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in this thread we discuss everything involving those wonderful ways in which humanity hurls epithets at each other via the invisible magic of RADIO WAVES you've got questions? we've got really wordy answers typed by a guy that probably likes radio stuff a little too much focus on ham/scanning/shortwave but we cover all the waves in all the spectrums "the spectrum?" yep. the spectrum.  Electromagnetic waves (we'll call them radio waves) all have a period of oscillation which is inversely proportional to their frequency. They travel pretty much at the speed of light in a vacuum or air, so we often refer to a particular frequency range based on how long one wavelength is at nominal c. 300 Mhz is one meter. 50 Mhz is six meters. 440 Mhz is 70cm, you get the idea. "what's this 'shortwave' stuff?" The terms 'shortwave' and 'HF' or 'high frequency' are interchangeable. reframe your context to like 1920 or so. everybody's starting to mess with radio, but the tech sucks so bad that they can only operate on a few hundred kilohertz. Wavelength here is long, on the order of miles sometimes. Then they got better equipment and could transmit on higher frequencies. Thus, 'shortwave'. The shortwave band is the band that is most strongly affected by YE OLDE IONOSPHERE. These frequencies have wavelengths that treat the ionized layers of the ionosphere as a mirror, more or less. If you are on Earth, and send a signal to the horizon, it'll eventually bounce off that ionosphere and head back towards the Earth, pretty far away. The ionosphere is almost 100% affected by our friendly little yellow nuclear fusion reaction in the sky. Specifically, sunspots. Basically, as the sun comes up over an area, lower layers of the ionosphere are 'activated' by solar energy, which basically brings your mirror closer to Earth, shortening propagation. As the sun sets, these layers dissipate and your mirror rises again. You can once again talk to Europe from the US! The higher the number of sunspots, the stronger propagation gets. These ebb and flow on a roughly 22 year cycle. Right now we are right around the peak of a somewhat-lackluster solar cycle, but conditions are still pretty good. Around 2018, my shortwave radios will probably go into storage for five years during the solar minimum. The main appeal of shortwave is: the ionosphere. You can bounce poo poo over the horizon, and if you're lucky it will bounce again off the earth and back up into the ionosphere. You can get allll the way around the world with this (and matter of fact, if conditions are right, you can briefly transmit and hear your echo about 90 mS later after its gone all the way around the world.) The main disadvantage of these bands are that antennas are large, and propagation is inconsistent. Monday might be gangbusters, then the sun sneezes and the next day you can't hear a god drat thing. Now, as you go up in frequency, the waves stop bouncing off the ionosphere. however, they start to become better and better at point to point transmission in free air. This goes allll the way up to visible light and beyond (yep, light is this same energy, just at really high frequencies. You got antennas in your head) Also, shorter wavelengths are attenuated less by obstructions, to an extent. So, if you don't need the range boosts from shortwave propagation, or if you can't fit a big antenna, and you just need local coverage, you go up in frequency. 100 Mhz is your FM radio. 150-ish used to be the primary law enforcement band. Then for a while the cops moved to systems around 460 MHz, and now the most common systems run around 850 MHz or so. Engineering challenges go up as your frequency does. It's really easy to build a 1 MHz transmitter - it's really hard to build a 1 Ghz transmitter. Tolerances are low, precision must be high. "what the hell is an antenna, anyways" A piece of metal. that's it. As radio waves pass through an antenna, they induce an alternating current between the 'halves' of the antenna. This voltage is transmitted by your feedline, which can take many forms, into your radio receiver. The exact opposite happens on transmission - your radio produces a voltage, it is presented to the antenna, and the antenna takes that energy and converts it into radio waves - the better tuned the antenna, the better it does its job. If the piece of metal has dimensions such that it is 'resonant' at the frequency of the waves, its properties will reinforce and enhance the voltage presented at the feedline, giving you a stronger signal. If it's not a resonant length, it becomes more complex and could possibly work well, or possibly be awful. "you talked about two halves. But my car antenna only has one piece!" Not quite. Your car antenna uses the vehicle as a 'ground' reference. It's not actually connected to the earth, but it is a big enough piece of metal that it will also pick up the radio waves and be the 'other half' of the antenna. This concept is called a 'counterpoise'. This translates to fixed antennas, too. Those big AM broadcast antennas use the earth as a counterpoise. In order to effectively do this, you usually lay down a network of ground wires, directly on or in the earth, and use that as your counterpoise. There is a LOT of copper in a broadcast antenna's field. "What's HAM radio?" First of all, not an acronym. it's just ham radio. I will take a US-centric view, as I am a US amateur operator. Just to get this out of the way, I was first licensed 23 years ago at age 11, and held a Technician class license with limited HF privileges until 2007 until I upgraded to Extra, the terminal license class. These are on a ten-year renewal and do not require retests, so i will be an Extra until I die. In the early 20th century, the vast majority of technical