GrowMoreWeed
7th February 2009, 06:13
Kitz said he'd be interested in seeing what I get up to on the radio so I thought I'd make a thread in case anyone else was interested too.
First of all, radio is supposed to be fun. It's all about experimenting and generally "cocking about" with technology! I love building antennas and trying new modes of communication.
First a little bit about how "freebanding" works. In Europe and the US, there is a standardised set of frequencies that you are allowed to use (26.965 - 27.405MHz) known as the "Mid band" (aka CEPT40 and FCC40). Here in the UK, we have a UK specific band too (27.60125 - 27.99125MHz) known as the UK40 (aka "the muppets" after both the people on there and the original MPT27/81 standard sticker that was on all the radios). Freebanding (or outbanding) is operating outside these frequencies, usually in the bit inbetween the 2 bands (27.415 - 27.600 and somtimes higher) or sometimes below the mid band down on 26MHz. Generally, anywhere on the 11 metre band (11m is the length of one wavelength).
Frequencies get allocated by national/international agreement so they are standardised wherever possible. For example, you don't want kids walkie talkies on the same frequency as air traffic control! The frequencies I am talking about are either not allocated at all, not allocated in every country or may in fact be allocated as a Citizens band in some other country.
Each country tends to have a specific frequency (or channel) used for calling out for contacts but there are also international calling frequencies, 27.555MHz and 26.285MHz are probably the most popular using Single Side Band modulation (https://secure.wikimedia.org/wikipedia/en/wiki/Single-sideband_modulation), usually USB (Upper Side Band), rather than FM, AM or indeed LSB (Lower Side Band) although these are used around the band.
SSB allows for much greater efficiency of your output power ie: you'll get further using 10 watts of SSB than you would with 10 watts using FM. Not only that but the 11m band is susceptable to ionospheric propagation where your signal doesn't fly off into space, it actually bounces off the upper atmosphere and comes back down to Earth again, possibly thousands of miles away from where you are! This is where my interest lays.... DXing (trying to contact distant stations).
The great thing about propagation is that when it's strong, you don't need a monster antenna or loads of power, sometimes even a wet bit of string and 4w is enough to make contacts all over the planet. There are several different types of propagation and it's a massive subject in itself, way beyond the scope of this post. Most of it is influenced by the Sun's activity (solar flares and the like). The sun has an eleven year cycle of activity and we're currently at the solar minimum (which means very little propagation) but reasonably long contacts (inter-EU for example) are still possible.
"So what do I need to do this?" I hear you ask. Basically, you need:
A radio capable of SSB
Mic
Power supply or car battery if you are mobile
Coax cable between radio and antenna
Antenna
A desire to tinker with stuff
Some courtesy once you get on air
Thats the bare minimum but it's all too easy to get carried away with all the boxes with flashy lights and switches and BUTTONS!!
I'm currently into sending and receiving data over radio. Pictures, text and even binary files are all possible. Have a look at MixW and EasyPAL for this sort of thing.
I think I've rambled enough for now! Fire away with any questions and I'll also try and get some pics up. :D
Further reading:
http://www.transmission1.co.uk
http://www.ukcb.org
http://www.11mdx.co.uk
http://signalengineering.com/ultimate/
First of all, radio is supposed to be fun. It's all about experimenting and generally "cocking about" with technology! I love building antennas and trying new modes of communication.
First a little bit about how "freebanding" works. In Europe and the US, there is a standardised set of frequencies that you are allowed to use (26.965 - 27.405MHz) known as the "Mid band" (aka CEPT40 and FCC40). Here in the UK, we have a UK specific band too (27.60125 - 27.99125MHz) known as the UK40 (aka "the muppets" after both the people on there and the original MPT27/81 standard sticker that was on all the radios). Freebanding (or outbanding) is operating outside these frequencies, usually in the bit inbetween the 2 bands (27.415 - 27.600 and somtimes higher) or sometimes below the mid band down on 26MHz. Generally, anywhere on the 11 metre band (11m is the length of one wavelength).
Frequencies get allocated by national/international agreement so they are standardised wherever possible. For example, you don't want kids walkie talkies on the same frequency as air traffic control! The frequencies I am talking about are either not allocated at all, not allocated in every country or may in fact be allocated as a Citizens band in some other country.
Each country tends to have a specific frequency (or channel) used for calling out for contacts but there are also international calling frequencies, 27.555MHz and 26.285MHz are probably the most popular using Single Side Band modulation (https://secure.wikimedia.org/wikipedia/en/wiki/Single-sideband_modulation), usually USB (Upper Side Band), rather than FM, AM or indeed LSB (Lower Side Band) although these are used around the band.
SSB allows for much greater efficiency of your output power ie: you'll get further using 10 watts of SSB than you would with 10 watts using FM. Not only that but the 11m band is susceptable to ionospheric propagation where your signal doesn't fly off into space, it actually bounces off the upper atmosphere and comes back down to Earth again, possibly thousands of miles away from where you are! This is where my interest lays.... DXing (trying to contact distant stations).
The great thing about propagation is that when it's strong, you don't need a monster antenna or loads of power, sometimes even a wet bit of string and 4w is enough to make contacts all over the planet. There are several different types of propagation and it's a massive subject in itself, way beyond the scope of this post. Most of it is influenced by the Sun's activity (solar flares and the like). The sun has an eleven year cycle of activity and we're currently at the solar minimum (which means very little propagation) but reasonably long contacts (inter-EU for example) are still possible.
"So what do I need to do this?" I hear you ask. Basically, you need:
A radio capable of SSB
Mic
Power supply or car battery if you are mobile
Coax cable between radio and antenna
Antenna
A desire to tinker with stuff
Some courtesy once you get on air
Thats the bare minimum but it's all too easy to get carried away with all the boxes with flashy lights and switches and BUTTONS!!
I'm currently into sending and receiving data over radio. Pictures, text and even binary files are all possible. Have a look at MixW and EasyPAL for this sort of thing.
I think I've rambled enough for now! Fire away with any questions and I'll also try and get some pics up. :D
Further reading:
http://www.transmission1.co.uk
http://www.ukcb.org
http://www.11mdx.co.uk
http://signalengineering.com/ultimate/