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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QGBCLWKKW434THUXKYXVS44BSEHPABII/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "693682E7994243418EFDBB1692138DAC01DD22164094@venus.rfdesign.co.za",
    "message_id_hash": "QGBCLWKKW434THUXKYXVS44BSEHPABII",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/ZJNMZJLJHHPKANCXOA2X2KEHIHKB7NTW/?format=api",
    "sender": {
        "address": "allan (a) rfdesign.co.za",
        "mailman_id": "df41e8d85c7b48b7be90951a75107b15",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/df41e8d85c7b48b7be90951a75107b15/emails/?format=api"
    },
    "sender_name": "Allan Saul",
    "subject": "[amsat-bb] Re: Arrow 10W Duplexer Performance Measurements",
    "date": "2009-10-21T18:32:38Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/XGHEHLLUP7MZ4XU3NIU3PSGKN6FPYWCN/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/CLOTNTKBLBSP5REDOI6NEYVGORSWQZOI/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi Bruce,\n\nI am afraid you are very much mistaken in your logic here.\nFor mode J on AO51 say, The 5W signal you transmit on 2m will\ncompletely drive that 70cm preamp between the antenna and duplexer\ninto saturation unless you put a very good filter on the input \n(the desense issue). That insertion loss might negate any gains you make\non the preamp, increase your noise floor by 20dB and add a lot of hassle,\nand more importantly weight.\n\nActually, the 1.2dB insertion loss is better than I was expecting\nand good enough for the short cable run to the HT. It is what it is\nand its good enough for the job it was intended for.\n\n73's\nAllan\n\n\n-----Original Message-----\nFrom: Bruce Robertson [mailto:[email protected]] \nSent: 21 October 2009 02:01 PM\nTo: Allan Saul\nCc: [email protected]\nSubject: Re: [amsat-bb] Arrow 10W Duplexer Performance Measurements\n\nI'm grateful to everyone who has contributed to this discussion.\n\nIt strikes me that the greatest improvement we could make to hand-held\nyagis would be to somehow integrate a low noise preamp circuit very\nclose to the 70cm port. I have an indoor-style ARR preamp that I've\nthought of connecting to the boom with cable ties. A powersupply using\nAA batteries and a DC to DC buck-boost chip from, e.g., Maxim, would\nkeep the whole thing light. (Alternatively, I see that the max voltage\nfor my ARR is pretty high: I might get away with a pair of Nicad '9v'\nbatteries.)\n\nLike so much of amateur radio, it's more of a challenge of\nconstruction than anything else.\n\nHas anyone experimented with this sort of improvement?\n\n73, VE9QRP\nBruce\n\nOn Wed, Oct 21, 2009 at 8:21 AM, Allan Saul <[email protected]> wrote:\n> Quite a lot of guys are using the handy Arrow Model 10W\n> duplexer for the handheld 146/437 antenna and mine arrived here\n> today so I thought I would put it on the network analyser\n> and see how it performs.....\n>\n> >From the Radio cable to the 2m antenna connector an Insertion Loss of\n> 0.75dB was measured with a rejection of 57dB at 70cm. The VSWR at 2m was\n> 1.24:1\n>\n> >From the Radio cable to the 70cm antenna connector an Insertion Loss of\n> 1.2dB was measured with an attenuation of 56dB on the 2m signal. The VSWR\n> at 70cm was 1.29:1\n>\n> The VSWR on the 2m port was 1.21:1 and on the 70cm port was 1.20:1\n>\n> For those guys wanting to look at the actual plots they can be found here\n> http://www.rfdesign.co.za/default.asp?pageID=785423593&filePath=D:\\SoftPage_V5\\files\\5645456\\Download-Library\\Amateur-Radio\\ZS1LS\\Mode-J-Filter\n>\n> 73's\n> Allan ZS1LS\n>\n>\n>\n>\n>\n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>\n\n",
    "attachments": []
}