advances in the new radio field were by non-professional experimenters playing with spark gaps and big coils in their garages. The government realized that the 'amateurs' were contributing a lot of help to the new tech, and allocated them specific frequency ranges in which they could talk to each other. To preserve the economic appeal of official licensing and regulation, all commercial traffic was banned. This provided basically a safe area free of high-power commercial broadcasters where guys who just liked to tinker with radios could put them on the air and talk to other tinkerers. Over the past 100 years, hams have provided a lot of technical advancements to the radio art, and this continues to this day. Hams brought the world single-sideband transmission (greatly enhances long distance shortwave), moonbounce (literally bounce a signal off of the moon), various digital modes of transmitting information, and so on. The trend continues, with a lot of software-defined-radio development being done in the ham radio world today. To ensure we have the ability to be proficient in many styles of communication, hams are allocated a wide variety of allowed bands of operation across the spectrum. Here's a real quick breakdown of what each major band is really like:
"You mentioned CB, how's that doing?" Weirdly. it's kind of fun to hear truckers and such, but everybody runs illegal power now through dirty transmitters, so the band is full of distorted shouting rednecks hitting sound-effects boxes and trying to make their neighbor's TVs blow up. It's basically the fyad of radio. We'll get more into CB on some later posts. OP is getting big and fat, so I will wrap this one up with a quick list of what I have done with radio so far: -Been the fourth youngest licensed amateur in North Carolina at the time of my licensing -Won an award for being a coordinator for a ham-radio based score reporting network at a national soccer tournament -Talked to the bass player from .38 special and Ronnie Milsap (both famous hams) as they toured through my area -Said hi to astronauts on the ISS and cosmonauts on Mir -On a camping trip, hooked a laptop to a battery powered HF radio, threw a wire in a tree and basically IRC'ed with South Africans and Europeans -Used VHF and UHF bands to speak to hams in Vancouver, California and Michigan - by using low-earth-orbit satellites The last item is my current obsession, and we will be talking more about satellite communications soon. this weekend i'll try to get a good camera setup and maybe we'll have a youtube or two of what you can listen to, who you can talk to and what it's all about. We'll also cover scanners, commercial shortwave and other common ways you can snoop on invisble energies to figure out what they're ordering at the nearest drive-thru.
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Feb 21, 2014 20:15
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I WANNA LISTEN TO THE COPS You can probably still do this! But now that we have COMPUTERS, maybe not. See, cops hate it when people listen to what they're up to. So, the past 20 years has been a long push for digital radio and encryption, accelerating greatly after 9/11. Digital radio is generally monitorable if it's not encrypted. If it's encrypted DONT EVEN WORRY ABOUT IT BECAUSE YOU WILL NEVER DECRYPT IT. A good rule of thumb is that the more a police department humps encryption, the shadier they are. See, the 'if you've got nothing to hide you've got nothing to fear' works both ways. Encryption is not scrambling. Scramblers are easily defeatable and are a good indication that your local PD is both cheap and secretive. Law enforcement and public services are on VHF, or increasingly UHF bands. It's all line of sight, local stuff. They use repeaters and linked networks just like hams to extend their range. Your first step is to go look up your jurisdiction on http://www.radioreference.com/apps/db/ If the organizations that you want to listen to are using a "P25" system, that's the most common digital voice modulation these days. Generally monitorable. "MotoTRBO" is a proprietary digital voice network that does not have commercial receivers out yet. You have to hook a laptop to a radio and do some hacking. Pain in the rear end, but doable. Generally all other transmissions are going to be able to be listened to, with a few exceptions. You will also see references to 'trunked' and 'conventional' systems. Trunking radio systems basically add a layer of abstraction between the user and radio network, so that each radio has logical channels, or 'talkgroups' on it. These do NOT correspond to actual frequencies, and radios may hop frequencies between transmissions or even in the middle of one depending on how it operates. However, the radios and base stations are all communicating digitally to keep the talkgroups straight, so that if your radio is only set to police dispatches, your radio won't pick up the fire department. Conventional systems use the old school method - Police Dispatch is on 460.025, Police Tac is on 462.225, whatever. You tune the radio to talk to the people you want. Almost every scanner can decode and follow trunked analog systems. Trunked P25 systems require a scanner thats a couple hundred more (99% of the price difference goes to IP licensing royalties for the voice decoder chip - the actual tech is trivial). My main scanner is a Uniden BCD396t, decodes P25, PC programmable, built like a brick shithouse. I bought it november 06 and it has been rocking every day since, and I'm not exaggerating that - probably on my 12th set of NiMH AA's. I have a couple Radio Shack shitscanners too that I use just for particular systems, and the VHF/UHF ham rig in my car tunes in the public service bands too, so I can do limited monitoring on that as well.
