Wanting to play with SDR - Page 1
Forum section: electronics / rf-microwave

author: Red Squirrel
author_rank: Super Contributor
timestamp: April 15, 2017, 02:07:07 am
content: I want to setup a RPI (will the 1st gen work?) as a SDR server, basically something like these:http://websdr.org/I imagine there's all sorts of software that can be used to create that interface, open to suggestions. I like the idea of it being web based. I may or may not open it to the public. I do have the bandwidth for it but there is also the privacy issue I need to investigate. (ex: if someone somehow manages to snoop on any kind of private info that is generating wireless waves either intentionally or not...I doubt it... just something I need to evaluate)As for the hardware, is this pretty much what I need:Tuner:https://www.amazon.ca/gp/product/B01HA642SW/ref=ox_sc_act_title_5?smid=A2ODZQFKJKWN4I&psc=1Optional board that allows more frequency ranges (I'm curious how exactly that works if anyone wants to explain, and if there's any disadvantage)https://www.amazon.ca/gp/product/B009LQT3G6/ref=ox_sc_act_title_4?smid=A2ODZQFKJKWN4I&psc=1Balun for if I want to make a long wire antenna or experiment with other types:https://www.amazon.ca/gp/product/B00R09WHT6/ref=ox_sc_act_title_3?smid=A2ODZQFKJKWN4I&psc=1Cable to connect the parts together:https://www.amazon.ca/gp/product/B00SUVVXIY/ref=ox_sc_act_title_2?smid=AQMXZMVD5PL9J&psc=1Is there anything else I might be missing?Also if I want to play around with APRS at some point, would this work for that? (receive only)

author: awallin
author_rank: Frequent Contributor
timestamp: April 28, 2017, 12:47:32 pm
content: The Dutch websdr software is not available publicly. You may or may not get it from the original author by asking.openwebrx is available under an open license:http://sdr.hu/openwebrxThe user-interface doesn't have as many features as websdr.I believe there is a fork of openwebrx made specifically for the kiwiSDRhttps://github.com/jks-prv/Beagle_SDR_GPSit has much better zooming and a spectrum-view and other features not (yet?) in the original openwebrx.let us know if you find some other open and freely available solutions for web-SDRs!In the long-term a sub-project of gnu-radio for web-enabled GUI widgets would be awesome...

author: Red Squirrel
author_rank: Super Contributor
timestamp: April 29, 2017, 12:49:29 pm
content: I ended up ordering the stuff I linked to, did not really get a chance to play with it though. I guess there arn't all that many programs out there then? I kinda figured there would be a flood of them. I'll check out OpenWebRX.As a side note I picked up a shortwave radio in the same order, never played with one before. Actually picking up some stuff from the states, pretty neat. 10Mhz is rather interesting. Skip propagation is a fun thing.

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 10, 2017, 12:58:15 pm
content: do you ever play with an SDR?How many people live in you area?Does Cable TV available in your Area?

author: james_s
author_rank: Super Contributor
timestamp: May 10, 2017, 06:39:51 pm
content: I've been using those RTL dongles for years, they're awesome for the price. I use mostly SDR# in Windows. I have one on a Raspberry Pi too that runs Dump1090 to receive ADSB transponders, and there's RTL433 that picks up various wireless thermometers, weather stations and light switches.

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 10, 2017, 06:51:10 pm
content: maybe you look into:http://forums.radioreference.com/It is an US forum for sdr and radio stuff.

author: Codebird
author_rank: Regular Contributor
timestamp: May 11, 2017, 09:56:39 am
content: A good starting point is an RTL-SDR - for they are cheap as dirt. Obviously SNR, sensitivity, etc won't be as good as a higher-end device, and they can't tune low enough for the HF bands (VHF works easily, though), but they are a good way to become familiar with the software and technology so you will be better informed when you decide what to spend the big money on. Plus they are really easy to make network-accessible.

author: BigBoss
author_rank: Regular Contributor
timestamp: May 16, 2017, 12:03:36 am
content: For who wants to play the SDRs.https://myriadrf.org/

author: retrolefty
author_rank: Super Contributor
timestamp: May 16, 2017, 12:18:10 am
content: I tried some SDR but found the UI of the software just not as satisfying as rotating knobs and flipping switches on a real hardware receivers. But then again I'm old.

author: Codebird
author_rank: Regular Contributor
timestamp: May 18, 2017, 07:59:42 am
content: QuoteI must make a correction: I have purchased a second rtl-sdr for myself, this time with the direct sampling mod, and can personally confirm that it does indeed tune the HF bands. I hear long-wave radio from Europe, barely, even with a really tiny stick-antenna. Once I stick a proper dipole on this thing it should work better. Picks up a ton of noise though from it's own local oscillator, even though that component has no purpose in direct sampling mode.

