67 miles on 50w SSB

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KK4YWN, Nov 18, 2014.

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  1. KK4YWN

    KK4YWN Ham Member QRZ Page

    So the cushcraft is a stack of four three element arrays? How do they come up with 20 elements? I must be missing something in the old manual I found online.

    I was going to build two ten element yagis with horizontal elements on the same boom as vertical elements (but offset 1/4 wave) so the phasing lines are equal in length (I'm being weird about losses I know). I plan to stack both antennas in he horizontal plane. I figure if I'm careful I'll get 12.5dbi plus 2.3dbi from stacking. With both polarities lit I end up somewhere back in the 12dbi range.

    I don't think this will net circular polarization so I haven't considered the need for switching left/right. My understanding is that this array would produce eliptical polarization, and with all the hills/valleys in the Carolina's, I should have better results. Worse case scenario is I get the performance if a ten element beam.

    35-40 ft height is all I can get. The lay of the land makes talk towers a waste of time. I'm on a bit if a hill, but there are a lot if taller places around.

    The fellow I spoke with at 67 miles is behind a peak that's almost 1000 ft higher than either of us. To get line if site there would require much steel.
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page


    The old DX Array was 20 elements because it was really a 16 element colinear (four colinear bays, each bay counts as four elements because it's a colinear so each "bay" is 1-WL wide, not 1/2-WL like a Yagi, and they're fed in phase using crossed lines) with a 1/2-WL director element in front of each bay, so it's 16+4 = 20 elements. Each one is 7' wide and 10' tall and about 4' deep, so it takes up some space. I had two of them on a 26' mast over the tower, one above the other, fed in phase using a coaxial power divider. A popular system was to use for of them in an H-frame, for 80 elements. Lots of folks had those. Problem is the mast has to be quite strong to support all that; I used 2.125" OD chromolly, which is strong but very heavy, and had to modify the mast mounting brackets to accommodate that diameter.

    Not sure what you mean by stacking them in the horizontal plane, but if you mean "side by side," you'll need a non-conductive cross boom, otherwise the boom that supports them will be in the way of the horizontal elements.

    Actually, if you phase them correctly, you can achieve circular polarization and of course using remote relays can switch from LH to RH. KLM made a bunch of VHF and UHF cross yagis that had that feature built in, with the relay board mounted on the antenna boom. But unless you're working someone who is also CP, there's no reason to switch and one or the other works fine when working guys who are just horizontal or just vertical.

    For sure, unless you're on a prominent mountaintop, 67 miles isn't line of sight for anybody. It certainly isn't for me. I think 99% of my 2m contacts are way over the horizon. I work up into the Bay Area (350 miles) on 2m SSB all the time, and can "see" maybe 5 miles in that direction, because there's a 3400' hill about 5 miles away that is right in that path. The signal scatters over it, of course with loss...maybe quite a lot of loss. But don't disregard the importance of antenna height. The higher they are, the better the squint angle for scattering a signal over the mountains and it's amazing how much difference that makes.

    In my case, my 2m beam is about 65' above ground with the tower "up" and about 35' above ground with the tower "down," and with it "down" I absolutely cannot work the Bay Area no matter who is up there and what they're using. With it "up," I can, and fairly easily. And that difference is only about thirty feet. If I could get it up 100 feet, it would be much better but I'm on a city lot and a tower that high would be a bit of an issue.

    My terrain here is "rugged," and likely more rugged than most places east of the Rockies except perhaps some parts of VA, NC, TN. I'm at 850' asl and have nearby hills to 3400', and slightly farther hills at 6200' (about 20 miles away) and then higher hills to 8800' at about 50 miles away, and some over 10,000 feet about 70 miles away. The San Gabriels run to over 10K feet and the San Bernardino Mtns run to 11,500 feet, all right here in southern CA and not very far from L.A. Then, the Sierras run up to 14,500 feet another 100 miles farther, but thankfully they're far enough away that it doesn't really matter.

    But CA is not very VHF-UHF friendly, unless you operate portable and from the top of one of those hills. Still, I make 400-mile SSB contacts any time I try to (assuming someone is "on" from Phoenix or wherever). You can do it.
     
  3. KK4YWN

    KK4YWN Ham Member QRZ Page

    I'm still lost.

    Two full wave directors.
    Two full wave reflectors.
    One half wave director.

    That's four and a half electrical elements per bay.

    Multiply by four: 18 elements.

    Unless, for impedance matching reasons, the full waves are a quarter wave longer than two full waves. Man my head is starting to hurt.

    I made a mistake earlier: I'm stacking horizontally. On atop the other. Elements will form an X (to minimize interaction with the pole). Sorry for the confusion. English is barely my first language and I have no second language.
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    A single colinear system is two elements: It's two half-wave elements.

