Multiband antenna shootout… EZNEC style. 88′ doublet the victor!

By , September 16, 2010 4:57 pm

I have tried many different multiband ‘quick deploy’ portable/temporary antennas over the years.  I have an idea of which ones seemed to work better than others, and I was interested to see if EZNEC agrees.  I used the version 5 demo program of Roy Lewallen W7EL’s excellent antenna modeling software EZNEC to model these antennas.

The exercise:  I created EZNEC models of several different multiband ‘quick deploy’ portable/temporary antennas which I have used in the field and then compared a vertical slice of the far-field radiation pattern along the azimuth bearing of the highest gain of all the antennas.  For this exercise I chose antennas which cover 80m, 40m, 30m and 20m, are easy to set up and can be supported on a single Jackite 31′ pole.

The antennas were modeled with #26 AWG teflon coated copper wire at 1 foot over a high accuracy very poor quality ground using a split current source of 2W power.  The transmission line was not modeled.

The Antennas

Wire models of 7 antennas

The Contenders - Wire models of 7 antennas

The antennas:

I chose to model two vertical antennas.  One 28′ long vertical and one 50′ vertical.  28′ has a low enough impedance for most tuners to be able to tune it on 20m and it can be tunes on 30m and 40m also.  It’s a bit short for 80m.  50′ is about the longest practical vertical I would consider in the field, it’s tough to find tree branches higher than that.  It’s long enough to be easily matched on 80m as well.

For doublets, I chose four designs.  The 88′ doublet is a favorite of antenna guru L. B. Cebik W4RNL.  On 20m, an 88′ doublet forms an extended double zepp (EDZ), an antenna with at least 3dB gain over a dipole, so it performs particularly well on that band, and can be casually tuned on 30m and 40m as well.  With a good tuner, it can also be tuned on 80m where is performs surprisingly well for it’s limited length.  I also modeled a 132′ off center fed dipole fed at the 44′ point.  This is a popular antenna is sold commercially as the buckmaster OCF dipole.  I modeled both the horizontal and inverted-vee variants of those with the center at 31′ (e.g. supported by a Jackite 31′ pole), and in the inverted vee I took the ends down to 6′ above ground (supported by 6ft driveway markers).

I also added an inverted-L, a 31′ vertical run and then a 90′ horizontal run, fed against the same pair of 16′ and 32′ counterpoises as the verticals.  I call this one ‘The Bear’.  Dunno why :lol:

Finally, Bob VA3QV asked me about how the 88′ doublet compares to a W3EDP, so I did a separate 88′ doublet vs W3EDP comparison (both Bob’s twinlead counterpoise version and the standard version):

3 styles of W3EDP

3 styles of W3EDP

So how do they compare?

20m Far Field

20m Far Field Elevation Patterns

20m Far Field Elevation Patterns

The horizontal 88′ doublet (as an extended double-zepp EDZ) was the clear winner on 20m with a maximum gain of 9.3dBi at 30° elevation broadside to the antenna, which is a good 2dB higher than the 132′ off center fed doublet and the 121′ inverted-L.  Bringing the ends of both doublets down to 6ft above the ground makes a big difference also, the there is 4dB less gain from the 88′ inverted-vee than if it is horizontal.  Interestingly, the horizontal 88′ doublet at 31′ has higher gain at lower elevations (3°-15°) than either of the verticals (with only 2 counterpoise wires).

So it looks like the horizontal 88′ doublet is a good choice for maximizing my 1.5W input signal as long as I do not need an omni-directional pattern.

How does the W3EDP compare to the horizontal 88′ doublet on 80m?

88ft EDZ vs W3EDP

88ft EDZ vs W3EDP

So, the 88′ EDZ is still coming out ahead of the W3EDP by a wide margin,  but the W3EDP has a little more gain than an inverted-vee 88′ EDZ.  Compared to the 132′ horizontal doublet and the 121′ inverted-L the W3EDP is in the same ballpark but it does have a little more gain that either of them at lower elevation angles.

40m Far Field

40m Far Field Elevation Patterns

80m Far Field Elevation Patterns

The 88′ horizontal doublet has marginally more overall gain than the 132′ horizontal doublet but the pattern of the 132′ horizontal doublet could mean less noise (since there’s less gain at 90°), and its more omnidirectional.  So while the 132′ horizontal doublet may be a better antenna on 40m, the 88′ horizontal doublet is still a very strong contender, and since it’s much better on 20m I think I will still favor the 88′ horizontal doublet on 40m.  All the other antenna designs are down at least 3dB from those two.

How about the 88′ horizontal doublet versus the W3EDP on 40m?

