[schoenbe]

Is this the design for your DBGH with L1 and L2 for CH13?

Forum member holl_ands does antenna modeling. He might be able to answer your question about how well your current DBGH will do on CH7.

You are correct, I built this model: www.user.dccnet.com/jonleblanc/Canada_TV_Stations/Gray-Hoverman/DBGH_VHF_hi_Antenna.pdf
Optimized for channel 13 (L1 = 28", L2 = 10"). This would probably be called a DBGH6n2 (only 2 NARODs per bay).

NARODS on this antenna are just horizontal straight, not hat-shaped like the models at nikiml's Antenna pages. I guess therefore I cannot go by the gain sweeps shown for those models.

 

[rabbit73]

Thank you for the additional information. I hope that it will be sufficient for holl_ands to answer your question.

I found it interesting that the WVNY signal is LOS because of the high elevation of the transmitting tower, but small changes in location in your area can make a considerable difference in the strength of the received signal.

You have built a very effective DBGH to receive WVNY; well done.

Best regards,
rabbit

 

[holl_ands]

After verifying 4nec2 model dimensions (against Leblanc diagram cited above), subject DBGH6n3 [Optimizd fo Ch13] was originally posted by 300ohm [way back when] on 14Feb2009, see post #4 in fol. Thread:
https://www.digitalhome.ca/forum/186-antenna-research-development/99907-gh-narods-vhf-hi-uhf.html

Fol. is nikiml's EVAL RESULTS for Ch13 Optimization (L1=28-in, L2=10-in):
Note loss of Gain and also POOR SWR on Ch7....and ALSO lowest UHF Channels [fixed by nikiml Optimizations]:

Input file : C:\Python35\DBGH6n3_L1=28_L2=10_300ohm_14Feb2009.nec
Freq sweeps: [(174, 6, 8), (470, 12, 29)]e
Autosegmentation: NO

         --- Gain ---              -- Ratios -- -- Impedance --
   Freq    Raw    Net   SWR BeamW    F/R    F/B    Real    Imag  AGT  corr
==========================================================================
  174.0   6.44  -1.03 20.26  73.9  -2.36  -2.36   16.28  -94.44 1.00 -0.02
  180.0   7.37   3.66  7.25  68.2  -1.03  -1.03   41.45   -9.84 1.00 -0.02
  186.0   8.51   7.85  2.20  66.9   2.30   2.30  140.94   47.24 1.00 -0.02
  192.0   9.77   9.47  1.69  68.1   5.33   5.33  177.68   12.56 1.00 -0.02
  198.0  11.90  11.28  2.15  69.6  12.72  12.72  141.88  -35.37 0.99 -0.03
  204.0  11.57  10.83  2.31  72.4  16.23  26.27  130.18   15.36 0.99 -0.03
  210.0  11.10  10.59  2.00  74.4  11.66  12.34  153.41   40.65 0.99 -0.03
  216.0  10.66  10.25  1.86  75.9   7.99   7.99  165.24   39.14 0.99 -0.03

