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Interpeting NEC results

10K views 72 replies 6 participants last post by  jandrcbrt 
#1 · (Edited)
Hey folks, I am back again with more questions. :)


I am hoping to find out how to interpret nec results of Raw, Net, SWR, BeamW, F/R, F/B, Real, Imag, AGT, & corr.


Which ones have the most impact on the antenna results?


From my reading on this site, I am assuming the most advantageous things to look for are: higher Net , Lower SWR, higher BeamW, the rest I am not sure about. :(


Should the other readings be higher or lower for best results?


Which categories impact the results from the most to the least?


Is a lowest net gain of 9.5 @ 470 MHz - 698 MHz & higher in between those frequencies considerered a good 4 bay bow antenna?

I am hoping to build a 4 bay bowtie antenna without a reflector to get the most channels from the front and back of the antenna.

The lowest net gain I mentioned above is the lowest net gain, the frequencies in the middle of that range would be a net gain of about 12 or so.
 
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#2 ·
What finally matters is only CINR (SNR) ratio at demodulator.

In general, television is free of interferences (in-band or neighbour band higher than IP3 dynamic block range).
Also, in OTA, environment noise temperature is highest at desired location, so beam pattern do not influence antenna noise temperature (it matters a lot for antennas directed into sky)

If your task is only to catch fringe signal, only dBi & SWR matters. Two very differennt antennas should perform identically - voltmeter will show the same signal and demodulator will show the same SNR.

When RF is directly attached to antenna (not count loss and impedance transformation in cable), influence of SWR is counted as degradation of RX noise factor:

Nf (effective) = Nf (nominal) + 10*log((2+SWR+1/SWR)/4)

SWR=2 and SWR=3 is equal to degradation of LNA noise factor by 0.5 and 1.25 dB respectively.

2 antennas, 10 dBi & SWR=1 vs 11.25 dBi & SWR=3 will show the same signal strength when connected to voltmeter or LNA directly (zero-length coax cable).

Non-zero length mismatched line acts as impedance transformator. When its length is proportional to 1/2 lambda (0.5, 1.0, 1.5 ...) it has no effect on TR-ratio.
When its length is shifted by 1/4 lambda (0.25, 0.75, 1.25, 1.75) than it has maximum possible transformation ratio.

By the time signal reaches RX input, SWR can be different and it depends on combination of Z=R+jX.

Here is my Excel version of TR-line calculator: https://goo.gl/w8z9U2

Assume we have antenna Z=150+j0 (SWR=2 at Z=75+j0 load).
At length proportional to 1/2 lambda (0, 0.5, 1.0) no influence, SWR=2 at tuner input feed.
At length proportional to 1/4 lambda (0.25, 0.75, 1.25) it acts as 4:1 transformer, Z=37.5+j0 (SWR=2 at Z=75+j0 load).

Assume we have antenna Z=37.5+j0 (SWR=2 at Z=75+j0 load).
At length proportional to 1/2 lambda (0, 0.5, 1.0) no influence, SWR=2 at tuner input feed.
At length proportional to 1/4 lambda (0.25, 0.75, 1.25) it acts as 1:4 transformer, Z=150+j0 (SWR=2 at Z=75+j0 load).

So at any coax length, SWR will be always <SWR@input for resonant antenna (when im=X=0).
 
#5 ·
The following is an example of a NEC initial test run result I have received thus far for a 4 bay bow tie no reflector antenna, if that helps answering my original question.


