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NVIS Ant for qrp

Discussion in 'QRP Corner' started by KD2RON, Mar 6, 2017.

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  1. KD2RON

    KD2RON Ham Member QRZ Page

    I used a NVIS on 40m with 100w with good results two years ago. It was a dipole about 7 ft high with three reflictor wires on the ground. I was thinking of making a portable version for this summer for qrp-ish use (rig puts out 7-8 watts). Anyone use NVIS with qrp ? Any reason not to? Thanks
     
  2. KA5IVR

    KA5IVR Premium Subscriber QRZ Page

    I wouldn't think Watts would matter more than watts normally do for any other antenna. Hopefully the band is working when you try.
     
  3. KL7KN

    KL7KN Ham Member QRZ Page

    I used a PRC-104/AS-2259GR for a number of years. 20 watts. Worked fine most of the time, again, as noted, if the bands are working.

    Good luck, a NVIS can make a marked difference for contact s up to ~300 miles.
     
  4. KL7AJ

    KL7AJ Ham Member QRZ Page

    Since NVIS uses the lower frequency bands, you will have the same issues whenever running QRP. Absorption tends to be a lot higher on the lower bands. However, it's worth a try. For optimum NVIS, you want to be operating about 10% below the critical frequency, so it helps to become familiar with local ionosondes.
    Eric
     
    AI3V and W9AMM like this.
  5. W6OGC

    W6OGC Ham Member QRZ Page

    I bet you did not know that term "NVIS" is derived from an old Indian expression meaning "the smoke goes straight up."
     
    AD5KO, WC3T and KA0HCP like this.
  6. KD2RON

    KD2RON Ham Member QRZ Page

    I hope my 7watts doesn't smoke up to many clouds.
     
  7. KB7NRN

    KB7NRN Ham Member QRZ Page

    I have used an FT-817 and IC-703 with a 40mtr NVIS antenna. I tried it in the woods on the back side of my property and when out hiking in the Cascade Mtns.
    With the 817 I only ran 0.5-1.5 watts and the 703 was running 5 watts. All SSB contacts. Had no problem getting out. Contacts maxed out to 300-400 miles or No. Cal to northern Washington state but the best contacts (S-9) were within 100 miles of where I was set up western Oregon.
     
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  8. W1VT

    W1VT Ham Member QRZ Page

    http://hfpack.com/propagation/
    Check out this map at the appropriate times to see whether or not you have any NVIS propagation on 40. The low solar flux numbers have really affected 40M NVIS--the openings are a lot shorter than they use to be just a few years ago.
     
    KD2RON likes this.
  9. K8JD

    K8JD Ham Member QRZ Page

    My Idea for a NVIS antenna is something like a dipole of full wave loop up a quarterwave . Your 7 ft high antenna is a dirt warmer. Half it's near field is underground !
    . I have run QRP on an 80M dipole up 0.12 wavelength high and a 40M square loop up 0.25 wavelengths and this worked very well. My 160M dipole is only up 0.07 waves but it is a work in progress. It works fairly well where it is, worked east, Gulf, and west coast with it and 100 W. Very Strong signals in the surrounding states.

    I ran a dipole up about 25 ft on 80M when I was a novice and worked all over s. MI, n OH, n. IN and s. ON with about 4 W. Back then nobody called it NVIS :D
     
    Last edited: Mar 22, 2017
  10. KF5FEI

    KF5FEI Ham Member QRZ Page

    We made a tuned version of the military NVIS antenna and it works great on 40 meters. (20m and 40m inverted Vs from same feedpoint @ 16 feet) The first time we tried it was for the Texas State Parks On The Air contest, running an FT-817 on 40m phone. We were getting signal reports equal to 100 watt stations and won the QRP category on our first attempt.
     

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