  470.0  14.68  11.45  6.27  41.9  13.29  13.29   57.03  129.28 1.00  0.02
  482.0  15.29  12.75  4.98  42.1  14.17  14.17  100.52  237.21 1.00  0.02
  494.0  15.71  13.91  3.80  42.0  15.47  15.47  224.53  365.45 1.00  0.02
  506.0  15.99  14.82  2.90  41.8  17.18  17.18  547.01  377.74 1.00  0.02
  518.0  16.20  15.47  2.30  41.4  19.42  19.42  685.18  -43.51 1.00  0.01
  530.0  16.34  15.85  1.97  40.8  22.34  22.34  422.12 -212.72 1.00  0.01
  542.0  16.46  16.05  1.85  40.1  25.93  25.93  266.40 -173.40 1.00  0.01
  554.0  16.56  16.14  1.87  39.1  26.49  28.14  196.04 -113.41 1.00  0.01
  566.0  16.63  16.16  1.94  38.2  23.55  26.23  163.69  -60.10 1.00  0.01
  578.0  16.62  16.12  1.99  37.4  20.36  23.99  151.60  -14.71 1.00  0.01
  590.0  16.43  15.94  1.97  37.7  17.38  23.83  153.24   21.86 1.00  0.01
  602.0  16.05  15.60  1.92  39.5  15.13  28.29  161.60   46.64 1.00  0.01
  614.0  15.70  15.26  1.90  41.4  13.72  39.78  167.79   63.48 1.00  0.01
  626.0  15.51  15.05  1.93  42.4  12.89  23.66  171.08   80.33 1.00  0.01
  638.0  15.51  15.02  1.98  42.4  12.49  18.34  176.34  102.02 1.00  0.02
  650.0  15.76  15.27  1.97  41.7  12.43  15.18  193.56  128.24 1.00  0.02
  662.0  16.08  15.71  1.81  40.9  12.53  13.03  233.68  145.19 1.00  0.02
  674.0  16.21  16.04  1.50  40.2  11.65  11.65  289.11  119.30 1.00  0.02
  686.0  16.17  16.16  1.13  38.9  11.06  11.06  295.40   36.08 1.00  0.02
  698.0  16.19  16.05  1.44  36.8  10.91  10.91  210.23  -17.10 1.01  0.04

  710.0  16.27  15.26  2.67  34.0  10.85  10.85  112.75   19.51 1.01  0.04
  722.0  15.91  12.99  5.65  30.5  11.01  11.01   59.67  103.89 1.01  0.04
  734.0  14.21   9.40 10.00  25.1  10.30  12.25   43.91  202.66 1.01  0.04
  746.0  11.23   5.83 11.76  20.7   5.85  17.43   54.86  319.35 1.01  0.04
  758.0   9.64   4.78 10.15  21.4   3.12  15.02  108.59  481.80 1.00 -0.01
  770.0  10.21   6.34  7.62  32.5   3.53   9.92  315.65  738.01 1.00 -0.01
  782.0  11.03   8.19  5.51 104.2   4.52   8.28 1138.90  747.54 1.00 -0.01
  794.0  11.45   9.47  4.06  97.8   4.85   7.67 1039.78 -415.96 1.00 -0.01
  806.0  11.83  10.48  3.14  90.2   4.86   7.49  444.59 -416.88 1.00 -0.01

 

[holl_ands]

Post #20 in that same Thread, 300ohm posted his 4nec2 File & Charts for Ch8-10 Optimization.

And in Post #35, I posted 4nec2 File and ANALYSIS for that Ch9 Optimization [L1=30.25-in, L2=11.5-in], also found here:
https://imageevent.com/holl_ands/grayhoverman/dbghcombo

nikiml's EVAL RESULTS for Ch9 Optimization:
Again, note Gain Loss and high SWR on lowest UHF Freqs:

Input file : C:\Python35\DBGH6n3_Ch9_L1=30-25_L2=11-5_300ohm_31Jan2009.nec
Freq sweeps: [(174, 6, 8), (470, 12, 29)]
Autosegmentation: NO

         --- Gain ---              -- Ratios -- -- Impedance --
   Freq    Raw    Net   SWR BeamW    F/R    F/B    Real    Imag  AGT  corr
==========================================================================
  174.0   8.65   7.54  2.81  67.3   4.24   4.24  117.79  -88.72 0.99 -0.06
  180.0  11.12  10.47  2.19  67.7   6.47   6.47  151.54  -85.83 0.99 -0.06
  186.0  11.60  10.17  3.25  70.4  15.40  15.40  100.89  -86.26 0.99 -0.06
  192.0  11.24   9.87  3.17  72.8  15.85  25.61   96.40  -38.02 0.99 -0.06
  198.0  10.82   9.80  2.68  74.8  11.94  13.09  112.17   -5.76 0.99 -0.06
  204.0  10.44   9.65  2.38  76.2   8.87   8.87  126.38    6.66 0.99 -0.06
  210.0  10.10   9.24  2.46  77.2   6.36   6.36  121.99   13.04 0.99 -0.06
  216.0   9.80   8.59  2.94  77.7   4.55   4.55  103.51   34.76 0.99 -0.06

