The imaginary part of the impedance is most important. It determines conductor reactance and it changes most rapidly with frequency.
Understood. Would that mean that the equivalent diameter calculation increases in accuracy with higher frequencies ?


A question on FM. While lower SWR is always better, what would you consider the maximum amount of SWR tolerable on an FM antenna, non digital ?

(Im in the process of evolving my POS Winegard suburban antenna here: http://www.digitalhome.ca/forum/showthread.php?t=147493 into a decent channel 6 and 12 antenna, and maybe including FM 94.1 into it. Just want to know how high an SWR is tolerable. Gain on it is easy to get flat 82 to 100 mhz at about 5+ dBi with 1 additional reflector. )

Understood. Would that mean that the equivalent diameter calculation increases in accuracy with higher frequencies ?

I don't see why it would.


A question on FM. While lower SWR is always better, what would you consider the maximum amount of SWR tolerable on an FM antenna, non digital ?

I don't think of things that way. Usually I want to optimize a combination of forward gain and F/R, with the latter most important at my location. I don't care about SWR except for the reduction in forward gain it causes due to mismatch loss. So I optimize forward gain minus mismatch loss since that determines the signal level my receiver sees. That figure trades-off against F/R. I let the optimizer work out how much SWR to tolerate. Often it makes SWR low over the entire band. But sometimes it lets it rise near the high end. Evidently the increased mismatch loss there is compensated by an increase in gain elsewhere, or by an increase in F/R. The beauty of doing things this way is that you don't have to make an arbitrary decision about how much SWR to tolerate. You just let things work out naturally and optimally.

Brian

You just let things work out naturally.
Yeah, thats what Im doing, but just wondering if 5 or 6:1 SWR is too high for non digital FM. Im tweaking the real channel 6 digital SWR down to about 2:1 SWR. Just thinking of the negative impacts, but on the other hand, my main purpose for 94.1 is for Eagles football games, no real music, so my point may be mute for my purposes anyway, heh. I get the station on my old Motorola tube radio with a twin lead antenna (antenna indoors) and the car radio, but not on any transistor radio/stereo set I have. So I guess a 3.5 dBi Net Gain (Raw Gain minus the mismatch loss) antenna outdoors should be more than enough. So 5:1 may be OK if the raw gain is enough. :)

One thing to keep in mind is that monophonic FM has a pronounced threshold where the signal gets quiet very quickly with a small increase in signal level. The effect is nonlinear and counterintuitive.

A zero-cost trick is to tilt your dipole to take advantage of circular polarization:

http://ham-radio.com/k6sti/tilted.htm

Brian

Most FM stations use right-circular polarization. To enhance their reception, orient a horizontal dipole broadside to the desired station. Then looking through the dipole toward the station, lower the right end until the angle is about 45°. For a left-circular signal, lower the left end.
Good tip, Ill give it a try.

Quote:
Originally Posted by 300ohm View Post
Understood. Would that mean that the equivalent diameter calculation increases in accuracy with higher frequencies ?
I don't see why it would.


I dont know either. At wifi frequencies, I believe the equivalent diameter calculation has to become extremely tricky.

Keep in mind, Im not knocking the equivalent diameter calculation, its great to have less wires and simplify things.

I use two rules of thumb to quickly estimate mismatch loss: 0.5 dB at SWR 2, and 1 dB at SWR 3. The latter figure is not that accurate, but I can't get it out of my head. I'm trying to retrain myself on a new number given below.

Brian


SWR Loss Approx
1.5 0.18 0.2
2 0.51 0.5
2.7 1.03 1
3 1.25 1.2
4 1.94 2
5 2.55 2.5
10 4.81 5
25 8.30 8
50 11.14 11
100 14.07 14

Holl_ands earlier posted an easy peasy mismatch calculator link:

http://www.bessernet.com/Ereflecto/tutorialFrameset.htm

@holl_ands, re. X0814

The downward radiation angle is due to the asymmetric feed and the phase shift across the transmission line. The 1/2 wave of transmission line between the two element arrays is only a half wave at one frequency which is going to narrow the useful bandwidth compared to a single rhombic. At Fo*2, I would expect the upper array to be fed 180° out of phase, (that should knock the net gain down a bit).

I'll look into a balanced feed system... such as the center feed on the typical 4-bay panel. Again, my goal is more on the order of a cut for channel than broadband antenna.

Thanks for providing the FR and RP cards... plenty to 'chew on' :D

In 4nec2, looking at the Pattern image, information, it gives the "fb" which either equals the Fr/back data OR it equals the Fr/rear data, OR it doesn't match either of these shown on the plot below the gain plot, depending on the frequency selected

Is this correct ? :confused:

After selecting Pattern windows box, depress the "i" key [not found in menus] for
additional info display. The "m" key cycles through ALL, Horiz only & Vert. only.