88' Doublet vs 84' W3EDP on 40m

The twinlead counterpoise version of the W3EDP is almost equivalent (<1dB) to the 88′ horizontal doublet and is certainly easier to erect, but since the 20m pattern is more favourable I would still prefer to erect an 88′ horizontal doublet is I was planning on operating on both bands.

80m Far Field

80m Far Field Elevation Patterns

80m Far Field Elevation Patterns

On 80m, the 132′ horizontal off-center fed doublet is marginally better for overall gain than the 88′ doublet, but it’s very close (<1dB).  The 121′ inverted-L is quite a bit down (2.5dB) from the 132′ horizontal off-center fed doublet.  The antenna choice for this band is less clear-cut.  With an antenna tuning unit with a good matching range, the 88′ doublet is probably the best all-around choice, since it works so well on 20m and is also near the top of the pack on 40m.  But my KX1 has a limited matching range on 80m and will not tune an 88ft doublet there.  So for me, taking down one end and adding 44′ on 80m is probably the best solution.

What about the W3EDP?

88ft Doublet vs W3EDP

88ft Doublet vs W3EDP

EZNEC predicts a 2.5dB difference between the 88′ doublet and the twinlead version of the W3EDP, with the 88′ doublet being the better of the two.  The W3EDP had better low angle radiation so should be a little better for DX.

Conclusion

As un-scientific as this is 8-) …  The conclusion that I draw is that as long as I use an external tuner on my KX1, the 88′ doublet is the best overall choice for an easy to deploy multiband portable antenna as long as I intend to operate on 2 or 3 bands.  It’s also a great antenna for 20m single-band operations.  For operation on 40m/80m there are better options, but the 88′ is nearly as good.

11 Responses to “Multiband antenna shootout… EZNEC style. 88′ doublet the victor!”

  1. va3sie says:

    Raw data:

    Antenna 1) 28ft vertical. 1 X 16′ & 1 X 32′ counterpoise wires.
    Teflon coated #24 & #26 wire.
    1 foot above poor ground.

    Elevation Gain:

    20m: 0.31dBi @ 23 degrees (in direction of 16′ counterpoise).
    40m: -2dBi @ 31 degrees (in direction of 32′ counterpoise).
    80m: -4dBi @ 31 degrees (in direction of 32′ counterpoise).

    Antenna 2) 50ft vertical. 1 X 16′ & 1 X 32′ counterpoise wires.
    Teflon coated #24 & #26 wire.
    1 foot above poor ground.

    20m: 2.5dBi @ 50 degrees (in direction of 16′ counterpoise).
    40m: -0.5dBi @ 24 degrees (in direction of 32′ counterpoise).
    80m: -2.5dBi @ 29 degrees (in direction of 32′ counterpoise).

    Antenna 3) Horizontal 88ft Doublet @ 31′.
    Teflon coated #26 wire.

    20m: 9.5dBi @ 32 degrees (broadside).
    40m: 6dBi @ 83 degrees (broadside).
    4dBi @ 30 degrees (broadside).
    80m: 3.5dBi @ 90 degrees (broadside).
    -1dBi @ 30 degrees (broadside).

    Antenna 4) Inverted-vee 88ft Doublet @ 31′ (ends at 6ft).
    Teflon coated #26 wire.

    20m: 5dBi @ 90 degrees (broadside).
    1dBi @ 30 degrees (broadside).
    40m: 3.5dBi @ 83 degrees (broadside).
    0dBi @ 30 degrees (broadside).
    80m: -0.5dBi @ 90 degrees (broadside).
    -5.5dBi @ 30 degrees (broadside).

    Antenna 5) Horizontal 88/44ft OCF Doublet @ 31′.
    Teflon coated #26 wire.

    20m: 7.5dBi @ 33 degrees (2 lobes in broadside).
    40m: 5.5dBi @ 60 degrees (endfire).
    -0.25dBi @ 30 degrees (endfire).
    80m: 4dBi @ 90 degrees (broadside).
    -0.5dBi @ 30 degrees (broadside).

    Antenna 6) Inverted-vee 88/44ft OCF Doublet @ 31′ (ends at 6ft)..
    Teflon coated #26 wire.

    20m: 4.5dBi @ 75 degrees (endfire/high angle).
    -1dBi @ 30 degrees (endfire/high angle).
    (broadside pattern all < -1dBi).
    40m: -0.5dBi @ 60 degrees (endfire).
    -3dBi @ 30 degrees (endfire).
    80m: 0.5dBi @ 90 degrees (endfire).
    -4dBi @ 30 degrees (endfire).

    Antenna 7) Inverted-L 90/31ft with 16′ & 32′ counterpoises..
    Teflon coated #26 wire.

