ad: Alphaant-1

QRPGuys Mini No Tune End Fed Half Wave Antenna Build

Discussion in 'Amateur Radio News' started by WJ6F, May 6, 2021.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: abrind-2
ad: Left-2
ad: L-MFJ
ad: Radclub22-2
  1. K4MID

    K4MID Ham Member QRZ Page

  2. KD9CKB

    KD9CKB Ham Member QRZ Page

    i dont know whats going on over at qrpguys.com . i ordered an antenna and the sent me the wrong item, i e-mailed them with no reply so i waited and eventually got paypay involved and they would not respond to paypal either and paypal returned my money, i would have rather just had the correct item but they will not respond to emails
     
  3. KD2MIC

    KD2MIC Ham Member QRZ Page

    Odd. In the past 4 weeks I placed two orders for 3 items and have them all and built.
     
  4. K7LZR

    K7LZR Ham Member QRZ Page


    EFHW antennas are actually quite efficient in terms of power delivered into the antenna wire from the matching transformer so long as chosen wire lengths are such that the antenna is naturally resonant - i.e. no tuner needed - on harmonically related frequencies.
     
    AG6QR and N1RBD like this.
  5. AG6QR

    AG6QR Premium Subscriber QRZ Page

    That's true, though of course an EFHW, by definition, can only be an EFHW on one band (only on one frequency if you really want to nitpick). It will work efficiently on harmonically related frequencies. But the pattern will have lobes with nulls between them. That may be okay, as long as the station you're trying to reach isn't deep in one of the nulls.

    I've built the QRPKits SOTA EFHW tuner, and it works very well. It's a similar design to the kit described in the original posting, except it includes a Tayloe bridge with an LED SWR indicator, along with a variable capacitor in the matching circuit, so can be quickly and easily tuned to accommodate frequencies where the element isn't quite a perfect half-wavelength long. The tuning also works to accommodate a bit of coupling with the ground or nearby objects. The unit I have, with its tuning ability, is about twice the price of the kit shown in the video, but still not very expensive, at $40. It's similarly tiny and lightweight, good for ultra-portable QRP.

    http://www.qrpkits.com/sota.html

    Like the kit described in the video, you have to supply your own half-wavelength radiating element, and another wire to use as counterpoise. Since the kit doesn't include a radiating element, I think it's best described as an EFHW matching unit, rather than an EFHW antenna.
     
    KA0USE, WN1MB and K0UO like this.
  6. VE3VXO

    VE3VXO Guest

    ^^ TRUTH. The auto transformer designs with fixed turns ratio and fixed wire lengths may be pruned to resonance and work well in a permanent type installation but if your intent is to have something to take places and erect it over different ground type, proximity to objects (including how close the end of the wire is to that tree foliage and or the ground) lossy metal objects etc. etc. you are well advised to use a variable L-network for the matching once you have the correct wire length. A small air variable and suitable inductor wound on a reasonable size core is easy, cheap, and can still be small and light for QRP.
     
    WN1MB, W9BRD, K0UO and 1 other person like this.
  7. W9BRD

    W9BRD Ham Member QRZ Page

    An effficient, tunable matching network is especially important for QRP work in the sense that at QRP levels, inefficient coupling/matching components may not do you the favor of getting warm enough to the touch to signal their lossiness.
     
    VE3VXO likes this.
  8. VE3VXO

    VE3VXO Guest

    @W9BRD Exactly. You see this kind of thing come up all the time with QRP gear. QRP'ers get away with stuff all the time that if the same approach was used at QRO power levels the losses would result in destruction but instead nothing bad happens so ignorance is bliss eh? The criterion seems to be, "Well I make contacts with it so it works." meanwhile maybe half of ther precious watts are going in the dumper.
     
  9. K4MID

    K4MID Ham Member QRZ Page

    The best antenna is the one you have with you.

    My resonant dipoles at the QTH are fantastic but I can’t/won’t try to bring them portable with me. The whole point of having the KX2 is to be so light and portable that it can, and does, go anywhere with me so I need antennas that are also light and portable to use with it. One size does not fit all in radio.
     
  10. N8KRO

    N8KRO Ham Member QRZ Page

    Great video tks
     
  11. F5RAZ

    F5RAZ XML Subscriber QRZ Page

    Hello friends,
    I use this principle with my end fed antenna which works in half wave on 80-40-20 and 10 m - The ring is a 240/43 and the power 100 W. I use it fixed in vertical and on vacation in horizontal in V inverted or in L configuration. Very good functioning.
    Have fun
     

Share This Page

ad: elecraft