(Red) Front/Back Ratio, "fb", is Forward Gain (90-deg) divided by Rear Gain (270-deg).
(Green) Front/Rear Ratio is Forward Gain divided by WORST CASE Gain in rearward
direction. Included rearward angle MIGHT be +/- 90-deg (per IEEE standard),
but I'm not really sure....In the Optimizer menus, it can be set by the user.

What is displayed in the Gain/F2B/F2R Curves might not always match...carefully
check azimuthal angle displayed at top of Gain/F2B/F2R display box....4nec2 will
"lock onto" the angle which gives Max Gain on the lowest freq in the sweep, which
might not be 90-deg assumed as the Forward direction in the Pattern display.
If Gain on the lowest sweep frequency is higher in the REVERSE direction, then
azimuthal angle will be 270-deg, which will become the assumed FORWARD direction.

I provided some alternative RP Cards which will force 4nec2 to calculate Forward
Gain....but for some reason it fails to also calculate F2B/F24. I can usually get
around this limitation by changing the lowest freq in the sweep so that it is the
first one with positive Gain in the Forward direction.

ERRATA: Fixed reversal of "Front/Back" and "Front/Rear"...."fb" really does mean "Front/Back".

Thank you, I was obviously getting the information mixed up. I will read up more on 4nec2.


(Red) Front/Rear Ratio, "fb", is Forward Gain (90-deg) divided by Rear Gain (270-deg

I assume regarding Rear Gain (270 degrees), you are referring to the rear gain averaged on Phi (90 to 270 degrees), and at Theta (- 90 degrees) ? So if I want to optimize for Front/Rear Ratio what example d-Phi (+/- values) should be used in the evolver to cover part of the rear azimuth (Phi from 90 degrees to 270 degrees)...

(Green) Front/Back Ratio is Forward Gain divided by WORST CASE Gain in rearward
direction. Included rearward angle MIGHT be +/- 90-deg (per IEEE standard),

So "rearward direction" is Phi=180 degrees (rear), and "included rearward angle" might be Theta +/- 90 degrees, is this correct...


The 4nec2 help refers to this:

It is possible to specify a certain forward- and/or backward-region for which the Gain or F/B ratio should be averaged. This is done by specifying a certain resolution in combination with a delta-Phi and/or delta-Theta (d-Phi, d-Theta) value. Averaging is performed for angles between Phi – d_Phi and Phi + d_Phi. The same holds for the Theta and d_Theta angles.



BTW, I always thought "fb" on the pattern view was the abbreviation for Front/Back Ratio, and so I ASSUMED Front/Rear Ratio was NOT shown on the pattern view.

Thanks again for the clarifications.

ACCCKKKKKI!!!! I messed up and reversed "Front/Back" and "Front/Rear"!!!!
Back, Rear....Rear, Back....what's the difference???? Even I get confused.....

"fb" really does mean Front/Back (DIRECTLY BACK, precisely 270-deg).
And I'll try to remember...."Rear" is anywhere you can wiggle your butt.....

After selecting Pattern windows box, depress the "i" key [not found in menus] for additional info display.

??? Thats just the same thing as clicking on Show > Info from the Pattern windows box menu. :confused: :confused:

HA!!!! I glanced at it and it didn't register, cuz it looks like a "T"!!!!

I would recommend someone do a comparison test....
Re: Comparison test between Wire Outline modeling and Wire Diameter Equivalency modeling.

OK, I did. Im in the process of getting ready to modify my 1970s Winegard Suburban antenna into something useful for me, ie a combo channel 6 and 12 antenna, just using stuff I already have on hand. (the uhf section will be taken off and used in something like a HD-9032 project later). I found to produce low SWR on both channels, I needed to turn the straight dipoles into folded dipoles, besides cutting them down. I dont have a 6 ft piece of 3/8" tubing, but I do have plenty of .75" wide, .06" thick alulminum bar (its not really bar, but its old style inside moulding. More about the moulding in another post, as this is just for wire outline vs wire diameter equivalency).
For .75" wide, .06" thick wire, the round wire equivalency is .434" diameter (.217" radius) http://fermi.la.asu.edu/w9cf/equiv/index.html

The results on channel 12:
Wire outline raw gain 9.95 dBi, SWR 1.17 at 207 mhz.
Wire equivalency raw gain 9.93 dBi, SWR 1.12 at 207 mhz.
So Raw Gain and Net Gain are about the same, SWR is a bit more with the wire outline method.

The results on channel 6:
Wire outline raw gain 6.56 dBi, SWR 2.62 at 85 mhz.
Wire equivalency raw gain 6.53 dBi, SWR 1.86 at 85 mhz.
So the Raw Gain is about the same, but the Net Gain is about .53 dBi less with the wire outline modeling due to the much higher SWR.