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Feb 21, 2014 20:50
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French Canadian posted:every time i'm on a road trip and someone breaks out a handheld cb radio i never hear any interesting trucker chat. it sucks and totally ruins my illusions of trucker chat on the wide open road. what gives? It's a piece of poo poo! Specifically, the antenna. Radio's as fine as any other CB in that price range. Wavelength at CB is 11 meters (actually "11 meters" used to be a ham band, and hams still refer to CB as 11) so a quarter wavelength is just over 2.5 meters - this is the reason for the big rear end 102 inch CB whips. As your antenna size goes down, so does performance, and it becomes more finicky about tuning. Those rubber duck antennas on the handheld CBs are basically just resistors - barely antennas at all. I have one of those handhelds in my car (Cobra HH 38) and it works fine when I hook it up to a proper antenna. Right now I don't have a dedicated antenna for it, but that's going on in the next couple of weeks (if I ever get sick of CB I can retune the antenna to use it on the 10 meter ham band).
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Feb 21, 2014 20:56
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Phoning It In posted:prob going to take the ham nerd test so i can send PACKETS of my own Nah guys use it for other random stuff too. It's not really two-way chatsville, but they won't hunt you down if you put a "email to blah@gmail.com" type thing in there. Now that I have a spare 2m radio, i'm going to set up an APRS node with a raspberry pi, i think. --- DID YOU KNOW? The most hated, reviled troll on the 20 meter amateur band.....is a canadian? meet karol madera, VE7KFM https://www.youtube.com/watch?v=BGwwIJ6sQao
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Feb 21, 2014 21:03
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Nope, spam away. im trying to find good youtubes and getting some drafts cleaned up  im sure it'll pick up after a bit
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Feb 21, 2014 21:08
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i'll try to do some little sub-focus things QRP QRP is the international code for "reduce power". Hams in the US are allowed to transmit on most bands with up to 1500 watts of radiated RF power, with no limits on antenna gain. however, the technical wording of the law is that we are allowed to use "the minimum power necessary to communicate, with a hard limit of 1500 watts power". This isn't a strictly enforced law, more of an agreement to keep excess unneeded RF off the bands. However, some hams take this as a technical challenge, and practice QRP operations - turning the power as low as they possibly can, and using operator skill, efficient modes and good antennas to make up the power difference. The brag number is just distance divided by power output, miles per watt. If you're transmitting more than 10 watts, you are not QRP. here's a video of a guy on the 40 meter band making some single-sideband (voice) contacts with just a few watts of power. https://www.youtube.com/watch?v=GvBVbZBHPX4 "QRPp" specifically refers to the hardest core of the weak signals. You can't claim QRPp unless you are putting out less than one watt. And here's a guy using a 450 mW transmitter communicating between SC and NY, giving over 1300 miles per watt of power. https://www.youtube.com/watch?v=-SxxKCN6oXY
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Feb 21, 2014 21:20
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If your radio can eat 12 volts (automotive systems generally run on 13.8 volts peak but we refer to it as 12v nominal), you can just hook up directly. For low current stuff, just clips or clamps to the battery post is fine. If you need 5 volts or 6 or something like that to the radio, you can get a little converter board. Marine battery has about 100 amp-hours of storage (it's a product, higher amps mean less time and vice versa) so if you radio draws about 2/3 of an amp at 12 volts, it'll run for a week straight more or less.