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 19, 2017, 07:33:04 am
content: I did not get a chance to play with mine yet but I also got a "hamitup" which is suppose to allow for very low frequencies. It just plugs into the SDR via coax and then you plug the antenna in it. How does this work, from a technical standpoint? Like if the SDR is only capable of handling certain frequencies how does putting a device between it and the antenna change that? And will the OS/software know? Or does it do it kinda virtually by upconverting the signal to frequencies the SDR can understand and I have to make that distinction in software? So say, 100Mhz is actually 100Khz's data being "rebroadcast" on 100Mhz. That's the only way I see it could be doing it, but I'm kind of new to this stuff so learning.

author: Codebird
author_rank: Regular Contributor
timestamp: May 19, 2017, 08:52:38 am
content: "Or does it do it kinda virtually by upconverting the signal to frequencies the SDR can understand and I have to make that distinction in software? So say, 100Mhz is actually 100Khz's data being "rebroadcast" on 100Mhz."You got it. Yes, that's how it works, and there's a setting somewhere in the software to tell it you are using an upconverter.The other way to get the low frequencies on SDR is to use a direct sampling receiver - either one designed for the purpose (ie, pricy) or an RTL-SDR with the appropriate bodge-wire fitted (You can get these pre-made).

author: technix
author_rank: Super Contributor
timestamp: May 19, 2017, 09:04:44 am
content: You can start with the RTL-SDR stack (a $10 USB dongle and you can start listening.) Invest in a SA612 mixer module if you want to hear the lower end of the band (converting the 0-50MHz band up to somewhere RTL-SDR can tune into, like the 200-250MHz band.)Here are some interesting bands you can hear with straight RTL-SDR:* FM broadcast* Airports and airplanes (can be interesting, can be devastating. I had a lot fun listening to Shanghai Hongqiao Int'l Airport Tower which I live very close to.)* Marine radio* CB radio* Some walkie-talkiesWith the SA612 mixer you gains access to:* AM broadcast* Shortwave broadcastSince RTL-SDR (including the SA612 add-on) functions as a scanner (wide-band radio receiver) it is very likely you can operate it unlicensed. Going from there you will want to get a HAM license since you will be speaking into the radio spectrum.Since SDR operation depends on the efficiency of FFT (receiving) and iFFT (sending,) you may want to invest in a moderately powerful GPU (like nVidia GTX 1060 or AMD Radeon RX 470) and make sure OpenCL works on the card so your computer can handle the encoding and decoding of baseband RF signals in real time. I have an R9 380 on my machine (and 16 CPU cores in another) to make SSTV over RTL-SDR work in real time.

author: Codebird
author_rank: Regular Contributor
timestamp: May 19, 2017, 12:36:19 pm
content: QuoteAmateur radio 2m and 70cm bands. Hang with the hams.Also a great many 'mystery signals' that must serve some purpose, even if it's very hard to figure out what exactly they are.

author: w2aew
author_rank: Super Contributor
timestamp: May 19, 2017, 12:47:17 pm
content: Quote from: Red Squirrel on May 19, 2017, 07:33:04 amYes, it does a frequency up-conversion. You might find these video explanations helpful:And for some more background on mixers and frequency conversion:

author: HoracioDos
author_rank: Frequent Contributor
timestamp: May 19, 2017, 12:54:01 pm
content: HiGet this book. It shows a lot of interesting areas to explore with SDR. Many projects and software available.https://www.amazon.com/Hobbyists-Guide-RTL-SDR-Software-Defined-ebook/dp/B00KCDF1QI/ref=sr_1_1?ie=UTF8&qid=1495197858&sr=8-1&keywords=THE+HOBBYIST’S+GUIDE+TO+RTL-SDRI started to play with unitrunk this year and switched later to trunk-recorder to listen trunked radio systemshttps://github.com/robotastic/trunk-recorderPS:If you want to learn GNU radio and some basics. Get these too.https://www.amazon.com/Field-Expedient-SDR-Introduction-Software-ebook/dp/B01M15DO0S/ref=pd_sim_351_5?_encoding=UTF8&psc=1&refRID=HGMB6C0HZE9ERPK29ZWBhttps://www.amazon.com/Field-Expedient-SDR-Basic-Analog-ebook/dp/B01LXKJRSA/ref=asap_bc?ie=UTF8

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 22, 2017, 11:22:57 pm
content: is there anythink between the Cheap SDR and the very expensive Wideband SDR?

