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thanks Holl_Ands, points taken! so much to learn, so little time....

I made several mods to the wire order, thats why my numbering scheme was off, but I didnt go back to correct it!

I wanted to see if this was better than the dual, and apparently it is quite a bit worse, in terms of gain, AGT, complexity, :confused:

but you definately improved it, thanks
 

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FYI: Fol. Cebik article compares 1 vs 3 segment SOURCE wires, as well as split SOURCE at an Apex,
which is relevant to the Rhombic's AGT problem:
http://guests.antennex.com/rooms/w4rnl/col0708/amod125.html
FREE registration required. A 3 segment SOURCE was better than 1 segment at an Apex.
[Does NOT say 1 segment shouldn't be used....YMMV....]

For Autosegment(21) the SOURCE wire was 3 segments, but this forced the other wires to have
an extremely large number of segments (nearly 5000!!!), so I didn't wait around for the results....

It would be worthwhile to rerun the above Autoseg(9) file and simply change to a 3-segment SOURCE.
[Don't forget to also change the EX card to point to the middle segment.]

TA-DA!!!! AGT=1.0 (-0 dB) with Rsrc=0.0016.
Yup, the Raw Gain curve drops by about 1 dB, although the shape is somewhat different,
ranging from 14.3 at low freq to 17.5 at higher freqs.

So Quad Rhomboid is WORSE than Dual Rhomboid.....
 

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So in this case more is less...:eek: I wonder why all the excitement about it then!

cebik also discusses blunting the resistor ends in his 3-4 part rhombic series evaluation, and I believe smaller diameter wire helps a little with gain, I think he said its better..

i didnt find any improvement for this on the quad
 

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Hi there. Great stuff in here. Now I will have to get new PC soon. My old one is ,,,,,well ,,,,tired ,,just like me :) OK back to antenna desing. That round one just few pages back remind me antenna we build decades ago. It was square desing, shunt-excited antenna. Can't remeber size of it,but was prety small.
4"-5"??Problem with that antrenna is induction of loop that shunt creates. That is offset by capacitor. But what i remember it worked fine even without it. Behind few(4"-5") was reflector apr.1/2" bigger in size(4 1/2"-5 1/2"). I will try to find some more details. For it size that antenna was prety good.:D
 

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Hi again. I just run in another antenna from Fracarro, model Sigma. Unlike PU-4 at begining of this thread this one is Yagi 17 dBi, but what is interesting directors look very similar as "Shorted Ultra Wide Band Bowtie " presented here by 300 ohm. Also i found another antenna from Fracarro. Similar desing as Sigma 6HD just that one was HI VHF/UHF and behind reflector had ,,,,NARODS" ???? but I lost it :eek:) I will try to find it again :D If you go to Fracarro web-site details of directors are right on page 1
 

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Fracarro describes Sigma as being a "Loop Yagi", in which case the crossbars would be made of
insulating material. OTAH, if the crossbars ARE conductive, directors are Shorted Bowtie Loops (SBL).
In either case, the most important element, the driven element, remains a fat Dipole, so SBL
advantages would be lost.

Aerial Catalog *.pdf is dated Feb2010 and they say "Available from May"...so not for sale at this time:
http://www.fracarro.com/international/index.php?option=com_docman&task=cat_view&gid=88&&Itemid=262
See front cover and pg24-25.
 

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"Shorted Ultra Wide Band Bowtie " presented here by 300 ohm.
That I got from a google John Carr book for UWB antennas for 2 to 10 Ghz. IIRC, it was a couple of Japanese guys that patented the design. We just refined it for UHF TV use. The best of the simple to do bunch is the X560. :p
 

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VU-120XR chopped up

A Radio Shack VU-120XR chopped up, leaving only the first three pairs of elements, makes a pretty decent LPDA VHF-Hi antenna.

3D pattern at 195 mhz:


Raw Gain:


SWR:


The NEC file:

CM VU-120 : Radio Shack VU-120XR, converted with 4nec2 on 11-Nov-08 23:22
CM Cut all but 3 front pairs of vhf elements
CM Auto Segmentation = 21, AGT = 1.0 at 195mhz
CE
GW 10 27 -27.031457 1.73217594 0 -6.0242913 38.1307043 0 0.15
GW 11 27 -27.031457 -1.7322319 0 -6.0242913 -38.13076 0 0.15
GW 12 23 -14.170039 1.72875783 0 4.2165355 33.3371255 0 0.15
GW 13 23 -14.170039 -1.7288138 0 4.2165355 -33.337182 0 0.15
GW 14 19 0 1.72454405 0 15.1110236 27.454098 0 0.15
GW 15 19 0 -1.7246 0 15.1110236 -27.454154 0 0.15
GW 16 15 -11.035787 11.499972 -3 -11.035787 -11.500028 -3 0.15
GW 23 3 0 1.72454405 0 0 -1.7246 0 0.18
GW 24 5 -27.031457 1.73217594 0 -20.600748 1.68107e-3 -0.5 0.05094856
GW 25 5 -20.600748 1.68107e-3 -0.5 -14.170039 -1.7288138 0 0.05094856
GW 26 5 -14.170039 1.72875783 0 -7.0850196 2.07892e-3 -0.5 0.05094856
GW 27 5 -7.0850196 2.07892e-3 -0.5 0 -1.7246 0 0.05094856
GW 28 5 -27.031457 -1.7322319 0 -20.600748 -1.737e-3 0.5 0.05094856
GW 29 5 -20.600748 -1.737e-3 0.5 -14.170039 1.72875783 0 0.05094856
GW 30 5 -14.170039 -1.7288138 0 -7.0850196 -2.1349e-3 0.5 0.05094856
GW 31 5 -7.0850196 -2.1349e-3 0.5 0 1.72454405 0 0.05094856
GS 0 0 0.0254 ' All in in.
GE 0
EK
EX 0 23 2 0 -1 0
LD 5 10 0 0 24900000
GN -1
FR 0 1 0 0 174 0
RP 0 1 10 1510 90 0 0 20 0 0
 

