.
RADAR too! I forgot that, as AI7PM noted. Now they really do nothing. There is a slight delay, but the signals are traveling at the speed of light. You're looking at completely unnoticeable delay.

Chicago Center(Aurora) used to have a beautiful log periodic hf antenna. :( it probally ended up in scrap very sad.....I had never caught anything on close call vhf or uhf Govt freqs for FAA other then reg close call hits on VHF air
It was a HF log periodic used as a backup system from ARTCCs to Headquarters/Command Center in Washington D.C. Now it's satellite phones.
 

JDrisc3480

Member
Joined
Aug 10, 2010
Messages
189
Location
Shannon, North Carolina
They were used for communications to the RCAG sites through various relay stations and such. All fiber now.




You're using common sense. Can't be doing that when you think about why the government does the things they do. At the end of the day, it comes down to cost, and the effort associated with maintaining two completely separate systems and equipment. The costs are truly astronomical. As technology improves, you're going to see a lot of systems go away.
I understand the reasoning behind it however, I am of the mind set that technology is great, as long as it works. What happens when the newer systems go down and there is no back up?
 

nr2d

Member
Premium Subscriber
Joined
Dec 28, 2003
Messages
498
Location
Laurel Springs, NJ
The FAA is looking into several backup systems using LTE and Iridium satellite. When I was still in Airways Facilities out of Trenton Mercer County airport we had RCL sites at Imlaystown and South River, NJ. I spent many an hour doing line runs at each site. I think the sites relayed radar info from the ARSR radar in Trevose, PA and Phily Intl Airport. I'm pretty sure both sites have been decommissioned for many years.

I know the RML and TML sites at the FAA Tech Center have been decommissioned and dismantled.

As someone said the log periodics at the centers were for backup communications to FAA HQ. We had an LPA and a sterable discone HF system at the Tech Center but again the system has been decommissioned for at least 5 years.
 

Lynch_Christopher

Member
Database Admin
Joined
May 28, 2006
Messages
820
Location
Bethpage, NY
The FAA is looking into several backup systems using LTE and Iridium satellite. When I was still in Airways Facilities out of Trenton Mercer County airport we had RCL sites at Imlaystown and South River, NJ. I spent many an hour doing line runs at each site. I think the sites relayed radar info from the ARSR radar in Trevose, PA and Phily Intl Airport. I'm pretty sure both sites have been decommissioned for many years.

I know the RML and TML sites at the FAA Tech Center have been decommissioned and dismantled.

As someone said the log periodics at the centers were for backup communications to FAA HQ. We had an LPA and a sterable discone HF system at the Tech Center but again the system has been decommissioned for at least 5 years.
Very interesting thanks for the info. Interesting that they are considering LTE and Iridium satellites for backup capabilities. I also remember when I used to live in New Hampshire would visit the FAA regional office in Burlington, Mass a few times and noticed that there was a large HF antenna on the roof but looks like that has long been decommissioned, so the regional offices must have also had the HF backup capabilities to communicate with FAA Headquarters.
Now that I live on Long Island it looks like there is a big FAA relay site in Wantagh and was always curious if that was used for the center or the New York TRACON
 
Status
Not open for further replies.
Top