The wire outline modeling produces the more conservative figures.
The question then becomes, which is closer to real life testing ?

The wire outline NEC file:
CM 1970s Winegard Suburban Antenna Retro Fit by 300ohm
CM Test model using drawn outline wires of .75 inches wide, .06 inches thick
CM Design Goal : Channel 6, 94.1 FM and Channel 12
CM And less than 7 ft long, using existing structure as much as possible
CM Added 1 reflector for Channel 6 and 4 directors for Channel 12
CM AGT = 1.0 (0 db) at 207 mhz, 1.17 (-0.67 db) at 85 mhz Autoseg = 21
CE
GW 1 23 0 3.5 0 0 33.57 0 0.1875
GW 2 23 0 -3.5 0 0 -33.57 0 0.1875
GW 3 7 10.5 3.5 0 10.5 13.62 0 0.1875
GW 4 7 10.5 -3.5 0 10.5 -13.62 0 0.1875
GW 5 1 10.5 2.1 0 9.425 2.1 0 0.0285341
GW 6 1 9.425 2.1 0 8.35 2.1 0 0.0285341
GW 7 1 10.5 -2.1 0 9.425 -2.1 0 0.0285341
GW 8 1 9.425 -2.1 0 8.35 -2.1 0 0.0285341
GW 9 1 10.5 2.1 0 10.5 1.75 0 0.0285341
GW 10 1 10.5 -1.75 0 10.5 -2.1 0 0.0285341
GW 11 1 10.5 -1.75 0 9.575 -1.75 0 0.0285341
GW 12 1 9.575 -1.75 0 8.65 -1.75 0 0.0285341
GW 13 1 10.5 1.75 0 9.575 1.75 0 0.0285341
GW 14 1 9.575 1.75 0 8.65 1.75 0 0.0285341
GW 15 1 10.5 1.75 0 10.5 1.4 0 0.0285341
GW 16 1 10.5 -1.75 0 10.5 -1.4 0 0.0285341
GW 17 1 0 -2.1 0 1.075 -2.1 0 0.0285341
GW 18 1 1.075 -2.1 0 2.15 -2.1 0 0.0285341
GW 19 1 0 2.1 0 1.075 2.1 0 0.0285341
GW 20 1 1.075 2.1 0 2.15 2.1 0 0.0285341
GW 21 1 0 2.1 0 0 1.75 0 0.0285341
GW 22 1 0 -2.1 0 0 -1.75 0 0.0285341
GW 23 1 0 1.75 0 0.925 1.75 0 0.0285341
GW 24 1 0.925 1.75 0 1.85 1.75 0 0.0285341
GW 25 1 0 -1.75 0 0.925 -1.75 0 0.0285341
GW 26 1 0.925 -1.75 0 1.85 -1.75 0 0.0285341
GW 27 1 0 1.75 0 0 1.4 0 0.0285341
GW 28 1 0 -1.75 0 0 -1.4 0 0.0285341
GW 29 1 2.3 -0.19 1.2 3.70625 -0.19 1.2 0.0285341
GW 30 1 3.70625 -0.19 1.2 5.1125 -0.19 1.2 0.0285341
GW 31 1 5.1125 -0.19 1.2 6.51875 -0.19 1.2 0.0285341
GW 32 1 6.51875 -0.19 1.2 7.925 -0.19 1.2 0.0285341
GW 33 1 1.85 1.75 0 2.075 0.78 0.6 0.0285341
GW 34 1 2.075 0.78 0.6 2.3 -0.19 1.2 0.0285341
GW 35 1 2.6 0.19 1.2 4.00625 0.19 1.2 0.0285341
GW 36 1 4.00625 0.19 1.2 5.4125 0.19 1.2 0.0285341
GW 37 1 5.4125 0.19 1.2 6.81875 0.19 1.2 0.0285341
GW 38 1 6.81875 0.19 1.2 8.225 0.19 1.2 0.0285341
GW 39 1 2.15 2.1 0 2.375 1.145 0.6 0.0285341
GW 40 1 2.375 1.145 0.6 2.6 0.19 1.2 0.0285341
GW 41 1 7.925 -0.19 1.2 8.1375 -1.145 0.6 0.0285341
GW 42 1 8.1375 -1.145 0.6 8.35 -2.1 0 0.0285341
GW 43 1 8.225 0.19 1.2 8.4375 -0.78 0.6 0.0285341
GW 44 1 8.4375 -0.78 0.6 8.65 -1.75 0 0.0285341
GW 45 1 2.3 0.19 -1.2 3.70625 0.19 -1.2 0.0285341
GW 46 1 3.70625 0.19 -1.2 5.1125 0.19 -1.2 0.0285341
GW 47 1 5.1125 0.19 -1.2 6.51875 0.19 -1.2 0.0285341
GW 48 1 6.51875 0.19 -1.2 7.925 0.19 -1.2 0.0285341
GW 49 1 2.6 -0.19 -1.2 4.00625 -0.19 -1.2 0.0285341
GW 50 1 4.00625 -0.19 -1.2 5.4125 -0.19 -1.2 0.0285341
GW 51 1 5.4125 -0.19 -1.2 6.81875 -0.19 -1.2 0.0285341
GW 52 1 6.81875 -0.19 -1.2 8.225 -0.19 -1.2 0.0285341
GW 53 1 2.3 0.19 -1.2 2.075 -0.78 -0.6 0.0285341