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Feb 21, 2014 21:50
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 Say hi to OSCAR. This Orbiting Satellite Carrying Amateur Radio was launched in 1961 and simply transmitted "HI" in Morse code (easy cause it's only dits, no dahs) in the 10 meter band. Over the next 22 days (until it deorbited), thousands of hams worldwide excitedly tuned in to provide reception reports of the very first amateur radio satellite. Over the next 53 years, we launched over 130 satellites with various transponders, repeaters, and beacons. During the 80s and 90s, a great deal of energy was put into the satellite program, and this is generally considered the Golden Age. In the late 80s through mid-90s, we had several satellites in orbit, giving virtually complete earth coverage, including a few High Earth Orbit satellites that had a very elliptical orbit. At apogee, these satellites would hang out on end of orbit for hours at a time, giving line of sight coverage to almost 40% of the earth and staying in a relatively fixed location in the sky. I never got enough equipment ready fast enough to operate these birds, but the stories abound about long extended chats between opposite sides of the Earth. Sadly, funding and interest has dropped significantly. we no longer have any high-orbit satellites, and only a handful of birds active, all in relatively low polar orbits. However, it is still an exciting specialization, and teaches a lot about astronomy, physics, and engineering. Doppler Shift becomes a very real concept once you learn that you have to tune two radios at the same time in opposite directions! Low earth orbit ("leo sats") have rapid polar orbits, basically letting the earth rotate under them as they orbit north-south-north over the poles. Their altitude at 600-800 miles means that each spot on earth generally gets about two to three usable orbits (passes) during a session. Each pass gives about 16-20 minutes of usable communication. Basically, if it's over the horizon for two people, they can talk on the satellite. Contacts are fast and general "hello, here's your signal report, ok signing off" to avoid hogging the bird. Low earth orbit birds are easy to hit with a simple antenna and radio; you can get started with a handheld, even. Believe it or not, you can get full scale signals from a solar powered satellite on VHF/UHF with a handheld antenna, quite simply because it's line of sight! People (like me) often do build higher-performance stations, with directional antennas that can not only be turned horizontally (azimuth) but have elevation rotators to aim them above the horizon. Then you wire up some computer control interfaces to your rotators, fire up your satellite tracking program, and let your software tune the radios and point your antennas. it's pretty bad rear end. I really hope that in the next few years we have a resurgence in interest in satellite in general - it appears that we are getting a steady volume of the low earth orbit birds up - but I'd really like to see us get high orbit satellites up there again. I've specialized my radio purchases towards units that have good performance on the best satellite bands,and can use the special modes and features that are required for the high orbit birds. My vintage Icoms will be ready. Jonny 290 fucked around with this message at 01:26 on Feb 22, 2014 |
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Feb 22, 2014 00:57
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Oh, I forgot the funniest ham satellite http://en.wikipedia.org/wiki/SuitSat HEY WE GOT AN OLD SPACE SUIT FROM RUSSIA WHAT SHOULD WE DO WITH IT? LETS PUT A RADIO ON IT AND JUST PUNT THAT MOTHERFUCKER OUT THE AIRLOCK  it only worked for a couple months, but you could receive transmissions from a space suit. cmon. Fax Sender posted:I have a cobra 45wx. it is a handheld cb. can I and should I hook it up to a real antenna? Possibly! Do you want to run it in the car or check it out at the house? i have antenna recommendations for both situations. also advise if you'd be willing to diy/solder as it means your first experimentation can be sooooper cheap
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Feb 22, 2014 01:11
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Fax Sender posted:i love to diy, and idk, i'd probably use it more often at home than on the road. i take it on trips only, not every day driving alright, to get any sort of usable signal into that thing, you're going to need an external antenna. For now let's set something up at your home QTH (location) and see what we can pick up! So, the very simplest real antenna is the dipole. Two metallic thin elements a quarter wavelength each in length, pointed 180 degrees away from each other and fed from the center. This antenna has 75 ohms free-air impedance which provides a reasonable match to the 50 ohms that most radios expect. Just look at the numbers for now, dont worry about what impedance actually is- we'll hit that poo poo way later. Closer numbers = better for now. Now, what you can do is take one element, and instead of having the mirror element, feed it against a counterpoise as I mentioned in the OP. This can be the earth itself, a resonant ground plane (star or cone shaped array of 1/4 wave metallic elements), a car body, basically anything RF conductive and big. Tin roof? Holy poo poo what a ground plane. Long metal gutter? Not bad. You now have a monopole antenna. CB largely operates with vertically polarized antennas - elements pointing up and down. So, what it comes down to is that you're going to need about 17 feet of vertical antenna, OR about 8.5 feet of vertical antenna right above some sort of ground plane. However, antennas like to be higher up off the ground if possible, so it's not really helpful to put up an 8.5 footer mounted at ground level. Much better is to mount it up in a tree or on your roof, up as high as possible, and use some counterpoise wires maybe stretched across the roof or even just hanging down from the tree limb. From the center of the antenna, you're going to need to run a coax cable feedline into the house to the radio. Length is not SUPER important at CB frequencies, but you still want to keep the run as short as possible. Lower-loss coax is WAY pricey and like a half inch around, so you want to try to keep the run to less than maybe 50 feet or so. In that context, do you have some sort of tree that you could throw a rope over, or a roof that you're comfortable with climbing on? If we can get a 1/4 or 1/2 wave antenna like 15 feet off the ground or so, you are virtually bound to hear anything going on in a few mile radius, and you might be a lot luckier than that. Jonny 290 fucked around with this message at 02:01 on Feb 22, 2014 |
