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Thank you! I've got a screencap of the code table for the Retevis radios, assuming this will work if I input them all to the corresponding bands in CHIRP yes?
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May 3, 2019 01:23
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eddiewalker posted:The UV5R can scan for squelch codes, but we’re still at the legality of this plan. Based on a really cursory search, if he's in Canada then I think he's legal as long as he only transmits at 2 watts and doesn't use the 467mHz channels.
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May 3, 2019 14:36
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I don’t think they allow you to use random radios with removable antennae either
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May 3, 2019 14:39
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I'm pretty new to Radio, but I'm studying computer engineering and recently got an RTL2832U and have been exploring the local spectrum with SDR# in windows and attempting to introduce myself to GNU Radio. So we have a local college radio station with FM Frequency 88.1, but I'm also picking it up on a CB frequency of ~26 Mhz. Is it normal for an FM station to also broadcast on a CB channel? Or am I picking up some kind of harmonic?
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May 3, 2019 15:50
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The Scientist posted:I'm also picking it up on a CB frequency of ~26 Mhz Is it AM or FM at 26 Mhz?
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May 3, 2019 17:08
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As motronic is hinting at you are likely seeing some kind of spurious image of the original fm broadcast that's being produced within the rtlsdr itself. The station probably wouldn't be broadcasting FM in the AM/SSB CB band, so that's a pretty big tell on its own. If you had another radio around that could tune the same area like a shortwave receiver that could also establish if the issue is rtlsdr-specific Ways to fix: - turn down the gain - get an fm filter like this
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May 3, 2019 21:59
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Well I am having trouble reproducing what I thought I saw last night. I was thinking of waiting until tonight to try again, because I know that radio stations use different broadcast power at night time. Although I thought that the way it worked was that they use lower power at night, so that doesn't really make sense. But I will try and see what happens. edit: Although the fact that I can't reproduce the situation hints that its some kind of errant signal, as you all suggested. So does this have something to do with frequency harmonics? Because what confused me was that ~27 MHz didn't seem like a harmonic of 88.1 MHz. Also, is that band-stop filter the equivalent of a "cable trap"? I wonder if they still use those, especially since all tv at least in the US is digital now. whose tuggin fucked around with this message at 22:34 on May 3, 2019 |
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May 3, 2019 22:27
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It's basically what happens when you shove the entire RF spectrum into a $2 ADC chip that is operating out of its design specifications. You get images and overload _everywhere_. This is NOT to poo poo on the RTL sticks. I have several and really like them. You just have to be aware of their limitations and ideally have some sort of way to control the level of the RF input. I have a little preselector box (receive-only device that only lets a certain band of frequencies through) that I leave hooked to mine; that way the 50,000 watt KOA firehose doesn't show up every 10khz between 100khz and 30 MHz, as it does without the preselector.
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May 3, 2019 22:38
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Partycat posted:I don’t think they allow you to use random radios with removable antennae either Yeah, something I didn't think about when I was responding to Mister Speaker: using the UV-5R to transmit on FRS or GMRS frequencies (in the US, at least; can't speak for Canada) is illegal and the FCC can, has, and will continue to fine the poo poo out of people they catch doing it, since those radios aren't type-accepted for those services. Can't tell folks how to live their lives (hell, I do it myself at work), just...understand the risks.
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May 4, 2019 23:36
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So, one of the things that I wanted to play around with was demodulation of some signals I find throughout the spectrum using my RTL2832U. Its a pretty cheap device and it looks like its subject to some interference (already bought the RF FM frequencies band-stop filter, btw). But am I gonna find that an 8-bit DAC doesn't have a high enough resolution to reliably demodulate different digital signals? I mean, I figure if its capable of demodulating HD TV signals as it was presumably designed to do, I should be able to do some stuff with it, right? How advanced would I have to get with antennae and cabling to get good enough quality to do this? The kit I bought came with what seem like pretty low-tech antennae https://www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Telescopic/dp/B011HVUEME/ref=sr_1_19?keywords=sdr&qid=1556899290&s=gateway&sr=8-19, but I've already bought a couple more simple ones. Similarly, I bought some adapters so I can use standard coax cable because I assume its shielding will be helpful.
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May 5, 2019 04:45
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What are you trying to demodulate specifically? I've used my RTL-SDR to listen to listen to a bunch of different trunked mobile networks using just SDR# and Unitrunker and DSDPlus.