  470.0  14.83  11.72  6.02  40.4  12.46  12.46   61.56  143.10 1.00  0.02
  482.0  15.40  13.03  4.69  40.3  13.19  13.19  115.55  257.80 1.00  0.02
  494.0  15.78  14.17  3.50  40.1  14.17  14.17  277.95  385.41 1.00  0.02
  506.0  15.99  15.02  2.62  39.6  15.19  15.19  635.86  280.58 1.00  0.02
  518.0  16.07  15.51  2.06  39.1  15.94  15.94  577.90 -133.34 1.00  0.02
  530.0  15.99  15.64  1.77  38.9  16.08  16.08  342.89 -181.10 1.00  0.02
  542.0  15.71  15.43  1.67  39.5  15.65  15.65  238.16 -123.69 1.00  0.02
  554.0  15.23  14.96  1.64  41.5  14.57  15.37  198.72  -68.95 1.00  0.02
  566.0  14.77  14.51  1.64  44.3  13.54  16.28  186.27  -30.69 1.00  0.02
  578.0  14.48  14.21  1.65  46.1  12.90  18.46  181.78   -6.58 1.01  0.06
  590.0  14.46  14.15  1.71  46.3  12.43  21.46  175.50   10.05 1.01  0.06
  602.0  14.67  14.28  1.83  45.5  12.30  23.19  165.91   28.64 1.01  0.06
  614.0  15.04  14.56  1.97  44.2  12.44  21.19  159.21   53.46 1.01  0.06
  626.0  15.47  14.92  2.06  42.9  12.64  18.23  160.46   82.37 1.01  0.06
  638.0  15.90  15.33  2.08  41.8  12.87  15.80  172.50  112.39 1.01  0.04
  650.0  16.21  15.71  1.99  40.9  12.92  14.04  199.79  138.94 1.01  0.04
  662.0  16.41  16.06  1.77  40.0  12.72  12.89  246.80  148.56 1.01  0.04
  674.0  16.55  16.40  1.45  38.5  12.16  12.16  301.26  112.94 1.01  0.04
  686.0  16.69  16.68  1.08  36.8  11.62  11.62  299.78   22.54 1.01  0.04
  698.0  16.88  16.70  1.50  34.7  11.16  11.16  202.48  -25.61 0.99 -0.04

  710.0  16.81  15.69  2.81  32.3  10.80  10.80  107.34   21.30 0.99 -0.04
  722.0  16.14  13.25  5.60  29.3  10.71  10.71   60.57  106.05 0.99 -0.04
  734.0  14.24   9.67  9.33  24.5  10.48  11.47   46.90  201.55 0.99 -0.04
  746.0  11.27   6.08 11.10  20.8   6.04  15.18   57.37  315.16 0.99 -0.04
  758.0   9.68   4.90  9.92  21.8   3.20  16.29  108.65  474.20 0.99 -0.03
  770.0  10.38   6.49  7.66  33.8   3.67  10.89  305.20  728.12 0.99 -0.03
  782.0  11.35   8.43  5.65 103.5   4.87   9.08 1128.86  780.57 0.99 -0.03
  794.0  11.81   9.76  4.17  95.4   5.32   8.38 1047.12 -446.70 0.99 -0.03
  806.0  12.02  10.63  3.19  87.9   5.19   7.88  429.51 -420.99 0.99 -0.03

 

[holl_ands]

Subject DBGH7n3 with Ch7 Optimization [L1=31.5-in, L2=12.5-in]:

nikiml's EVAL RESULTS for Ch7 Optimization:
Significant Gain increase on Ch7, but a bit worse SWR. And again, note Gain Loss and high SWR on lowest UHF Freqs:

Input file : C:\Python35\DBGH6n3_Ch7_L1=31-5_L2=12-5_300ohm_31Jan2009.nec
Freq sweeps: [(174, 6, 8), (470, 12, 29)]
Autosegmentation: NO

