tomatoes
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Post by tomatoes on Nov 17, 2016 7:36:58 GMT 10
I am a complete beginner at the communications stuff. I've read a few threads here and end up a little lost. There is ham radio but I think I read discussion about needing a licence for that? And I think there's a different sort - perhaps like a little cheap set of two that I bought from Dick Smiths yrs ago that say they have a range of about 4 km??? I just read the thread here describing the set up for bobs etc with solar chargers and that looked really interesting.
But I just don't really understand the different options, benefits, etc, or what is needed. Would someone be able give a really simple overview of it all or point me to a book or other resource? No rush, but if you have time? Just the basics in simple language and without jargon, so I can read the other posts with better understanding.
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paranoia
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Post by paranoia on Nov 17, 2016 8:30:31 GMT 10
^^ ditto what frost said
You can talk to anyone from your neighbour to people on the other side of the world...you can send anything from morse code, to voice, to data/text/pictures over radio.
What do you want to communicate and to who?? The sky is not the limit, can bounce signals off the moon or talk to the space station... Up to you how deep you want to go down the rabbit hole.
If you just want to gather intel maybe a scanner will do you.
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shinester
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Post by shinester on Nov 17, 2016 13:33:23 GMT 10
The 'very' simple version, this is a big, deep and complex subject that I'm hardly an expert in.
Hand held CB [Citizen] radios - 477Mhz - Typically Baofengs $20-60 - line of sight, which is typically a few KMs. No license required. You 'can' get better quality radios. Lots of accessories and options for antennas. Legal wattage to 5W. Used for person to person communication over short ranges. Very useful if you want to talk to bob a couple of streets away. Most of us preppers have a few units like this for nearby communication. Has 80 channels [which are set frequencies all close to 477Mhz]
Car mounted/base station CB radios - 477Mhz - many brands etc. Typically you'll have a 'taller' antenna and get slightly better ranges, though again, it's line of sight. Line of sight can be quite some distance, for instance mobile phones are line of sight and have less transmission power than CB, which is why you see the towers all up high. Similarly a taller antenna gives you greater range.
Legacy CB - 27Mhz - This is the old AM frequency that will usually get longer ranges for the same power output and potentially more less disrupted by obstacles/terrain. It's hardly used anymore.
Scanner - it searches frequencies/channels looking for transmissions and will 'receive' them if it finds them.
HAM - everything else - as already described the sky is the limit. You need a HAM license for this. The license isn't especially difficult, though if you do the wrong thing you might get a great deal of heat and huge fines so you do need to know what you're doing. Radio could potentially go right around the world using the stratosphere and good atmospheric conditions, or it could also be frequencies just outside normal CB, it just depends on what you're trying to achieve.
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paranoia
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Post by paranoia on Nov 17, 2016 14:14:07 GMT 10
I'll also say the 4km range listed with handhelds is only valid with perfect line of sight, when you're standing on your head, its the third tuesday of the month and you have a perfectly charged battery.
I'd encourage you to do some tests to really know their range.
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paranoia
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Post by paranoia on Nov 17, 2016 15:17:02 GMT 10
We covered upper and lower side band modulation in the HAM licence. Maybe at one stage you didnt need to operate SSB through cirtain frequencies but I'm pretty sure it's all tied up now in regulated bands.
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shinester
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Post by shinester on Nov 17, 2016 18:48:05 GMT 10
We covered upper and lower side band modulation in the HAM licence. Maybe at one stage you didnt need to operate SSB through cirtain frequencies but I'm pretty sure it's all tied up now in regulated bands. This is the proof that I don't have a clue about HAM.
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paranoia
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Post by paranoia on Nov 17, 2016 19:04:37 GMT 10
So there are two main types of modulation (the method of combining your data/voice signal into your carrier signal to create your transmit signal).
Frequency modulation (FM), changing the frequency of the transmitted signal within a band of say 6,000 Hz (+/- 3000 Hz of the 'transmit frequency') using the voice/data (modulator)
Amplitude modulation (AM), changing the power of the transmitted signal using your data as a reference (modulator).
Other types of AM modulation: SSB (single side band), LSB (lower side band), USB (upper side band) are methods to increase transmit distance on limited power.
When you transmit on a frequency, you not only transmit on your selected frequency, but on one a little above and a little below, these are called side bands.
Filtering out all else but the upper or lower side band before transmitting, increases your transmit signal relative to the power being put into the antenna, giving you extra distance/clarity as you're not transmitting what you're not using.
Hope this makes sense?
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VegHead
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Post by VegHead on Nov 17, 2016 19:23:37 GMT 10
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tomatoes
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Post by tomatoes on Nov 17, 2016 19:38:03 GMT 10
Thanks so much for the replies - have been offline all day and prob for the rest of the evening now so will have to read them carefully tomorrow.
Re the purpose, I think it will be a matter of priorities with a very limited budget. I'll have to think about it. I know what I'd really like as a priority but I think it would be too expensive at least initially.
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paranoia
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Post by paranoia on Nov 17, 2016 19:47:32 GMT 10
We'll stick to analogue systems as they're easier to understand.
OK, so think about a microphone connected to an amplifier... connected to a speaker.
You have;
[MIC] --> [AMP] --> [SPEAKER]
The microphone changes air waves into a voltage by moving the element in the mic through a magnetic field and generating electricity. You end up with a voltage signal that looks like this;
In the above scenario you simply filter out any noise, increase the signal with the amplifier and turn it back into sound waves by vibrating the speaker.
To transmit to another radio we need to add a few things.
The oscillator generates a signal based on the frequency you're choosing to use. The modulator combines (as described above) the amplifier output into the carrier wave to it can be thrown into the antenna which sends out the RF signal.