Code:
  --- Gain ---   -- Ratios -- -- Impedance --           
   Freq  Raw Net SWR BeamW F/R F/B Real Imag AGT corr
==========================================================================
   54.0  -4.54 -31.47 1968.25 91.5 0.00 0.00 0.17 -98.99 1.18 0.71
   60.0  -5.11 -31.59 1776.72 91.6 0.00 0.00 0.18 -71.72 1.18 0.71
   66.0  -6.23 -32.45 1670.96 91.9 0.00 0.00 0.18 -47.34 1.18 0.71
   72.0  -9.01 -35.11 1628.89 92.7 0.00 0.00 0.19 -24.96 1.34 1.29
   78.0  -14.18 -40.28 1627.80 95.7 -0.04 0.00 0.18 -3.90 1.34 1.29
   84.0  -26.83 -52.91 1621.00 62.5 -1.97 0.00 0.19 16.36 1.34 1.29
   90.0  -8.58 -34.35 1510.12 85.0 -0.02 0.00 0.20 36.31 1.34 1.29
  174.0  3.58 2.86 2.29 83.4 0.00 0.00 145.49 89.30 1.02 0.08
  180.0  3.56 2.52 2.72 82.9 0.00 0.00 128.34 111.81 1.02 0.08
  186.0  3.54 2.24 3.08 82.3 0.00 0.00 119.60 133.42 1.02 0.08
  192.0  3.52 2.02 3.35 81.7 0.00 0.00 116.10 153.94 1.02 0.08
  198.0  3.47 1.84 3.55 81.1 0.00 0.00 116.28 173.55 1.02 0.11
  204.0  3.44 1.72 3.67 80.6 0.00 0.00 119.36 192.50 1.02 0.11
  210.0  3.41 1.65 3.74 80.0 0.00 0.00 124.98 210.93 1.02 0.11
  216.0  3.38 1.61 3.74 79.2 0.00 0.00 133.04 228.91 1.02 0.11
  470.0  10.18 9.69 1.97 53.6 0.00 0.00 395.40 -217.76 0.98 -0.09
  476.0  10.31 9.90 1.85 52.7 0.00 0.00 357.54 -196.17 0.98 -0.09
  482.0  10.44 10.11 1.74 51.9 0.00 0.00 326.77 -173.15 0.98 -0.09
  488.0  10.56 10.30 1.64 51.1 0.00 0.00 301.87 -149.58 0.98 -0.09
  494.0  10.68 10.47 1.54 50.3 0.00 0.00 281.87 -125.96 0.98 -0.08
  500.0  10.80 10.64 1.46 49.5 0.00 0.00 266.02 -102.56 0.98 -0.08
  506.0  10.92 10.80 1.39 48.6 0.00 0.00 253.73 -79.50 0.98 -0.08
  512.0  11.04 10.94 1.34 47.7 0.00 0.00 244.57 -56.81 0.98 -0.08
  518.0  11.16 11.08 1.30 46.8 0.00 0.00 238.26 -34.47 0.98 -0.08
  524.0  11.27 11.20 1.28 46.0 0.00 0.00 234.60 -12.44 0.98 -0.07
  530.0  11.38 11.31 1.29 45.3 0.00 0.00 233.54 9.35 0.98 -0.07
  536.0  11.50 11.42 1.31 44.5 0.00 0.00 235.12 30.92 0.98 -0.07
  542.0  11.61 11.51 1.35 43.8 0.00 0.00 239.46 52.33 0.98 -0.07
  548.0  11.72 11.60 1.39 43.1 0.00 0.00 246.84 73.54 0.98 -0.07
  554.0  11.83 11.68 1.45 42.5 0.00 0.00 257.68 94.45 0.98 -0.07
  560.0  11.94 11.76 1.51 41.8 0.00 0.00 272.52 114.82 0.98 -0.07
  566.0  12.05 11.83 1.57 41.2 0.00 0.00 292.13 134.20 0.98 -0.07
  572.0  12.15 11.89 1.63 40.6 0.00 0.00 317.45 151.75 0.98 -0.07
  578.0  12.25 11.95 1.70 40.1 0.00 0.00 349.57 166.02 0.98 -0.07
  584.0  12.34 12.00 1.76 39.4 0.00 0.00 389.51 174.61 0.98 -0.07
  590.0  12.43 12.05 1.83 38.7 0.00 0.00 437.75 173.74 0.98 -0.07
  596.0  12.52 12.09 1.89 38.0 0.00 0.00 493.10 157.97 0.98 -0.07
  602.0  12.60 12.12 1.96 37.5 0.00 0.00 550.74 120.71 0.98 -0.07
  608.0  12.67 12.14 2.02 36.9 0.00 0.00 600.15 57.00 0.98 -0.07
* 614.0  12.75 12.18 2.09 36.3 0.00 0.00 625.71 -30.92 0.98 -0.09
  620.0  12.80 12.17 2.16 35.8 0.00 0.00 613.75 -128.78 0.98 -0.09
  626.0  12.84 12.16 2.23 35.3 0.00 0.00 563.26 -214.43 0.98 -0.09
  632.0  12.86 12.12 2.31 34.8 0.00 0.00 488.23 -270.94 0.98 -0.09
  638.0  12.86 12.07 2.39 34.4 0.00 0.00 407.62 -295.10 0.98 -0.09
  644.0  12.87 12.02 2.47 33.9 0.00 0.00 334.76 -293.95 0.97 -0.12
  650.0  12.81 11.90 2.55 33.5 0.00 0.00 275.08 -277.13 0.97 -0.12
  656.0  12.72 11.75 2.62 33.0  0.00 0.00 228.96 -252.36 0.97 -0.12
  662.0  12.58 11.56 2.68 32.5 0.00 0.00 194.46 -224.77 0.97 -0.12
  668.0  12.40 11.34 2.74 31.9 0.00 0.00 169.25 -197.36 0.97 -0.12
  674.0  12.10 11.01 2.78 31.3 0.00 0.00 150.96 -171.89 0.99 -0.05
  680.0  11.84 10.71 2.83 30.6 0.00 0.00 137.40 -149.21 0.99 -0.05
  686.0  11.57 10.40 2.89 29.6 0.00 0.00 126.52 -129.45 0.99 -0.05
  692.0  11.31 10.07 2.98 28.3 0.00 0.00 116.63 -111.85 0.99 -0.05
  698.0  11.07 9.73 3.12 27.2 0.00 0.00 106.99 -95.10 0.99 -0.05
 
#6 ·
In simple terms: only Net Gain matters.
Net Gain = RawGain - SWR-related losses (so it includes SWR).
------------------------

In very rare cases, when receiption of weaker signal is blocked by stronger signals from different tower, you might want to carefully select radiation pattern to reduce signal from undesired direction.
 
#8 ·
I disagree....RAW GAIN is more important than NET GAIN for the fol. reason:

SWR "Mismatch" occurs when Complex LOAD Impedance (NOT exactly 75-ohms, Resistive) is NOT exactly equal to Complex SOURCE Impedance...which for most Antennas is very Irregular]. This results in some of the Energy received by the Antenna being Reflected BACK from the LOAD (e.g. Preamp Input or Tuner Input if NO Preamp) to the Antenna, where SOME is Reflected BACK towards the LOAD...except with a DELAY of twice the Electrical Cable Length [Electrical Length is a bit LONGER due to slower Propagation "Velocity Factor"]. Esp. see "The Importance of Timing":
Formation of Standing Waves
https://physics.info/waves-standing

If you were to monitor the VOLTAGE along the length of the Cable, on any particular Frequency, you would find that it jumps around. IF and ONLY IF Electrical Length is an Integer Multiple of 1/2-Wavelength, will you see "Standing Waves" every 1/2-Wavelength along the Cable, as the PHASE of the Reflected Wave is the OPPOSITE of the Incoming Wave and hence results in Maximum Cancellation.....and at any OTHER Phase Relationship (NOT 1/2-Integer Multiple) is RANDOM. The full extent of the "Mismatch Loss" [the Maximum] is ONLY experienced at the END OF THE CABLE under these UNIQUE conditions....and NOT on most other Frequencies, when Electrical Length is usually NOT an integer multiple. Hence my recommendation to try ADDING random lengths of spare cables to the end of your Downlead trying to MOVE the Standing Wave to A DIFFERENT, hopefully not used, Frequency.

Hence, NET GAIN is ONLY Measurable at the END of the Downlead (or END of Coax between Antenna and Preamp)....and ONLY WHEN Electrical Length is an Integer Multiple of 1/2-Wavelength at ONE (or TWO) Frequencies. Otherwise, the Reflected Signals do NOT form Standing Waves, instead experiencing random fluctuations of Constructive and Destructive Interference...resulting in much lower amount of Mismatch Loss.
 
#9 ·
Raw Gain, SWR (actually Mismatch-Loss in dB), F/R Ratio, F/B Ratio and Beamwidth can ALL be important....or just Raw Gain....or just Beamwidth....depending on your APPLICATION/SITUATION.

In downtown NYC, stations are coming in from MANY Directions, which makes Antenna Choice very problematic. You would think that a TRUE OMNI Antenna would be the "Best" with a Beamwidth of [hopefully] 360-deg, but there are very few available (esp for INDOORS). The Bi-Directional Hi-VHF-Rabbit-Ear/UHF-Loop [abt 60+ deg Forward and 60+ deg Rear Beamwidth] may also be a viable choice, but it (and the OMNI) also lets in LOTS of MULTIPATH Interference. Hence, a "Better" alternative MAY be a DIRECTIONAL UHF Antenna, such as Terk HDTVi/a....if you are successful in receiving stations off the "Back" of the Antenna.
https://imageevent.com/holl_ands/omni [TRUE OMNI's with GOOD Specs are NOT Small]

In other locations, stations might be at different ranges with different angles of arrival. So you MIGHT need a fairly WIDE Beamwidth Antenna (A-D C2 has highest BW=70-deg across entire UHF Band, with resultant Low Gain) or a significantly higher Gain 4-Bay (typ. 60 to 50-deg BW, lower on upper UHF Channels)....or TWO Separate Antenna with or without Channel Filters.

