Antenna Survey @DL2LSM

The standard antenna setup @DL2LSM consists of:

  • a three band spider beam at a height of about 13m, and
  • a 2-by-20m dipole fed by a symmetrical antenna tuner AT-502 at about 12m.

The ground conditions are pretty good with ground water close to the soil. In principle the antenna setup is rather small. Nevertheless, it works amazingly well and allowed for some nice contest scores, e.g. the actual World Record of the Single Operator Assisted QRP category of the CQ WWDX contest. Additionally, a couple of different temporary antennas have been used, e.g. 40m delta loop, 2-by-27m double zepp, 80m wire pyramid, and 80m horizontal quad loop. None of these antennas — although often praised as killer antennas with gain several S units above a dipole — has been really convincing. In order to put the practical observation into perspective a numerical analysis with the 4NEC2 package has been performed. The results are presented in the following.

Introduction

This survey has been inspired by the work of Charles, W8JI, who did analyze quite a few of his transmitting antennas. Today, tools to numerically analyse antennas are available. The 4NEC2 implementation of the NEC-2/NEC-4 code has been used. It is freely available and runs on almost all Windows based home computer. Despite being free-of-charge it is quite comfortable and full of useful features.

The gain of antennas is mostly given by dBi or dBd. However, these numbers are most of the times quite misleading since most of our antennas — at least on the short wave bands — are far away from being in free space. A normal dipole at a reasonable height develops as much as 8.5dBi over real ground. The appropriate numerical analysis can be found here. Thus, one needs a reasonable model antenna to compare antenna gain.

2-by-20m-dipole-sketchThe model antenna in my case will be the 2-by-20m double zepp antenna described in the following. The antenna has been built by DL2LSM in the early nineties and replaced a W3DZZ used for the short wave. It is a simple 2-by-20m dipole (resonant at the bottom end of the 80m band) with a symmetrical remote antenna tuner AT-501 at the feed point. It transforms the complex impedance to 50Ω right there allowing for direct coax feed. The antenna was mounted originally at a height of 20m at its center sloping down to about 12m at its end points. However, it needed to be lowered to about 12m in the middle when the spider beam has been set up. The antenna can be tuned and used on all bands from 160m up to 10m. The antenna direction is Westnorthwest to Southeast. It is slightly bent with an opening angle of about 150 degrees.

Most of the time antenna performance is reduced to a single number, i.e. maximum gain. However, it is normally quite difficult to conclude the real performance from that number. Therefore, it has been decided to display performance for different regions of interest for contesting, i.e.

  • North America (315 degrees)
  • Russia and Japan (45 degrees)
  • Caribbean (270 degrees)
  • Africa (180 degrees)

The numbers in brackets correspond to the approximate beam headings from the DL2LSM QTH (Maidenhead locator: JO61GH).

Reference Antenna: 2-by-20m Dipole

Description

  • 2-by-20m dipole @12m
  • aligned Westnorthwest to Southeast, 150 degrees opening angle
  • average ground
  • sketch
  • coordinates
  • simulation source files: 40m, 80m, 160m

Results

The pictures show the total gain in the vertical plane of the reference antenna (blue line) for the low bands 160m, 80m, and 40m, respectively.

160m: The directional response pattern is almost omnidirectional. High angle radiation dominates. It has a slight minimum towards the US as expected by its installation direction.

Total Gain [dbi] (vert. plane)
45 (UA/UA9/JA)
2-by-20m_dipole_12m_bent_160_045deg
315° (W/VE)
2-by-20m_dipole_12m_bent_160_135deg
270° (Caribbean)
2-by-20m_dipole_12m_bent_160_180deg
180° (Africa)
2-by-20m_dipole_12m_bent_160_270deg
θ [°]
0 3.1 3.1 3.1 3.1
15 2.8 2.6 2.6 2.8
30 2.0 1.0 1.2 1.8
45 0.4-1.6-1.1 0.1
60-2.3-5.3-4.5-2.8
75-7.7-9.9-9.4-8.1

80m: The directional response pattern is again almost omnidirectional. High angle radiation dominates. The minimum towards the US and the Caribbean becomes stronger.

