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I would think it would rather depend on what you "shove" (that's a technical term) down the leaky coax. Presumably there has to be some sort of wide bandwidth receiver that picks up the RF signals and drives them into the coax. If it only operates in the VHF spectrum, it's not going to retransmit MW spectrum signals.There are probably many more reasons than that. I'll bet syhprum has a much better answer!
Higher the frequency permits the wave to pass through most solid structured matter, with less or no interference.
Quote from: tommya300 on 27/09/2010 16:14:36Higher the frequency permits the wave to pass through most solid structured matter, with less or no interference.Isn't it usually the other way around? Waves tend to go through/around things that are smaller than their wavelength without being disturbed. Higher frequency means shorter wavelength, which means it would pass through less matter undisturbed. Lower frequency means longer wavelength, which means it can pass through more matter.This is why you can hear the bass beat of your noisy neighbor's stereo, but not the treble. It's low frequency so it goes through the wall easily.
Not sure if the audio analogy is quite right though. I think the reason you can hear the bass is because it has so much more power than the higher audio frequencies that it causes your walls to act as a secondary speaker rather than actually passing through the wall.
When I worked in central London I used to drive home via the Blackwall tunnel which in those days had no 'leaky coax' system but rather smooth reflective walls.I found this was a useful place to test the efficiency of various car radio antenna systems.with my Ford I could get about 200m into the tunnel before I lost the signal but when I upgraded to a BMW it was nearer 400m, I think the reason why MF reception is not provided is because of the high level of interference generated at low frequencies by the fluorescent lighting and often car electrical systems.
The Ford was just a 2 liter not a gas guzzler, the FM held up for about 200m then flutered out.
In a grill the important scale is the length of the wires, which make it up. These are much longer than the microwave wavelength. In the same way that a long wavelength e/m wave doesn't see a small solid object, it also doesn't see a small hole, so the grill is apparently solid to the microwaves.To the very short wavelength light, the grill looks like a grill, the diffraction effect is of order a micron, so the grill looks like a grill, light goes through the holes but not the wires.
is it simply because the wavelength of FM matches the entrance of the tunnels so it diffracts/bends around corners better?
Here is the bit about AM/FM. I'm afraid it's all a bit anecdotal."They also wanted to put in AM/FM radio over the airways and rebroadcast in the tunnels, so we had to provide for all four of those," Chen said. "Any time you have four different RF sources, the chances of having co-channel interference is higher."To avert problems, the carrier created specially made cross-band couplers to eliminate interference. But the challenges did not end there. Chen said AT&T also had to adhere to power limitations. If it put more power into the system than Bell Atlantic or the Port Authority did, it would create interference."From: http://connectedplanetonline.com/wireless/mag/wireless_trouble_tunnels/
Quote from: mcjhn on 29/09/2010 00:41:00is it simply because the wavelength of FM matches the entrance of the tunnels so it diffracts/bends around corners better?I am having a bit of difficulty trying to verify this.Can you help me find any creditable information to back this up?Please display a URL that will lead me to this, highly curiousI thought I seen something about 5 meters referring to what you are saying, but I can not seem to find it again