OTOH, you may need a narrow Beamwidth Antenna (e.g. 30-40 deg) in order to suppress STRONG Local stations in order to receive weaker, distant stations that are not quite in the same direction....and in extreme cases two Antennas with one of the Baluns REVERSED so that it is Out-Of-Phase can be used to steer a NULL towards one station, while receiving a desired station on one of the two BEAMS formed on either side of the NULL.

F/R Ratio is typically cited in mfr specs, being the Ratio (in dB) between Gain Directly FORWARD (0-deg at Max Gain Azimuth) and Gain Directly to REAR (180-deg). However, F/B Ratio is much more meaningful, being the Ratio (in dB) between Gain Directly FORWARD (0-deg at Max Gain Azimuth) and Gain towards the ENTIRE BACK (I use 90-deg thru 270-deg). [PS: 4NEC2, et.al. convention is to use Max Gain at 90-deg!!!!] On some Freqs, some Antennas have a Gain Lobe directly to the Rear and some a Gain NULL with Lobes to either side....F/B Ratio is suited to provide a fair characterization of EITHER, since it is very unlikely that Interference or Multipath Distortion will be limited to EXACTLY 180-deg. Whether you NEED a VERY HIGH F/B Ratio (e.g. 20 dB)....or can get away with a more typical 15 dB....or a measly 10 dB....will depend on your situation wrt Co-Channel, Adjacent Channel, Multipath and Man-Made Noise Sources.

A Mis-Match Loss of 1 dB corresponds to an SWR of about 2.7, which is MY DESIGN GOAL when modeling Antennas...although SWR=3 still isn't TOO bad, with Mis-Match Loss of 1.25 dB....and I worry when SWR=4, which is Mis-Match Loss of about 2 dB:
https://www.microwaves101.com/calculators/872-vswr-calculator

BTW: Dr. Obed Bendov [former Chief Engineer at Dielectric (TX) Antennas] determined that SWR has an ADDITIONAL degradation to DIGITAL Waveform Detection due to the DELAYs between Incident and Reflected (and RE-Reflected, etc) signals traveling up and down a LONG Coax (NOT a problem with short Coax to Preamp) acting as Short-Delay Type Multipath, which Adaptive Equalizer is NOT designed to overcome. So one more reason to try to keep SWR no higher than 2.7 or so.
 
#10 ·
Wow! My head is spinning. Ty so much holl_ands & Yurii for the responses.


So I guess I will look more closely to higher Raw Gain, SWR lower than 2.7, Beam width, & F/B.


SWR= 2.7 = ~1 dBi loss
SWR = 4 = ~ 2 dBi loss


The antenna I will eventually build is for 'country' use that has multiple '2 edge' tvfool stations. So I assume I would welcome a large beam width. Should the F/B be higher or lower for distant stations?


Thank you so much!
 
#12 ·
The antenna I will eventually build is for 'country' use that has multiple '2 edge' tvfool stations. So I assume I would welcome a large beam width. Should the F/B be higher or lower for distant stations?
In the "country" with 2Edge Signals likely means you need a HIGH Gain Antenna....and since Forward Gain is the Numerator in F/B and F/R Ratio formulas, you will also likely end up with an Antenna that ALSO has medium or better F/B and F/R Ratios.....which is a GOOD Thing to suppress the strong Multipath components , mostly coming in from the sides and rear.

We could provide more specific comments, esp. re unusual local conditions, if you can provide a Link to your TVFool Results......
 
#11 ·
F/B and F/R is needed for 2 reasons:
1) combat multi-path reflections (in analogue TV it was seen as washy picture shifted by some delay, in digital it decrease SNR, since this signal is noise for demodulator)
2) reject strong signal from rear direction (both in-band and side-band)

Even small F/B is enough in most cases. Only zero F/B (2-directional, reflector-less designs) are not good choice.

Zero F/B antenna is not convenient for another reason: it is very hard to provide clear space for reflector-less type of antennas.
Reflector shield backward radiation from any conductive surfaces: walls, cables, mast.
You can hang screen-type antenna close to wall, but cannot do this with reflector-less antenna.
 
#13 ·
Thank you again for your response holl_ands!


In the country is exactly what my antenna build, for that location will be facing. Pretty much everything is '2 edge', or worse on the tvfool report. I do know that back in the day of analog tv, an antenna, at that location,did receive many stations.


I was hoping to build a reflector less antenna with high gain in both the front and rear directions, I would welcome any suggestions. ;)


I was hoping for at least a 30 degree beam width to the front and the rear.


Code:
 29 - 44 degrees - midpoint = 36 degrees
 ---------------
WSTQ-LP CW(14)  RF 14 37 deg  -123.7 dBm -121.14 Doubtful Reception
 CW 6
WSPX ION(56)  RF 15 29 deg    -108.94?
 ION
 qubo
 IONLife
WSYR ABC(9)  RF 17 44 deg  -87/91.9 dBm -89.03 ?
 ABC 9
 ME-TV
 Bounce TV
 Laff
WSYT FOX(68)  RF 19 33 deg  -62 dBm  -67.16
 Fox 68
 Cozi Tv
WSTM NBC(3)  RF 24 37 deg  -81 dBm  -83.63
 NBC 3
 CW 6
 Comet TV (3 Weather Plus)
WCNY PBS(24)  RF 25 37 deg  -85 dBm  -87.23
 PBS
 Create
 PBS Encore
 PBS Kids 24/7
WNYS MYTV(43) RF 44 33 deg  -65 dBm  -71.96
 MyTV
 GetTV
WTVH CBS(5)  RF 47 37 deg  -88 dBm  -89.69 ?
 CBS 5
 Charge!
 TBD
 
 Back side desired Channels

 232 - 245 degrees
 -----------------
WETM NBC(18)  RF 18 232 deg  -79 dBm
 NBC 18
 Independent
 Laff
 Escape
WSKA PBS(30)  RF 30 244 deg  -90 dBm
 PBS
 World Channel
 Create
 Audio - WSKG-FM
 Audio - WSQX-FM
 PBS Kids 24/7
WENY ABC(36)  RF 36 245 deg  -86 dBm  -96.90
 ABC
 CBS
 CW+ 2
WYDC FOX(48)  RF 48 244 deg  -97 dBm
 Fox
 My TV
 Comet TV

TVFOOL Report:
Code:
[B][url=http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d60ed531bd0d3b1]TV Fool[/url][/B]
[B]
[/B]

I am assuming a very high powered preamp would not be frowned upon.
 
