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/D42ILOYD4G6YDKL2BL2JCFQU7ZCN3DQP/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "009901c7fe31$92b2ea40$6701a8c0@sierrap4dual",
    "message_id_hash": "D42ILOYD4G6YDKL2BL2JCFQU7ZCN3DQP",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/D42ILOYD4G6YDKL2BL2JCFQU7ZCN3DQP/",
    "sender": {
        "address": "jkopala (a) gmail.com",
        "mailman_id": "083d74d034614b08876fb7affa0a2348",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/083d74d034614b08876fb7affa0a2348/emails/"
    },
    "sender_name": "John Kopala",
    "subject": "[amsat-bb] Re: Mounting antennas on a tower",
    "date": "2007-09-23T22:32:04Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Eric,\n\nHere is another approach to the problem.\n\n1.  You need a rotor base plate that can be mounted at any level in the \ntower.  Basically, it should rest on and be secured to the cross braces \nbetween the tower legs.\n2.  Next use a thrust bearing at the top of the tower.\n3.  Your mast needs to be heavy enough to withstand whatever winds you may \nencounter from storms when extended several feet beyond the top of the \ntower.  At least half of the mast will remain in the tower.\n4.  The mast can be positioned vertically within the tower using a pulley at \nthe top of the tower and a rope secured to the mast near the base.  Helpers \non the ground use the rope to raise and lower the mast while a person on the \ntower guides and secures the mast at the desired height using the thrust \nbearing.\n5.  You then attach the elevation rotor with its cross boom and antennas in \nas many steps as required to do so.\n6.  Using the rope to control the mast height, loosen the thrust bearing \nscrews and raise the entire structure so that the satellite antennas have \nthe necessary clearance above the HF beam.\n7.  Secure the thrust bearing screws and attach the HF beam.\n8.  Again raise the mast so that he HF antenna is at the desired height plus \nabout 1 foot and secure it in place.\n9.  Attach the rotor base and rotor to the tower just below the base of the \nmast.\n10.  Lower the mast to the top of the rotor and secure it in place.\n\nThat is how I set up my current HF installation.  Rather than having a \nsatellite setup on top, I have an Cushcraft R-7 vertical which extends \nanother 22 feet above the top of the mast and is spaced about 5 feet above \nmy triband beam.  You can put anything up there you want.  I was not \nthinking satellites when I set this up many years ago, so my satellite \nantennas are on a roof mount.\n\nI prefer center mounted antennas because I can mechanically balance the \nentire antenna system.  I have balanced it front to back, side to side, and \nup and down.  Basically I mount my antennas on a fiberglass cross boom and \nadjust the antenna positions (with coax attached) so that the whole setup is \nbalanced front to back.  Then I use another pipe and clamps to determine the \nrotor position so that the setup is balanced from side to side.  Finally, I \nmount the heaviest antenna on the bottom side of the crossboom and the \nremaining antennas on the top side to further eliminate imbalance as the \nantennas rotate vertically.  The idea is to minimize the stress on the rotor \ngears and bearings.  Ideally, the rotor is not lifting or supporting any \nextra weight when it moves the antennas.  The antenna structure could be \nmoved with one finger if the rotor was not holding it in place.  With end \nmounted antennas, the rotor brake and  gears must support and lift the \nentire weight of the antennas every time the antenna elevation changes.\n\nI'll also send you a picture of my current satellite setup.  This is NOT the \nideal setup because the rotor is not mounted in a tower section and there is \nno lateral support above the rotor for the mast.  But it does give you a \nlook at a setup with center mounted antennas on a cross boom with an \nelevation rotor all mounted above a 6 meter beam.  The satellite antennas do \nrotate a full 180 degrees of elevation and clear the 6 meter beam.  The \nlongest antenna is an old KLM 2 meter circular polarized antenna that is 12 \nfeet in length.  Note that with the cables attached, the balance points move \nsomewhat toward the rear of the antennas.  Also, note the preamps just below \nthe azimuth rotor.\n\nAnd DON'T FORGET the preamps.\n\nJohn Kopala\nN7JK\n\n\n----- Original Message ----- \nFrom: \"Eric Christensen\" <[email protected]>\nTo: \"AMSAT-BB\" <[email protected]>\nSent: Friday, September 21, 2007 7:03 PM\nSubject: [amsat-bb] Mounting antennas on a tower\n\n\n> I'm contemplating antennas and a tower at the new homestead and I have a\n> question.\n>\n> If I can figure out how to mount an elevation rotator at the top of a\n> pole and have the azimuth rotator rotating said pole from the tower\n> would I have any problems with putting a small HF tri-band beam on the\n> pole, below the elevation rotator, and then mount all my satellite\n> antennas to the elevation rotator's pole?  Has anyone done a combination\n> like this?\n>\n> 73s,\n> Eric Christensen, W4OTN\n> AMSAT Area Coordinator - Southeastern Virginia USA\n> AMSAT Member 35360 \n\n",
    "attachments": []
}