Posted: 7/23/2012 5:01:06 PM EDT
| I like to listen to air traffic controllers at work. My office is on the 43rd floor and I can see Hartsfield International airport when I look out the window. But when I tune in the frequency for any of Atlanta's towers, approach, departure, ATIS, etc. on my scanner I cannot hear anything. I know my scanner works, because when I'm at home I can hear the pilots speaking, but not the controllers. I know I shouldn't hear the controllers because I don't have line of sight with them at home. Any thoughts on what might be causing the problem? |
| Hmmm, if you know you are on the right frequencies, then front end overload may be desensing the reciever. Try removing the antenna to de-sensitize the reciever. The de-sense may be coming from a source other than the airport, especially if your building has any antennas on top of it. How does it act on FM listening to the NOAA WX broadcasts? |
|
IIRC the air controllers use a frequency close to 2 meters.
When I was taking my ham test I remember that 7cm is preferable to 2 meters inside buildings because the building materiels tend to block 2 meter transmissions Maybe the signal is being blocked by all the glass and walls. FWIW |
| I never thought of the building blocking the signal. The mutten bars on the windows are aluminum and about 24 inches apart. Maybe the building is acting as a faraday cage. I did try taking the antenna off and that didn't work. Any way to overcome the building blocking the signal? |
|
Quoted:
Any way to overcome the building blocking the signal? Outside antenna? Or scotch tape a little wire antenna on the window. I'd be more tempted to think you have a front end overload. Try opening the squelch and see what you hear, if it's just the normal static or if it's garbled other kinds of transmissions. |
|
The aircraft are much closer to the tower than this scanner. It doesn't seem likely that it is front end overload. I used to run around an airport with a scanner and it never overloaded. The entire overload argument seems a bit far fetched. Much more likely is the building problem. Not only is all of the steel and aluminum an issue, but most hi-rise buildings use metallic coatings on the glass windows to reduce solar heat gain. These coatings will seriously interfere with radio reception. How well does a regular FM radio work inside your office? |
|
Quoted:
The aircraft are much closer to the tower than this scanner. It doesn't seem likely that it is front end overload. I used to run around an airport with a scanner and it never overloaded. The entire overload argument seems a bit far fetched. Much more likely is the building problem. Not only is all of the steel and aluminum an issue, but most hi-rise buildings use metallic coatings on the glass windows to reduce solar heat gain. These coatings will seriously interfere with radio reception. How well does a regular FM radio work inside your office? I'm thinking this^^ Had that problem picking up wifi in a highrise with directional antenna. |
|
Quoted:
Regular FM radio works just fine. I'll stop by Radio Shack and see if I can get an antenna to tape to the window and see if that works. The FM runs of a frequency range much lower than the airport band. Whole the upper end of the FM band is 108 Mhz, the Air band, IIRC correctly is in the 130 Mhz range. Closer to the 2 meter nband than the FM band. All of this is just me sayin' and very well may mean nothing. |
|
Quoted:
The aircraft are much closer to the tower than this scanner. It doesn't seem likely that it is front end overload. I used to run around an airport with a scanner and it never overloaded. The entire overload argument seems a bit far fetched. Aircraft radios have good front end filters and are limited to the aviation band, your scanner you used to run around the airport with was not at 400 feet up. The nature of most scanners is they have poor front end filtering and are highly susceptible to overload. You pick up a whole lot of signals at high levels when you're 400 feet up in a metropolitan area. Unless the overload is coming from RF inside the building the outside/window antenna may just make it worse. I don't know if you'd get enough attenuation from a 1/4 wave coax stub as a bandpass filter to be useful or not. |
|
Quoted:
Regular FM radio works just fine. I'll stop by Radio Shack and see if I can get an antenna to tape to the window and see if that works. FM broadcast is also in the neighborhood if not north of 5-10kW transmit power where as the ATC radios are in the 10W range and the aircraft transceivers are abound 25W. |
|
Quoted:
Quoted:
The diff's between FM radio band and AM aviation band aren't that significant. Let's see how he makes out with the antenna experiment. The experiment didn't go well. No signal. Do you have the tools/ability/inclination to mess with coaxial cable and connectors? Next suggestion would be to construct a 1/4 wave shorted stub as a bandpass filter for the aviation band, to knock down the out of band signals and (probable) front end overload. |
|
Yep, if you have an FM broadcast stn nearby you might get some overload/desense w/ your scanner.
Try it somewhere else. Also try other frequencies in the aviation AM band. Navaids are from abt 108 to 118 mc and voice coms from abt 118 to 135 mhz. You can rapidly look up all of them by airport or navaid/state at airnav.com. http://www.airnav.com/ |
|
Quoted:
Yep, if you have an FM broadcast stn nearby you might get some overload/desense w/ your scanner. Try it somewhere else. Also try other frequencies in the aviation AM band. Navaids are from abt 108 to 118 mc and voice coms from abt 118 to 135 mhz. You can rapidly look up all of them by airport or navaid/state at airnav.com. http://www.airnav.com/ There is a broadcast ant. for a local radio station on an adjacent building. I think it's a 25KW station. |
|
Quoted:
Quoted:
Yep, if you have an FM broadcast stn nearby you might get some overload/desense w/ your scanner. Try it somewhere else. Also try other frequencies in the aviation AM band. Navaids are from abt 108 to 118 mc and voice coms from abt 118 to 135 mhz. You can rapidly look up all of them by airport or navaid/state at airnav.com. http://www.airnav.com/ There is a broadcast ant. for a local radio station on an adjacent building. I think it's a 25KW station. That's most likely the source of your troubles. Go over and see if they will shut down so you can test the front end overload theory. 
|
|
Quoted: Quoted: Quoted: Yep, if you have an FM broadcast stn nearby you might get some overload/desense w/ your scanner. Try it somewhere else. Also try other frequencies in the aviation AM band. Navaids are from abt 108 to 118 mc and voice coms from abt 118 to 135 mhz. You can rapidly look up all of them by airport or navaid/state at airnav.com. http://www.airnav.com/ There is a broadcast ant. for a local radio station on an adjacent building. I think it's a 25KW station. That's most likely the source of your troubles. Go over and see if they will shut down so you can test the front end overload theory. Yeah, but...if that station was causing overload (desensitization, really) then no other FM radio stations would come in either. Can the OP receive other FM radio stations? |
|
There is a broadcast ant. for a local radio station on an adjacent building. I think it's a 25KW station.
What frequency is it on? Something like this might be worth trying if it's front end overload? |
|
Quoted:
Quoted:
Quoted:
Quoted:
Yep, if you have an FM broadcast stn nearby you might get some overload/desense w/ your scanner. Try it somewhere else. Also try other frequencies in the aviation AM band. Navaids are from abt 108 to 118 mc and voice coms from abt 118 to 135 mhz. You can rapidly look up all of them by airport or navaid/state at airnav.com. http://www.airnav.com/ There is a broadcast ant. for a local radio station on an adjacent building. I think it's a 25KW station. That's most likely the source of your troubles. Go over and see if they will shut down so you can test the front end overload theory.
Yeah, but...if that station was causing overload (desensitization, really) then no other FM radio stations would come in either. Can the OP receive other FM radio stations? Knot neccesarilly... 
|