#20 · (Edited)
Yes, I am confused. This is what confused me:
I wanted to report that I am at my parents winter home and he is receiving a channel that the rabbitears website says is -98.20 dBm/Bad/2Edge. He has an omnidirectional antenna. That gives me some hope for the NY address mentioned above.
and this confused me:
Thank you again for your response holl_ands!

In the country is exactly what my antenna build, for that location will be facing. Pretty much everything is '2 edge', or worse on the tvfool report. I do know that back in the day of analog tv, an antenna, at that location,did receive many stations.

I was hoping to build a reflector less antenna with high gain in both the front and rear directions, I would welcome any suggestions. ;)

I was hoping for at least a 30 degree beam width to the front and the rear.

Code:
 29 - 44 degrees - midpoint = 36 degrees
 ---------------
WSTQ-LP CW(14)  RF 14 37 deg  -123.7 dBm -121.14 Doubtful Reception
 CW 6
WSPX ION(56)  RF 15 29 deg    -108.94?
 ION
 qubo
 IONLife
WSYR ABC(9)  RF 17 44 deg  -87/91.9 dBm -89.03 ?
 ABC 9
 ME-TV
 Bounce TV
 Laff
WSYT FOX(68)  RF 19 33 deg  -62 dBm  -67.16
 Fox 68
 Cozi Tv
WSTM NBC(3)  RF 24 37 deg  -81 dBm  -83.63
 NBC 3
 CW 6
 Comet TV (3 Weather Plus)
WCNY PBS(24)  RF 25 37 deg  -85 dBm  -87.23
 PBS
 Create
 PBS Encore
 PBS Kids 24/7
WNYS MYTV(43) RF 44 33 deg  -65 dBm  -71.96
 MyTV
 GetTV
WTVH CBS(5)  RF 47 37 deg  -88 dBm  -89.69 ?
 CBS 5
 Charge!
 TBD
 
 Back side desired Channels

 232 - 245 degrees
 -----------------
WETM NBC(18)  RF 18 232 deg  -79 dBm
 NBC 18
 Independent
 Laff
 Escape
WSKA PBS(30)  RF 30 244 deg  -90 dBm
 PBS
 World Channel
 Create
 Audio - WSKG-FM
 Audio - WSQX-FM
 PBS Kids 24/7
WENY ABC(36)  RF 36 245 deg  -86 dBm  -96.90
 ABC
 CBS
 CW+ 2
WYDC FOX(48)  RF 48 244 deg  -97 dBm
 Fox
 My TV
 Comet TV

TVFOOL Report:
Code:
[B][url=http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d60ed531bd0d3b1]TV Fool[/url][/B]
[B]
[/B]

I am assuming a very high powered preamp would not be frowned upon.
What location do you need an antenna for now?

I thought a signal report was needed because holl_nds asked for one. Did I also misunderstand that?
We could provide more specific comments, esp. re unusual local conditions, if you can provide a Link to your TVFool Results......
Every location is unique and requires a custom solution.

We need to see a signal report to give you accurate advice. Otherwise, your general questions will only get general answers.

Perhaps that is all you wanted in the first place.:confused:
 
#15 ·
Thank you Yurii for your response.


When you said to look for Nf. Are you referring to the Preamp? I was pondering getting the RCA TVPRAMP1R.


Quote from Amazon customer ...
A technician @ Antennas Direct who goes by “ADTech” on the digital home web site had previously characterized this model around Christmas time and shared what he found on that forum. He has access to some pretty impressive HP test equipment for characterizing preamps. including an HP8569B Spectrum Analyzer & an HP 8970A Noise Figure Meter.


Here is what he found for the RCA TVPRAMP1R:
Low VHF - 3.9 dB NF/16 dB gain
High VHF - 3.1 dB NF/16.2 dB gain
UHF - 2.6 dB NF/23.7 dB gain

There is a RCA TVPRAMP1Z also that sounds like it is pretty much the same.
 
#16 ·
10..25 dB is just fine. High-gain are 30...40 dB, not needed for home antennas, used in bigger networks (e.g. roof antenna for many flats in condo).

75 Ohm and multi-input preamp I find as too complicated and expensive.
You still need balun, coax line from balun to your pream, coax from preamp to TV. Two extra connectors.

Direct-mount 300 Ohm (balun + LNA) are simple, cheap and reliable.

My favourite is ALN-187, cost $3, UHF only (has VHF filters), 1-stage 13 dB (no overload and stability issues), fully metal shielded, built-in DC stabilizer from +3 to +12V. Noise factor Nf=2 dB + mismatch losses (probably 3...3.5 dB effective Nf)


Another popular:
cost $1, UHF+VHF (no filters), 2-stage 20...25 dB, no shields, works from +4 to +12V, Nf=1.5 dB + mismatch
direct coax screw (no connector)
 
#19 ·
Again Thank you for the replies Yurii, holl_ands, & rabbit73!


Yurii, I like those cheap alternatives, I would be interested in the VHF/UHF versions, but I am not sure where to purchase it & would not know how to supply the power to it for that matter.


holl_ands, Thank you for that chart, from my limited knowledge acquired here thus far, it would appear that the RCA model I mentioned is a good choice as well as the Kitztech 500, however the $100+ Price tag for that one is not an option.


rabbit73, I think you are slightly confused and perhaps I am partially to blame. The tvfool link in this thread and the ones mentioned in the other thread you mentioned are for a NY address. Who has a winter home in NY? LOL


I mentioned in the other thread, Post #13, about readings that I received at my parents winter home but that is a totally different state/address. I merely mentioned my parents winter home readings to indicate what signals I have personally observed with an Omni-directional antenna. Sorry for any confusions I may have introduced. You are correct that front and rear stations would be welcomed in the NY location you are referring to. :)
 
#21 ·
rabbit73, I will apologize one last time, just because.


I have, up to this point in time, only gave tvfool results for a NY address. I am not sure why you are thinking I am referring to multiple locations. I stated in my last post here in this thread that you were correct that the NY address was the one that was being discussed further here. You even quoted the post #13 that I apologized for in my last post that discussed an omnidirectional antenna and then I mentioned that it gave me hope for the NY address that I was inquiring about.