         --- Gain ---              -- Ratios -- -- Impedance --
   Freq    Raw    Net   SWR BeamW    F/R    F/B    Real    Imag  AGT  corr
==========================================================================
  174.0   9.89   8.07  3.83  70.1   9.49   9.49   89.64 -109.28 0.99 -0.06
  180.0  11.52  10.08  3.27  71.4  16.12  16.12  100.73  -89.56 0.99 -0.06
  186.0  11.15   9.74  3.23  73.7  15.63  24.99   95.93  -51.38 0.99 -0.06
  192.0  10.71   9.70  2.68  75.8  11.99  13.47  112.30  -15.71 0.99 -0.06
  198.0  10.31   9.65  2.20  77.6   9.17   9.26  136.19   -0.18 0.99 -0.06
  204.0   9.96   9.39  2.07  78.8   6.74   6.74  144.71   -4.33 0.99 -0.06
  210.0   9.65   8.87  2.36  79.7   4.92   4.92  126.93   -2.43 0.99 -0.06
  216.0   9.37   8.11  3.00  80.1   3.45   3.45  100.58   23.79 0.99 -0.06

  470.0  14.77  11.68  5.97  40.7  12.11  12.11   62.08  142.85 1.01  0.02
  482.0  15.33  12.99  4.64  40.8  12.77  12.77  116.51  257.15 1.01  0.02
  494.0  15.67  14.09  3.46  40.7  13.59  13.59  279.45  382.20 1.01  0.02
  506.0  15.83  14.89  2.58  40.6  14.37  14.37  627.04  274.21 1.01  0.02
  518.0  15.80  15.27  2.02  41.0  14.89  14.89  572.82 -121.04 1.00  0.02
  530.0  15.58  15.25  1.74  42.0  15.23  15.23  351.00 -174.49 1.00  0.02
  542.0  15.30  15.03  1.65  43.2  16.04  16.04  246.55 -126.92 1.00  0.02
  554.0  15.11  14.83  1.66  43.5  16.46  17.55  199.96  -76.67 1.00  0.02
  566.0  14.95  14.65  1.69  42.9  15.21  19.40  181.39  -34.82 1.00  0.02
  578.0  14.71  14.41  1.69  42.4  13.78  21.50  177.10   -5.16 1.01  0.06
  590.0  14.59  14.27  1.73  42.4  12.72  24.19  174.37   13.21 1.01  0.06
  602.0  14.75  14.37  1.83  42.6  12.34  25.44  166.77   30.62 1.01  0.06
  614.0  15.12  14.64  1.95  42.5  12.38  22.09  160.41   54.29 1.01  0.06
  626.0  15.58  15.04  2.05  42.0  12.61  18.61  161.52   82.63 1.01  0.06
  638.0  16.00  15.45  2.06  41.5  12.95  16.23  173.69  112.42 1.01  0.05
  650.0  16.31  15.83  1.97  40.7  13.20  14.70  201.28  138.09 1.01  0.05
  662.0  16.53  16.19  1.76  39.6  13.25  13.65  247.41  146.48 1.01  0.05
  674.0  16.71  16.57  1.44  38.0  12.78  12.82  300.20  110.87 1.01  0.05
  686.0  16.87  16.87  1.08  36.1  12.09  12.09  297.33   21.45 1.01  0.05
  698.0  17.04  16.86  1.52  34.1  11.44  11.44  199.72  -24.20 0.99 -0.04

  710.0  16.87  15.75  2.83  31.9  10.93  10.93  106.82   23.99 0.99 -0.04
  722.0  16.07  13.23  5.51  28.8  10.75  10.75   61.71  107.87 0.99 -0.04
  734.0  14.10   9.65  9.06  24.2  10.49  11.48   48.45  202.22 0.99 -0.04
  746.0  11.17   6.08 10.84  20.9   5.82  15.47   58.77  315.01 0.99 -0.04
  758.0   9.67   4.93  9.81  22.4   3.01  16.62  109.63  473.40 0.99 -0.03
  770.0  10.40   6.51  7.66  35.7   3.48  10.83  304.88  727.58 0.99 -0.03
  782.0  11.34   8.41  5.67 104.6   4.66   8.95 1135.72  783.06 0.99 -0.03
  794.0  11.69   9.64  4.17  96.8   5.12   8.10 1037.55 -454.54 0.99 -0.03
  806.0  11.71  10.33  3.17  91.3   4.89   7.35  425.25 -417.20 0.99 -0.03

 

[rabbit73]

You are correct, I built this model: www.user.dccnet.com/jonleblanc/Canada_TV_Stations/Gray-Hoverman/DBGH_VHF_hi_Antenna.pdf
Optimized for channel 13 (L1 = 28", L2 = 10"). This would probably be called a DBGH6n2 (only 2 NARODs per bay).