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2017, 12:46:32 am
content: Sure, there's the HackRF, and there's another SDR that is more midrange, something like $130, I forget what it's called.Nothing comes close to the cheapness of the RTL dongles though, they were a revolution in SDR, dropping the price of entry by orders of magnitude almost overnight.

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 23, 2017, 01:52:19 am
content: Thanks everyone for links and videos, will check those out when I get the chance.Looks of cool stuff that can be done with it.

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2017, 04:11:15 am
content: Found a page listing a bunch of options.http://www.rtl-sdr.com/roundup-software-defined-radios/The SDRPlay is the one I was thinking of earlier but there are some others here that I wasn't familiar with. Still, the cheap RTL dongle is enough to do a lot of really cool stuff.

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 23, 2017, 09:52:48 am
content: Quotea German Dealer want:HackRF One Platine 329.00 € + 11€ Shipping.That isnt cheap in my eyes.Quotea lot of SDR with the Same boring Chip: R820T2

author: Codebird
author_rank: Regular Contributor
timestamp: May 23, 2017, 11:59:07 am
content: QuoteIt's cheap. It works well enough. And it's cheap. Eight bit capture is hardly ideal, but... it is cheap.If you want high-end SDR, you can get that too. Just be prepared to pay.

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 23, 2017, 12:15:10 pm
content: the company offer the sdr for 1XX$ but the are never available for the price.I call it scam!

author: borjam
author_rank: Unknown
timestamp: May 23, 2017, 12:31:24 pm
content: HackRF is interesting only if you intend to transmit with it.For reception, the good mid range options are (in my opinion):Only for HF: Cross Country Wireless SDR-4+. There is a very interesting dual diversity version as well. If you order from them, be patient. It's a one man show and it can take time to have your order shipped. But the receiver is really good. Only 192 KHz of bandwidth however.Broadband: SDRPlay and AirSpy. Both are quite a step above the typical RTL. AirSpy doesn't cover HF without an up converter, though.

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 23, 2017, 12:44:48 pm
content: http://www.sdrplay.com/docs/161115%20RSP2%20flyerV3a.pdfcost ~200€ with shipping.it goes just to 2 GHzjust "Up to" 10 MHz visible bandwidthAIRSPY-R2 Airspy R2 SDR 232.00 €AIRSPY-MINI Airspy Mini SDR 138.00 €+ 11€ shippingthe arent any cheaper.In my case I run 2x ADSB + 2 ACARS and for the future I will run 20 more.So 10 or 15 AIRSPY-R2 will cost up to 3500€.

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2017, 03:40:19 pm
content: $329 *is* cheap for SDR, or it was until the insanely cheap RTL dongles appeared. Before those showed up on the scene $1k was considered cheap SDR, hence I never got into it until then. The reason the dongles are so cheap is that they're mass produced TV tuners intended for the consumer market. The SDR market is far more of a specialized niche.Being able to transmit would be lots of fun, haven't needed it badly enough yet to justify the price though.

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 23, 2017, 03:45:16 pm
content: Sadly i found no software who would allow me to send something on a win pc.

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2017, 04:56:06 pm
content: Yeah a lot of that stuff seems to be Linux based. You can dual boot Linux on a Windows PC easily enough though.

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 23, 2017, 05:04:51 pm
content: I will try with an Virtual pc.Paybe someone know how i can connect my Soundmodem to my CB?https://www.eevblog.com/forum/rf-microwave/connect-a-soundmodem-with-my-cb-radio/

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 23, 2017, 08:48:39 am
content: I finally got around to playing with this, I had the hardware and just kind of forgot about it. For now I'm not using the upconverter, figured I'd play with it as is first. Just using a basic antenna that came with an ADS-B receiver, I will experiment with different antennas over time. Long wire is probably the easiest I would imagine.I setup OpenWebRX. One question though, and sounds stupid but can't find anything, how do I set the frequency range? It defaults to about 143-145 Mhz. I imagine there's a setting somewhere to set the range to something wider?