I will say this one last time, I mentioned my parents winter home readings only to indicate what signal levels were being received at that location, which in turn gave me hope for the dismal signal levels that tvfool reports for the NY address. I may just climb under a rock. Again thank you to all that have helped me thus far in my previous questions.

FYI You also quoted my tvfool report at the bottom of your last quote of me. ;)
 
#22 · (Edited)
I have, up to this point in time, only gave tvfool results for a NY address. I am not sure why you are thinking I am referring to multiple locations.
The report I gave for holl_ands IS for the same location, because holl_ands didn't know there was another thread about the SAME location.

If holl_ands had known about and understood your other thread, would he have asked for a report?

I thank you for your apology, but I don't know what kind of help you need with your dismal signal levels, other than what has already been provided.

If a bi-directional antenna doesn't work, you will need an antenna and preamp for each direction.

Just because you WANT a bi-directional antenna to work at your location, doesn't mean that it WILL work.

I have seen a lot of talk about this project, but I haven't seen much testing by you to find out what will work.
 
#23 ·
I have seen a lot of talk about this project, but I haven't seen much testing by you to find out what will work.

You, sir, are correct there. I kind of figured that it might be wiser to consult the people that are more knowledgeable than myself in building antennas, prior to me building a bunch of antennas that are inherently flawed to the multiple 2 edge signal situation I have previously mentioned.


Should I just start building numerous antennas and post the results that most likely will not be most advantageous to the particular NY situation I have mentioned?


I thank you again for previously teaching me how to map out the lines to the towers in the other threads that you mentioned. That was awesome!
 
#25 ·
Thank you again for replying rabbit73.


I am also contemplating a 4-bay bowtie antenna like you were thinking of. It will not be of wood construction as you recommended not to do. I have previously checked out those links that you mentioned. Thank you.


I have, in the past few weeks, been simulating antenna builds, and I would like to ask all here if the NECs that I have come up with should be posted here or somewhere else perhaps? I don't want to confuse the situation again if possible.
 
#26 ·
I have, in the past few weeks, been simulating antenna builds, and I would like to ask all here if the NECs that I have come up with should be posted here or somewhere else perhaps? I don't want to confuse the situation again if possible.
Now that you have clarified the needs of your specific location, there will be no further confusion about that.

This is the proper thread to post the details of your simulations because it matches the thread title and would be on-topic.

I am not qualified to comment on your simulations because I don't care to do computer modeling. I prefer to do proof of performance tests and measurements that come AFTER modeling.

I will leave it to Yurii and holl_ands to comment on your simulations.
 
#27 ·
Ok, This is my first submitted VHF-HI frequency antenna results.