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May 6, 2019 17:25
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Internet Wizard posted:What are you trying to demodulate specifically? I've used my RTL-SDR to listen to listen to a bunch of different trunked mobile networks using just SDR# and Unitrunker and DSDPlus. I didn't have anything in particular in mind, I just thought it would be an interesting experiment to find some signals, identify them and figure out how to demodulate them just to kind of explore the spectrum. I am seeing tons of signals but I am having a hell of a time identifying any of them. They all just look like blips on the FFT Spectrum graph, and none of the demodulators built into SDRSharp can demod them in a meaningful way.
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May 7, 2019 18:07
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The Scientist posted:I didn't have anything in particular in mind, I just thought it would be an interesting experiment to find some signals, identify them and figure out how to demodulate them just to kind of explore the spectrum. Yeah you can demod a hell of a lot of stuff with one of them, but most of the time I see the weirder stuff being played with in gnuradio, like this talk: https://www.youtube.com/watch?v=drsgh_PZmJ8 idk what the best alternative is if you dont want to deal with linux
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May 7, 2019 18:38
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Its funny that you would post Balint, I have been non-stop watching his videos and Con presentations. I'm pretty sure that it was his Defcon 2012 talk "Hacking the Wireless World" that inspired me to buy a $30 RTL2832U. I will check out his Blind Signal Analysis talk for sure! One of my professors said he has a couple $2000 SDR's - I assume they're the USRPs. He said he might let me play with them, all I have to do is agree to help with some Wireless Communications research 
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May 7, 2019 22:03
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The Scientist posted:One of my professors said he has a couple $2000 SDR's - I assume they're the USRPs. He said he might let me play with them, all I have to do is agree to help with some Wireless Communications research SDRs are fun as hell. I have a HackRF knockoff and although gnu radio stuff seems fussy, it's a neat little toy.
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May 8, 2019 03:03
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The Scientist posted:One of my professors said he has a couple $2000 SDR's - I assume they're the USRPs. He said he might let me play with them, all I have to do is agree to help with some Wireless Communications research If he's a ham, I'd assume a $2k SDR would be a FlexRadio unit of some kind.
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May 8, 2019 03:16
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Update: he says they're N210 USRPs from Ettus research. I'm not 100% about his level of involvement, but I think this implies that Balint from the above posted videos would have had some hand in their design. Except that they're ~8 yrs old.
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May 8, 2019 23:46
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in my defense, we are still on SA, the shitpost haven https://twitter.com/KC4YLV/status/1126351372025155584
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May 9, 2019 06:03
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Joining SDR chat, I took my Technician test earlier this week and am now to be globally known as KN1UIW (I'm just happy I got a whiskey in my assigned callsign). I've got multiple RTL-SDRs and I've camped out on 146.520MHz and never heard a thing. I've also tried to tune into some repeaters in my area and never picked anything up either. Is there a better frequency in the cheapie SDR's range I should sit on to hear people? My antenna is just a 510mm piece of solid core 20AWG jammed into a Type N connector with another 510mm piece of that same wire crushed under a nut on the barrel of that connector so I don't have a ton of range either.
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May 9, 2019 22:57
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It will probably be a weird gain issue in the software. Welcome to the world of ham radio. Amazon has some neat antenna stuff depending on what you want to listen to.
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May 10, 2019 05:19
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The thing with analog FM call is you need to be sitting on it to hear anything and people don’t chat there normally. More than once I’ve driven from NY through Chicago on the 90, or cutting through Canada, and I haven’t heard jack poo poo. APRS has a suggested operating method to let people know you’re there - really you just have to “call” and it will stop People’s scanners and that and maybe they will call back. Locally some guys would chat on .52 which would get up into Toronto and make people mad they were talking on the call channel but man it’s not like there is a pile up and then you know someone is out there.
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May 11, 2019 04:17
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Partycat posted:The thing with analog FM call is you need to be sitting on it to hear anything and people don’t chat there normally. More than once I’ve driven from NY through Chicago on the 90, or cutting through Canada, and I haven’t heard jack poo poo. This is the first time I've started in earnest to try to pick up VHF since I've usually only worked with decoding digital stuff in the 915MHz ISM band and building my own transmitters for talking on that. Thanks for the info, I'll keep poking around and set up a scanner myself to hop around the frequencies and hopefully catch someone making a call. It's more of just a personal goal to be able to pull a conversation from the air like magic more than a desire to chat with people.