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 23, 2017, 09:07:33 am
content: the most hardware support 2Mhz max.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 23, 2017, 09:30:38 am
content: Hmmm arn't some of these used for ADS-B? That is 1090Mhz.I found a setting center_freq which lets me change the frequency, but not sure how to change the range. Some web SDRs go from 0-30Mhz for example.I'm not sure if it's my antenna or something else but when I set it to my local radio station I see it on the waterfall, but I don't hear anything. Just static.

author: james_s
author_rank: Super Contributor
timestamp: December 23, 2017, 06:23:19 pm
content: The common USB tuner dongles cover from around 50MHz up to 2GHz. What software are you using? The entire FM broadcast band should be easily covered.

author: stj
author_rank: Super Contributor
timestamp: December 23, 2017, 08:13:12 pm
content: Quote from: Red Squirrel on December 23, 2017, 09:30:38 ami dont know what software your using,but the one i played with you have buttons to select the decoding.so you have to manually select AM,FM,FM-narrow,SSB etc.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 23, 2017, 10:52:36 pm
content: Oh sorry thought I mentioned but didn't. It's OpenWebRX. In the config file I can set the centre frequency, but it then only displays like maybe 0.1Mhz on both sides. I imagine there must be a setting somewhere to specify a larger range but can't find it. I thought maybe the sample rate would affect it but it seems anything but default makes it really choppy. Either lower or higher.Looks like a nice piece of software though, once I figure out how to use properly.I'm not really picking up anything at this point, like that large area where I'm set to should be the local FM station but I only get static and the oddball slight sound of a voice or music, but that might just have to do with my antenna which is just a ballun with two pieces of wire sticking out hanging behind my server rack, not tuned or anything. The server stuff probably generates lot of EMI.Half the fun is going to be experimenting with different antenna types. What I'll probably do is see if I can run coax to a location that's more convenient than my hot aisle then play with antennas there.

author: stj
author_rank: Super Contributor
timestamp: December 23, 2017, 11:31:23 pm
content: yes, when i got mine i learned real fast that i should have also got a BNC adapter at the same time!!i think an outdoor wideband "scanner" antenna is probably a good investment.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 24, 2017, 03:33:39 am
content: Actually would Cable TV Coax work? I don't really know that much about impedance and all that but from what I understand you can only use certain impedance cable in certain applications. I don't have cable TV anymore but I have coax running right to my server room from outside. I could put some BNC ends and a SMA to BNC adapter and then just buy a couple premade antennas to play with. Probably easier and later on I can experiment with DIY once I understand more about the theory. I do want to look at getting into ham radio and get licensed at some point, lots of reading to do though! Figure playing with this is going to at least make me able to listen on some stuff and get started with the basics.

author: james_s
author_rank: Super Contributor
timestamp: December 24, 2017, 04:33:05 am
content: An outdoor antenna is not a bad idea, but I can easily pick up dozens of stations all across the FM broadcast band, as well as police, fire, business band, FRS radios, ADS-B, etc using just the crummy little antenna that comes with the dongles.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 24, 2017, 05:04:29 am
content: Yeah probably will experiment with indoor antenna first, just need to either buy a premade one or google some designs that are better than me sticking random pieces of wire in it.What I find odd though is how the waterfall display has a very clear indication of something yet I only hear static. Is that to be expected with a bad antenna? If I unplug the antenna then I get no waterfall, so it's doing something. I guess it's just picking up so much noise on top of the signal which is probably why I can't hear much. I'm working now so I'll play with this again after Christmas time. I also need to figure out why I get such a narrow range of frequencies, I presume that's a setting somewhere.

author: james_s
author_rank: Super Contributor
timestamp: December 24, 2017, 07:03:29 am
content: You should be able to get a bunch of local FM broadcast stations with nothing more than a paperclip if the hardware and software is working correctly. A reasonably strong station will come in with nothing at all connected to the antenna socket. Focus on getting things working first, then look at antennas.Did you try setting the tuner gain?