GW 54 1 2.075 -0.78 -0.6 1.85 -1.75 0 0.0285341
GW 55 1 2.6 -0.19 -1.2 2.375 -1.145 -0.6 0.0285341
GW 56 1 2.375 -1.145 -0.6 2.15 -2.1 0 0.0285341
GW 57 1 8.35 2.1 0 8.1375 1.145 -0.6 0.0285341
GW 58 1 8.1375 1.145 -0.6 7.925 0.19 -1.2 0.0285341
GW 59 1 8.65 1.75 0 8.4375 0.78 -0.6 0.0285341
GW 60 1 8.4375 0.78 -0.6 8.225 -0.19 -1.2 0.0285341
GW 61 1 2.15 2.1 0 1.85 1.75 0 0.0285341
GW 62 1 1.85 -1.75 0 2.15 -2.1 0 0.0285341
GW 63 1 8.35 2.1 0 8.65 1.75 0 0.0285341
GW 64 1 8.65 -1.75 0 8.35 -2.1 0 0.0285341
GW 65 1 7.925 -0.19 1.2 8.225 0.19 1.2 0.0285341
GW 66 1 8.225 -0.19 -1.2 7.925 0.19 -1.2 0.0285341
GW 67 1 5.4125 -0.19 -1.2 5.1125 0.19 -1.2 0.0285341
GW 68 1 5.1125 -0.19 1.2 5.4125 0.19 1.2 0.0285341
GW 69 1 2.6 -0.19 -1.2 2.3 0.19 -1.2 0.0285341
GW 70 1 2.6 0.19 1.2 2.3 -0.19 1.2 0.0285341
GW 71 1 1.075 2.1 0 0.925 1.75 0 0.0285341
GW 72 1 0.925 -1.75 0 1.075 -2.1 0 0.0285341
GW 73 1 9.425 2.1 0 9.575 1.75 0 0.0285341
GW 74 1 9.425 -2.1 0 9.575 -1.75 0 0.0285341
GW 75 1 8.1375 1.145 -0.6 8.4375 0.78 -0.6 0.0285341
GW 76 1 8.1375 -1.145 0.6 8.4375 -0.78 0.6 0.0285341
GW 77 1 4.00625 0.19 1.2 3.70625 -0.19 1.2 0.0285341
GW 78 1 6.81875 0.19 1.2 6.51875 -0.19 1.2 0.0285341
GW 79 1 3.70625 0.19 -1.2 4.00625 -0.19 -1.2 0.0285341
GW 80 1 6.51875 0.19 -1.2 6.81875 -0.19 -1.2 0.0285341
GW 81 1 2.075 -0.78 -0.6 2.375 -1.145 -0.6 0.0285341
GW 82 1 2.075 0.78 0.6 2.375 1.145 0.6 0.0285341
GW 83 1 10.5 2.1 0 10.5 3.5 0 0.0285341
GW 84 1 10.5 -2.1 0 10.5 -3.5 0 0.0285341
GW 85 1 0 -2.1 0 0 -3.5 0 0.0285341
GW 86 1 0 2.1 0 0 3.5 0 0.0285341
GW 87 3 10.5 -1.4 0 10.5 1.4 0 0.105
GW 88 7 0 0 0 9 0 0 0.5
GW 89 19 14.75 12.33 0 14.75 -12.33 0 0.1875
GW 90 19 25.02 12.19 0 25.02 -12.19 0 0.1875
GW 91 19 37.27 12.05 0 37.27 -12.05 0 0.1875
GW 94 19 51.52 11.93 0 51.52 -11.93 0 0.1875
GW 92 51 -27.76 33.96 0 -27.76 -33.96 0 0.1875
GW 93 21 0 13.88 -1.125 0 -13.88 -1.125 0.1875
GW 95 3 0 -33.57 0 0 -33.57 -2.25 0.1875
GW 96 3 0 33.57 0 0 33.57 -2.25 0.1875
GW 97 3 0 -33.57 -2.25 0 -29.620588 -2.25 0.03
GW 141 3 0 -29.620588 -2.25 0 -25.671176 -2.25 0.03
GW 142 3 0 -25.671176 -2.25 0 -21.721765 -2.25 0.03
GW 143 3 0 -21.721765 -2.25 0 -17.772353 -2.25 0.03
GW 144 3 0 -17.772353 -2.25 0 -13.822941 -2.25 0.03
GW 145 3 0 -13.822941 -2.25 0 -9.8735294 -2.25 0.03
GW 146 3 0 -9.8735294 -2.25 0 -5.9241176 -2.25 0.03
GW 147 3 0 -5.9241176 -2.25 0 -1.9747059 -2.25 0.03
GW 148 3 0 -1.9747059 -2.25 0 1.97470588 -2.25 0.03
GW 149 3 0 1.97470588 -2.25 0 5.92411765 -2.25 0.03
GW 150 3 0 5.92411765 -2.25 0 9.87352941 -2.25 0.03
GW 151 3 0 9.87352941 -2.25 0 13.8229412 -2.25 0.03
GW 152 3 0 13.8229412 -2.25 0 17.7723529 -2.25 0.03
GW 153 3 0 17.7723529 -2.25 0 21.7217647 -2.25 0.03
GW 154 3 0 21.7217647 -2.25 0 25.6711765 -2.25 0.03
GW 155 3 0 25.6711765 -2.25 0 29.6205882 -2.25 0.03
GW 156 3 0 29.6205882 -2.25 0 33.57 -2.25 0.03
GW 98 3 10.5 -13.62 0 10.5 -13.62 -2.25 0.1875
