Joined: 03 December 2012
I'm working on a project which involves designing a private mobile radio (PMR) for a stadium and i'm struggling to find the attenuation for regular building materials at 450 MHz to do the modelling.
Any help or advise would be appreciated in this regard.
The building materials i'm working on are concrete, blockwork with concrete in-fill, drywall, external and internal glass, wood and metal.
Joined: 15 January 2005
Bit of a black art this subject.
The attenuation of building materials will vary with frequency and the amount of metal.
Glass and wood will only attenuate about 10%, but getting into reinforced concrete and it goes up to 80% or 90%.
Even 'professional' prediction programs in free air are just a guide until the real world takes over.
In another life I used to run wide area duplex PMR systems. Our Sutton Coldfield worked like a dream until one day music starting being broadcast over the system. A lot of investigating discovered that a mix of our transmit frequency, Radio 4, Radio 2 and another PMR system on the site intermodulated with the new Classic FM test transmissions and come out spot on our receive frequency - and round and round it went. Radio broadcasts come under the Home Office in those days and even though it was only test broadcasts, they would not move. No other frequencies were available to us, so it had to be shut down as unusable.
You will need to do a lot of assuming and short of 'brute force' power levels, you are almost bound to get dead spots. These can be minimised by identifying the best base antenna(s) location.
Best I can do and I hope it helps.