Code:
CM
CM MY 4 Bay Horizontal VHF-Hi Whisker antenna
CM
CM Inspirational VHF-Hi antenna results based on a prior antenna model seen sweep 174-216 = Raw Gain Avg = 8.67, Net Gain Avg = 8.64  9.02 high/8.25 low 9' 0" length
CM
CM My Desired Antenna Specs:
CM 3 Feet or less in length
CM 40 Inches or less in Height
CM 4 Feet or less in Width
CM Bi-Directional ie. close to same gain from the front and rear of antenna
CM Fairly equal db gain across entire VHF-HI frequency range
CM
CM PYTHONSEG(21), AGT=1.0 (0.0 dB).
CM
CM My Testing results with above specs taken into account:
CM
CM     7.80 Highest Net Gain
CM     7.24 AVG Net Gain
CM     6.87 Lowest Net Gain
CM
CM     1.81 AVG SWR
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' Optimization Settings:
'
' Target Ranges:
'CMD--OPT --sweep=(54,6,7) --target-level=(11,11) --swr-target=2.7   ' 69  mid point Frequency VHF-LO
CMD--OPT --sweep=(174,6,8) --target-level=(11,11) --swr-target=2.7   ' 195 mid point Frequency VHF-HI
'CMD--OPT --sweep=(470,6,39) --target-level=(15,15) --swr-target=2.7   ' 584 mid point Frequency UHF
'
' Functions:
'CMD--OPT --target-function=(max_ml+16*max_gain_diff+4*max_f2r_diff+max_f2b_diff) '
'CMD--OPT --target-function=-ave_net_gain      ' 1)
CMD--OPT --target-function=(2*max_ml+8*max_gain_diff)/10    ' 2) 
'CMD--OPT --target-function=(4*max_ml+8*max_gain_diff)/12    ' 3)
'
CMD--OPT --de-np=90 --restart=restart.log
CMD--OPT --auto-segmentation=21 --char-impedance=300 --num-cores=4
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' Evaluation Settings:
'
'CMD--EVAL -s(174,3,15) -s(470,6,39) --total-gain --publish
CMD--EVAL --vhf-lo --vhf-hi --uhf --total-gain --publish
CMD--EVAL --auto-segmentation=0 --char-impedance=300 --num-cores=4
CE
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' SYmbols used as variables:
'
' SOURCE Wire Radius, Adjusted for AGT=1.0
SY Rsrc=0.1006
'
' Bowtie Separation in FRONT of Reflector (which is at X=0):  [NOT USED HERE]
SY RS=0
'
' Radius (in inches) of BOWTIE elements:
SY Rbow=0.051
' Radius (in inches) of FEEDLINE wires
SY Rfeed=0.051
' Conductivity (Copper=3.0e7, Alum=2.0e7, Stainless Steel=2.5e7)
SY Cond=3e+07
'
'
' Depth dimensions of tines: 36 Max
'
SY Bay2XPtToPhaseLine=21.38863' 20.72, 21.72
'
SY Bay3XPtToPhaseLine=6.384182' 5.67, 6.67
SY Bay4XPtToPhaseLine=6.413942' 5.85, 6.85
'
SY Bay5XPtToPhaseLine=13.91284' 13.3, 14.3
'
'
' Width dimensions of tines: 23 Max
'
SY OuterYTinePtBay2=22.97256' 22, 23
'
SY OuterYTinePtBay3=21.69222' 21.35, 22.35
SY OuterYTinePtBay4=9.207783' 8.9, 9.9
'
SY OuterYTinePtBay5=22.98973' 22, 23
'
'
' Height dimensions of tines: 40" Max total
'
SY UpperZTinePtBay2=11.67993' 11.18, 12.18
'
' 1.33 was minimum allowed \/ \/ ;)
SY UpperZTinePtBay3=1.377431' 1.33, 2
SY UpperZTinePtBay4=19.99767' 19, 20
'
SY UpperZTinePtBay5=13.63307' 13.36, 14.36
'
'
' Distance from center of Feedline Cross-Over to center of OUTER Bowties:
SY XCrossNeg=2.296987' 1.65, 2.75
SY XCrossPos=1.726022' 1.25, 2
'
' Separation between two FEEDLINE wires:
SY FeedSep=1.144573' 0.75, 1.75
'
'
' Calculated from above INPUT Values:
'
' Distance between the centers of the two INNER bowties:
SY XDistanceInner=Bay4XPtToPhaseLine-Bay3XPtToPhaseLine
'
' X value of center of two inner bays of antenna
SY AntennaCenterX=XDistanceInner/2
'
SY MidBay2Bay3XPt=Bay2XPtToPhaseLine-XCrossNeg
SY MidBay4Bay5XPt=Bay5XPtToPhaseLine-XCrossPos
'
SY Xover1ToPhaseLine=MidBay2Bay3XPt-XCrossNeg
SY Xover2ToPhaseLine=MidBay4Bay5XPt-XCrossPos
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
'  # segs X1   Y1   Z1   X2    Y2  Z2 radius
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' SIMULATED SOURCE WIRE:
GW 1  1 AntennaCenterX  -FeedSep/2  0   AntennaCenterX   FeedSep/2 0 Rsrc ' Feed Point Separation: Lt Y pt to Rt
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' OUTER BOWTIE Tines:
'
' Bay 2 BOWTIE Tines:
GW 2  15 -Bay2XPtToPhaseLine OuterYTinePtBay2 UpperZTinePtBay2 -Bay2XPtToPhaseLine  FeedSep/2 0 Rbow ' Bay 2 Upper Right Tine
'                 ' - -/ Right Y point to Left/Upper to lower
GW 3  15 -Bay2XPtToPhaseLine OuterYTinePtBay2 -UpperZTinePtBay2 -Bay2XPtToPhaseLine  FeedSep/2 0 Rbow ' Bay 2 Lower Right Tine
'                 ' - -/ Right Y point to Left/Lower to Upper
GW 4  15 -Bay2XPtToPhaseLine -FeedSep/2  0 -Bay2XPtToPhaseLine -OuterYTinePtBay2 UpperZTinePtBay2 Rbow ' Bay 2 Upper Left Tine
'                 ' - -/ Left Y point to far Left/Lower to Upper
GW 5  15 -Bay2XPtToPhaseLine -FeedSep/2  0 -Bay2XPtToPhaseLine -OuterYTinePtBay2 -UpperZTinePtBay2 Rbow ' Bay 2 Lower Left Tine
'                 ' - -/ Left Y point to far Left/Upper to lower
'
'
' Bay 5 BOWTIE Tines:
GW 6  17 Bay5XPtToPhaseLine OuterYTinePtBay5 UpperZTinePtBay5 Bay5XPtToPhaseLine FeedSep/2 0  Rbow ' Bay 5 Upper Right Tine
'                 ' - -/ Right Y point to Left/Upper to lower
GW 7  17 Bay5XPtToPhaseLine OuterYTinePtBay5 -UpperZTinePtBay5 Bay5XPtToPhaseLine FeedSep/2 0  Rbow ' Bay 5 Lower Right Tine
'                 ' - -/ Right Y point to Left/Lower to Upper
GW 8  17 Bay5XPtToPhaseLine -FeedSep/2  0 Bay5XPtToPhaseLine -OuterYTinePtBay5 UpperZTinePtBay5 Rbow ' Bay 5 Upper Left Tine
'                 ' - -/ Left Y point to far Left/Lower to Upper
GW 9  17 Bay5XPtToPhaseLine -FeedSep/2  0 Bay5XPtToPhaseLine -OuterYTinePtBay5 -UpperZTinePtBay5 Rbow ' Bay 5 Lower Left Tine
'                 ' - -/ Left Y point to far Left/Upper to lower
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' INNER BOWTIE Tines:
'
' Bay 3 BOWTIE Tines:
GW 10  13 -Bay3XPtToPhaseLine OuterYTinePtBay3 UpperZTinePtBay3 -Bay3XPtToPhaseLine FeedSep/2 0  Rbow ' Bay 3 Upper Right Tine
'                 ' - -/ Right Y point to Left/Upper to lower
GW 11  13 -Bay3XPtToPhaseLine OuterYTinePtBay3 -UpperZTinePtBay3 -Bay3XPtToPhaseLine FeedSep/2 0  Rbow ' Bay 3 Lower Right Tine
'                 ' - -/ Right Y point to Left/Lower to Upper
GW 12  13 -Bay3XPtToPhaseLine -FeedSep/2  0 -Bay3XPtToPhaseLine -OuterYTinePtBay3 UpperZTinePtBay3 Rbow ' Bay 3 Upper Left Tine
'                 ' - -/ Left Y point to far Left/Lower to Upper
GW 13  13 -Bay3XPtToPhaseLine -FeedSep/2  0 -Bay3XPtToPhaseLine -OuterYTinePtBay3 -UpperZTinePtBay3 Rbow ' Bay 3 Lower Left Tine
'                 ' - -/ Left Y point to far Left/Upper to lower
'
'
' Bay 4 BOWTIE Tines:
