Email Detail

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/RQWA7EOLFQBR3JTBRO2QX2HRZMY5Z5HT/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "CAGkenmeRSBDn-zsbwYj1H1RrDdd3J9AFtpjVs4kLwjCNTGdQnw@mail.gmail.com",
    "message_id_hash": "RQWA7EOLFQBR3JTBRO2QX2HRZMY5Z5HT",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/IYBS4KXJ4KFL43NRMAWWIKLKOXLAGSI4/?format=api",
    "sender": {
        "address": "rbutler (a) tsss.org",
        "mailman_id": "7d1973824b814588ab990efab2d162b7",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/7d1973824b814588ab990efab2d162b7/emails/?format=api"
    },
    "sender_name": "Ryan Butler",
    "subject": "Re: [amsat-bb] AirSpy & LNA questions",
    "date": "2018-07-13T14:41:09Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/IYBS4KXJ4KFL43NRMAWWIKLKOXLAGSI4/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QWUEFD6CLKX4WYGJS4C2XPOO72MSOWOJ/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Yes you are on the right track, check out the following two links (similar\ndesigns) but also provides a description of why bandpass filtering is a\nmust with an SDR.\n\nhttps://www.rtl-sdr.com/designing-low-noise-uhf-front-end-sharp-filtering-sdr/\nhttps://sivantoledotech.wordpress.com/2015/01/27/a-selective-and-robust-uhf-front-end/\n\nRyan, NF0T\n\n\nOn Fri, Jul 13, 2018 at 9:30 AM Hans BX2ABT <[email protected]>\nwrote:\n\n> Man, this sat stuff is difficult and I was getting a bit frustrated with\n> lack of progress, to be honest. But just when I thought I didn't get\n> anywhere, I went a big leap forward. But I'm not there yet, so I need\n> your input.\n>\n> My goal is to get some decent reception of the major telemetry sats,\n> e.g. Funcube-1. I have two rigs: an ICOM IC820H and an AirSpy Mini SDR\n> running on a Linux box with GQRX as front-end. I have a Chinese Arrow\n> Alaska clone pointing 200 degrees with 20 degree elevation. The other\n> antenna currently is a turnstile tuned for 137 MHz, but I have 2/70 DCAs\n> as well (they had to come down this week because of a typhoon. Will be\n> up again shortly).\n>\n> The bare antennas do fine on terrestrial signals, but up till now very\n> few sats were heard (mostly the Xiwang sats and Athenoxat-1) and signals\n> were very very weak. I got myself some proto boards and PGA103+ MMICs\n> and built two LNAs according to schematics found on the web. On the\n> workbench they perform as they should and give some 15-25 dB gain\n> depending on what frequency is used. I use an old AM/FM signal generator\n> and an RTL-SDR as crude scope since I don't have a real one.\n>\n> I mounted the LNAs as close as possible to the antennas and they are fed\n> with a bias-T from Minikits.com.au. The first results were\n> disappointing: I used the AirSpy and noticed a lot more signal but also\n> an increased noise floor. With the AirSpy there is a lot of fiddling\n> going on in the software and I managed to get some improvement by\n> tweaking the LNA gain, Mix gain and IF gain. Still I couldn't hear any\n> sat signals.\n>\n> This afternoon I switched from the AirSpy to the IC820H and\n> lo-and-behold very strong beacon signals from XW2A and F; the strongest\n> I've ever heard. Even the AirSpy did detect a signal, although\n> not-at-all as great as the IC820H. To get a cleaner signal from the\n> IC820H I did have to engage the attenuator on the set, though. Using the\n> IC820H I also heard a very weak beacon signal from CO-65, but the AirSpy\n> failed there. Conclusion: the IC820H could detect signals that the\n> AirSpy could not detect at all or detect them much better.\n>\n> Pretty happy with this step forward, but not satisfied. Question is how\n> to improve even more.\n>\n> Q1: is the LNA desensing the AirSpy (and to a lesses extend, the IC820H)\n> and if so, how to fix that? I read something about an attenuation\n> network after the LNA to improve the front-end of the receiver. Might\n> that help?\n>\n> Q2: when not powered, MMICs seem to have a very high insertion loss. Is\n> there a way to remotely bypass the LNA in order to compare reception\n> with and without the LNA?\n>\n> Q3: would filtering help? E.g. bandpass filters for 2m and 70cm. I do\n> realize that this would mean another couple of dB of insertion loss, but\n> maybe that disadvantage outweighs the advantages.\n>\n> I would appreciate any input on the above and also would like to hear\n> from others who use the AirSpy Mini for sat reception. I already did a\n> lot of googling, but can't find any clear cut answers. Hope you all can\n> help me go into the right direction. Cheers,\n>\n> Hans\n> BX2ABT\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": []
}