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May 11, 2019 12:34
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also, where is the antenna located? if it's not relatively in the clear outside you will be fairly deaf. You don't need it 50 feet in the air, even 10-20 feet of height will get you coverage of an urban area, but anything outside is way better than in a window or on your fridge.
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May 11, 2019 16:34
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CapnBry posted:Huh I did not know that. I'm surprised because there's so many amateur radio clubs and resources out there that I expected I'd be able to wander around the dial and pick up conversations happening at any time. Honestly we could probably remove like 2/3 of the repeaters here in the US and be fine. Probably even increase activity. edit: that's more of what HF is with lots of different conversations happening all over the bands, but we're currently at a solar minimum meaning propagation is pretty bad.
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May 11, 2019 22:14
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fordan posted:Honestly we could probably remove like 2/3 of the repeaters here in the US and be fine. Probably even increase activity. Denver is incredibly bad about this. There’s probably a couple dozen club 2m repeaters or more and maybe 3 get any daily activity??? Jonny290 can preach it too
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May 11, 2019 22:39
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CapnBry posted:Huh I did not know that. I'm surprised because there's so many amateur radio clubs and resources out there that I expected I'd be able to wander around the dial and pick up conversations happening at any time. Here in Albuquerque, I hear people on 146.520 probably 1/10 times I'm in the pickup. There's also a state-wide linked repeater system which gets a big chunk of traffic, and beyond that there's one or two repeaters which actually have people using them on a regular basis. In my experience, 2m is pretty quiet 90% of the time--like at any given time, I could probably scan the entire band and not hear a conversation. Weekday mornings often have nets going on, which are the most boring thing on amateur radio but at least they're predictable.
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May 11, 2019 22:59
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Yeah I guess the point I was trying to get to was that on that sort of call channel, if you’re not calling people won’t know you are there and vice versa
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May 12, 2019 02:26
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This is, I'm sure, old news to everyone but me, but I just found out that you can search FCC licenses by a crazy amount of criteria, like frequency or location. Seems super useful: https://wireless2.fcc.gov/UlsApp/UlsSearch/searchLicense.jsp Then at https://fcc.report you can even get technical documents for devices that have FCC certs. For example, this highly technical computer on a table made of 2x4's: https://fcc.report/FCC-ID/H52PT-3030/120894.
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May 14, 2019 06:44
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The Scientist posted:I didn't have anything in particular in mind, I just thought it would be an interesting experiment to find some signals, identify them and figure out how to demodulate them just to kind of explore the spectrum. There’s a good chance you’re looking at digital signals, and SDR# only had analogue demodulating built in. You’ll need something like unitrunker and DSD+ to demodulate digital signals, even voice. I recommend starting by identifying the frequencies you’re seeing the signals at and searching around for what type of transmissions use those freqs in your country
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May 14, 2019 19:34
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This site is useful for identifying digital signals by ear/waterfall https://www.sigidwiki.com/wiki/Signal_Identification_Guide
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May 14, 2019 19:48
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So, I’d like to upgrade my portable setup for event support, looking for any ideas - including buying new gear. I can spend 8 - 12 hours in a rental truck running SAG for bike races. I currently bring a marine battery box with 4x 7Ah SLA batteries which won’t carry me all day. I take two fused 8AWG leads from Walmart amp wiring kits and wire to the vehicle battery. That comes over the cowl and through the door to a fuse block, which has a power pole lead on it. That plugs right into a high strand count lead with power pole ends (this sort of thing https://www.progressiverc.com/parallel-6x-xt30-charge-cable.html) That plugs in with my Garmin GPS8X, the DM700, and a cig lighter plug. The battery bank filters the engine and charging noise excellently. Since the trucks are aluminum half the time now. I take a steel folding chair with me and bungee it in the bed, and slap a mag mount 3/8 dual band on it. My issues are it looks like a messy pile of poo poo, so I’d like to clean up the wiring I don’t need the cig lighter and would rather have USB This goes in front of the middle seat in the truck so it is in the way . The dm700 has a remote head , and I’d love to use my iPad for aprs map - is there a better solution or idea with the battery sink? Can I shrink it since I’m running from the vehicle battery and use ____ to put the equipment up on the dash somehow ? Are there good suction cup products ? Gonna be hanging wires if so. How would you tackle this ? I can run APRS on my iPhone with the USB lead instead of on RF to cut some wires down but I’d like the capability or option if reasonable .