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Real-world experience backs that up! Having to wrestle a full-up 120 in the attic was getting exasperating, so I left off the back end the last time I moved it. RF 7 and 9 from DC still work fine at 45 miles and 1-edge path.
 

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Yeah, the Net Gain is only a tiny bit less than original, if at all. The VU-160XR looks to have the same 3 pairs of vhf-hi elements as the VU-120XR. The VU-190XR and VU-210XR look to be using the first four pairs of elements for vhf-hi.
Of course, chopping off the back end isnt good for all LPDA antennas. Modeling shows that if I clip off the back end of my CM1221, it would significantly impact vhf-hi performance. But it does look like the Radio Shack VU series can be successfully chopped.
 

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RCA ANT115 (passive) and ANT585 (amplified) Rabbit Ears both performed poorly in this test:
http://www.walb.com/Global/story.asp?s=8346127&clienttype=printable
https://licensing.fcc.gov/cdbs/CDBS...?appn=101317948&qnum=5200&copynum=1&exhcnum=1

Whereas R-S 15-1864 came in right at 0 dBd (2 dBi) for VHF in Kerry Cozad's Antenna Range Tests:
[The VU-Graph presentation shows the R-S antenna....NOT the RCA "Loop" mislabeled on the chart.]
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=170117&d=1268674946
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=170118&d=1268674946
http://www.avsforum.com/avs-vb/showthread.php?p=18315283
 

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VHF Batwing antenna as a reflector

Are any of you guys familiar with the Batwing antenna? To me, it looks like it could be used as a reflector for a GH thus making a UHF/VHF combo. (even if the antenna had separate UHF and VHF connections)

Here is a link too a site for the batwing:
http://www.qsl.net/kd2bd/batwing.html

I tried to model it in 4nec2 but I did something wrong so I'm still trying to get it to work properly. (I realize that this is not the place to get help with 4nec2 so I won't be asking)
 

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As mentioned in the article, Cebik did a NEC modeling study of the Batwing:
http://www.cebik.com/content/radio.html [FREE Registration Required]

If you "Search This Thread" for individual posts, you'll find several like this 4nec2 model:
http://www.digitalhome.ca/forum/showthread.php?p=1004148

A single Batwing has just over 5 dBi Gain and can be readily stacked for more.
Separation between the two halfs controls the desired impedance.

But it requires a lot of work to solder all of those connections, which could
just as easily have gone into a UHF/Hi-VHF M4 Multi-Bay build with higher Gain.....
And most solder connections don't hold up when exposed to the elements....

Good luck trying to get an SBGH with Batwing Reflector to work....the SBGH
will INTERACT against the Batwing....
 

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X0936 SGH (Simplified Gray Hoverman)

I started out trying to model the bi-quad shown in posting #2 of http://www.digitalhome.ca/forum/showthread.php?t=124542
I began with a bowtie, and added 1 more degree of reflection to complete the bi-quad. It wasn't until part-way through the modelling that I realized that I had left the gap at the top and bottom. I tried closing the ends, but that made the gain drop and the SWR go up, so I left the gap in there. I had originally intended to call the design "BBQ" (Broken Bi-Quad), but I noticed that it was actually 2/3rds of an SBGH. I figure that SGH (Simplified Gray Hoverman) is a more accurate name.

Without a reflector the channel 14 to 51 gain ranged from 7 to just under 10 db with SWR from 1.5 to 3. With reflectors, that jumps to 10.5 to 13 db, with SWR from 1.03 to 2.21. While this not in the same league as the super-duper DBGH versions, it's a very respectable gain for its size. Model and 4NEC2 output follows...