GW 99 3 10.5 13.62 0 10.5 13.62 -2.25 0.1875
GW 100 3 10.5 -13.62 -2.25 10.5 -9.7285714 -2.25 0.03
GW 113 3 10.5 -9.7285714 -2.25 10.5 -5.8371429 -2.25 0.03
GW 114 3 10.5 -5.8371429 -2.25 10.5 -1.9457143 -2.25 0.03
GW 115 3 10.5 -1.9457143 -2.25 10.5 1.94571429 -2.25 0.03
GW 116 3 10.5 1.94571429 -2.25 10.5 5.83714286 -2.25 0.03
GW 117 3 10.5 5.83714286 -2.25 10.5 9.72857143 -2.25 0.03
GW 118 3 10.5 9.72857143 -2.25 10.5 13.62 -2.25 0.03
GW 101 1 0 -33.57 -2.25 0 -33.57 -3 0.03
GW 102 1 0 33.57 -2.25 0 33.57 -3 0.03
GW 103 3 0 -33.57 -3 0 -29.620588 -3 0.03
GW 125 3 0 -29.620588 -3 0 -25.671176 -3 0.03
GW 126 3 0 -25.671176 -3 0 -21.721765 -3 0.03
GW 127 3 0 -21.721765 -3 0 -17.772353 -3 0.03
GW 128 3 0 -17.772353 -3 0 -13.822941 -3 0.03
GW 129 3 0 -13.822941 -3 0 -9.8735294 -3 0.03
GW 130 3 0 -9.8735294 -3 0 -5.9241176 -3 0.03
GW 131 3 0 -5.9241176 -3 0 -1.9747059 -3 0.03
GW 132 3 0 -1.9747059 -3 0 1.97470588 -3 0.03
GW 133 3 0 1.97470588 -3 0 5.92411765 -3 0.03
GW 134 3 0 5.92411765 -3 0 9.87352941 -3 0.03
GW 135 3 0 9.87352941 -3 0 13.8229412 -3 0.03
GW 136 3 0 13.8229412 -3 0 17.7723529 -3 0.03
GW 137 3 0 17.7723529 -3 0 21.7217647 -3 0.03
GW 138 3 0 21.7217647 -3 0 25.6711765 -3 0.03
GW 139 3 0 25.6711765 -3 0 29.6205882 -3 0.03
GW 140 3 0 29.6205882 -3 0 33.57 -3 0.03
GW 104 1 10.5 -13.62 -2.25 10.5 -13.62 -3 0.03
GW 105 1 10.5 13.62 -2.25 10.5 13.62 -3 0.03
GW 106 3 10.5 -13.62 -3 10.5 -9.7285714 -3 0.03
GW 107 3 10.5 -9.7285714 -3 10.5 -5.8371429 -3 0.03
GW 108 3 10.5 -5.8371429 -3 10.5 -1.9457143 -3 0.03
GW 109 3 10.5 -1.9457143 -3 10.5 1.94571429 -3 0.03
GW 110 3 10.5 1.94571429 -3 10.5 5.83714286 -3 0.03
GW 111 3 10.5 5.83714286 -3 10.5 9.72857143 -3 0.03
GW 112 3 10.5 9.72857143 -3 10.5 13.62 -3 0.03
GW 119 1 10.5 -9.7285714 -2.25 10.5 -9.7285714 -3 0.03
GW 120 1 10.5 -5.8371429 -2.25 10.5 -5.8371429 -3 0.03
GW 121 1 10.5 -1.9457143 -2.25 10.5 -1.9457143 -3 0.03
GW 122 1 10.5 1.94571429 -2.25 10.5 1.94571429 -3 0.03
GW 123 1 10.5 5.83714286 -2.25 10.5 5.83714286 -3 0.03
GW 124 1 10.5 9.72857143 -2.25 10.5 9.72857143 -3 0.03
GW 157 1 0 -29.620588 -2.25 0 -29.620588 -3 0.03
GW 158 1 0 -25.671176 -2.25 0 -25.671176 -3 0.03
GW 159 1 0 -21.721765 -2.25 0 -21.721765 -3 0.03
GW 160 1 0 -17.772353 -2.25 0 -17.772353 -3 0.03
GW 161 1 0 -13.822941 -2.25 0 -13.822941 -3 0.03
GW 162 1 0 -9.8735294 -2.25 0 -9.8735294 -3 0.03
GW 163 1 0 -5.9241176 -2.25 0 -5.9241176 -3 0.03
GW 164 1 0 -1.9747059 -2.25 0 -1.9747059 -3 0.03
GW 165 1 0 1.97470588 -2.25 0 1.97470588 -3 0.03
GW 166 1 0 5.92411765 -2.25 0 5.92411765 -3 0.03
GW 167 1 0 9.87352941 -2.25 0 9.87352941 -3 0.03
GW 168 1 0 13.8229412 -2.25 0 13.8229412 -3 0.03
GW 169 1 0 17.7723529 -2.25 0 17.7723529 -3 0.03
GW 170 1 0 21.7217647 -2.25 0 21.7217647 -3 0.03
GW 171 1 0 25.6711765 -2.25 0 25.6711765 -3 0.03
GW 172 1 0 29.6205882 -2.25 0 29.6205882 -3 0.03
GS 0 0 0.0254 ' All in in.
GE 0
EK
LD 5 0 0 0 2.49e7 0
EX 0 87 2 0 1 0
GN -1
FR 0 1 0 0 207 0


