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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/YXXYTZDIZF3OBXCGKNPW22TNFFSCRU7K/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "CAN6TEUc=SekxW=W008Kwj9xBm8zPJF_=ij7QN9e8-YoKjGZb7g@mail.gmail.com",
    "message_id_hash": "YXXYTZDIZF3OBXCGKNPW22TNFFSCRU7K",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/QS4ZNLSO25FWR4LQYKRNIYRQWKS6ROD4/?format=api",
    "sender": {
        "address": "amsat-bb (a) wd9ewk.net",
        "mailman_id": "21664df01bef4757931b7cdb42a9e768",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/21664df01bef4757931b7cdb42a9e768/emails/?format=api"
    },
    "sender_name": "Patrick STODDARD (WD9EWK/VA7EWK)",
    "subject": "Re: [amsat-bb] RTL-SDR downlink",
    "date": "2016-06-16T22:36:34Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/ZBL5IQZPO77SAO4NE53B4MKFHNJREM7S/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi Peter!\n\nYou are correct. The inexpensive RTL-SDR dongles are a great way to\ngive SDR a try. With the low prices, there should also be appropriate\nexpectations. Since these were originally made as television\nreceivers, they were designed for use with stronger signals than\nwhat we typically see from our satellites. Can they work as a\ndownlink receiver? Sure. Just like a Baofeng HT can be used to\nwork FM satellites. Not the best thing, but they can work.\n\nI've tried a few of these devices as downlink receivers for working\nsatellites. In my case, these receivers need to be able to handle\nnearby RF on a different band, which is a problem for some of these\ndevices. My list of devices I have tried are:\n\n1. RTL-SDR dongles. No front-end filtering, not as sensitive as\nother devices, they shut down in the presence of 5W or less when I\nam transmitting to a satellite. Even as little as 500mW can be a\nproblem for these devices. I might have spent more time using these\nif I only wanted to receive. Also, I would like to have something that\ndidn't require an upconverter to cover the HF spectrum above 24\nMHz. I keep one plugged into a PC at my office, and use that to\nlisten to FM stations and occasionally the local fire or state\ntrooper dispatch channels (still in analog around Phoenix).\n\n2. FUNcube Dongle Pro (not the Pro+). A better receiver than the\nRTL-SDRs, but also lacking front-end filtering. No good for me as\npart of my satellite station, but could have been fine for receive-only\nsetups.\n\n3. FUNcube Dongle Pro+. Nice receiver, has front-end filtering\nincluding SAW filters at 2m and 70cm, directly compatible with the\nFUNcube Dashboard and FoxTelem programs. Only drawback for me is the\n192 kHz maximum bandwidth. The 240-420 MHz frequency gap is not a\nbig deal, but is for some who like hearing the military aircraft or\nsatellites in this range.\n\n4. HackRF. This is a wideband transceiver, covering from around 100\nkHz to 6 GHz, with a maximum bandwidth of 20 MHz. It is nice to use\none of these to watch the entire FM broadcast band, but its receiver\nreally isn't up to the task as a downlink receiver for our current\nsatellites at 10m (AO-7 mode A), 2m, or 70cm. I have the Great Scott\nGadgets HackRF One and the crowdfunded HackRF Blue version. Other\nthan the crowdfunded version using some different components and\ncosting about $100 less, the HackRF Blue functions the same as\nthe HackRF One. The HackRF devices lack front-end filtering,\nand come with warnings about using them in the presence of strong RF,\nso I have not tried using one of these along with an FT-817 or\nHT to work satellites, but its receive-only performance is not\nimpressive.\n\n5. SDRplay. This is what I have been using for satellite work for\nthe past year. With 100 kHz-2 GHz unblocked, maximum 8 MHz bandwidth,\nand bandpass filtering across that range, it has worked very well for\nme - even in Los Angeles. I use this with an 8-inch Windows 10\ntablet and HDSDR software, which is a low-overhead program that does\nfine on these low-end tablets. FUNcube Dashboard and FoxTelem\ncannot directly use an SDRplay, but with something like HDSDR and\na virtual audio cable I can make use of the SDRplay with those\nprograms. Or I can make RF recordings of the passes in HDSDR, then\nplay back the recording later through a virtual audio cable into\nthose programs to decode telemetry.\n\nI have not tried either the Airspy or Airspy Mini. These units do\nnot cover below 24 MHz, and require an upconverter if you want to use\nthem for HF reception, but they will cover the bands currently used\nfor our satellites, starting at 10m and going up. There is a US-based\ndistributor for Airspy, so you don't have to order these from\noverseas.\n\nOf course, your location will determine how much interference you\nwill have to withstand. I didn't have that to deal with at a recent\ndemonstration I gave in Long Beach earlier this year, when I used my\nSDRplay and tablet as the downlink receiver to work a couple of the\nXW-2 satellites. I don't have those issues at my house here in the\nPhoenix area, and have yet to run into a place where there is a lot\nof interference to deal with. I have used my SDRplay/HDSDR combination\nfrom many locations across the US and Canada in the past year, and\nhave yet to run into a situation where the local RF swamps my SDRplay.\n\nSDRplays are sold at HRO in the US for $149. FUNcube Dongle Pro+\nis sold by its UK manufacturer, and including FedEx shipping to\nthe US runs around $200 depending on exchange rates. The HackRF One is\navailable for around $300. I have 3 SDRplays, two that go with me for\ndemonstrations or presentations, and one as a backup. I also have a\ncouple of FUNcube Dongle Pro+ receivers, which will eventually\nbe used for an unattended receive-only setup at home with the FUNcube\nDashboard and FoxTelem programs on a PC.\n\nI would recommend either the FUNcube Dongle Pro+ or SDRplay if you are\nwanting to work satellites using one of these receivers for the\ndownlink side of your station. If you want to see some examples of\nwhat I have received using my SDRplays, I have lots of RF recordings\nat http://dropbox.wd9ewk.net/ - look for the folders with YYYYMMDD\ndates at the start of the file names, followed by the satellite name\nand the grid I operated from. You are welcome to download them and\nrun them through HDSDR or some other SDR software. And, yes, there\nis a lot of data up in that Dropbox space. :-)\n\n73!\n\n\n\n\n\nPatrick WD9EWK/VA7EWK\nhttp://www.wd9ewk.net/\nTwitter: @WD9EWK\n\n\n\nOn Thu, Jun 16, 2016 at 8:33 PM, Peter Laws <[email protected]> wrote:\n\n>\n> The $20 versions are well worth the effort if you've never played with\n> an SDR of any sort before.  For satellite downlinks?  Dunno, never\n> tried.  Surely as you describe!\n>\n> Has anyone done any kind of \"shoot out\" comparing the cheapos to the\n> real ones or even between the real ones (FCD, SDRPlay)?  Before I\n> plunk down $200, I'd like to see what I'm getting ...  over and above\n> what my $20 dongle can do, of course.  :-)  I read what you typed, but\n> I'd like to see numbers.\n>\n>\n>\n",
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}