Total Gain [dbi] (vert. plane)
45° (UA/UA9/JA)
2-by-20m_dipole_12m_bent_80_045deg
315° (W/VE)
2-by-20m_dipole_12m_bent_80_135deg
270° (Caribbean)
2-by-20m_dipole_12m_bent_80_180deg
180° (Africa)
2-by-20m_dipole_12m_bent_80_270deg
θ [°]
0 6.2 6.2 6.2 6.2
15 6.0 5.6 5.7 5.9
30 5.4 3.8 4.2 5.1
45 4.1 0.8 1.6 3.5
60 1.7-3.6-2.1 0.8
75-3.5-9.5-7.7-4.4

40m: The directional response pattern loses its omnidirectionality. Radiation is shifted more into low angle radiation towards the dipole broadside. The minimum towards the US and the Caribbean becomes very strong.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_dipole_12m_bent_40_045deg315° (W/VE)2-by-20m_dipole_12m_bent_40_135deg270° (Caribbean)2-by-20m_dipole_12m_bent_40_180deg180° (Africa)2-by-20m_dipole_12m_bent_40_270deg
θ [°]
0 6.4 6.4 6.4 6.4
15 6.6 5.4 5.6 6.4
30 6.9 2.7 3.5 6.1
45 6.7 -1.9 -0.1 5.2
60 5.2 -7.1 -4.6 3.0
75 0.8-12.9-10.7-1.9

Hang’em higher

Description:

It is planned to bring back the feed point of the reference antenna at its nominal height of 20m as a first measure to improve the antenna performance. The dipole becomes slightly inverted-V shaped.

  • 2-by-20m inverted-V dipole, feed point @20m, end points @12m
  • aligned Westnorthwest to Southeast, 150 degrees opening angle
  • average ground
  • sketch
  • coordinates
  • simulation source files: 40m, 80m, 160m

Results:

The pictures show the total gain in the vertical plane of the reference antenna (red line) and this antenna (blue line) for the low bands 160m, 80m, and 40m, respectively.

160m: The characteristic of the directional response pattern doesn’t change. However, a small increase of 2 to 3dB of the total gain can be noted.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_dipole_20m_bent_160_045deg315° (W/VE)2-by-20m_dipole_20m_bent_160_135deg270° (Caribbean)2-by-20m_dipole_20m_bent_160_180deg180° (Africa)2-by-20m_dipole_20m_bent_160_270deg
θ [°]
0 4.8 4.8 4.8 4.8
15 4.6 4.3 4.4 4.5
30 3.9 2.9 3.1 3.7
45 2.4 0.5 0.9 2.1
60 -0.2 -3.0 -2.3 -0.6
75 -5.4 -7.8 -7.3 -5.7

80m: The characteristic of the directional response pattern doesn’t change. However, a marginal increase of the total gain can be noted.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_dipole_20m_bent_80_045deg315° (W/VE)2-by-20m_dipole_20m_bent_80_135deg
270° (Caribbean)2-by-20m_dipole_20m_bent_80_180deg
180° (Africa)2-by-20m_dipole_20m_bent_80_270deg
θ [°]
0 6.0 6.0 6.0 6.0
15 5.9 5.5 5.6 5.8
30 5.7 4.1 4.5 5.3
45 4.8 1.7 2.5 4.3
60 2.8 -1.9 -0.6 2.0
75 -2.0 -7.2 -5.8 -2.9

40m: The characteristic of the directional response pattern changes. The gain values for lower elevation angles increases. This is mostly dominant for the North-America and Caribbean direction.

Total Gain (vert. plane)
45° (UA/UA9/JA)
2-by-20m_dipole_20m_bent_40_045deg
315° (W/VE)
2-by-20m_dipole_20m_bent_40_135deg
270° (Caribbean)
2-by-20m_dipole_20m_bent_40_180deg
180° (Africa)
2-by-20m_dipole_20m_bent_40_270deg
θ [°]
0 1.4 1.4 1.4 1.4
15 2.4 0.9 1.2 2.1
30 4.6 -0.2 0.8 3.6
45 6.5 -1.9 0.1 4.8
60 6.7 -3.6 -1.2 4.4
75 3.3 -6.3 -4.6 0.7

2-by-27m Double Zepp

Description:

A double-zepp antenna with 27m dipole elements has been temporarily erected in order to have a second low band antenna for contest operation during night time.

  • 2-by-27m inverted-V dipole, feed point @16m, end points @11m/10m
  • aligned roughly Westnorthwest to East, 150 degrees opening angle
  • average ground
  • sketch
  • coordinates
  • simulation source files: 40m, 80m, 160m

Results:

The pictures show the total gain in the vertical plane of the reference antenna (red line) and this antenna (blue line) for the low bands 160m, 80m, and 40m, respectively.