The wire equivalency NEC file:
CM 1970s Winegard Suburban Antenna Retro Fit by 300ohm
CM Test model using equivalent diameter of wires of .75 inches wide, .06 inches thick = .434 dia, .217 radius
CM Design Goal : Channel 6, 94.1 FM and Channel 12
CM And less than 7 ft long, using existing structure as much as possible
CM Added 1 reflector for Channel 6 and 4 directors for Channel 12
CM AGT = 1.0 (0 db) at 207 mhz, .97 (-0.1 db) at 85 mhz Autoseg = 21
CE
GW 1 23 0 3.5 0 0 33.57 0 0.1875
GW 2 23 0 -3.5 0 0 -33.57 0 0.1875
GW 3 7 10.5 3.5 0 10.5 13.62 0 0.1875
GW 4 7 10.5 -3.5 0 10.5 -13.62 0 0.1875
GW 5 1 10.5 2.1 0 9.425 2.1 0 0.0285341
GW 6 1 9.425 2.1 0 8.35 2.1 0 0.0285341
GW 7 1 10.5 -2.1 0 9.425 -2.1 0 0.0285341
GW 8 1 9.425 -2.1 0 8.35 -2.1 0 0.0285341
GW 9 1 10.5 2.1 0 10.5 1.75 0 0.0285341
GW 10 1 10.5 -1.75 0 10.5 -2.1 0 0.0285341
GW 11 1 10.5 -1.75 0 9.575 -1.75 0 0.0285341
GW 12 1 9.575 -1.75 0 8.65 -1.75 0 0.0285341
GW 13 1 10.5 1.75 0 9.575 1.75 0 0.0285341
GW 14 1 9.575 1.75 0 8.65 1.75 0 0.0285341
GW 15 1 10.5 1.75 0 10.5 1.4 0 0.0285341
GW 16 1 10.5 -1.75 0 10.5 -1.4 0 0.0285341
GW 17 1 0 -2.1 0 1.075 -2.1 0 0.0285341
GW 18 1 1.075 -2.1 0 2.15 -2.1 0 0.0285341
GW 19 1 0 2.1 0 1.075 2.1 0 0.0285341
GW 20 1 1.075 2.1 0 2.15 2.1 0 0.0285341
GW 21 1 0 2.1 0 0 1.75 0 0.0285341
GW 22 1 0 -2.1 0 0 -1.75 0 0.0285341
GW 23 1 0 1.75 0 0.925 1.75 0 0.0285341
GW 24 1 0.925 1.75 0 1.85 1.75 0 0.0285341
GW 25 1 0 -1.75 0 0.925 -1.75 0 0.0285341
GW 26 1 0.925 -1.75 0 1.85 -1.75 0 0.0285341
GW 27 1 0 1.75 0 0 1.4 0 0.0285341
GW 28 1 0 -1.75 0 0 -1.4 0 0.0285341
GW 29 1 2.3 -0.19 1.2 3.70625 -0.19 1.2 0.0285341
GW 30 1 3.70625 -0.19 1.2 5.1125 -0.19 1.2 0.0285341
GW 31 1 5.1125 -0.19 1.2 6.51875 -0.19 1.2 0.0285341
GW 32 1 6.51875 -0.19 1.2 7.925 -0.19 1.2 0.0285341
GW 33 1 1.85 1.75 0 2.075 0.78 0.6 0.0285341
GW 34 1 2.075 0.78 0.6 2.3 -0.19 1.2 0.0285341
GW 35 1 2.6 0.19 1.2 4.00625 0.19 1.2 0.0285341
GW 36 1 4.00625 0.19 1.2 5.4125 0.19 1.2 0.0285341
GW 37 1 5.4125 0.19 1.2 6.81875 0.19 1.2 0.0285341
GW 38 1 6.81875 0.19 1.2 8.225 0.19 1.2 0.0285341
GW 39 1 2.15 2.1 0 2.375 1.145 0.6 0.0285341
GW 40 1 2.375 1.145 0.6 2.6 0.19 1.2 0.0285341
GW 41 1 7.925 -0.19 1.2 8.1375 -1.145 0.6 0.0285341
GW 42 1 8.1375 -1.145 0.6 8.35 -2.1 0 0.0285341
GW 43 1 8.225 0.19 1.2 8.4375 -0.78 0.6 0.0285341
GW 44 1 8.4375 -0.78 0.6 8.65 -1.75 0 0.0285341
GW 45 1 2.3 0.19 -1.2 3.70625 0.19 -1.2 0.0285341
GW 46 1 3.70625 0.19 -1.2 5.1125 0.19 -1.2 0.0285341
GW 47 1 5.1125 0.19 -1.2 6.51875 0.19 -1.2 0.0285341