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May 14, 2019 21:57
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Partycat posted:So, I’d like to upgrade my portable setup for event support, looking for any ideas - including buying new gear. Can't help too much with the technical details of your rig, but I'm a little surprised that the cigarette lighter adapter can draw enough current to keep the battery bank topped off. In my experience, those cigarette lighter sockets are fused and can only provide so much power without modification. Would a cheap solar panel from Harbor Freight do anything for you? ....... This is a bit silly: https://www.nytimes.com/2019/05/04/us/key-fobs-north-olmsted-ohio.html People in a town outside of Cleveland found that their car keyfobs for their cars were mysteriously not working. It's interesting to me because I recently discovered https://github.com/F5OEO/rpitx, which lets you turn any Raspberry Pi into a radio transmitter with literally no additional hardware. One thing I was considering playing around with was this: https://www.rtl-sdr.com/using-an-rtl-sdr-and-rpitx-to-unlock-a-car-with-a-replay-attack/ . I used my rtl-sdr to record the keyfob signals for an older VW and a Ford F-150, but their signals are pretty strange and I can't decode them just yet. The other thing is that using the code, you can transmit on an arbitrary frequency between 50Khz - 1500 Mhz, and the current on the GPIO pins can conceivably go up to 50 mA, so that's potentially 0.165 Watts. I'm new to radio but I know FCC-wise I'm not supposed to just broadcast on any arbitrary frequencies. I would prefer not to jam someone's IoT Heart Pacemaker or something. whose tuggin fucked around with this message at 00:39 on May 17, 2019 |
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May 16, 2019 16:45
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The Scientist posted:The other thing is that using the code, you can transmit on an arbitrary frequency between 50Khz - 1500 Mhz, and the current on the GPIO pins can conceivably go up to 50 mA, so that's potentially 0.165 Watts. I'm new to radio but I know FCC-wise I'm not supposed to just broadcast on any arbitrary frequencies. I would prefer not to jam someone's IoT Heart Pacemaker or something. AFAIK pacemakers and other medical electronics mostly use 2.4ghz (Bluetooth).
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May 17, 2019 09:57
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Winlink VHF Packet station wont hear my packets anymore but i can see the beacon signal. I havent changed anything so whyyyyyy???  I have calibrated my signal and its maoedulating p. nicely.so much for worlds northernmost Winlink RMS :/
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May 20, 2019 14:23
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If they are running a TNC can you talk to it ? Is it in a network maybe you can get near it and grab MHEARD or something ?
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May 20, 2019 22:38
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Partycat posted:If they are running a TNC can you talk to it ? Is it in a network maybe you can get near it and grab MHEARD or something ? I am gonna try and rig usb signalink and baofeng and send packets. I can see the volume indicator turn up when it receives my signal and the tnc is activated in RMS.
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May 21, 2019 21:07
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Oh you’re running it . I have no idea how software TNC emulation works to be honest . Kantronics KPC3s should be cheap as dirt since no one cares about packet BBS any more - we use those for winlink email and whatever other packet here
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May 21, 2019 22:12
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Partycat posted:Oh you’re running it . I have no idea how software TNC emulation works to be honest . Nah, the station is running in the clubhouse and the log window for connections is always displayed on a pc screen. It is using a KPC3 incidentally tho. Anyway voxing with baofeng and signalink was more trouble than its worth, not surprising. I know its probably just some obscure radio amateur thing that is the reason for my problems so it makes it pretty irritating :/
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May 21, 2019 23:10
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Well, I’m not super familiar with Winlink but I can ask my winlink guy anything. Normally the issue is that the TNC is hosed up or someone touched the link radio so it is doing tone decode or is on a split program or something.
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May 21, 2019 23:12
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Partycat posted:Well, I’m not super familiar with Winlink but I can ask my winlink guy anything. Normally the issue is that the TNC is hosed up or someone touched the link radio so it is doing tone decode or is on a split program or something. yeah... sysop is on vacation lol. I think ill wait for him to return, the last thing i will do before that is to try peer to peer connection and see if i actually can send good packets to someone else.
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May 21, 2019 23:14
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