160m: The characteristic of the directional response pattern doesn’t change. However, a small increase of 1 to 2dB of the total gain can be noted.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-27m_double_zepp_bent_160_045deg315° (W/VE)2-by-27m_double_zepp_bent_160_135deg270° (Caribbean)2-by-27m_double_zepp_bent_160_180deg180° (Africa)2-by-27m_double_zepp_bent_160_270deg
θ [°]
0 4.2 4.2 4.2 4.2
15 3.9 3.9 3.8 4.0
30 2.8 2.7 2.3 3.2
45 1.0 0.7 -0.1 1.8
60 -2.0 -2.3 -3.4 -0.9
75 -7.2 -6.9 -7.4 -6.3

80m: The characteristic of the directional response pattern doesn’t change. However, a small increase of 2 to 3dB of the total gain can be noted for the North-America direction.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-27m_double_zepp_bent_80_045deg315° (W/VE)2-by-27m_double_zepp_bent_80_135deg270° (Caribbean)2-by-27m_double_zepp_bent_80_180deg180° (Africa)2-by-27m_double_zepp_bent_80_270deg
θ [°]
0 6.5 6.5 6.5 6.5
15 6.1 6.1 5.9 6.4
30 5.2 4.8 4.1 5.9
45 3.4 2.7 1.1 4.9
60 0.6 -0.5 -2.7 2.6
75 -4.7 -5.7 -7.8 -2.4

40m: The characteristic of the directional response pattern changes for all directions but the South. For the latter the total increases by a small amount of about 3dB. The total gain for the North-East direction decreases by about 6db. For the North-America and Caribbean the total gain for low elevation angles increases by a small amount.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-27m_double_zepp_bent_40_045deg315° (W/VE)2-by-27m_double_zepp_bent_40_135deg270° (Caribbean)2-by-27m_double_zepp_bent_40_180deg180° (Africa)2-by-27m_double_zepp_bent_40_270deg
θ [°]
0 6.8 6.8 6.8 6.8
15 5.9 5.6 4.8 7.2
30 3.5 1.9 -0.3 7.9
45 -0.1 -1.9 0.1 8.3
60 -3.4 -2.0 -0.8 7.4
75 -6.7 -4.2 -5.1 3.3

2-by-20m Double Zepp

Description:

This is an imaginary antenna where the 27m dipole elements of the antenna above are shortened to 20m.

  • 2-by-20m inverted-V dipole, feed point @16m, end points @11m/10m
  • aligned roughly Westnorthwest to East, 150 degrees opening angle
  • average ground
  • sketch
  • coordinates
  • simulation source files: 40m, 80m, 160m

Results:

The pictures show the total gain in the vertical plane of the reference antenna (red line) and this antenna (blue line) for the low bands 160m, 80m, and 40m, respectively.

160m: The characteristic of the directional response pattern doesn’t change. However, a small increase of 1 to 2dB of the total gain can be noted.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_double_zepp_bent_160_045deg315° (W/VE)2-by-20m_double_zepp_bent_160_135deg270° (Caribbean)2-by-20m_double_zepp_bent_160_180deg180° (Africa)2-by-20m_double_zepp_bent_160_270deg
θ [°]
0 4.1 4.1 4.1 4.1
15 3.7 3.7 3.6 3.9
30 2.7 2.6 2.2 3.1
45 0.9 0.6 -0.3 1.6
60 -2.1 -2.5 -3.7 -1.0
75 -7.5 -7.2 -7.9 -6.4

80m: The characteristic of the directional response pattern doesn’t change. However, a small increase of 2 to 3dB of the total gain can be noted for the North-America direction.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_double_zepp_bent_80_045deg315° (W/VE)2-by-20m_double_zepp_bent_80_135deg270° (Caribbean)2-by-20m_double_zepp_bent_80_180deg180° (Africa)2-by-20m_double_zepp_bent_80_270deg
θ [°]
0 6.2 6.2 6.2 6.2
15 5.9 5.8 5.7 6.1
30 5.0 4.7 4.1 5.7
45 3.5 2.8 1.3 4.7
60 0.7 -0.2 -2.6 2.5
75 -4.5 -5.4 -7.9 -2.5

40m: The characteristic of the directional response pattern changes for all directions but the South. For the latter the total increases by a small amount of about 3dB. The total gain for the North-East direction decreases by about 6db. For the North-America and Caribbean the total gain for low elevation angles increases by a small amount.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_double_zepp_bent_40_045deg315° (W/VE)2-by-20m_double_zepp_bent_40_135deg270° (Caribbean)2-by-20m_double_zepp_bent_40_180deg180° (Africa)2-by-20m_double_zepp_bent_40_270deg
θ [°]
0 4.6 4.6 4.6 4.6
15 4.5 4.4 4.1 5.1
30 4.3 3.7 2.2 6.2
45 3.7 2.3 -0.6 7.0
60 1.9 0.0 -3.5 6.3
75 -2.7 -4.8 -7.6 2.4

It should be noted that the performance of this antenna is almost the same as that of the 2-by-27m double-zepp described above.