GW 48 1 6.51875 0.19 -1.2 7.925 0.19 -1.2 0.0285341
GW 49 1 2.6 -0.19 -1.2 4.00625 -0.19 -1.2 0.0285341
GW 50 1 4.00625 -0.19 -1.2 5.4125 -0.19 -1.2 0.0285341
GW 51 1 5.4125 -0.19 -1.2 6.81875 -0.19 -1.2 0.0285341
GW 52 1 6.81875 -0.19 -1.2 8.225 -0.19 -1.2 0.0285341
GW 53 1 2.3 0.19 -1.2 2.075 -0.78 -0.6 0.0285341
GW 54 1 2.075 -0.78 -0.6 1.85 -1.75 0 0.0285341
GW 55 1 2.6 -0.19 -1.2 2.375 -1.145 -0.6 0.0285341
GW 56 1 2.375 -1.145 -0.6 2.15 -2.1 0 0.0285341
GW 57 1 8.35 2.1 0 8.1375 1.145 -0.6 0.0285341
GW 58 1 8.1375 1.145 -0.6 7.925 0.19 -1.2 0.0285341
GW 59 1 8.65 1.75 0 8.4375 0.78 -0.6 0.0285341
GW 60 1 8.4375 0.78 -0.6 8.225 -0.19 -1.2 0.0285341
GW 61 1 2.15 2.1 0 1.85 1.75 0 0.0285341
GW 62 1 1.85 -1.75 0 2.15 -2.1 0 0.0285341
GW 63 1 8.35 2.1 0 8.65 1.75 0 0.0285341
GW 64 1 8.65 -1.75 0 8.35 -2.1 0 0.0285341
GW 65 1 7.925 -0.19 1.2 8.225 0.19 1.2 0.0285341
GW 66 1 8.225 -0.19 -1.2 7.925 0.19 -1.2 0.0285341
GW 67 1 5.4125 -0.19 -1.2 5.1125 0.19 -1.2 0.0285341
GW 68 1 5.1125 -0.19 1.2 5.4125 0.19 1.2 0.0285341
GW 69 1 2.6 -0.19 -1.2 2.3 0.19 -1.2 0.0285341
GW 70 1 2.6 0.19 1.2 2.3 -0.19 1.2 0.0285341
GW 71 1 1.075 2.1 0 0.925 1.75 0 0.0285341
GW 72 1 0.925 -1.75 0 1.075 -2.1 0 0.0285341
GW 73 1 9.425 2.1 0 9.575 1.75 0 0.0285341
GW 74 1 9.425 -2.1 0 9.575 -1.75 0 0.0285341
GW 75 1 8.1375 1.145 -0.6 8.4375 0.78 -0.6 0.0285341
GW 76 1 8.1375 -1.145 0.6 8.4375 -0.78 0.6 0.0285341
GW 77 1 4.00625 0.19 1.2 3.70625 -0.19 1.2 0.0285341
GW 78 1 6.81875 0.19 1.2 6.51875 -0.19 1.2 0.0285341
GW 79 1 3.70625 0.19 -1.2 4.00625 -0.19 -1.2 0.0285341
GW 80 1 6.51875 0.19 -1.2 6.81875 -0.19 -1.2 0.0285341
GW 81 1 2.075 -0.78 -0.6 2.375 -1.145 -0.6 0.0285341
GW 82 1 2.075 0.78 0.6 2.375 1.145 0.6 0.0285341
GW 83 1 10.5 2.1 0 10.5 3.5 0 0.0285341
GW 84 1 10.5 -2.1 0 10.5 -3.5 0 0.0285341
GW 85 1 0 -2.1 0 0 -3.5 0 0.0285341
GW 86 1 0 2.1 0 0 3.5 0 0.0285341
GW 87 3 10.5 -1.4 0 10.5 1.4 0 0.225
GW 88 7 0 0 0 9 0 0 0.5
GW 89 19 14.75 12.33 0 14.75 -12.33 0 0.1875
GW 90 19 25.02 12.19 0 25.02 -12.19 0 0.1875
GW 91 19 37.27 12.05 0 37.27 -12.05 0 0.1875
GW 94 19 51.52 11.93 0 51.52 -11.93 0 0.1875
GW 92 51 -27.76 33.96 0 -27.76 -33.96 0 0.1875
GW 93 21 0 13.88 -1.125 0 -13.88 -1.125 0.1875
GW 95 3 0 -33.57 0 0 -33.57 -3 0.1875
GW 96 3 0 33.57 0 0 33.57 -3 0.1875
GW 98 3 10.5 -13.62 0 10.5 -13.62 -3 0.1875
GW 99 3 10.5 13.62 0 10.5 13.62 -3 0.1875
GW 125 49 0 33.57 -3 0 -33.57 -3 0.217
GW 126 21 10.5 -13.62 -3 10.5 13.62 -3 0.217
GS 0 0 0.0254 ' All in in.
GE 0
EK
LD 5 0 0 0 2.49e7 0
EX 0 87 2 0 1 0
GN -1
FR 0 1 0 0 207 0

