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The Truth About the G5RV antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W0BTU, Apr 7, 2011.

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  1. W5DXP

    W5DXP Ham Member QRZ Page

    Choice of a favorite frequency with no tuner, 88 kHz with a built-in autotuner, and maybe 3.7-3.9 MHz with a wide-range tuner. I'll probably do that for my next antenna.
     
  2. N4MXZ

    N4MXZ Ham Member QRZ Page

    Many years ago, I tried modeling the Zapper I described with EZnec, and never got the results that the real world installations seem to have. It is likely that I missed something, but had I relied in the software, I never would have tried it. There are probably 30 or so in use that I know of, all with similar characteristic results. Of course situationally specific installations make alot of difference.

    For example; K1DX was able to get his up between his towers over the barn almost 120', and he thought his fp imp on 160m was about 35-40 ohms if I remember correctly(I need to call him to be sure). At the beach with a pretty substantial apex angle and 30' off the ground (I do use plastic stakes to keep the ladder line off the ground) I get around 20 ohms. Near Field ground conductivity, height, surrounding objects, apex angle, materials, even coaxial cable length...sheesh.

    Maybe I will reload EZnec and try again. :rolleyes:
     
    Last edited: Apr 7, 2011
  3. KC9SYJ

    KC9SYJ Ham Member QRZ Page

    I have read with great interest this thread on the G5RV. I recently purchased one and just waiting for the rainy Indiana weather to go away long enough to get it up. That aside,I have had a somewhat heated discussion via email with a local ham who INSISTS that my FT-950's internal tuner IS the external tuner that my radio's operating manual and my antenna's instruction sheet/booklet is the external tuner both are referring to and will NOT need an additional tuner to tune my G5RV antenna. Yet,my antenna( an MFJ 1778) manual says that a tuner IS required and operating the antenna without one is NOT recommended. Even the manual for the radio says that an external tuner will be needed for this antenna type as the radio's internal tuner may not have the range to tune it on all HF amateur bands. How in the hell can the radio's built-in tuner be considered the external tuner that my fellow local ham claims it is and will not need an additional tuner on top of that? He made the statement that the G5RV is not much of an antenna if you have to have an additional tuner to tune it when the radio's built-in tuner will tune it just fine,...yet the radio's manual says an external tuner is necessary as does the antenna's manual. The antenna is the standard model(102' long) and will be used as an inverted-v. Soooo,... after having blown off a bit of steam at this guy and being in disagreement with him over the tuner deal,..can you tell me which bands the radio's built-in tuner might be able to tune it and which bands an external tuner will be necessary? Please help,...I am at my wit's end as he
    refuses to believe me and what my radio's manual and antenna manual says in regards to external tuners.
    This antenna comes with a 450 ohm ladder line(about 32 ft. length) with SO-239 connector at the end and is set up to work 80m to 10m WITH a tuner. One last thing,...the rig will be ran barefoot 100 watts with an MFJ-941E tuner. If I had an amp,MFJ recommends the 962 or 986 tuners,but they told me that since I am running barefoot the 941E tuner will work fine.
     
  4. G3TXQ

    G3TXQ Ham Member QRZ Page

    Here's some text lifted from my web site which may help:

    Full description is here: http://www.karinya.net/g3txq/g5rv/

    Impedances will vary slightly from installation to installation, and the matching range of internal tuners also varies from radio to radio, but the table on that web page should be a useful guide.

    Also note that the longer the coax section the more the loss, and the more likelihood that the internal tuner is able to match the impedance. Again, lifting text from my web page:

    73,
    Steve G3TXQ
     
  5. N2NJZ

    N2NJZ Ham Member QRZ Page

    Mine works pretty darned well on 80/75 meters with a tuner. Lowest SWR is down at the bottom end of the band, but there's nothing that can't be matched through the whole band.

    Mine doesn't match too well on 15 meters, and I've got some RF currents floating around that drive my LDG auto-tuner nuts. I need to sort that out...
     
  6. G3TXQ

    G3TXQ Ham Member QRZ Page

    15m is the ZS6BKW's "worst" band - the impedance at the end of the ladderline section is typically >2000 Ohms at the top of the band.

    73,
    Steve G3TXQ
     
  7. EI4GMB

    EI4GMB Ham Member QRZ Page

    Steve G3TXQ's site is an excellent resource for information about the G5RV. It is certainly worth checking out. ;)

    Best Regards

    Fred EI4GMB
     
  8. K7KBN

    K7KBN Ham Member QRZ Page

    Running a "G", having a "Q".
     
  9. G0GQK

    G0GQK Ham Member QRZ Page

    Do the job properly ! Make an 80 metre halfwave dipole, feed it with open wire feeder, a 4:1 balun into an ATU and SWR meter and you'll have every band from 10 metres to 80 and 160 for a short range. If 135 ft is too long, drop the ends vertically.
     
  10. G3TXQ

    G3TXQ Ham Member QRZ Page

    Tuner Balun: 4:1 or 1:1 ?

    Steve G3TXQ
     
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