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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/74BS6B5MKIRKYGRET5BUSMZIHN3TPHML/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "74BS6B5MKIRKYGRET5BUSMZIHN3TPHML",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/BYGCWI5JWOUWP3ZYHLKUYN56DMQETTNZ/?format=api",
    "sender": {
        "address": "oz1my (a) privat.dk",
        "mailman_id": "b2f56900318d4d1193159750f39aa3fe",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/b2f56900318d4d1193159750f39aa3fe/emails/?format=api"
    },
    "sender_name": "Ib Christoffersen",
    "subject": "[amsat-bb] Re: Mount an Arrow on rotator with 2mverticalorhorizontal",
    "date": "2013-04-20T21:16:44Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BZOLV5RLGGW3LJLYADSP5UQNLQ7YZ4ZW/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hello Domenico, Art and the -bb,\nMy comment here is with the ARROWS antennas.\n\nI think one thing is overlooked here.\nWe are dealing with two antennas on different frequencies.\n\nAnd yes in this it may work since 435 MHz is 3 times the 145 MHz.\nSo 1 quarter wavelength on 145 MHz becomes 3 quarter wavelength on 435 MHz.\nTherefore it may work impedance wise.\n\nHowever there may be a problem with coupling between the two frequency\nbands.\n\n73 OZ1MY/Ib \n\n-----Oprindelig meddelelse-----\nFra: [email protected] [mailto:[email protected]] På vegne\naf Art McBride\nSendt: 20 April 2013 19:47\nTil: 'i8cvs'; 'Douglas Phelps'; 'R.T.Liddy'; 'Amsat - BBs'\nEmne: [amsat-bb] Re: Mount an Arrow on rotator with 2mverticalorhorizontal\n\nDomenico,\nThere are two solutions to use coax to combine two 50 Ohm antennas. 70.7 Ohm\ncable (50 to 100) [Two 50 ohm antennas transformed by two lines to 100 Ohms\neach, in parallel = 50 Ohms] and your suggestion using 35.4 Ohm cable\nsection (25 to 50) = [Two 50 ohm antennas connected in parallel = 25 Ohms,\ntransformed to 50 Ohms] \n\nThe interesting part is you do not save anything when using 75 Ohm coax as\n1/4 wave sections (two in parallel =37.5 Ohms) VS two separate 75 ohm\nsections one to each antenna.\n\nArt, KC6UQH\n\n\n-----Original Message-----\nFrom: [email protected] [mailto:[email protected]] On\nBehalf Of i8cvs\nSent: Wednesday, April 17, 2013 5:00 AM\nTo: Douglas Phelps; R.T.Liddy; Amsat - BBs\nSubject: [amsat-bb] Re: Mount an Arrow on rotator with 2m\nverticalorhorizontal\n\nHi Douglas,\n\nUsing two identical 50 ohm coax lenght you can't  transform each 50 ohm\nantenna impedance into 100 ohm but if you connect both 50 ohm coax cables\nto a T connector than the resulting impedance at the common output of the T\nconnector will be 25 ohm i.e. two 50 ohm impedances in parallel and your\nradio will see a VSWR of 50/25 = 2 and this is the reason it will not work !\n\nBTW if you connect the above 25 ohm impedance to the input of a 1/4\nelectrical wavelenght long coax cable of 36 ohm impedance than at the output\nof it you will get an impedance of  36^2 / 25 =  52 ohm toward the main feed\nline with a good VSWR of about 1 in TX and RX\n\nTo build a 1/4 electrical wavelengt long of a transmission line of 36 ohm\nimpedance you can connect in parallel two 1/4 electrical wavelenght of\n75 ohm coax cable like RG-59 or  RG-11 i.e. 34,13  centimeters or 13,38\ninches long  for 145 MHz\n\nBTW in this situation if both antennas are mounted in parallel one Vertical\nand the other one Horizontal and if the elements are mounted on the same\nplain with respect to the space than the resulting polarization of the\nradiated field can be at 45 degrees like \\ or at 135 degrees like /\ndepending at wich side of the dipoles the inner conductors of the 50 ohm\nfeed lines are connected.\n\n\n73\" de\n\ni8CVS Domenico\n\n----- Original Message -----\nFrom: \"Douglas Phelps\" <[email protected]>\nTo: \"R.T.Liddy\" <[email protected]>; <[email protected]>\nSent: Tuesday, April 16, 2013 8:31 PM\nSubject: [amsat-bb] Re: Mount an Arrow on rotator with 2m vertical\norhorizontal\n\n> Any reason why, using identical coax lengths, you could not transform the\n> impedance to 100 ohms and then use a T connector to sum both antenna\n> signals and achieve 50 ohms to the radio? I know Transmit power will be\n> 3 dB down at either antenna but is there any reason it will not work?\n> Any antenna gurus out there?\n>\n\n_______________________________________________\nSent via [email protected]. Opinions expressed are those of the author.\nNot an AMSAT-NA member? Join now to support the amateur satellite program!\nSubscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n\n_______________________________________________\nSent via [email protected]. Opinions expressed are those of the author.\nNot an AMSAT-NA member? Join now to support the amateur satellite program!\nSubscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n\n\n",
    "attachments": []
}