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 24, 2017, 08:59:00 am
content: Hmmm I kind of thought so. I built a rudimentary crystal radio using a sheet of foil and paper as the tuning capacitor and picked up the local FM station so not like it takes much. Maybe there definitely is a problem then. I set the gain to 0 which lets the tuner adjust itself. I may have to play with different values.Anything else worth looking at as well?This is interesting:Notice that anomaly in the middle, when it did that, I was able to hear the radio for a sec. When I get around to it (at work now) I may move the entire setup upstairs away from the server rack just to rule out any kind of interference. It is sitting on a shelf above the two network switches and wonder if it's picking up noise from all the ethernet cables or something. Might be worth getting a small USB extension so I can put the dongle a bit away from the PI too just to try to eliminate possible issues.

author: stj
author_rank: Super Contributor
timestamp: December 24, 2017, 10:33:49 am
content: one thing worth pointing out is on Linux atleast, the hardware driver has variable gain.i thought my setup was shit and hardly working till i found the gain control existed and was at about 10%!! jacked it to max and now find loads of stuff.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 26, 2017, 10:31:43 am
content: Yeah I played around with the gain. I'm thinking I have a source of high noise though so I will need to play with the physical setup and move it completely once I'm done work just to rule out the server rack equipment being a source of noise.

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 26, 2017, 01:37:52 pm
content: depend on the country its could be illegal to receive police and other.

author: rhb
author_rank: Super Contributor
timestamp: December 26, 2017, 02:39:05 pm
content: I bought an SDRplay RSP2. It's quite remarkable for the price and at 12 bits has 24 dB greater dynamic range than the RTL-SDR. Be aware that the design of the front end means it will be crushed by a nearby transmitter in band. This is true of all the cheap SDRs. The RSP2 improved the input preselection filters over the set in the RSP1, but a notch filter or other external preselection may be needed. With the addition of a BG7TBL noise generator you can use the RSP2 to test filters. Having a 10 MHz BW is a big help for that.I chose the RSP2 because it covered HF without needing an external convertor. Another advantage to the RSP2 is the external reference clock input and output. This will let you do interesting things by phase locking multiple units which makes diversity reception, direction finding and other neat things possible. At least if you're prepared to do some programming.If you are at all curious, you will learn a lot playing with an SDR no matter what make. You really can't go wrong. I think the RSP2 hit the sweet spot and SDRplay have been very responsive when I ran into issues. A Windows update borked the software, but I got a fix in the form of a link to an MS patch very quickly.Have Fun!RegBTW You can certainly use 75 ohm coax. Ideally you should have a 75-50 ohm transformer at the radio. However, the impedance of a dipole at the feedpoint of the antenna varies with the height above ground so the impedance is not necessarily 50 ohms. Many years ago as a grad student I ran a 6L6 and a rock using an inverted Vee dipole and scavenged TV coax. The apex of the Vee was not very high, so based on a graph in the ARRL handbook I estimated it was about 75 ohms. You *should* have a balun, but I did not as I could barely afford to eat. It worked and I made some QSOs using a Panasonic RF-2200 as the station receiver. I quickly learned not to touch the dial after starting a QSO as I could never set it back correctly if I did.

author: stj
author_rank: Super Contributor
timestamp: December 26, 2017, 05:29:46 pm
content: Quote from: Lord of nothing on December 26, 2017, 01:37:52 pmwho cares, they listen to us.

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 26, 2017, 05:33:13 pm
content: especially in UK the Law about Drive Encryption is very restrictive.So if the search your house and see that you maybe do some illegal stuff and the take your hardware with you.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 27, 2017, 01:48:38 am
content: Quote from: stj on December 26, 2017, 05:29:46 pmYep and it's a beauty about radio, there is no way for them to track what we listen to. Unlike internet.Well I guess technically when you are capturing radio waves you are "using" the energy so there may be a way to track that but I think it would be extremely hard, because everything is capturing it passively too.I feel sad for the UK though they are really insane when it comes to mass surveillance and all that stuff, they might even be worse than the states.I did not get a chance to play with my SDR further, can't figure out why I can't hear anything but did not get a chance to physically do anything. I will need to move it just to rule out the server rack or anything physical going on.Also not sure how to increase the frequency range that I can view, there's got to be a setting somewhere but can't find any info. Only found a setting to change the centre frequency but not the range on both sides.

author: rhb
author_rank: Super Contributor
timestamp: December 27, 2017, 04:37:56 am
content: As I understood it, you bought an RTL-SDR. So far as I know that has a fixed frequency span of 96 or 192 KHz. That was a major reason for my picking an RSP2.FWIW It took me a while to get sound out of the RSP2. The software is "interesting".