GW 14  13 Bay4XPtToPhaseLine OuterYTinePtBay4 UpperZTinePtBay4 Bay4XPtToPhaseLine FeedSep/2 0  Rbow ' Bay 4 Upper Right Tine
'                 ' - -/ Right Y point to Left/Upper to lower
GW 15  13 Bay4XPtToPhaseLine OuterYTinePtBay4 -UpperZTinePtBay4 Bay4XPtToPhaseLine FeedSep/2 0  Rbow ' Bay 4 Lower Right Tine
'                 ' - -/ Right Y point to Left/Lower to Upper
GW 16  13 Bay4XPtToPhaseLine -FeedSep/2  0 Bay4XPtToPhaseLine -OuterYTinePtBay4 UpperZTinePtBay4 Rbow ' Bay 4 Upper Left Tine
'                 ' - -/ Left Y point to far Left/Lower to Upper
GW 17  13 Bay4XPtToPhaseLine -FeedSep/2  0 Bay4XPtToPhaseLine -OuterYTinePtBay4 -UpperZTinePtBay4 Rbow ' Bay 4 Lower Left Tine
'                 ' - -/ Left Y point to far Left/Upper to lower
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' Horizontal Phase Lines to CROSS-OVER Phase LINES:
'
' Inner Phase Lines to CROSS-OVER Phase LINES:
' Bay 3
GW 18  6 -Bay3XPtToPhaseLine FeedSep/2  0 -Xover1ToPhaseLine FeedSep/2  0   Rfeed ' Rt Bay 3 Phase Ln to Rt Xover inner Pt
'                  ' Inner to Outer/- -/- -
GW 19  6 -Bay3XPtToPhaseLine -FeedSep/2  0 -Xover1ToPhaseLine -FeedSep/2  0   Rfeed ' Lt Bay 3 Phase Ln to Lt Xover inner Pt
'                   'Inner to Outer/- -/- - '
'
'
' Outer Phase Lines to CROSS-OVER Phase LINES:
' Bay 4
GW 20  3 Xover2ToPhaseLine FeedSep/2  0 Bay4XPtToPhaseLine FeedSep/2  0   Rfeed ' Rt Bay 4 Phase Ln to Rt Xover outer pt 
'                   ' Outer to Inner/- -/- -
GW 21  3 Xover2ToPhaseLine -FeedSep/2  0 Bay4XPtToPhaseLine -FeedSep/2  0   Rfeed ' Lt Bay 4 Phase Ln to Lt Xover upper pt 
'                   ' Outer to Inner/- -/- -
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' CROSS-OVER LINES:
'
' Bay 2 CROSS-OVER LINES:
GW 22  2 -MidBay2Bay3XPt  0   FeedSep/2 -Bay2XPtToPhaseLine -FeedSep/2 0   Rfeed ' Lt Bay 2 Xover Ln to Lt Xover upper pt
'                   ' In to Out/R to L/Upper to lower
GW 23  2 -MidBay2Bay3XPt  0   -FeedSep/2 -Xover1ToPhaseLine -FeedSep/2 0   Rfeed ' Lt Bay 2 Xover Ln to Lt Xover lower pt
'                   ' Out to in/R to L/Lower to Upper
'
GW 24  2 -Bay2XPtToPhaseLine FeedSep/2  0  -MidBay2Bay3XPt  0  -FeedSep/2  Rfeed ' Rt Bay 2 Xover Ln to Rt Xover Lower Pt
'                   ' Out to in/R to L/Upper to lower
GW 25  2 -Xover1ToPhaseLine FeedSep/2  0  -MidBay2Bay3XPt  0  FeedSep/2  Rfeed ' Rt Bay 2 Xover Ln to Rt Xover Upper pt 
'                   ' In to Out/R to L/Lower to Upper
'
'
' Bay 5 CROSS-OVER LINES:
GW 26  1 MidBay4Bay5XPt  0   FeedSep/2 Xover2ToPhaseLine  -FeedSep/2 0  Rfeed ' Lt Bay 5 Xover Ln to Lt Xover upper pt
'                   ' Out to In/R to L/Upper to lower
GW 27  1 Xover2ToPhaseLine FeedSep/2  0  MidBay4Bay5XPt   0  -FeedSep/2 Rfeed ' Rt Bay 5 Xover Ln to Rt Xover Lower Pt
'                   ' In to Out/R to L/Upper to lower
'
GW 28  1 MidBay4Bay5XPt  0   FeedSep/2 Bay5XPtToPhaseLine  FeedSep/2 0  Rfeed ' Rt Bay 5 Xover Ln to Rt Xover upper pt
'                   ' In to Out/L to R/Upper to Lower
GW 29  1 Bay5XPtToPhaseLine -FeedSep/2  0  MidBay4Bay5XPt   0  -FeedSep/2 Rfeed ' Lt Bay 5 Xover ln to Lt Xover lower pt
'                   ' Out to in/L to R/Upper to Lower
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' Inner Phase Lines:
'
' Bay 3
GW 30  4 AntennaCenterX  FeedSep/2  0  -Bay3XPtToPhaseLine  FeedSep/2 0  Rfeed ' Right Tine #3 to Right Feed Point
'                   ' In to Out/- -/- -
GW 31  4 AntennaCenterX  -FeedSep/2  0  -Bay3XPtToPhaseLine  -FeedSep/2 0  Rfeed ' Left Tine #3 to Left Feed Point
'                   ' In to Out/- -/- -
'
' Bay 4
GW 32  4 Bay4XPtToPhaseLine FeedSep/2  0  AntennaCenterX   FeedSep/2 0  Rfeed ' Right Feed Point to Right Tine #4
'                   ' Out to in/- -/- -
GW 33  4 Bay4XPtToPhaseLine -FeedSep/2  0  AntennaCenterX   -FeedSep/2 0  Rfeed ' Left Feed Point to Left Tine #4
'                   ' Out to in/- -/- -
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
GS 0 0 0.0254     ' CONVERT ABOVE FROM INCHES TO METERS FOR NEC.
GE 0       ' No Ground Plane
EK 0       ' Enable Extended Kernel
'
LD 5 0 0 0 Cond 0  ' Conductivity
'
EX 0 1 1 0 1 0  ' SOURCE on GW1, seg 1
GN -1       ' Free Space
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' FR Freq Sweep choices in order of increasing calculation time (fm holl_ands):
' FR 0 0 0 0 213 0  ' Fixed Freq
' FR 0 29 0 0 470 12  ' Freq Sweep 470-806 every 12 MHz - OLD UHF BAND
' FR 0 77 0 0 470 3  ' Freq Sweep 470-698 every 3 MHz
' FR 0 34 0 0 410 12  ' Freq Sweep 410-806 every 12 MHz - Even Wider Sweep
' FR 0 39 0 0 470 6  ' Freq Sweep 470-698 every 6 MHz - PREFERRED FOR UHF
' FR 0 153 0 0 470 1.5  ' Freq Sweep 470-698 every 1.5 MHz
' FR 0 71 0 0 300 10  ' Freq Sweep 300-1000 every 10 MHz - WIDEBAND SWEEP
'
' FR Hi-VHF choices:
' FR 0 15 0 0 174 3  ' Freq Sweep 174-216 every 3 MHz
FR 0 29 0 0 174 1.5  ' Freq Sweep 174-216 every 1.5 MHz - PREFERRED
' FR 0 45 0 0 162 1.5  ' Freq Sweep 162-228 every 1.5 MHz - Add +/- 12 MHz BW
' FR 0 43 0 0 174 1  ' Freq Sweep 174-216 every 1 MHz - Hi-Rez
' FR 0 23 0 0 198 1  ' Freq Sweep 198-220 every 1 MHz - Hi-Rez - Ch13 SPECIAL
' FR 0 26 0 0 150 6  ' Freq Sweep 150-300 every 6 MHz - WIDEBAND SWEEP
'
' FR Lo-VHF choices:
' FR 0 19 0 0 54 3  ' Frequency Sweep every 3 MHz for Ch2-6 + FM
' FR 0 35 0 0 54 1  ' Frequency Sweep every 1 MHz for Ch2-6
' FR 0 36 0 0 75 1  ' Frequency Sweep every 1 MHz for Ch5 + Ch6 + FM
' FR 0 28 0 0 54 6  ' Wide Freq Sweep every 6 MHz for Ch2-13
' FR 0 64 0 0 54 12  ' Super Wide Freq Sweep 54-810 every 12 MHz
' FR 0 127 0 0 54 6  ' Super Wide Freq Sweep 54-810 every 6 MHz
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
'
' RP choices in order of increasing calculation time:
' RP 0 1 1 1510 90 90 1 1 0 0 ' 1D Gain toward 0-deg Azimuth - SIDE GAIN
' RP 0 1 1 1510 90 0 1 1 0 0 ' 1D Gain toward 90-deg Azimuth - FORWARD GAIN
' RP 0 1 1 1510 90 180 1 1 0 0 ' 1D Gain toward 270-deg Azimuth - REVERSE GAIN
' RP 0 1 37 1510 90 0 1 5 0 0  ' 2D (Left only) Azimuthal Gain Slice
RP 0 1 73 1510 90 0 1 5 0 0 ' 2D Azimuthal Gain Slice - PREFERRED
' RP 0 73 1 1510 90 0 5 1 0 0  ' 2D Elevation Gain Slice
' RP 0 73 73 1510 90 0 5 5 0 0  ' 3D Lower Hemisphere reveals antenna (Fixed Freq)
' RP 0 285 73 1510 90 0 5 5 0 0 ' 3D Full Coverage obscures antenna (Fixed Freq)
'
EN
'
'--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