NARODS on this antenna are just horizontal straight, not hat-shaped like the models at nikiml's Antenna pages. I guess therefore I cannot go by the gain sweeps shown for those models.

I don't do modeling and prefer to make on-the-air antenna comparisons. But, if I understand the results by holl_ands, your choices are to modify your present DBGH for CH7, build a second DBGH for CH7, or add a VHF antenna to your present DBGH and combine the two antennas with a UVSJ.

 

[oldtvguy]

Eznec is only a tool to help make rough predictions.
Only real world construction and testing compared to a reference dipole will give you accurate gain figures.

 

[majortom]

Haven't seen anyone using or discussing EZNEC here.

 

[orbot]

Continuing with the reflector grid idea, based on nikiml's GH10: nikiml's Antenna pages - GH10 UHF antenna , based on holl_ands' screen grid reflector: UHF SBGH + 2ea 36"x18" Screen Grid Refl. , based on Yurii Pylypenko's continuous reflector: https://ypylypenko.livejournal.com/82831.html

SBGH (AWG10 elements) with 36x48" continuous reflector grid (2x2" AWG16): Raw Gain 13.3 to 15.5 to 14.1, SWR max 2.3
2xGH (AWG10 elements) with 64x48" continuous reflector grid (2x2" AWG16): Raw Gain 15.9 to 17.9 to 16.3, SWR max 2.3
3xGH (AWG10 elements) with 92x48" continuous reflector grid (2x2" AWG16): Raw Gain 17.5 to 19.6 to 17.7, SWR max 2.3
4xGH (AWG10 elements) with 120x48" continuous reflector grid (2x2" AWG16): Raw Gain 18.6 to 20.7 to 18.9, SWR max 2.3

nec files: https://ln2.sync.com/dl/5d729e850/pq2wmcpz-qpu252te-pj5i6x46-gwr5ytw2
For measurements, copy/paste nec file text into nikiml's nec viewer nikiml's Antenna pages - Nec Viewer

Decreasing the spacing between the reflector's horizontal lines from 2" to 1" or 0.5" will increase gain and F/B ratio, and slightly increase SWR a bit:

A thicker gauge wire for reflector will also increase gain and F/B ratio a bit while keeping the SWR the same:

 

[orbot]

These are two "nuGH" antennas (for the new UHF band 470-608MHz, copied from holl_ands) with their frames attached together and pointed 90° from each other. The antennas aren't combined, they are two separate antennas with their own cable runs that go into two separate tuners. I had this idea because I wanted to add an extra antenna pointed in a different direction without losing any space on the mast.

Here's an album with 4nec2 results and pictures: https://imgur.com/a/xaUCBdh

For each antenna, raw gain was 13.7-15.5 dBi with side lobes <0 dBi, swr was <1.9, F/B & F/R ratios were >20dB.

The array I modeled was of AWG10 aluminum for the GH elements and AWG16 1x1" mesh hardware cloth for the reflector grid spacing (I used AWG19 0.5x0.5" spacing on my actual antennas for improved front-to-back/rear ratios). Each antenna is only 36x36" total. You can get a bit better results by using a 48" tall reflector, and even more bit better results by making the GH structure itself taller as well, but my mast space was limited. There were virtually no negative effects from the antennas being so close together, only some minor warping of the back/rear beams.

Here are the dimensions: nikiml's Antenna pages - Geometry viewer

The layout of the GH elements is the same as nikiml's optimized GH10 nikiml's Antenna pages - GH10 UHF antenna except for one point in each quadrant that I moved by one inch to improve results for use with a screen grid reflector in the new uhf band.

