Hey technogeek
dept can you please tell me if heavy rain can interfere with radio signal propagation???, IE with your UV5R phase pistols still reach as far if its persistantly raining heavily, and if I can be cheeky does heay low cloud and fog affect radio signals ?
Respects NR
Rain can effect radio waves, .........the raindrops can obsorbs power from the radio waves.
Fog should also to be seen as another form of rain in this instance, because fog is made up of moisture,... it depends on so many things, the time of year, daytime, nighttime,..and how heavy the weather is
Hmmmm more contentious issues for me to chew over, does and increase in power output from the transmitters overcome the loss of signal strength or is the strength of signal unimportant?
The strength of the output will always help you, the more power the stronger the signal,.. but the propagation is always there,
Propergation is also to do with radio waves penertrating building and mountains, not just the weather,.. the higher the frequency the shorter the wave lengths so building can be a problem... HF is not the way to go for most people
Vhf, has wider wavelengths and so can deal with obsticals better,... but the weather will always be an added problem
Gracias Senor Highlander, noting the shite weather at the moment I got to think that its when its absolutely worst when we are most likely to need our emergency radios, and accordingly I'm back to my old grumble that 4 or 5 watts isnt going to cut the mustard, I'll not persue this subject further cos its only going to start the arguments and counter arguments off yet again.
The higher the frequency (shorter the wavelength), the worse it is affected by rain, fog, etc. sky satellite TV reception, which is in the gigaHertz range, is often disrupted in very heavy rain.
So correct me if I am wrong but is PMR 446 of 440 to 447 Mhz higher than CB radio at 28 to 30 Mhz ?
and is amplitude modulation better in shit weather than frequency modulation??
I think I am right in saying that you tend to get more interference with AM than you do with FM.
I dont think you would need to worry too much about the weather,..all thats been said is correct, but you would not be trying to get hold of anyone in China, I think our needs would be closer to home,..so I dont think the weather wouldnt effect our communications to any great degree,..it woulde depend on lots of things,... including the antenna being used at the time
Most communications might well be from mobile sets, or hand held radios,.. these often rely on `repeaters`, electrical gadgits placed on radio masts, that help bounce the signals from sets on to a more distant receiver, if the emergency is say a solar flare, then these repeaters would be wiped out,..so mobile sets and hand held would be little more than `line of sight`,.. maybe as little as a mile [or less] unless you were on high ground
I should say that my first paragraph regarding the weather was realy refering to amature radio base stations, sets with a good antenna.
(24 November 2012, 23:49)NorthernRaider Wrote: [ -> ]So correct me if I am wrong but is PMR 446 of 440 to 447 Mhz higher than CB radio at 28 to 30 Mhz ?
and is amplitude modulation better in shit weather than frequency modulation??
Yep, PMr446 is UHF, CB is HF. I don't know if there's a difference between AM and FM as far as weather is concerned, but AM is subject to more interference, as has been mentioned, especially electrical interference.
UHF and above can be affected by very local weather conditions, whereas HF DX (long distance) is more affected by ionospheric conditions.
Personally, for short range (<10km) tactical communication, I'd go VHF. For more regional coverage I'd use HF with an NVIS antenna. This avoids need for line-of-sight. NVIS (Near Vertical Incidence Skywave) basically shoots your signal straight up in the air. It bounces off the ionosphere and comes scattering back down. Imagine pointing a garden hose straight upin the air and think about the fallout pattern of the water. You can make an NVIS antenna easily by taking any horizontal antenna (say a dipole or long wire) and moving it closer to the ground (or your earthed surface). For example, if you have a long HF whip antenna on your car, bend it over in an arc and tie the end down with some (insulating) cord - bingo, an NVIS antenna. NVIS won't work with VHF or above - the energy of the signal is too high and it will punch through the ionosphere.
Sorry if this is teaching grandmother to suck eggs, or if this has been covered elsewhere.
Thanks chaps I appreciate your information and advice, I dont want to sound negative or troublesome but the more I learn about radios and the various frequencies / systems the more I believe they wont be of any use to my group, They are just too limited and ineffective for practical use. At best on a clear day with line of site you still require LUCK to be on your side to be guarenteed any decent range from a handheld set, and in a normal urban or hilly, or wooded environment and / or day days with rain or low cloud their use is apparently even more limited.
I think RV points and couriers will be better suited to my own groups needs and the topograpghy in Co Durham.