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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/GKGXY26HPDEHPBI2PFOOI57P72VGCHLJ/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "GKGXY26HPDEHPBI2PFOOI57P72VGCHLJ",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/GQN66W4DHOQJYEXDIZCCLWG3525EQ6AV/",
    "sender": {
        "address": "rwmcgwier (a) comcast.net",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Robert McGwier",
    "subject": "[eagle] Re: Where we're heading for bands and services",
    "date": "2006-09-25T13:15:43Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/GELNKDFSPL5QACPZ3BF644QCFZGKUMDT/",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Tom Clark, K3IO wrote:\n> Lyle Johnson wrote:\n>   \n>> I discussed some of these ideas with Eric, N7CL, at the TAPR meeting. \n>> Eric is very good at antenna system design, did S band stuff for us at \n>> MMS and does this sort of thing now for DoD.\n>>\n>> Anyway, he suggested we consider Vivaldi's rather than patches.  We used \n>> Vivaldi's on our trucks at S Band and they work well, are trivial to \n>> fabricate (a piece of PC board - I know, radiation, but it is the \n>> concept I am wanting us to consider).  They are well behaved and have \n>> very little coupling to adjacent antennas.  I'm not an antenna guy, but \n>> you might want to consider the Vivaldi and/or communicate with Eric.\n>>\n>>   \n>>     \n> Eric also assisted me with the design of the Microsat 2M rcvrs -- which\n> bore a strange similarity to an MMS design.\n>\n> AFAIK, the Vivaldi and antipodal antennas are linearly polarized.\n> Multiple elements require crossed antennas, like Fig.9 in\n> http://www.ansoft.com/news/articles/04.09a_MWJ.pdf#search=%22vivaldi%20antenna%22\n> (note that the radiation is \"endfire\").\n>\n> A PhD thesis for a 2-8 GHz describing this antenna used for a Snow radar\n> is seen at\n> http://profusion.ittc.ku.edu/research/thesis/documents/ravi_prakash_rajaraman_thesis.pdf#search=%22vivaldi%20antenna%22.\n>   \n\nHaving read the papers my first quickest impressions are\n\n1) The vivaldi is attempting to solve a problem we do not have.  We are \nnot after an antenna that exhibits gain,  low return loss, polarization \nisolation, etc. over several GHz.\n2) It has gain a little lower than a vacuum dielectric patch at 4 dBi \nversus 6 dBi of our circular patches or cross dipoles or whatever.  We \nhave built in implementation loss in our calculations but I hate to give \nit up immediately.  We would have to have 50% more area to make up for \nthe lost gain over the patches with the increase complexity of feeding, etc.\n3) I dont' know what substrate we could use that we could fly outside \nthe spacecraft but we might be able to recess it into the structure in a \ntube and that would certainly reduce mutual coupling.  What else it \nwould do,  is beyond my EM theory to guess.\n4) It is a traveling wave antenna and/or end fire and according to \nrecent authors \"it is not well understood\".\n\nI am not rejecting them just giving my first impressions which might \neven be wrong but they are my first impressions.\n\nOff to the salt mines\nBob\n\n\n-- \nAMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,\nNJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman\n\"You see, wire telegraph is a kind of a very, very long cat.\nYou pull his tail in New York and his head is meowing in Los\nAngeles. Do you understand this? And radio operates exactly\nthe same way: you send signals here, they receive them there.\nThe only difference is that there is no cat.\" - Einstein\n\n",
    "attachments": []
}