40m Delta Loop

Description:

  • 40m delta loop, apex point @12m, bottom wire @3m
  • aligned Southsouthwest to Northnortheast (perpendicularly modeled to the 2-by-20m reference dipole)
  • average ground
  • simulation source file: 40m

Results:

The pictures show the total gain in the vertical plane of the reference antenna (red line) and this antenna (blue line) for the 40m band.

40m: The directional response pattern of this 40m delta loop antenna is characterized by to low angle lobes and a deep null for very high elevation angles. The total gain towards the Northeast and the South is always lower than that of the reference antenna. However, it is quite a bit higher at low angles towards North-America and the Caribbean.

Total Gain (vert. plane)
45° (UA/UA9/JA) 40m_deltaloop_sidefed_045deg315° (W/VE)40m_deltaloop_sidefed_135deg270° (Caribbean)40m_deltaloop_sidefed_180deg180° (Africa)40m_deltaloop_sidefed_270deg
θ [°]
0-25.5-25.5-25.5-25.5
15-17.9-11.0-10.9-12.5
30-10.0 -4.7 -5.0 -7.0
45 -5.7 -1.1 -1.6 -3.6
60 -3.5 0.7 0.1 -1.9
75 -4.0 0.0 -0.5 -2.6

It should be noted that such a signal difference has never been seen during operation. There might be several reasons for that behaviour:

  • The signals of interest arrive at higher angles.
  • The antenna pattern is disturbed by the close proximity of the reference antenna.
  • There are a number of houses just into the direction of the antenna which might block low angle radiation.

80m Horizontal Quad Loop

Description:

This oddly shaped 80m horizontal loop antenna has been erected for the CQ WPX SSB Contest 2016. It is called quad loop due to the fact that it is supported by four different trees 🙂 : a birch, a maple tree, a pine tree, and an oak tree, respectively.

  • 80m horizontal loop, corner fed, about 10m high
  • average ground
  • coordinates
  • simulation source file: 80m, and 40m

Results:

The pictures show the total gain in the vertical plane of the reference antenna (red line) and this antenna (blue line) for the 80m, and 40m band, respectively.

80m: The antenna response pattern is almost identical to that of the reference antenna. The total gain towards the Northeast and South is slightly lower.

Total Gain (vert. plane)
45° (UA/UA9/JA)80m_horiz-loop_DL2LSM_10m_80_045deg315° (W/VE)80m_horiz-loop_DL2LSM_10m_80_135deg270° (Caribbean)80m_horiz-loop_DL2LSM_10m_80_180deg180° (Africa)80m_horiz-loop_DL2LSM_10m_80_270deg
θ [°]
0 6.7 6.7 6.7 6.7
15 6.3 6.2 6.2 6.3
30 5.0 4.4 4.6 4.9
45 2.7 1.3 1.9 2.5
60 -0.8 -3.0 -2.0 -1.2
75 -6.8 -8.3 -7.7 -7.0

40m: The antenna response pattern towards the North East is almost identical. The total gain for low elevation angles towards North-America and the Caribbean is increased by about 3db whereas it decreases towards the South.

Total Gain (vert. plane)
45° (UA/UA9/JA)80m_horiz-loop_DL2LSM_10m_40_045deg315° (W/VE)80m_horiz-loop_DL2LSM_10m_40_135deg270° (Caribbean)80m_horiz-loop_DL2LSM_10m_40_180deg180° (Africa)80m_horiz-loop_DL2LSM_10m_40_270deg
θ [°]
0 5.1 5.1 5.1 5.1
15 6.2 4.7 5.5 4.6
30 7.3 3.5 5.6 3.6
45 6.9 1.6 3.7 1.4
60 4.5 -1.3 -0.7 -2.4
75 -1.0 -7.0 -7.4 -8.0

80m Wire Pyramid

Description:

The wire pyramid had been erected temporarily once in order to have a second low band antenna during the CQWW DX CW Contest 2014.

