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Vertical antenna stacking article

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W0BTU, Jan 10, 2011.

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  1. KM1H

    KM1H Subscriber QRZ Page

    Mike Id suggest optimizing elevation angles and use a spacing that offerers acceptable stacking gain.

    During my 80's to 90's contesting years I had four 4 el yagis stacked on 20-10M using the old W2PV design with 40/27/20' booms. Spacing was somewhat arbitrary due to guys and other stuff but they were at 40/80/120/160'; 30/60/90/120' and 25/50/75/100' respectively. The switching was set up for bottom, top, bottom pair, upper pair, and all. Independently rotatable. On the tall tower there were also 4 el 40M KLM's at 60/170'. While the gain was whatever the YO program spit out the elevation angle peaks were well known and long documented. Using worldwide propagation angle charts provided by N6BV/1 to YCCC members it was possible to cherrypick bands and angles and select the best antenna match. Sometimes antennas were pointed to diffferent areas, a few times it was necessary to point one at someone trying to poach the run frequency. Oft times different selections allowed another hop to predominate as when working coastal Western Europe and then going deeper. It all added up to repetitive contest wins or at least 2nd place. The WPX contest was a particular blast since all those USA/VE prefixes were multipliers so the direction switches really got a workout.

    In between contests I used the arrays to minimize wasting time in pileups for new band countries.

    Carl
     
  2. KM1H

    KM1H Subscriber QRZ Page

    Id take anything from Cebik or that Antennex group as far from gospel without independent confirmation.

    A meeting with him at GT where I was there in a business capacity and he was in a meeting gave me a very dim view that was later confirmed by others there.

    Carl
     
  3. W0BTU

    W0BTU Ham Member QRZ Page

    Carl! What an antenna system you had. :)

    I'd still like to read Cebik's article, though. Inquiring minds want to know.
     
  4. VK1OD

    VK1OD Ham Member QRZ Page

    Mike, you can create the outcome by modelling two long Yagis in NEC and varying the stacking distance.

    There is a NEC deck for such a Yagi at NEC-2 Models of DL6WU Yagis . Since they are truncated arrays, just delete the last 80 directors for a shorter (practical) 20 el array. To stack them, use the GS card to create a copy offset by the stacking distance which is then specified in only one place so it is easy to vary.

    If you stack them at say 150% the distance recommended in DL6WU-OD.xlt you should see the effect.

    Is that too easy?

    The article I referred to earlier was elsewhere to Cebik's long Yagi CD when I read it. I will see if I can find the article and relevant paragraphs to quote.

    Owen
     
  5. W8JI

    W8JI Ham Member QRZ Page

    The difference is to get high gain, a null has to be forced in an area with significant energy.

    If everything is at 0-5 degrees and the basic antenna can be several wavelengths above earth, additional nulls pushing into the main lobe don't cause a problem.

    On sky wave, they are devastating.

    Many people blame take of angle being too low for devastatingly poor performance, but it more often is a matter of forcing nulls into elevation angles useful for propagation.

    What I want for HF pattern is the cleanest widest single lobe without deep null in primary angles. Very few contacts are lost with 3 dB of gain change, but a 15 dB null in the middle of prime elevation range can be devastating.

    73 Tom
     
  6. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Yeah, I understand that. VHF is a very different animal. There's lots of stuff that works great at VHF that would not serve the purpose at HF due to the vagaries of sky wave propagation.

    I'm sure you get this, but some newbies might wonder why big HF contest stations often have several HF beams at all different heights above ground, and can often switch various combinations of those to the station. I've done that at large contest stations and the results can be amazing. Half the time the beams weren't even on the same tower.:p
     
  7. W0BTU

    W0BTU Ham Member QRZ Page

    I am just curious about the article, whether he was talking about HF or VHF+, and I would just like to see what Cebik claimed (in his own words), that's all.
     
  8. VK1OD

    VK1OD Ham Member QRZ Page

    He wrote articles about each. I have sent you an extract from this articles on VHF+

    Owen
     
  9. W8JI

    W8JI Ham Member QRZ Page

    The only reason there is ever a large change is because the stack pattern is unclean, and has a null at the angle that happens to work. Plan for a clean elevation pattern instead of maximum gain, and the contact rate goes way up.

    We consistently set world records on 40 meters because the pattern is clean and wide without giving up too much gain. About two years ago I disconnected the box that allows me to change elevation patterns. :)

    73 Tom
     
  10. W0BTU

    W0BTU Ham Member QRZ Page

    Thank you. From comments others have said, I thought he might have stated what I did in my article, but he didn't. Maybe in something else he wrote. Not that it's important, or that it would prove/disprove anything; I'm just curious to see what he said.
     
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