Should I use a balun for a G5RV?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KE0CPH, Oct 14, 2018.

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  1. N5WVR

    N5WVR Ham Member QRZ Page

    And if you find that you can't quite tune the band you want with your manual tuner, for a band where the doublet is at least 3/8 wavelengths, just add a few extra feet of balanced line and you'll probably be able to tune it.

    This assumes that you have a real tuner like an ATR-30, not just the limited-range autotuner built into your rig.
     
  2. N5WVR

    N5WVR Ham Member QRZ Page

    There's nothing wrong with the basic G5RV. It's not a perfect, optimized antenna, but it works pretty well.

    However, I have never understood why people buy commercial G5RV antennas. All you need is a roll of wire, a measuring tape, and the right length of 450-ohm window line, which is cheap. (Balun is helpful but not required.) It would be a better "teaching antenna" per KK5JY if people would take the time to build it themselves. You can then re-use the balun to build a modified doublet using different lengths of wire. I'm currently using a 135 ft doublet fed by window-line on 80 through 10 meters with good results, both in terms of performance and matching on all bands with my ATR-30.
     
    KK5JY, K2CAJ and N2EY like this.
  3. N2EY

    N2EY Premium Subscriber QRZ Page

    Yes it is.....but let's go all the way back to the source: the original 1958 RSGB Bulletin article (See below). Its 1958 date matches your 1960 date quite well.

    As far as I can tell, the 1958 article is the first mention of the "G5RV" in print, although Varney says that the antenna was first used in 1946 or so. Note that there are two versions, and that the version with a "tuner" uses a real balanced link-coupled tapped-coil matching unit. There was a 1966 article as well.
     

    Attached Files:

    N2SR likes this.
  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    But you may have missed one of Varney's own recommendations; specifically that if open-wire line is used all the way to the shack, then it should be fed with "an even or odd multiple of quarter wavelength at 14Mc/s".

    A 102ft center-fed dipole fed with open-wire feeder other than an even or odd multiple of quarter wavelength at 14Mc/s becomes something other than a G5RV.
     
    WB2UAQ likes this.
  5. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    Thanks!
     
  6. G8ADD

    G8ADD Ham Member QRZ Page

    That recommendation does not appear in the article that I quoted. Unless I'm missing something it doesn't even make sense! I will extend the quotation:

    "By far the most efficient feeder is the open wire type. A suitable length of such can be constructed in the same manner as that described for the open-wire matching section. If this form is employed, almost any length may be used from the centre of the antenna to the matching network (balanced) output terminals. In this case, the matching section becomes an integral part of the feeder. A convenient length of open wire feeder is 84 feet. It permits parallel tuning of the matching network circuit on all bands from 3.5 to 28 MHz...This is not a rigid feeder length requirement, and almost any mechanically convenient length may be used. Since this type of feeder will always carry a standing wave, its characteristic impedance is unimportant."
     
    N2EY likes this.
  7. W2AAT

    W2AAT XML Subscriber QRZ Page

    Then again.... there is always the W5GI Mystery Antenna....
     
  8. K8JD

    K8JD Ham Member QRZ Page

    Big Dipole/Balanced Feedline
    I put together an EDZ antenna for 20M (2X 5/8 waves center fed) and decided to feed it with a 450 Ohm balanced line to a tuner that is designed for balanced feeders (MFJ974) .
    That eliminates any chokes/BalUns with possible loss. It happens to be a length that is also a double Zepp for 30m (2 halfwaves center fed) and a halfwave dipole on 60M. This tuner actually matches all bands from 5 to 18 MHz and the antenna gets a fairly good signal out on all those bands.
     
  9. W2AAT

    W2AAT XML Subscriber QRZ Page

    Good point.... It's always better when possible, to build one's antenna. Unfortunately, these are the days of appliance ham radio operators. Most don't even know what 60/40 means... A shame... The problem here with these kinds of posts, is that the people get so technical that they scare away the first time builder. After all the math, physics and "this is the best ways", a newbie most likely feels that it is better going the commercial direction.
     
  10. N5WVR

    N5WVR Ham Member QRZ Page

    This is where the local Elmer (rather than Internet Elmer) comes in. "Here, let me come over to your house and I'll walk you through making an antenna. You don't have a soldering gun? No problem, I'll bring one, and bring a tennis ball launcher to get it up in the tree. See you tomorrow."

    You can show how easy and unthreatening it really is when you can show instead of tell.

    The Internet is not a substitute for your local club and friendly neighborhood Elmer.
     
    AG5CK likes this.

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