Which is better G5RV or ZS6BKW?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K4SAV, Jul 4, 2014.

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  1. K4SAV

    K4SAV Ham Member QRZ Page

    You often hear recommendations for a ZS6BKW over a G5RV, or even just the opposite. You hear the ZS6BKW doesn't cover 80 meters, but many people use it there with a tuner. The ZS6BKW hits the bands a little closer than the G5RV so you may have to use the tuner more often with the G5RV but how do the gain and patterns compare? I decided to make an animated gif that could compare the antennas on all bands under equal conditions. This graphic doesn't show the SWR but the effect of feedline loss is included in the gain for both antennas.

    I wanted to see this comparison. I was a little surprised by the results on some bands. Since I went to all the trouble of making this, I decided to share it. Maybe someone else will find it useful.

    1. From my perspective it appears that 80, 40, and 30 is a toss-up, although both are poor on 30 meters due to high SWR.
    2. 20 meters is interesting. The ZS6BKW has more gain in two of the 6 lobes than the G5RV, but the G5RV has more gain in the other 4 lobes. I would have to give the nod to the G5RV based on better area coverage.
    3. On 15 meters both are poor performers due to high SWR and poor patterns, but the G5RV appears to have a small edge.
    4. On 17, 12, and 10, I think the ZS6BKW is better, although 12 is a real mess of lobes (10 for each antenna).

    Jerry, K4SAV

    Details:
    1. G5RV: 102 ft wire, 34.8 ft Wireman 551 ladderline, 80 ft RG-213
    2. ZS6BKW; 93.5 ft wire, 40 ft Wireman 551 ladderline, 75 ft RG-213
    3. Both over average ground at 40 ft height
    4. For 40 and 80 meters the comparison was done at 30 degrees elevation. The take-off angle on those bands is 90 degrees and the gain is higher at 90 degrees.
    5. No tuner losses were included in the comparison but with a good tuner this should be negligible.
    6. Notice that the outer ring of the plots is set to 8 dBi for all plots.
    7. The antenna position relative to the patterns can be visualized as the antenna running horizontally across the center of the plot.
     

    Attached Files:

  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Great analysis.

    Would be interested in the difference at 60' above ground level, and maybe also at 25' or so to simulate a more ideal and less ideal height.

    Would also be interested to directly compare everything with a simple 120' long center-fed doublet at 40' fed with ladder line 100' long, as is another fairly typical installation.

    These are really simple compromise antennas but quite popular.

    It's funny a neighbor of mine swears by his Sterba Curtain optimized for 17m and strung up between trees at maybe 45' above ground. When I get on with my LPDA beam, I completely "clobber" him at every distance, in every direction -- including hearing signals he cannot hear at all. We're only about a mile apart, same elevation, same ground conditions.

    "Everything works," but some animals are more equal than others.:p
     
    CX7RL likes this.
  3. G3TXQ

    G3TXQ Ham Member QRZ Page

    Unless I missed it I see no mention of the coax losses? That's the factor that can make one of these antennas more attractive than the other on a particular set of bands.

    Steve G3TXQ
     
  4. G4ALA

    G4ALA Ham Member QRZ Page

  5. K4SAV

    K4SAV Ham Member QRZ Page

    It was a long post with a lot of detail and the feedline info could be overlooked. It's under "details" at the bottom of my post.

    The feedline losses have a significant contribution to the performance of these two antennas. Both antenna models have the same total length of feedline, about 115 ft. That feedline loss is the main contributor to the very low gain of both these antennas on 30 and 15 meters, and also for the poor performance of the G5RV on 10 meters. Of course the very skinny lobes and small area coverage of the pattern of both these antennas on 30 and 15 make it an even poorer performer. Notice that I used RG-213 in the model. Someone using RG-58 or RG-8X is going to have significantly less gain.

    WIK wanted to see a comparison which included a 120 ft doublet fed only with ladderline. That would eliminate most of the feedline losses and increase the gain by a lot on 10, 15, and 30 meters, but that would not be all the difference. The longer antenna would significantly change the pattern on the high bands. That's the antenna I usually recommend for someone wanting to work all bands 80 thru 10 and wants to do it all from only one antenna.

    Jerry, K4SAV
     
    Last edited: Jul 5, 2014
  6. W5DXP

    W5DXP Ham Member QRZ Page

    Those radiation patterns and feedpoint impedances are on the following web page. TLDetails can be used to calculate feedline losses.

    http://www.w5dxp.com/notuner.htm
     
  7. W6OGC

    W6OGC Ham Member QRZ Page

    It was Steve, G3TXQ who pointed out when I complained about the 10M performance of the G5RV I initially had up that with feedline losses on the ~100' or so of RG-8X that only something like .04 watts was making it to the wire out of the 5 watts output at the transmitter, leaving no wonder why I was getting no replies on 10M.

    Given all the limitations of these compromise antenna, I don't understand the popularity. A twin lead fed dipole with a decent tuner is going to be a better performer just about every time, all other things being equal. The dipole I replaced the G5RV with certainly is far and away a better performer in every respect, other than total cost since it needs a tuner, in my case the AH-4 Icom remote tuner, and limited to 120 watts.
     
  8. K4SAV

    K4SAV Ham Member QRZ Page

    I don't know of any simple all-band wire antenna that isn't a significant compromise on one or more bands, however you are correct that a ladderline fed dipole is a better performer than a G5RV or a ZS6BKW. Most people don't consider a ladderline fed dipole because of the difficulty of bringing the ladderline into the house. In my case I can't have a ladderline fed dipole because of high lightning density at my location and the difficulty of protecting my home from a hit on that antenna.

    Jerry, K4SAV
     
  9. N5YPJ

    N5YPJ QRZ Moderator QRZ Page

    I agree with you however in certain cases a G5RV is a blessing. In my case there's not enough room for a 130 ft dipole to be able to work 80 meters and I really don't have the room for more than 1 wire antenna. In addition to 80 meters my G5RV has allowed me to make numerous contacts on 17 and 12 meters.
     
  10. G3TXQ

    G3TXQ Ham Member QRZ Page

    Jerry - apologies, I didn't spot it!

    The G5RVs I see sold in the UK are invariably bundled with a length of RG-58 - of course it helps improve the SWR :rolleyes:

    Steve G3TXQ
     
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