  • 80m wire pyramid, apex point @12.5m, bottom wire @2.5m
  • average ground
  • simulation source file: 80m

Results:

80m: The total gain of the 80m wire pyramid antenna is almost on all occasions lower than that of the reference antenna. There is only a tiny increase for low angle radiation towards North-America which hasn’t been seen during operation.

Total Gain (vert. plane)
45° (UA/UA9/JA)80m_wire-pyramid_045deg 315° (W/VE)80m_wire-pyramid_135deg270° (Caribbean)80m_wire-pyramid_180deg
180° (Africa)80m_wire-pyramid_270deg
θ [°]
0 1.8 1.8 1.8 1.8
15 1.6 1.6 1.6 1.6
30 0.9 0.9 0.9 0.9
45 -0.3 -0.3 -0.4 -0.3
60 -2.4 -2.4 -3.0 -1.9
75 -6.1 -6.0 -8.3 -4.5

2-by-20m Double Zepp (proposed)

As can be seen by the simulations above as well as the performance ‘On The Air’ none of the antennas above outperform the reference antenna respectively when the feed point will be again raised to about 20m. However, a second low band antenna will be needed. So, taking into consideration that the weak direction of the reference dipole is towards the US the erection of a second 2-by-20m double zepp antenna will be considered. It could be hung Southwest to Northeast from the feed point of the reference antenna to a newly to built mast.

Description:

  • 2-by-20m double zepp @20m
  • aligned Southwest to Northeast
  • average ground
  • sketch
  • simulation source files: 40m, 80m, 160m

Results:

The pictures show the total gain in the vertical plane of the reference antenna (red line) and this antenna (blue line) for the low bands 160m, 80m, and 40m, respectively. It should be noted that the reference antenna in this case is the 2-by-20m dipole with the feed point raised to 20m.

160m: The antenna response pattern is almost identical to the one of the reference antennas. As expected the total gain towards the Northeast is slightly decreased whereas it increases towards North-America.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_double_zepp_new_160_045deg315° (W/VE)2-by-20m_double_zepp_new_160_135deg270° (Caribbean)2-by-20m_double_zepp_new_160_180deg180° (Africa)2-by-20m_double_zepp_new_160_270deg
θ [°]
0 5.8 5.8 5.8 5.8
15 5.2 5.6 5.4 5.4
30 3.6 4.9 4.3 4.3
45 0.6 3.6 2.3 2.3
60 -4.0 1.0 -0.9 -0.9
75 -9.9 -4.3 -6.3 -6.3

80m: The antenna response pattern is almost identical to the one of the reference antennas. As expected the total gain towards the Northeast is slightly decreased whereas it increases by about 3dB towards North-America.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_double_zepp_new_80_180deg315° (W/VE)2-by-20m_double_zepp_new_80_135deg270° (Caribbean)2-by-20m_double_zepp_new_80_180deg180° (Africa)2-by-20m_double_zepp_new_80_270deg
θ [°]
0 6.2 6.2 6.2 6.2
15 5.7 6.2 6.0 6.0
30 4.2 6.2 5.2 5.2
45 1.2 5.7 3.8 3.8
60 -3.9 4.0 1.1 1.1
75-11.3 -0.7 -4.1 -4.1

40m: The antenna response pattern changes quite drastically in comparison to the one of the reference antenna. There is a strong increase of total antenna gain towards North America by up to 12dB for the interesting angles of radiation. On the other hand it is drastically reduced towards the Northeast. The total gain towards the Caribbean is slightly increased whereas it decreases for the South direction.

Total Gain (vert. plane)
45° (UA/UA9/JA)2-by-20m_double_zepp_new_40_045deg315° (W/VE)2-by-20m_double_zepp_new_40_135deg270° (Caribbean)2-by-20m_double_zepp_new_40_180deg180° (Africa)2-by-20m_double_zepp_new_40_270deg
θ [°]
0 -4.7 -4.7 -4.7 -4.7
15 -4.1 -3.2 -3.6 -3.6
30 -2.4 2.2 0.0 0.0
45 -3.9 7.0 2.4 2.4
60-10.7 8.9 1.8 1.8
75-22.9 6.4 -2.4 -2.4

It can clearly be seen that this double zepp antenna will have considerable gain advantage especially on 40m towards North America and the Caribbean. Additionally, there might be the option to construct a T-Antenna by shortening the ladder line at its feed point and feeding it against ground. This construct might be an alternative on 160m.

This entry was posted on Tuesday, May 24th, 2016 at 1:52 pm and is filed under Technical Article. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.

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