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Feb 22, 2014 01:59
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CW, or NO THEY'RE NOT AUTISTS Continuous Wave (as opposed to the 'damped wave' that faded out from the old spark gap transmitters) is the oldest legal radio transmission mode. Classified by the FCC as Emissions class A1A, it is a digital mode and is the simplest thing you can do. Turn a transmitter on and off, really fast. It spits out a single frequency signal, with the effective bandwidth being roughly proportional to the speed of the code sent. Slower speeds can be picked out easier among a bunch of nearby signals. The only encoding used is ye olde Morse Code. I'll admit that I am no longer FLUENT fluent in CW (We call it CW, not Morse, even when we're doing things like generating a tone on an FM signal instead of true A1A emissions) but I possess enough to pick out some stuff here and there at reasonable speeds, and can send at about 10 words per minute. I passed the 5 words per minute test back in like '94, and that applied as credit towards my Extra license (its true that you no longer need the code, but I got my Extra before they dropped that requirement, because i wanted to cluck about it) In order to transmit CW, you need a way to generate it. The simplest is a straight key - a simple on-off switch. Here's a guy using a straight key to make a short contact. https://www.youtube.com/watch?v=v0QddynWDt0 The other type of mechanical key is the semi-automatic, or 'bug'. Synonymous with Vibroplex, the largest manufacturer, these use a left-right action instead of up-down, and have a short sprung pendulum assembly to allow the automatic sending of repeated 'dits' (the short ones). Dahs (long) are still sent via a manual action. Here's a guy cranking it out at pretty good speed (oh yeah these things have a minimum speed they can be set to, so if you can't crank about 20-25 wpm, dont even try it): https://www.youtube.com/watch?v=Lo9uFGJS0vY After that, some fellas set up the electronic equivalent of the Vibroplex's dit-dit-dit circuit, and added one for the dahs as well. Then they just took a Vibroplex type left-right key, and instead of the spring circuit just made it contact one of two different terminals. And the paddle was born. https://www.youtube.com/watch?v=VmG8FxnIMF4 Some cool dude then figured out that if you had two paddles, one for each side, you could have a device that could close both contacts at once - and they used this to trigger an alternating pattern. So if you close the dah side first, then dit, it starts cranking out -.-.-.-. till you let go. Close the dit side first, and you get .-.-.-; furthermore, if you're sending a string of dits or dahs and you want to insert one of the other ones, just tap the other side and it'll add one in. now you combine this with the technique of the single paddle, and you get the iambic paddle! (note: This video is cool - these guys are using the 6 meter band, and bouncing their signals off of patches of aurora - it's really ionized, so sometimes it will reflect signals in the lower VHF range. The raspy tone on the remote station is due to the weird way the propagation works. this is a situation where CW shines - there is NO way these guys could use voice) https://www.youtube.com/watch?v=iJ2udTxn3SU And iambic paddles are pretty much the state of the art for hand-sent CW for poo poo, probably 50+ years now. Some dudes run high speed CW using computers, which can both send and recieve pretty flawlessly up to like 120 WPM, but there's a lot of hate for it. Sometimes the computers are necessary when doing extremely weak-signal work like moonbounce and meteor scatter, but that is very niche and accepted. and poo poo,now i'm motivated to go download some practice software and get my CW groove back. ughhhhhhhhh Jonny 290 fucked around with this message at 03:05 on Feb 22, 2014 |
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Feb 22, 2014 03:02
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PSK31 PSK31 was developed in the late 1990s as a digital mode that was simple and had one goal - to allow person-to-person chats. It's not used for email networks, not used for high speed data of any kind. As a matter of fact, it stands for "Phase Shift Keying, 31 Baud." It's designed from the ground up to provide the average bandwidth needed by a person typing in a conversation. It's a really simple encoding, only a little more complex than CW, really, once you get down to it: quote:In the most-commonly-used variant, BPSK31, binary information is transmitted by either imparting a 180-degree phase shift (a binary "zero") or no phase shift (a binary "one") in each 32ms symbol interval. The 180-degree phase shift for a "zero" bit code occurs at a null amplitude.