    The DX Array consists of four bays of colinear elements, so that's 4 x 4 elements = 16. The directors are half wave each, so that's four more. Total is 20.

    There aren't any full wave directors or full wave reflectors. There are two 1/2-wave colinear elements driven and then two 1/2-wave elements for the reflector. That's four elements. Then the 1/2-wave director adds one more = 5. And four bays like that = 20.

    If you look at a simplified version of this as a vertical omni for FM, a pair of 1/2-wave stacked colinear elements with a phase shift network between them so they radiate in phase is called a "two element vertical colinear." Now just turn it on its side.
     
  5. KK4YWN

    KK4YWN Ham Member QRZ Page

    Thanks for your patience. I got it.
    This is one bay:
    Half wave. Half wave.
    Half wave. Half wave.
    ....,.....half wave..........
    Total of five elements per bay.
    Four bays.
    20 elements.

    Do you happen to know how wide the beam was or what the pattern was like? I can kinda guess. Two stacked were probably a laser in elevation plane. Rear was probably pretty deaf. Side nulls probably rejected black holes :)
     
  6. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    In 1971, CushCraft came out with a 20-element colinear that had 4-additional elements, as directors, mounted in front of each 4-element "bay". One day, a truck pulled up in front of my house and unloaded a package that turned out to be one of the brand new 2-meter 20-element colinears. I had made a comment, in my CQ Magazine FM column about the 16-element colinear performing well but that it had a bad habit of losing elements.

    Included with the antenna was a note telling me that the problem with losing elements had been corrected and that the new design included directors. The antenna was mine to keep. I did use it for a while and then traded it off to WA5KKJ who used the antenna until he died in the early 1980s.

    The antenna did look a little unusual with half wave elements on each side of the center insulator as reflectors and driven elements and then another single half wave centered on the center insulator.

    Glen, K9STH
     
  7. K0RGR

    K0RGR Premium Subscriber QRZ Page

    I agree with your theory about circular polarization in mountainous terrain. I used both linear and circulars in California for a long time, and came to the conclusion that the circulars did work better in places where the reflections off the hills were unpredictable.

    I wish we could get most repeater owners to install circular antennas, so home stations could all use horizontals.
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The pattern was very clean, with a fairly broad front lobe compared to my previous long boom yagi (15L Telrex on a 28' boom) but huge nulls to the sides and a real absence of noticeable minor lobes (unlike Yagis, which almost always have minor lobes only 10-20 dB down from the main front one, offset from 20 to 60 degrees depending on boom length). It was an impressive performer. I didn't look this up but I "think" the front lobe, which was really the only one it had, was about 30 degrees wide at -3 dB points. Something like that. Certainly broader than the ol' 28-foot long Yagi, and that made it easier to use and less work for the rotator.

    The insulators between the colinear elements were some sort of plastic, but mine didn't fail and the elements never fell off!:p
     
  9. K4ISR

    K4ISR Ham Member QRZ Page

    Personally I think the biggest wall for newer hams getting into SSB is the cost of hardware and a lack of experience. While a basic 2m FM voice like Yaesu FT1900R can be had for under $150, adding in SSB (which typically includes a lot of other options) usually kicks up the price at least another $200+. At the same time, tossing money at something will not make a new ham any better, and may aggravate long time hams due to the interference of an improperly setup radio/antenna.

    So while SSB is a logical next step, newer hams like me tend to take it one step at a time, getting used to proper antenna height, propagation and experimenting before spending more money into something that may or may not work. I talked to some who got the license and threw all kinds of money at higher end radios and antennas, but because they never took the time to learn about elevation differences between them and the repeaters/people, propagation, antenna height and so on, they got discouraged quickly after $3000 in equipment couldn't contact his buddy 20 miles away. They failed to look at elevation maps, antenna height and the other details needed for local VHF/UHF voice.

    Since I personally took the time to look at elevation maps, I understand why my 4W HT connected to my homemade Jpole can reach the repeater 16 miles directly north of me, yet cannot reach the one 12 miles southwest nor 18 miles east.
     
  10. AI3V

    AI3V Ham Member QRZ Page

    A bit of advice when you start playing around with phasing/stacking and attempting circular pol.

    Do very careful a/b comparisons at every step.

    It is very easy to decrease signal.

    CP or dual vert/horiz is particuarly sensitive, if you rotate around the boom axis you will very likley find that one polarity is predominate.

    It's a bummer if you think h/v split is 50-50 when you really have one polarity down 20 db from the other.

    Rege

    P.S. congrats on the distance :)
     
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