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Antenna Day on Saturday 27th

This topic contains 5 replies, has 3 voices, and was last updated by  Angelo, N6QAD 1 week ago.

Viewing 6 posts - 1 through 6 (of 6 total)
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  • #10493

    Angelo, N6QAD
    Participant

    Hi,
    as announced at the meeting,in preparation for Field Day, we will have an Antenna day on Saturday 27th in the field by the fire house.
    We will build setup and test a Coupled Resonator 80-40-20m that Mike has been study. Depending on the time available we might also take a look at the spider beam and the delta loop. If not we will have a second day.
    Come join us it will be fun.

    I have also posted in the library the slides Neil and I presented in the March and April meetings.
    See you Saturday,
    Angelo

    #10494

    Paul, KJ6MPZ
    Participant

    I was wondering what time do you plan the start this event??

    #10495

    Angelo, N6QAD
    Participant

    And you are right. I forgot to say it is at 9:30am.

    #10505

    Mike, KJ6VCP
    Participant

    We had a successful tuning day! Here are the tuning lengths compared to the model.

    80M: modeled: 125.53 ft, actual: 128.5 ft
    40M: modeled: 67.0 ft, actual: 67.16 ft
    20M: modeled 33.65ft, actual: 33.15 ft

    The model was surprisingly close on 20M and 40M. 80M is tricky, because we are so close to the ground, ground and height really matters. I added 4 feet to the modeled length, and it was still a close call. These numbers are based on the trimming notes, I’ll check them against the actual antenna later.

    I uploaded the SWR plots from the analyzer to the library as 20m.pdf, 40m.pdf, and 80m.pdf. The 20m plot is probably not the final one; I’m pretty sure we were better when we finished up, and it doesn’t match my notes which say 14,200 @ 1.07:1 SWR, but that’s what was in the analyzer.

    #10509

    Mike, KJ6VCP
    Participant

    I found time over the weekend to check the balance on the antenna after tuning.
    Here are my measurements:

    Band	Left		Right
    20M	16' 0"		15' 6"
    40M	30' 1"		33' 5"
    80M	62' 3"		62' 2"

    Now, for 80M I’m not going to split hairs over an inch at 62′ – its well within measurement error since the antenna and tape were both hanging in the air, and it’s a fraction of a wavelength. But something was clearly wrong on 40M. I’m fairly sure we trimmed correctly, so the original cut or center marking had to be wrong. We were off by 40″, so I shifted the 40M element 20″ to the left. 20M is also off by 6″, but I left that alone for now since I can’t really check SWR at 10′ high. We can shift that quickly if needed.

    After trimming and tweaking, here are the final measurements:

    	design 	actual 
    20M 	33.65 	31' 4"
    40M 	67.0	63' 4"
    80M 	125.53 124' 5"
    

    So in the end, the model was fairly close to reality. The moral of the story is to double check the balance before and after trimming. Or, measure twice, cut once.

    #10511

    Angelo, N6QAD
    Participant

    Results from the Maypole simulations and testing have been uploaded to the library.
    Angelo

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