[4] It's actually so robust that in a pinch, you can make a contact by just setting your laptop next to your radio, holding the radio mic over the laptop speaker to transmit, and turning your radio up and using the laptop microphone to receive - as long as there isn't much ambient noise, it'll work. PSK31 is cool for three reasons: --It is very simple to encode, decode, send and receive --It is very bandwidth efficient --The error correction and simplicity means that good copy can be achieved with REALLY low signal levels. People rarely run more than like 25 watts of power in PSK31 operation, and QRP (sub-10 watts) is very common. You can use simple, energy-efficient radios to operate it, combined with a small laptop with onboard sound. It's becoming very popular for portable operations as well. Of course, there are iOS and Android apps to operate it and oh man I just remembered I have an old Droid I could use for this. Most operations center around agreed-upon frequencies towards the bottom of each HF band, and on a busy day you can see dozens of conversations in your receiver display. As with the SDR radios above, these programs use a waterfall display:  Most of the time you just click on one of the traces, the program sets your transmit frequency to the same as the received signal, and starts decoding the received signal. Wait till they stop transmitting (there's a distinctive end tone and then the carrier stops), and contact them back! Here is a 20 minute recording of some 20 meter PSK31 activity. If you have the option on your sound card to select a "What You Hear" type input for the soundcard, you can decode this stuff RIGHT NOW, NO RADIOS! --Set your recording input to "What U Hear" or whatever it is on your computer. --Download DigiPan and get it started up. --Play this video in the background and go back to DigiPan https://www.youtube.com/watch?v=qHNvp7FfP6E You will see the waterfall light up with the same pattern as you see in the video. The top right of the screen shows a sort of 'multi monitor' that tries to trace each conversation in the waterfall. To focus on one conversation, click a trace in the waterfall - obviously brighter is louder and you'll see them appear and disappear as they transmit and then stop. If you were actually listening to this on a radio, you would most likely have access to some rather sharp filters and notch circuits, that would allow you to twiddle knobs to block out most of the signals and focus on the one you want. Basically EQs on crack. This is a good recording with wide bandwidth so it's not evident, but you can shave off about 90-95% of the audio spectrum and just keep the signal you want. Starts to become obvious that this is really efficient and easy to get contacts around the world with fairly simple equipment!
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Feb 22, 2014 18:31
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no i was gonna get into superhets, go hog wild depcat inspired me the other night on IRC so i think over the next few days i'm going to collect the parts to build a basic crystal radio, then we'll do a LP while i build it and see if we can pick something up.
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Feb 22, 2014 20:11
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longview posted:
AAAAAAAH OH MY GOD I WANT YOUR RADIO we can talk boxes now thats cool my 2 meter radio that i loooooove. icom 271a  tune in some guys on FM simplex and it sounds like NPR. full range speaker, absolutely incredible and the receiver is so hot that you will get no noise on a signal that barely moves the meter. Then for 70cm, I picked this up for a song. the ic-475a  I grabbed it for 250 bucks because it needed an alignment and is about 1.6khz off frequency. Carefully shadetree-tweaked it more or less into working condition. Someday I'll have a 275a (2 meter) and 575a (10/6 meter) to go with it, but they run around a grand apiece for models in good condition. Probably some of the best single band VHF/UHF radios ever built. Then my HF rig is the venerable and absolutely indestructible ic-735.  i bought this thing in like 2003 or so, and it's been turned on most of the time since then. I may trade the other radios towards better satellite rigs, and may get another HF radio, but I will never get rid of this.
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Feb 22, 2014 21:24
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longview posted:strictly speaking I'm not allowed to put antennas up at all but nobody's complained about a mobile whip and a discretely installed Royal Discone on a tripod, and I hid a slim jim for the D-Star in a corner i love stealthing antennas and have had metal in the sky at every place in the past 10 years. My favorite was when I lived on the ground floor of 3 story apartment building, and right next to my radio room's window were a few vertical PVC pipes running all the way up the building for HVAC drains. I bought a few pieces of the same size and color PVC, built a vertical dipole inside it for 2 meters at the very top, and ran a second coax line up the inside and strung 40 feet of magnet wire onto it. Then under cover of night, I assembled it in the parking lot, threw it up next to the existing pipes and zip tied it to one of them. Then took a chunk of fishing line with a big sinker attached, flung it up in a tree, and pulled the magnet wire up so it was roughly horizontal and about 20 feet off the ground. Stayed up and nobody said a peep for 2 years.
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Feb 22, 2014 22:45
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longview posted:But we can do better, enter the superheterodyne receiver shamelessly borrowed from wikipedia: I call this trick "Two boxes, one radio" So I picked up a couple of these off ebay for about 30 bucks apiece. The Icom PCR-100 wideband computer controlled receiver:  This is *not* an SDR. This is a full wideband AM/FM/FM Wide receiver that covers 500 KHz to well over 1ghz. One day I was poking around and thought I'd try to use my HF radio as a final stage, and take the 10.7 MHz IF out of the PCR into the Icom. Found an appropriate point in the 10.7 section to pull a signal off, ran a little bit of coax to that point and connected it via a little bitty cap. Then put an RCA on the end of the coax, plugged it into the HF radio's RX antenna in, and tuned to 10.7 MHz. Then I fired up the PCR100 software and started tuning around. Signals started showing up on the 735! I basically made a tunable wideband receive converter that used the HF radio as a very tuned final stage - consider that I almost had two full radios' worth of filtering on the incoming signal! Very fun experiment and I did use it to successfully receive SSB from the VO-52 satellite.
