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Topic: Can Air Temperature Affect Radio Waves?
Username: Mr Spaceman
Posted 2004-01-14 22:58:37 and read 11961 times.

Hi guys.

I live 6 nautical miles southeast of Toronto's Buttonville Airport (YKZ). It's a GA airport with 2 runways and I live directly under the approach path for runway 33. Even though I'm not that far away from the airport, I can't normally receive the transmisions from the control tower. I've owned an airband receiver for over a year and have never been able to hear the controllers in the tower at buttonville airport, however, for the past 2 to 3 weeks I have been able to hear the controller in the tower. Sometimes his signal is weak, but it's mostly good & clear.

The only thing that's changed over the past 3 weeks is the weather. Toronto has been experiencing a very cold mass of Arctic air for several weeks now, which has brought with it daytime temperature highs of only -15 degrees Celcius.

This morning at 10 am the temp in Toronto was -22 degrees Celcius with a windchill factor of -32 C!!! (it's was just a tad cold outside.  Laugh out loud Toronto is currently under an extreme cold weather alert), and I could hear the controller at Buttonville Airport as clear as could be.

So I'm wondering ....... can air temperature affect radio signals? Does the colder, thus denser air allow radio signals to travel farther?

Part of my mind is telling me that the answer is NO. Perhaps the transmissions from the control tower have been improved and now they have a stronger signal, but, part of my mind keeps wondering about the weather because of the coincidence between the temperature and being able to hear Buttonvilles's control tower.

Any thoughts about this would be great.


Chris  Smile



Topic: RE: Can Air Temperature Affect Radio Waves?
Username: MITaero
Posted 2004-01-14 23:16:29 and read 10278 times.

Hey,

Radio waves, like light waves, infrared waves, microwaves, etc. are electromagnetic waves. The difference on a cold day when compared to a warmer day would be pretty insignificant, since the speed of light would change very little. A less subtle case would be transmitting through water instead of air (the difference in speed of light is what causes refraction). I think your gut instinct is right.

Topic: RE: Can Air Temperature Affect Radio Waves?
Username: Mr Spaceman
Posted 2004-01-14 23:24:42 and read 10279 times.

Hi guys.

I forgot to mention that I am aware of how a change in atmospheric conditions can cause what's known as SKIP. With regards to my question about Buttonville Airport, I've been able to receive the controller's transmisions steadilly, everyday, for a few weeks now, and SKIP doesn't normally affect radio signals for as long as that, at least not from my experience with Citizen Band radios (CB's), back in the 1970's.

Last sumer, I was able to hear the controllers in the 2 towers at Toronto International Airport (YYZ) on 4 different occasions (with different weather conditions & at different times). I figured that was caused by SKIP because I live 16 nautical miles from YYZ.

The control tower frequency at Buttonville Airport is 124.8. Is it possible that their radio signal has been made stronger? Can you increase the range of a 124.8 Megahertz signal? If so, how? All I know is that it's in the VHF Avionics Band.

Here's a photo of Buttonville Airport. I used to train there back in the mid 80's.  Big thumbs up


View Large View Medium
Click here for bigger photo!

Photo © Angus Wighton



PS, incase someone's curious, I have an ICOM IC-R2 communications receiver. It signal band range is from 0.495 MHz AM to 1309.995 MHz FM.

Chris  Smile

Topic: RE: Can Air Temperature Affect Radio Waves?
Username: Mr Spaceman
Posted 2004-01-15 00:07:11 and read 10261 times.

Hi guys.

> MITaero.

Thanks for your reply.

Yeah, as I mentioned, part of my mind (my gut feeling) was saying the answer would be NO, but I had to ask to find out for sure.

So then that leaves me with the sudden ability to hear the control tower at YKZ without knowing why. I guess they have made their transmiting signal stronger.

Can someone explain how a radio transmission signal on frequency 124.8 MHz can be made stronger and thus be given a farther receiving range?

PS, I first posted this topic in the Tech/Ops forum, but the A.net crew moved it over here. Any help with this question would be much appreciated.


Chris  Smile

Topic: RE: Can Air Temperature Affect Radio Waves?
Username: MikeTheActuary
Posted 2004-01-15 05:09:43 and read 10227 times.

I'm not sure it's safe to say that weather doesn't affect radio waves.

When a student at the University of Illinois - Urbana, there were a couple of times I was able to DX television stations from Chicago, during some unsettled weather conditions.

A quick Google-search provides a reference to http://www.4reference.net/encyclopedias/wikipedia/FM_DX.html Note the entry for tropospheric ducting.

However, that's probably not quite the phenomenon to explain the improved reception of the YKZ tower frequency.

Topic: RE: Can Air Temperature Affect Radio Waves?
Username: Mr Spaceman
Posted 2004-01-15 17:54:37 and read 9440 times.

HI guys.

>> MikeThe Actuary, Thanks for your reply & the link you provided.

Although the info in the link is good to learn, because it mentions a rise in air temperature, I don't think this has been the cause either, as you mentioned. Plus the weather hasn't been stable. There's been many cold & warm fronts moving through the area during the period when I could receive YKZ's control tower.

"Tropospheric ducting and tropospheric refraction tend to happen during periods of stable, anti-cyclonic weather. In these propagation methods, when the signal encounters a "rise" in temperature in the atmosphere instead of the normal decrease" ......

http://www.4reference.net/encyclopedias/wikipedia/FM_DX.html


Chris  Smile


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