The 'CMs' above state my intentions. Basically I wanted to create a small footprint VHF-HI antenna that has a steady gain across the entire frequency range. Please let me know of any improvements I can make to that NEC file above.


Below are some pics I snapped of the results from the above NEC file.


VHF-HI Frequency Range results:


VHF-HI Sweep results:
 
#28 · (Edited)
Your Hi-VHF 4-Bay Bowtie (No Reflector) provides fol. performance:
Hi-VHF Raw Gain = 7.3 to 7.8 dBi and SWR (300-ohms) Under 2.2.

I think you ended up with mediocre performance due to overly SMALL size constraints.
You might want try Re-Optimizing my UHF FF3 3-Bay Bowtie model with ~3X larger SYmbol variables.
Note that the "Free Form" model allows the Inner Bowtie to have DIFFERENT Dimensions, thereby
helping to minimize the natural tendency of Antennas to have lower Gain on lower Freqs:
https://imageevent.com/holl_ands/multibay/uhf3baybowtiesnorefl/uhfff3norefl
I estimate that it should provide Hi-VHF Band Gain of about 9-10 dBi with SWR under 2.7,
if Unconstrained. And of course LESS, if constrained to specific H x W maximums. I'll go ahead
and run the Unconstrained Hi-VHF FF3 and when done, you can try it with YOUR Size Constraints.

=========================================================
Compare to three different Optimizations I did for an UNCONSTRAINED Hi-VHF 2-Bay Bowtie
[about 4-ft H x 5-ft W] whose performance isn't all that much different than YOUR way too small 4-Bay:
https://imageevent.com/holl_ands/multibay/hivhf2bay
And a M4 Type 4-Bay (everything matchy-matchy) would be TWICE as high, whereas Unconstrained
Hi-VHF FF4 would probably be somewhat TALLER....which is why I didn't feel anyone would WANT it.

Alt a) Hi-VHF Raw Gain = 6.7 to 9.3 dBi and SWR (300-ohms) Under 2.6. ["Best" Overall, 44"Hx61"W]
Alt b)Hi-VHF Raw Gain = 5.7 to 8.1 dBi and SWR (300-ohms) Under 1.7. [Better SWR]
Alt c) Hi-VHF Raw Gain = 7.6 to 10 dBi and SWR (300-ohms) Under 3.5 [EXCESSIVE SWR].

You might also want to Re-Optimize my 2-Bay Model, subject to YOUR H x W Size Constraints....
 
#30 · (Edited)
Sorry....I was mislead by the (misuse???) of the term "4-Bay Whisker" and didn't pay enough attention to the "Horizontal" modifier. [We need to prevent confusion versus Horizontally Stacked 4-Bay Bowtie, which is Quite Different.] Surely there is a better NAME for this sort of antenna....perhaps "Hi-VHF 4-El Back-to-Back Bowtie LPDAs".....since I suspect that for Bi-Directional performance, the Feedline towards the Rear should be a Mirror Image of the Feedline towards the Front....similar to existing Topology. [I also believe that the Feedline for a Directional Antenna would have a LPDA type Crossovers between ALL adjacent Bowties.]

I finally got around to trying to understand your 4nec2 File....some quick comments:

1) You said your intention was to design a Bi-Directional Antenna, which is how the CMD-EVAL Statements are set-up. However, you allowed Dimensions of each Bowtie "Bay" to be independently determined....resulting in a very Directional Antenna except on lowest Hi-VHF Freqs. A Bi-Directional Antenna needs to be SYMMETRIC about the Y-Z Plane....so SYmbols for Rear Whiskers should be EQUAL to corresponding Front Whisker SYmbols.

2) You only allowed SYmbols to vary over a VERY Small Range....perhaps we are only seeing a secondary Refinement on the original Run??? Optimization Search Ranges should to be as wide as is reasonable.

3) Perhaps for Next TimE: I find the very LONG and WORDY SYmbol Names are difficult to understand (esp. cuz I wasn't the Author).....it also makes it more difficult to SEE them in the Selection Menu when doing 4nec2 PARAMETER Sweeps....
 
#31 ·
I honestly don't understand why the members of this site belittle antenna results that are submitted to this site.


I believe I submitted a fairly decent antenna model that pound for pound is better than any other VHF antenna model I have seen on this site.


A noticeably smaller footprint antenna that has a high constant gain across the VHF-Hi frequency range.


If anyone can show a better performing VHF-HI antenna model in the "small" footprint specs I specified, please do so.


CM 7.80 Highest Net Gain
CM 7.24 AVG Net Gain
CM 6.87 Lowest Net Gain


I have yet to see such a consistent VHF-HI antenna model results on this site.
 
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