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Feb 22, 2014 23:02
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yesterday i put a big rear end antenna on the truck. phear my movie maker skills https://www.youtube.com/watch?v=-y3zcBO279k more clips encoding
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Feb 23, 2014 16:05
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just get the UV5RA if you are wanting to keep it cheaper, or get the GT3 if you want a better display and can spend a few more bucks
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Feb 23, 2014 16:19
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Ah, go for one of those then (though that is a plus just b/c its an indication of a later firmware, not b/c there's anything between 480 and 520 at least in the US) encoding another video, CB this time - stand by Jonny 290 fucked around with this message at 16:48 on Feb 23, 2014 |
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Feb 23, 2014 16:45
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yes, OTA is fine. I was listening to FM broadcast via a remote receiver in Eugene last night CB PARTY https://www.youtube.com/watch?v=rBZINt_c4v4
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Feb 23, 2014 16:58
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Cold on a Cob posted:to clarify, this is a metal ceiling, not a metal roof. it's for ~*~*aesthetics*~*~ it will act as a sort of ground plane. as long as your OTA antenna is a few feet above it, you'll be fine. Just dont set it six inches off the thing and expect great operation
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Feb 23, 2014 17:03
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an example of the equivalent of AOL scrollers on 20 meters, and then some actual ham activity on 40 meters: https://www.youtube.com/watch?v=FQiut9ddSFQ
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Feb 23, 2014 17:32
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!!!! freeband CB pirates !!!! https://www.youtube.com/watch?v=_6d3tylJQHU
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Feb 23, 2014 18:27
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in about two hours we're going to go out and see if we can pick up Saudisat SO-50
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Feb 23, 2014 19:20
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congratulations you just received radio signals from a satellite in mothafuckin' SPACE I didn't hear poo poo on that pass because i plugged in the wrong antenna, lol trying again in about 5min (oh and im not transmitting i dont have the other radio set up)
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Feb 23, 2014 22:48
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good thing i hooked up an SWR meter this time around so I could see that i had !!!infinite SWR !!! and debugged it to not one but two broken conductors in the dual band mag mount i was using fixed, see if we can't find some more birds up there tonight turns out this Comet dual band antenna happens to have perfect SWR at 436, the satellite sub-band 2 meter kind of sucks tho =/ Next chance is about 20 minutes when VO-52 passes. This is a SSB/CW bird, so it is for the more hardcore fellas, but we have two decent passes this evening. Jonny 290 fucked around with this message at 00:06 on Feb 24, 2014 |
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Feb 24, 2014 00:03
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success again, receive only, but i brought out the 2 meter radio got a video of some signals from the satellite processing now
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Feb 24, 2014 00:48
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fun this afternoon: receiving the VO-52 downlink passband with my 2 meter radio now, one thing to understand about birds of this type is that they're transponders. They listen on a wide frequency range and retransmit everything they hear exactly as they hear it, in a little slice of another band. This means that A: there's a total power budget, so if you put out a stronger signal, you'll be retransmitted stronger and you're using more satellite power - this is rude B: several people can use the satellite at once, on different frequencies Transponders are usually inverting, which means that an upper sideband signal will come out as lower sideband and vice versa. The downlink is a mirror of the uplink, in a different band - shift your uplink frequency up and the downlink frequency will move down. transponders are more efficient and sensitive than FM style repeater satellites, because the signal stays as RF and is directly converted, whereas the other style receives it all the way to audio, then retransmits that audio. VO-52's transponder listens for earth stations between 435.225 and 435.275 MHz. It then shoves those down a 2-meter pipe back down to earth between 145.925 and 145.875 (not backwards, this nomenclature shows that it's an inverting transponder). In addition, there are beacon signals that the satellite continually transmits - the vid starts with us receiving one of those beacons' CW signal https://www.youtube.com/watch?v=qQbffGIwRyI
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Feb 24, 2014 01:32
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An SWR meter is pretty much just a directional wattmeter that can bet switched from forward to reverse. loled at iambic pentameter tho Kevin Mitnick P.E. posted:do you just have to take a test to get a ham radio license. basically i'm thinking of not actually messing with radios but getting a ham license and telling my wife that only licensed radio operators get to tune the car radio yeah theres no presentation or demo or essay questions, pass the multiple choice, get a thing in the mail
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Feb 24, 2014 15:37
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Yall ask "what would happen if you just get on the air and started spamming poo poo" James R. Winstead, KD5OZY shares your curious nature http://www.arrl.org/news/view/fcc-proposes-to-fine-texas-radio-amateur-7000-for-malicious-interference quote:According to the NAL, released February 19, an agent from the Commission’s Dallas Office on January 21 used direction-finding techniques to positively identify the source of the interfering transmissions as Winstead’s address. After monitoring the transmissions from the station for about a half-hour, the agent heard Winstead, an Amateur Extra class licensee, “replay multiple times short sentences or conversations that had just been transmitted, and occasionally speak the word ‘George.’”