    20m: 5.25dBi @ 30degrees (endfire off long end).
    40m: 2dBi @ 50 degrees (broadside).
    1dBi @ 30 degrees (broadside).
    80m: 1.5dBi @ 80degrees (endfire off short end).
    -2.5dBi @ 30 degrees (endfire off short end).

    Antenna 8) W3EDP with twinlead counterpoise.
    Teflon coated #26 wire.

    20m: 5dBi @ 30degrees (endfire off long end).
    40m: 5dBi @ 50 degrees (broadside).
    3dBi @ 30 degrees (broadside).
    80m: 1dBi @ 60degrees (endfire off short end).
    -1.5dBi @ 30 degrees (endfire off short end).

    Antenna 9) W3EDP with 6.5ft or 17ft ground counterpoise.
    Teflon coated #26 wire.

    20m: 3.5dBi @ 40degrees (endfire off long end).
    40m: 3.5dBi @ 50 degrees (broadside).
    1.5dBi @ 30 degrees (broadside).
    80m: -2.5dBi @ 60degrees (endfire off short end).
    -3dBi @ 30 degrees (endfire off short end).

  2. VE3WMB says:

    Martin :

    As I always say .. when in doubt about ground conductivity go horizontal. In his book, ON4UN actually advises against using an antenna that is vertically polarized unless the conductivity of the soil underneath it is very good. Generally speaking even a low dipole will outperform a vertical under most circumstances. However that being said some times it comes down to what is convenient … any antenna that you can make QSOs on is a good antenna when operating QRP portable ;-)

    Michael VE3WMB

  3. Dittie Bear,

    Great write up and explanation. I love this stuff and you brought a ton of info together in a nice format. Doggone it, now I’m gonna add another antenna to my pile… I’ve just managed to get a 44ft doublet to work as advertised. For some reason it was very hard and loads one time, not the next. Very sensitive to how high the ends are above ground and it did not like being set up as a sloper or vertical either.

    Aim that new beartenna down towards Florida… a few of us will be out this weekend.

    72,
    Kelly K4UPG PB #173

  4. Chuck Pool says:

    Sir,

    Could you include one more antenna for your comparison test?

    The antenna is “The All-Band Center-Fed Inverted-L”. It is 50 feet vertical and 50 feet horizontal with no radials and center fed with open wire feeders. Here is a link to this antenna:

    http://w4rnl.net46.net/ltv.html

    If you can, please email me and let me know what you found by modeling this antenna.

    Thank you for your consideration.

    73,
    Chuck Pool – AA5WG

  5. Chuck Pool says:

    Here is one lnk to the “All-Band Center-Fed Inverted-L” antenna:

    http://w4rnl.net46.net/download/fdim10.pdf

    73,
    Chuck Pool – AA5WG

  6. Myron Schaffer says:

    Martin,

    I like it. It confirms my modeling that I’ve done on EZNEC+. I am trying to make a sub 100g version, an EDZ on 20m with 12.9m #24 magnet wire and the same for 38mm spaced 600 Ohm Tx line. I calculated that 61 degrees is needed to match to 50 Ohms. It can wrap 180 degrees to make a match at either 3.5 or 13.5m line length. My fishing pole is 11.13m long so this will be my pack packing antenna. I am just amazed that you can get 10 dB gain from a wire.

  7. Marty says:

    Pretty much as I expected. However, how do you “quick deploy” an 88′ doublet at 31’? In many temporary situations it’s hard enough to get one support in the air, especially if trees are not available.

  8. va3sie says:

    @Myron good luck with your sub 100g version of the EDZ. It is nice to be able to get gain from a doublet :-D

  9. va3sie says:

    @Marty of course you need trees :) I usually just walk around until I find an unobstructed space between two trees which are at least 31′ high. I have string and fishing weights. I attach the strings to the wires and then toss the weights over the trees one at a time, securing the string to the main trunk of each tree. Pretty standard way of getting an 88′ doublet up I guess. Usually takes me ~10 – ~15 minutes to get the antenna up which I think is worth it for the extra gain. If there is only one tall tree I will prefer an inverted-L using the pole. If there are no trees then a vertical is is :-)

  10. WB0WQS says:

    Recently, I used the 88′ Doublet inv vee set up for field day. The Jackite 31′ pole was used as the support with 24 gauge used as the antenna elements and feedline. I had mixed results with it. What did you use for the feedline? Was it lite enough not to weigh down the fiberglass pole? My W4RNL Inverted L is described on my QRZ.com page. Looking forward to finding a secret weapon for a light, balanced feed line.

  11. va3sie says:

    @WB0WQS I used 300 ohm TV twinlead from Radio Shack as my feedline. It is fairly light and does not weight down the fiberglass pole much.

Leave a Reply

Panorama Theme by Themocracy