author: james_s
author_rank: Super Contributor
timestamp: December 27, 2017, 04:55:33 am
content: Quote from: Lord of nothing on December 26, 2017, 01:37:52 pmIf someone doesn't want me to listen to their transmissions, they need to keep their radio waves off my property. I'll listen to anything I damn well please, they can't search my house without probable cause and they'd have to catch me in the act. Perfectly legal to listen to the police in the US anyway.It was illegal to listen to analog cellular phones back when those were in use but it was completely un-enforcable. Every Pro-2004 to Pro-2006 scanner I've ever seen had the cellular band unlock hack done.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 27, 2017, 05:51:25 am
content: Quote from: rhb on December 27, 2017, 04:37:56 amHmm I thought it could go in the Mhz range even even low Ghz, don't people use these for ADS-B? Maybe that's why it's acting funny, it's trying to go into that range since that's what I set it to, but then it's not really working. This is the one I got:https://www.amazon.ca/gp/product/B01HA642SW/ref=oh_aui_detailpage_o09_s01?ie=UTF8&psc=1I also got a Ham It Up so I can play with the lower frequencies but have not hooked it up yet.

author: Dubbie
author_rank: Unknown
timestamp: December 27, 2017, 06:12:21 am
content: This might be the thread to ask. I have built a little transmitter (extremely short range, only a few meters, before you call the FCC on me) it is 915MHz. I plan to transmit FSK2 and a digital packet format @ ~ 10Kbaud. Is there a SDR that I could receive these packets with? I want to experiment a bit before building a matching receiver. The reason I have built my own is because I need an extremely unusual form factor.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 27, 2017, 07:58:11 am
content: I imagine it would work. May even be able to build a SDR as the receiver to decode it instead of a receiver from scratch (though a SDR will be more expensive and overkill probably). It's done for ADS-B (airplane transponder) and lot of other things. I guess you could do APRS too, though that's normally done via audio into the sound card. I'm a newbie myself so don't know much about how any of this is actually done though, just that it can be done.

author: stj
author_rank: Super Contributor
timestamp: December 27, 2017, 12:33:47 pm
content: the master of links.http://sdr.osmocom.org/trac/wiki/rtl-sdr

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 28, 2017, 02:15:47 am
content: Off work now, so played with this for a bit. Moved the setup in my office temporarily just to rule out server related noise. No change. Tried a USB extension as I read of people doing that, no go. Unplugging/plugging antennas changes the waterfall, but the sound always stays the same. It's like if what I'm hearing is not actually what it's producing. I just hear noise. Though I could have sworn I heard voices a few times, but sometimes that happens even when no radio is on.I may have to put the whole thing in a grounded tin can or something. I'll play with that further another time. Tried all sorts of gain settings but that does not seem to change anything. The waterfall colours change to show more/less intensity but the sound is always just noise.

author: rhb
author_rank: Super Contributor
timestamp: December 28, 2017, 02:28:10 am
content: How far are you from a broadcast tower? My SDRplay RSP2 is deaf during the day because of a local 1 KW AM station less than 2 miles away. Works just fine at night when they are off the air. A notch filter is on my ToDo list. This is an issue with all SDRs. They cannot hear anything which is -6 dB * # of bits below the strongest signal in the passband of the receiver. For the RTL-SDR line the filters are quite broad. With the narrow BW of the RTL-SDR, you may not even see the interfering signal in the waterfall.If you've got a signal source, hook that up, but make sure that you don't blow the front end. I had to build a -40dB attenuator for my RSP2 and monitored the signal level using a Tee to my scope before I connected the RSP2.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 28, 2017, 03:47:44 am
content: Hmmm there is a tower in front of my house, it has like 3 sets of cell sectors on it, and think OTA TV transmission. I know that if I plug a small piece of wire behind my TV I get a digital OTA channel in crystal clear HD while the others are snowy, so that TV signal is probably rather strong and may be from that tower.The neat thing with the Openwebrx software is that the web interface works on my phone so if I get a wifi router I could technically set this up as a portable system and view it with my phone. Might have to do that and drive out of town just to see if things change. Too cold to do that now though. Like -35 out there.I don't have anything in mind that can generate a signal though. Suppose a wave form generator might be my next toy if I want to get into this stuff.This is the tower in front of my house if curious:Guessing those straight antennas on top are TV. Or maybe lightning rods actually... The ones that look like bars off the sides are cell. Though there's a couple other possible antennas in there like that white round thing might be some sort of antenna.

