Review: 6m, 2m & 70cm Horizontal Loop Antennas by eBay Seller Freqtester

Discussion in 'Amateur Radio Equipment Reviews' started by W2WDX, May 19, 2018.

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  1. W2WDX

    W2WDX Subscriber QRZ Page

    I'll have to search out the Par analysis I saw. I found it when I was preparing this review. I was going to do a comparative study, but I found so many contradictory papers, pro and con, it seemed pointless and opted to just have my observations drive the review.
     
  2. W1BR

    W1BR Ham Member QRZ Page

    from his claims:
    Typical results are 2 to 5 DB.

    He clearly claims dB gain, not dBi, where is that alleged gain coming from? Ground reflection? dBd is a gain over a dipole. Even so, a 5 dB gain claim over dBi would be hard to swallow. Gain of−1 dBi to −1.7 dBi depending on directivity is more realistic.

    Regardless, this nothing new. The old Hi Par Saturn six halo was in use eons ago. And the CC Squalos are still production. Gain can be negative when measured against a standard. That is how attenuators work.
     
    Last edited: Jun 22, 2018
  3. W2WDX

    W2WDX Subscriber QRZ Page

    @K1ZJH I'm sorry ... I think you don't understand the fundamental reference figures. dBi references an isotropic. dBd is referenced to a dipole which is 2.15dB above dBi. So you cannot have negative dBi. It is the base reference, no gain, perfectly spherical pattern. On these loops 2dBi for one, 5dBi for a stacked pair. Seems about right to me. They are afterall halfwave dipoles folded in on themselves, so a little loss below dBd is expected.

    However, the convention has always been "db" is always referenced to isotropic, where dBd is always discriminated by the "d". The nomenclature dB and dBi are interchangeable since they both refer to the theoretical base reference. dBd is used for a more real world reference since it relates to a actual antenna type and not a theoretical one, like the isotropic. That's why understanding the fundamentals is important. When manufacturers use "db" the gain figures seems higher (by 2.15dB) than one designated dBd, however the figures may be accurate if you understand the reference, be it base or dipole.

    In reference to antenna gain, it any positive figure over isotropic which is a theoretical zero gain antenna. A dipole has gain, 2.15db above isotropic. Yagi's much more. Gain comes from directivity. You cannot have negative directivity. You cannot have negative gain below nothing. No gain is no gain. Zero. 0dBi antenna gain is an absolute minimum. It is not the same as other dB references, especially electrical figures, which is what attenuators are. You can have losses which can be summed to a gain figure, but the gain figure itself cannot be lower than 0dBi.
     
    Last edited: Jun 23, 2018
  4. W1BR

    W1BR Ham Member QRZ Page

    I have never seen dB and dBi used interchangeably. dBi is indeed isotropic gain. Both are relative numbers. If it is dB gain compared to isotrophic, then it best be stated as gain in dBi.

    F/B is hopefully a negative value in dB compared to forward gain and is usually a negative number. Since dB is relative, it certainly can have a negative value.

    Gain of a halo has been shown with negative value relative to dBi:

    https://en.wikipedia.org/wiki/Halo_antenna

    A "folded dipole" type of halo. Gain along Y axis 1.2 dBi, Gain along Z axis −1 dBi, Gain along X axis −1.7 dBi. Fed at the center of the bottom conductor (feed-line not shown), supported at the center of the top conductor which is at ground potential for RF. This is similar to the halo as originally patented.
     
    Last edited: Jun 24, 2018
  5. N0URW

    N0URW Ham Member QRZ Page

     
  6. N0URW

    N0URW Ham Member QRZ Page

    Wow, just found this thread, reads like a lot of smart ones out there. All kinds of numbers being thrown around. I hate numbers. You say a number, then you have to prove it. The original posts states that loops are working good for his location. The same type of antenna that works good in one place may or may not work as well some place else. Computer programs to model antennas? Never found one that I trusted. Or believe.
    And I have tried a bunch of them. 73
     
  7. N8FVJ

    N8FVJ Ham Member QRZ Page

    I had a 6 meter loop antenna. It did not hear well (not from your ebay seller) on a modern Yaesu FT-991A. I replaced it with a 16 foot J pole vertical antenna for much better receive. Later I replaced the J pole with a three element beam for even better receive.
     
  8. AA5CT

    AA5CT Ham Member QRZ Page

    re: "It did not hear well "

    Cross-pol (cross polarization) will do that. If the vert worked better, it says the other ops were vert too ...

    Low angle, near earth sigs get killed for horizontal propagation too.
     
  9. N8FVJ

    N8FVJ Ham Member QRZ Page

    Frankly, it would not hear well regardless of polarization. Most operators use horizontal for SSB and the loop was horizontal mounted. Further, the vertical J pole received SSB better across the board regardless of polarization. The loop antenna had to go.
     
  10. N0URW

    N0URW Ham Member QRZ Page

    Polarization is something you deal with on every contact, whether it is local or DX. If you don't have both vertical and horizontal antennas up. You are missing out. While most are on horizontal antennas of some kind. Some are still on vertical. During vhf contests, I run both a vertical yagi and horizontal yagi. (on two separate towers) You would not believe what a difference it makes. Loop antennas being omni directional have a big advantage over a directional beam. For one, you do not need a costly rotator for a loop. Second, if your directional beam is any good. You are only going to hear better in the direction it is pointing. During vhf contests I use the loops more than the yagi. If I can hear and work a station with the loop , I do. If the distant station has a pile up, I swing the yagi array around and use it. During vhf contests, you want to make as many contacts as possible. Why limit yourself to only hearing and working the stations you can hear in the direction your yagi is pointing. Not one type of antenna will fit all applications.
    It seems like now a days all I do is test different antennas during vhf contests. I will have as many as 5 different antennas up. Different boom lengths. Different number of elements. Different heights above ground. Over the years I have found it is all about height above ground and boom length. (not the number of elements) Higher is not always better. Four antennas vs a single is not always better. A yagi vs a loop is not always better. Not when it comes to DX. 73
     

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