As noted in my post above, my aluminum curved inside moulding isnt flat bar.

http://img259.imageshack.us/img259/3318/curvedaluminsidemouldin.jpg

As measured with my digital micrometer, its .75" wide and the metal is .06" thick. The crown measures .2 inches high when laid on a surface crown up.

My question is, should I use .75" by .06 diameter in the wire equivalency calculator or .75" by .2" ?

Ill probably be laying 2 pieces on top of each other and bolting/riveting them together for a very strong channel 6 reflector. That would basically make it an oblong tube .75" by .4". Hmm, using a equivalency diameter of .6" doesnt do anything for more gain on channel 6 than a .375" dia rod, but at least it would be sturdier.

Punch some numbers into the fol. Spread Sheet...I think you'll see
that the thickness has only a minor effect in the calculation:
http://photos.imageevent.com/holl_ands/files/hidden/Round%20Equivalency%20of%20Flat%20Element%20Sizes%20-%202Sep2010.xls

Ill probably be laying 2 pieces on top of each other and bolting/riveting them together for a very strong channel 6 reflector. That would basically make it an oblong tube .75" by .4".

This problem is treated in "Physical Design of Yagi Antennas" by Dave Leeson. See chapter 9. For an oval cross-section with perpendicular widths a and b, Leeson gives the equivalent radius as 0.25(a+b). He also gives a general formula for an arbitrary cross-section, but I think an oval is close enough for your geometry.

Brian

For an oval cross-section with perpendicular widths a and b, Leeson gives the equivalent radius as 0.25(a+b).
Sounds good, thanks. :)

But do you think in real life, using a bar of the same equivalent diameter as a rod would increase the SWR ? In some ways, that does make logical sense, as the RF waves would have to travel a more convoluted path over the metal bar.

But do you think in real life, using a bar of the same equivalent diameter as a rod would increase the SWR ?

No. The impedance would be the same so the SWR would be the same.

Brian