author: james_s
author_rank: Super Contributor
timestamp: December 28, 2017, 06:39:34 am
content: Either there's something wrong with your software setup or your hardware is defective. I have several different dongles and they all work painlessly. I can pick up dozens of signals all over the band using nothing more than a small piece of wire or the included stub antenna. You shouldn't need anything fancy at all.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 28, 2017, 06:48:49 am
content: Thing is the waterfall seems accurate. It shows more color where I expect to see a radio station, but the sound is just static. Anything software wise I can check to troubleshoot this?It also gets random spurts where I CAN hear stuff, but it's very short lived, like 1/4 second.

author: SeanB
author_rank: Super Contributor
timestamp: December 28, 2017, 07:22:17 am
content: Quote from: Red Squirrel on December 28, 2017, 03:47:44 amOutside are sector antennas, long rods are lightning rods, white block is GPS receiver for cell timing, and smaller antennas are for 4G/LTE services. Looks like a LED warning light as well. Pretty much a common low density area cell tower.

author: james_s
author_rank: Super Contributor
timestamp: December 28, 2017, 07:33:58 am
content: Doesn't look like LED to me. I suppose it could have been updated but most of those beacons of that style use a pair of 610W mogul prefocus base incandescent lamps. I forget what the beacon is called but it has an official designation, they're made in that style by several companies.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 28, 2017, 08:56:04 am
content: Yeah doubt it's led. That one is the flasher, there is one mid tower that stays on. I monitor these for my own company, among lot of other things, and the bulbs burn out often enough and have to be changed. Would be a fun job to go up there. Idealy in mild weather.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 28, 2017, 11:55:17 am
content: Quote from: Red Squirrel on December 28, 2017, 06:48:49 amLooking at your screenshots it seems to me that you are trying to receive wideband FM (about 100KHz deviation) with a receiver set to narrow band FM (12KHz). You will never get any meaningful audio like that.Give it a try with SDR#:https://airspy.com/download/

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 29, 2017, 03:18:02 am
content: Actually I was wondering that too, if maybe I should be able to capture a wider range as the area of the waterfall that shows signal is much wider than what it's letting me capture.Guess I will try Airspy or another software and see if it's better. Maybe I can also get access to the entire range since right now I need to change a setting and restart the server just to tune to a different frequency. Their readme file explains this saying that they did it that way since when you tune to another frequency it would affect every user if more than one person is listening... but that does not matter to me.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 30, 2017, 06:14:06 am
content: Reading further it really does sound like this does not support wide band FM. Weird. That was not my goal, but figured that would work too. I don't know of any other sources of radio I can look for, and because I can't figure out how to set a larger frequency range the only way to tune is to restart the server each time and manually input frequencies. Kinda defeats the purpose, as I was hoping I can get a waterfall that shows a large frequency range so that I can look for interesting stuff. Some of the SDRs on their site do have a larger selectable range though, so I don't get how they did that. There's got to be a setting somewhere that I just don't know about.A lot of people are requesting to be able to update centre frequency from the web page though, so I think I'm going to wait to see if they do add that feature. Hopefully in the process they just increase the range of the waterfall too. I downloaded the airspy one but I just get a single file, I'm assuming it's a Raspberry PI image. I don't want to reload the Pi just yet so I'll wait and see. I can probably throw this back in my server rack now that I know that was not the issue.I did pickup ADSB, it's basically just a constant beep. Will have to wait till there is no aircraft within a 300mi radius and see if it changes, just to confirm that what I'm getting is actually that. I have a separate ADSB receiver that feeds to Flightaware.

author: james_s
author_rank: Super Contributor
timestamp: December 30, 2017, 07:07:27 am
content: Quote from: Red Squirrel on December 28, 2017, 08:56:04 am

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 31, 2017, 05:07:36 am
content: This is a fun one too.Talk about one heck of a workout.

author: Jesset1996.5
author_rank: Regular Contributor
timestamp: January 02, 2018, 05:18:40 am
content: Another cool thing you can do with sdr is add it to your favorite old radio such as a TS 690s or an IC 706 with a Panoramic Adapter Tap Board and a rtl sdr of your choice. Those radio's in particular allow you to use CAT control to control your radio from your computer. Not only can you see the stations on hf but you can click on them and your computer will set your radio to that freq. AC8WP

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 02, 2018, 01:54:18 pm
content: I looking for an way to use an legal CB Radio with an ALE System.So an SDR could be the best solution to listen to all Frequency and if an freq works the CB Radio tune into the Freq.My Grandparents life ~500km away from our house the best place for an receiver station.