Its then received by the other radios antenna, the weak signal amplified, its then compared against an ideal signal of the same frequency as the transmitted signal and the original wave is recovered. Its simply filtered and amplified as you would in the [Mic, amp, speaker] scenario and put into the speaker... giving you the voice on the other end
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token
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Post by token on Nov 17, 2016 19:50:44 GMT 10
Great thread, shiny, you made a whole lotta sense for me and i have no idea but want to learn.
Can someone please tell me why i might want to consider Ham radio as a prepper? as i have no clue as to what i might want to do until i learn what can be done.
The other thing id like to know is, is Ham popular? I mean, is it likely that i could be in contact with heaps of people from around the world who are also preppers?
Also, what are the regulations for and how might you get found out if you did do the wrong thing, and isnt that gubmint monitoring that you dont want?
thanks for the lessons!
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VegHead
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Post by VegHead on Nov 17, 2016 19:58:26 GMT 10
Wireless Institute of Australia's website is the place to start. You'll be very surprised how many Australian Amateur Radio Operators there are and will be blown away by the numbers world-wide.
~ V ~
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paranoia
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Post by paranoia on Nov 17, 2016 20:16:41 GMT 10
Great thread, shiny, you made a whole lotta sense for me and i have no idea but want to learn. Can someone please tell me why i might want to consider Ham radio as a prepper? as i have no clue as to what i might want to do until i learn what can be done. The other thing id like to know is, is Ham popular? I mean, is it likely that i could be in contact with heaps of people from around the world who are also preppers? Also, what are the regulations for and how might you get found out if you did do the wrong thing, and isnt that gubmint monitoring that you dont want? thanks for the lessons!
Biggest thing for me is range. We could setup a country wide coms network that could operate on 12v power completely separate from any grid, phone system, internet. No other tech can do this that I know of.
If you're decent at electronics you can send text over radio and set up similar to a chatroom over radio. You can send images also.
Most HAMs just seem to be older electronics geeks to me the exception to this are all the emergency radio operators. People who run setups to be able to go into disaster areas and re-establish communications.
When the grid goes down, even hospitals, police and fire use radio to communicate... If your unit works and the other persons unit works that's all you need, no towers/infrastructure to worry about.
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paranoia
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Post by paranoia on Nov 17, 2016 20:21:01 GMT 10
My mate is a total radio nut with a 6m x 6m shed literally stuffed full of radio gear, a lot of it ex mil from decommissioned warships. He works maintaining NSW Police radio network. My understanding from conversations with him is that the ham network is dependant on repeater stations and the internet. Ie: your transmission arrives at a repeater station and is then transmitted over the internet to other repeater stations. Which makes me wonder why you wouldn't just use internet communication systems instead of ham radio. Or maybe I just misunderstood him. You *can* use repeaters to do all these things, but that's for things like 2m and 70cm bands. Mostly for handhelds and mobile units.
This allows low power units to do tricky things to talk all over the world but is a small subset of what can be done.
Where my main interest is in HF (10m - 160m) where this is more focused on radio to radio communications.
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Post by graynomad on Nov 17, 2016 20:22:15 GMT 10
No way HAM needs anything AFAIK. There may be some features that need infrastructure, for example with HF you can make a phone call to a normal phone number and that does need the network and a base station somewhere to translate. But basic HF only needs your transceiver and another transceiver to communicate, almost no matter where the two transceivers are located.
I don't know if the HAM frequencies overlap HF or not, but it will be just as independent, in fact it's the lack of dependence that attracts preppers etc to it.
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token
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Post by token on Nov 17, 2016 20:22:18 GMT 10
Thanks para!
So it doesnt use the inet?
Also, whats the cost of the license and what of the regulations? do you need a reason to have one?
Ive been thinking about this since the latest flood more and more as i sat listening to the uhf handheld and thought it would be great to be able to have the range to get out further to see how others were doing also.
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paranoia
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Post by paranoia on Nov 17, 2016 20:34:58 GMT 10
Thanks para! So it doesnt use the inet? Also, whats the cost of the license and what of the regulations? do you need a reason to have one? Ive been thinking about this since the latest flood more and more as i sat listening to the uhf handheld and thought it would be great to be able to have the range to get out further to see how others were doing also. As frost mentioned you can link repeaters using the internet. For example, I can on my handheld unit call the repeater, enter the numbers on the keypad to dial another station, link that repeater to one in another country and talk over the internet as though my handheld was 50-100 watts and in another country.
You can DX (talk to distant stations around the world) which is completely separate from the internet. During our licence weekend we contacted a group of people who were doing their licence in perth at the same time (3000km from Adelaide) completely independent of any internet.
The costs for the course was $85, including $15 to choose my own callsign (code you use to identify your station when talking to other people). Licence costs you $76 for the first year and $51 every year after that... discount if you sign up for 5 years.
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paranoia
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Post by paranoia on Nov 17, 2016 20:36:59 GMT 10
A repeater is a station that takes in signals on one frequency and broadcasts it on another... this allows you to talk on a handheld across a city where you wouldn't otherwise be able to do (they're much higher output). The linking happens less often and is a little gimmky in my mind.
Google "repeaters *mystate*" to see what you have around you...
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token
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Post by token on Nov 17, 2016 20:57:01 GMT 10
With ham, your obviously being listened to by anyone with a scanner though correct?
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paranoia
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Post by paranoia on Nov 17, 2016 21:06:42 GMT 10
With ham, your obviously being listened to by anyone with a scanner though correct?
There's a potential for it... but the HAM bands are huge. Its not like channelized communication on CB where there's 40 channels and its very quick to scan through them.
It takes a long time to scan out frequencies and if nobody is transmitting at the time your scanner is going through that frequency, you'll scan straight past. A scanner can also only listen to one frequency.
Its also against the rules to attempt to encrypt your signal or talk in code.
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