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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/ZYW5FEHXAJ73D6MWRJTSDY6HEZQIMTVH/", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/", "message_id": "CAJdc4v757xA2OzgnKjGoVxViH8P1z4cAh7U4b+ugFxvqQPSD1A@mail.gmail.com", "message_id_hash": "ZYW5FEHXAJ73D6MWRJTSDY6HEZQIMTVH", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/QS4ZNLSO25FWR4LQYKRNIYRQWKS6ROD4/", "sender": { "address": "rico.van.genugten (a) gmail.com", "mailman_id": "64397f008c1d4d7a8656e4f690b21e7f", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/64397f008c1d4d7a8656e4f690b21e7f/emails/" }, "sender_name": "Rico van Genugten", "subject": "Re: [amsat-bb] RTL-SDR downlink", "date": "2016-06-17T07:02:47Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/7JGAE7J54M6LEV5QHG4GSFU26MFGR2TM/", "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Hi all,\n\nI am using RTL-SDR's for downlink reception for quite some time now. I've\ngot one from the rtl-sdr blog in aluminum casing with TCXO. I can hear the\ndownlinks of pretty much all the LEO's (except SO-50) fine with it using\nindoor antennas. In my experience it is easier copying the downlinks of\nlinear birds, as the required SNR for a copyable signal in SSB is lower.\n\nI can also successfully decode ISS APRS packets using a vertical, RTL-SDR,\nGQRX and direwolf, so that makes for a very cheap ISS APRS receive setup.\nNote: the gnuradio FM demodulator in GQRX works way better than rtl_fm,\nusing the latter I cannot decode any packets. GQRX is pretty CPU-hungry\nthough, so a Raspberry Pi solution would be tricky. (/offtopic)\n\nAs others said, the RTL-SDR has no front-end filtering and therefore\nterrible desense, furthermore it has a pretty low dynamic range, so full\nduplex operation is not possible. Nonetheless I've made a couple of QSO's\nvia AO-85 using the RTL-SDR on the receiving end, just ignoring the audio\nwhen TXing.\n\nI have an AirSpy Mini on order now, I'm curious how it will perform with\nnearby TXing. AFAIK it doesn't have any front-end filtering like the\nSDRPlay or FunCube dongles have, but the dynamic range is way bigger than\nthe RTL-SDR's, so hopefully it will still perform a lot better. Otherwise\nI'll have to build some filters.\n\nRegards,\nRico PA3RVG\n\nOn Fri, Jun 17, 2016 at 1:08 AM, Eduardo PY2RN <[email protected]> wrote:\n\n> The cheap RTL dongles are as much sensible (or more) than the others more\n> expensive.Lack of filtering is the big issue although there are some\n> practical and easy workarounds to improve it.For ham satellites downlink\n> frequency stability should not be an big issue, there are some models\n> already been sold with 0.5PPM TCXO option which are still cheap.It is a\n> great opportunity to operate full-duplex on amateur satellites with very\n> low investment and improving operational capabilities.\n> EME (Moon bounce) audible signal RX comparison between TS-2000 / RTL /\n> FunCube Pro+ can be seen here:\n> https://youtu.be/3OxyO5ylwfs\n>\n> 73\n> ED PY2RN\n>\n>\n> From: Patrick STODDARD (WD9EWK/VA7EWK) <[email protected]>\n> To: \"[email protected]\" <[email protected]>\n> Sent: Thursday, June 16, 2016 5:22 PM\n> Subject: Re: [amsat-bb] RTL-SDR downlink\n>\n> Hi, (name or call?)!\n>\n> The inexpensive RTL-SDR dongles are a great way to get started with\n> SDR receivers. For amateur satellite work, other than the ISS and maybe\n> AO-85, they have a couple of significant drawbacks...\n>\n> 1. These dongles were designed to be TV receivers, working with\n> signals much stronger than we have from our satellites or even the\n> ISS ham station.\n>\n> 2. These dongles lack front-end filtering. This means that there could\n> be a strong signal near you that swamps the receiver that wipes out\n> what you're trying to hear. If you are trying to work satellites\n> full-duplex, it is possible that your transmitter will shut down\n> the dongle until you end your transmission. This was a problem I\n> experienced early on when I tried using one of these dongles as\n> my downlink receiver, and quickly moved on to something else.\n>\n> Unfortunately there isn't anything in the middle ground between these\n> dongles and devices like the SDRplay (sold by HRO in the US for $149)\n> or the FUNcube Dongle Pro+ (sold by its UK manufacturer for around\n> $200 depending on exchange rates, which includes FedEx next-day\n> shipping from England to most addresses in the continental USA). Both\n> of these devices do well as the downlink receiver for working\n> satellites. Both come with front-end filtering that the RTL-SDR\n> dongles lack, and still have sensitive receivers. The SDRplay\n> has a low-noise amplifier that is engaged when receiving at VHF or\n> higher, but you can reduce the amount of gain from the built-in LNA.\n> For my work, I keep that gain reduction value set to 0, so I have\n> maximum gain to hear the downlinks.\n>\n> Good luck, and 73!\n>\n>\n>\n>\n>\n> Patrick WD9EWK/VA7EWK\n> http://www.wd9ewk.net/\n> Twitter: @WD9EWK\n>\n>\n>\n>\n>\n> On Thu, Jun 16, 2016 at 2:30 PM, [email protected] <\n> [email protected]>\n> wrote:\n>\n> > Hello all! Been lurking a while here and just wanted to say hi and\n> thanks\n> > to everyone. Just started working the birds. VERY limited success so far\n> > on the linear transponders. Limited budget leads me to either have to run\n> > in half duplex (obviously not preferred) or come up with another low cost\n> > receiving option. I bought an RTL-SDR to see if it could be any help. I\n> > have to say I really like this little receiver. It’s a little buggy\n> > figuring things out but it receives really pretty well…UNTIL I try\n> > to receive CW and SSB on the transponders. I have no problem receiving FM\n> > repeaters and simplex and have monitored a few SO50 passes with it no\n> > problem, but for some reason I’m not hearing the same signals I can\n> > hear on the receiver of my FT100 with the EXACT same antenna. I A/B them\n> > and have nothing on the SDR. Is anyone using one of these? I am probably\n> > missing something simple. When I started receiving HF I couldn’t\n> make\n> > it work until I figured out I had\n> > to change the sampeling in the setup to direct from\n> > quadrature…only learned that through a forum and I assume\n> something\n> > like that will make the thing come to life. Lack of documentation on some\n> > of these things is kind of a pain. Thanks in advance for any help you can\n> > offer and my apologies to anyone I have frustrated working half duplex! I\n> > will figure out what I’m doing!\n> > ____________________________________________________________\n> >\n> _______________________________________________\n> Sent via [email protected]. AMSAT-NA makes this open forum available\n> to all interested persons worldwide without requiring membership. Opinions\n> expressed\n> are solely those of the author, and do not reflect the official views of\n> AMSAT-NA.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb\n>\n>\n>\n> _______________________________________________\n> Sent via [email protected]. AMSAT-NA makes this open forum available\n> to all interested persons worldwide without requiring membership. Opinions\n> expressed\n> are solely those of the author, and do not reflect the official views of\n> AMSAT-NA.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb\n>\n", "attachments": [] }