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Feb 24, 2014 15:52
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ADINSX posted:This thread rules Johnny, Short answer: very legit. I do a lot of antenna modeling and sort of use genetic algorithms to evolve and tune them. Take a couple parameters, wiggle them up and down programatically and test it at each iteration. When you find something good, move on to other variables. http://hamsoft.ca/pages/mmana-gal.php more greybeard software with ancient libraries and UI. works tho. wish it was threaded =/
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Feb 24, 2014 16:17
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I really hope there's some d-star action in denver because I WANT TO MESS WITH IT SO BAD
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Feb 24, 2014 19:15
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PuTTY riot posted:thats kinda where i was going w/ this.... back in the day a lot of repeaters had the autopatch into a POTS line for local calls. I will always remember, stars come up, then you pound them down - star to bring up the patch, dial the number, then pound to hang up "hi mom i'm on the radio"
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Feb 24, 2014 20:01
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longview posted:almost a 100% chance that running a 1500W 2.4GHz link and taking out wifi for the surrounding county will get you into some kind of trouble, european limit is 300W on VHF and up but anything above ~1W will take out wifi over a pretty large area This is my big thing. After the UPS debacle* I started viewing the FCC in a rather dim light, and am terrified that they're going to just razor shave down our bands one bit at a time if we don't say anything until they've destroyed all the ham bands for _very_ minor incremental advances in their own service *in the early 90s, UPS started crying and crying about how they needed a dedicated radio band for their trucks and how about 220-222 MHz out of the 220-225 MHz ham band, FCC said naw, UPS said BUT WE WANT IT and then FCC said okay and took it away from hams and then UPS said "aw jokes, jokes. Looks like 220-222 won't work out for us. We're good though - cellular data is here! Peace out" and the FCC never gave it back to hams.
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Feb 24, 2014 20:33
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afaik they resold it at much lower prices to other private services, so if you interfere with them, they call FCC, white van visits, Notice of Apparent Liability, five-figure check made payable to FCC
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Feb 24, 2014 20:38
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longview posted:in a word, yes Yep. this is also why I personally do not 100% discount the "my filling made me hear radio signals" stories. I think it's possible to have a semiconducting junction inside a bad filling, which could pick up enough energy to fire audio nerves. it'd be a 1 out of 100 million thing, but i want to believe
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Feb 24, 2014 21:07
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PuTTY riot posted:i guess im not good at this nomenclature thing. i was thinking of using ham freqs as like a P2P 'WAN' connection that u'd hook up to a wifi router on ur camping trip then VHF or w/e back to wherever u have an internet uplink It might or might not be permissible. If it a: violates any obscenity guidelines, or b: is of a commerical nature, it's verboten. If the traffic was encrypted at one time, it's fine as long as you pass it unencrypted over ham airwaves (TCP/IP and HTTP are both allowed and widely used on some packet networks). The white vans are rare, I think they have some on each coast and then chicago/dallas, and they travel onsite based on complaints. you won't find one in oxford unless the cops' radios or university PD is getting interfered with
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Feb 24, 2014 21:30
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coffeetable posted:is amateur radio astronomy a thing Coming back to this - didnt forget about you. I don't really know! But last night I got so deep in the satellite books that I taught myself what Lagrangian points are and now I want to join AMSAT (the amateur radio satellite org) and hook them up with some 2.0 millionaires who want to get press. They need like 5 million bucks to launch Phase 3E (the next wave of high orbit satellite) and its been just loving sitting in project hell for literally ten years now. thing is huge, will require a big rocket and a boost up to a big orbit of course any 2.0 millionaire is going to not be altruistic at all so it won't work. sorry we're not going to put streaming ads or your companys name on it Anyways i'm going to see if anybody is doing amateur radioastronomy stuff. As long as you can get some sort of receiver set up for the proper frequencies theres no reason you cant point an old TVRO dish at the sky and see what you hear
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Feb 24, 2014 22:10
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Payloads: -1 Molniya orbit satellite with transponders on five different band pairs, attitude thrusters, magnetorquers, deployable solar panels and redundant backup control systems -10cc semen, preserved, from Bill Nye
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Feb 24, 2014 22:41
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| # ¿ Apr 28, 2024 11:39 |
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PuTTY riot posted:consistently acing first half of tech exam. if you have any Q's ask them here and if i miss it/dont answer, PM me im excited for you! srs
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Feb 25, 2014 00:19
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