Your view: you’re never too old for modern technology

The metal garage door acts as a ‘Faraday cage’ and greatly decreases the signal strength but does not eliminate it.

With hindsight, I don’t think my explanation was very good, Beryl. A Faraday cage would surround the receiver, providing greater loss (attenuation) of the radio signal. Nevertheless, the effect of the metal garage door is to decrease the signal.

Hi Beryl

Although metal may act as a radio signal attenuator, different metals have different levels of attenuation. In a Faraday cage, the whole ‘cage’ is enshrouded in a fine metal mesh which importantly is well earthed, thus minimising any signal penetration.

A garage door, on the other hand, is hanging on hinges and is well insulated from the ground. So it may act as an passive director in the same way that the elements of an antenna are directors and reflectors to strengthen the signal.

Sometimes when you drive you car through a long tunnel, the radio may still continue to work throughout the tunnel. This is achieved by installing appropriate repeating antennas along the tunnel which passes the signal from antenna to antenna. These are called passive repeaters and are very common in Europe.

I’m guessing that your garage door acts as a passive repeater.

Another phenomena to try with your car key is to walk away from your car until the key can no longer open/close the lock (you’re out of range). Now hold the key firmly against your forehead with the pointed bit facing the car and activate the key again!

Hi Terfar and Wavechange

I am not at all sure exactly what I have let myself in for here but many thanks for the explanations – I got the gist of it! I was always under the impression a Faraday Cage was intended to distribute the electromagnetism penetration around the exterior thereby protecting the interior, which added to the confusion. The garage door is an up and over type and is not electronically operated, which is why I could not understand how the signal could penetrate through a metal door! I discovered this phenomenon one day when I couldn’t remember if I had locked the car after closing the garage door so promptly pressed the remote key to see what would happen [being too lazy to re open it] and was truly amazed at the result!

I will try the little experiment with the key as long as it doesn’t trigger a migraine headache in the process, but would hazard a guess that it has something to do with the amount of static my body emits!

I thought I was the only one who holds their car remote control against their head, as Terfar has described. I do this if I am not sure I have locked the door and am out of normal operating range. 🙂

Getting back to technology, I often put my MiFi (wireless version of a mobile broadband dongle) on the roof of the car when I stop for a break on a journey and want to use my iPad. That avoids the screening effect of the roof etc of the car.

In days gone by, cars used externally mounted aerials to compensate for the screening effect of the bodywork. Then we had some models that used the rear window heater as an aerial. My present car has excellent reception on both DAB and FM bands and I suspect that the aerial is at the edge(s) of the windscreen. I hope I am still interested in how things work when I get older.

Can you use an Apple tv box to link your iPad to you TV?

You can. Once you have a relatively inexpensive Apple TV connected to your set, simply select the HDMI channel to which it’s connected and the Apple TV will automatically sense the iPad. It’s then only a matter of selecting the app concerned and using the ‘airplay’ option to display the iPad screen on the TV.