Here's the nec file: https://pastebin.com/j7pNDd7v

 

[Mithrandir]

Re-scaling SBGH Antenna for 470Mhz to 602Mhz

Newbie question:

Interested in building Single Bay Gray-Hoverman for the following location at 30ft high.

Rabbitears
Tvfool

Not sure about putting it outdoors. Will try putting antenna in attic or by a window first to see how it works.

I have been trying to learn/use 4nec2 software to try and use Nikiml's Antenna or Jed's to design their antenna for 470Mhz to 602Mhz (channel 14-35) and Hi-Vhf 174Mhz to 216Mhz (channel 7-13). (It is not working well for me. Will need to practice more and watch more videos on its use)

Channels (from Philadelphia -- Roxborough (PA))
I'm interested in are:

Real	Virt	
2	2.1	ME-TV
6	6.1	ABC
9	35.1	PBS
13	12.1	PBS
17	17.1	PHL17
23	23.1	PBS
25	29.1	FOX
28	10.1	NBC
30	3.1	CBS
33	57.1	CW
34	61.1	ION

I know 2 and 6 are lo-Vhf but I am willing to tackle those 2 channels at another time.

• Can I use a scaling factor as indicated on Jed's page

I have had a number of requests for this antenna for use at other frequencies. If you want to adapt this design for use at a frequency other than 575 MHz, then simply scale the geometric measurements in the tables below by 575 MHz divided by the desired frequency. For example, to use the antenna at 525 MHz, multiply all the measurements by 575/525 = 1.095. In this case, a value such as 300mm in the table would become 329mm, or 12 and 15/16 inches. This scaling applies to all the numbers.

If yes, can Nikiml's or Jed's design be scaled from their peak dBi frequency using the above process.

• I really liked Jed's narrow band (dubbed X-GH8), but its a bit too narrow for the UHF channel range that I want (17-34 RF). Can the band be widened without losing too much of its peak gain (~18dBi). Another problem I had with Jed's X-GH8 is that it gets too tall for using indoor when I re-centered frequency to 550Mhz from 615Mhz.

• Is there any significant difference between using solid copper wire vs Aluminum elements for building the zig-zag part of the SBGH? If indoors resistance to weather should not be an issue. I know Aluminum is lighter/cheaper than copper and is better for outdoor use.

Thanks your your help in advance.

 

[majortom]

yes, for just about any antenna design, to frequency scale...
Multiply all dimensions by New Freq / Old Freq
I would start by only considering the UHF designs. Forget about the NAROD designs for a minute.
Generally I look for where the best SWR occurs, and see where I want to move that, rather than the gain of the antenna.
Antennas in an attic you are throwing away all the time and effort you put in.

 

[Mithrandir]

Thank you for your reply.

Based on that, for outdoor placement an aluminum antenna is better than solid copper for weather-resistance.

Did not think of looking at SWR and shifting design based on SWR frequency.

⚫ If I built a UHF only design, can NAROD elements be added to the antenna at a later time?


⚫ Is it practical to consider condensing the range of the antenna. (470Mhz-608Mhz %Ch14-Ch36%) if a UHF antenna is designed to receive (470Mhz-698Mhz %Ch14-Ch51%).

I haven't seen any new antennas that are designed to take advantage of the new frequency range. (I'm thinking that an antenna designed for these frequencies can have better reception than an antenna designed for a wider frequency range.)

Thank you for your feedback.😀

yes, for just about any antenna design, to frequency scale...
Multiply all dimensions by New Freq / Old Freq
I would start by only considering the UHF designs. Forget about the NAROD designs for a minute.
Generally I look for where the best SWR occurs, and see where I want to move that, rather than the gain of the antenna.
Antennas in an attic you are throwing away all the time and effort you put in.

 

[majortom]

yeah, salt sea spray would probably do a number on copper in short order.
holl_ands optimized hi free form antenna design for the new UHF band.
I would recommend these...
https://imageevent.com/holl_ands/multibay/4bayrefl/newuhffreeform4bayscreenreflopt