Code:
CM Simplified Gray-Hoverman experimental model
CE
SY wire_rad=0.075
SY base_side=10.5
SY base_ref_len=10.5
SY base_ref_x=-6
SY scale=1.0
SY side=base_side*scale
SY ref_len=base_ref_len*scale
SY ref_x=base_ref_x*scale
SY yangle=40
SY SIN_Y=sin(yangle)
SY COS_Y=cos(yangle)
GW   4    8     0     0.5     0       0       side*COS_Y      side*SIN_Y     wire_rad
GW      5       8       0       0.5     side*SIN_Y*2    0       side*COS_Y side*SIN_Y      wire_rad
GW      6       8       ref_x   ref_len 2.75    ref_x   0.5     2.75    wire_rad
GW      7       8       ref_x   ref_len 5.5     ref_x   0.5     5.5     wire_rad
GW      8       8       ref_x   ref_len 8.25    ref_x   0.5     8.25    wire_rad
GW      9       8       ref_x   ref_len 11      ref_x   0.5     11      wire_rad
GW      10      8       ref_x   ref_len 13.75   ref_x   0.5     13.75   wire_rad
GX      20      011
GW      1       1       0       -0.5    0       0       0.5     0       wire_rad
GW      2       8       ref_x   -ref_len        0       ref_x   -0.5    0  wire_rad
GW      3       8       ref_x   ref_len 0       ref_x   0.5     0       wire_rad
GS      0       0       0.0254          ' All in in.
GE      0
EK
EX      0       1       1       0       1       0
GN      -1
FR      0       1       0       0       590     0
RP 0 1 37 1501 90. 0. 0. 10. 0. 0.
 

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Before the Stealth-Hawk....before the Centipede....before the Gray-Hoverman....
even before the Hoverman....there was the Grand-Daddy of them all:

The Chireix Zig-Zag Antenna, see 1928 Canadian Cross-Patent CA285256A:
http://v3.espacenet.com/publication...C=A&FT=D&date=19281204&DB=EPODOC&locale=en_EP
Alternative source:
http://brevets-patents.ic.gc.ca/opi...uery=Chireix&start=1&num=50&type=basic_search
Note that Chireix's Patent also described the Curtain Quad Antenna, but left out the
double Zig-Zag configuration that was used for high HF and (by late 30's) VHF frequencies.

Later, Henri-Georges illustrated alternative feedlines and how to "fatten-up" the elements:
http://v3.espacenet.com/publication...C=A&FT=D&date=19510223&DB=EPODOC&locale=en_EP
[Curiously, they didn't cite earlier Patents.....alas, I couldn't locate Chireix's original French Patent.]

A Two-Square Chireix Zig-Zag Antenna is what you have re-invented....
http://imageevent.com/holl_ands/chireix

More Chireix and Chireix-Mesny (with Reflector Curtain) info:
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?reload=true&arnumber=1670129&isnumber=34990
http://books.google.com/books?id=lQ...lt&resnum=7#v=onepage&q=chireix mesny&f=false
 

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Would anyone be willing to run a model for me? I'm still using CocoaNec (can't get my brain to figure out the program you're using - but someday I will). CocoaNec does output a card deck that hopefully will run on your modeling programs.

The antenna is a modified biquad with a reflector. I've been playing with the numbers for awhile and I have an antenna that

1) has a gain of about 8.2 dbi across the UHF channels
2) has an impedance of 200 ohms
3) has a very low SWR across the UHF spectrum

Yes the impedance is really 200 ohms. I'm shooting for 165 ohms to use with a 2.2:1 balun.

Hopefully I typed these numbers in correctly. Let me know if you have any questions.

Code:
CM uhf biquad with reflector	
CE -------------
GW  1 13  0.000000 -0.015240 8.000000  0.000000  0.015240 8.000000 0.000645
GW  2 13  0.000000 -0.015240 8.000000  0.000000 -0.015240 8.015240 0.003175
GW  3 13  0.000000 -0.015240 8.015240  0.000000 -0.116673 8.116673 0.003175
GW  4 13  0.000000 -0.116673 8.116673  0.000000  0.000000 8.233345 0.003175
GW  5 13  0.000000  0.000000 8.233345  0.000000  0.116673 8.116673 0.003175
GW  6 13  0.000000  0.116673 8.116673  0.000000  0.015240 8.015240 0.003175
GW  7 13  0.000000  0.015240 8.015240  0.000000  0.015240 8.000000 0.003175
GW  8 13  0.000000  0.015240 8.000000  0.000000  0.015240 7.984760 0.003175
GW  9 13  0.000000  0.015240 7.984760  0.000000  0.116673 7.883327 0.003175
GW 10 13  0.000000  0.116673 7.883327  0.000000  0.000000 7.766655 0.003175
GW 11 13  0.000000  0.000000 7.766655  0.000000 -0.116673 7.883327 0.003175
GW 12 13  0.000000 -0.116673 7.883327  0.000000 -0.015240 7.984760 0.003175
GW 13 13  0.000000 -0.015240 7.984760  0.000000 -0.015240 8.000000 0.003175
GW 14 13 -0.165000 -0.165000 8.235714 -0.165000  0.165000 8.235714 0.009525
GW 15 13 -0.165000 -0.165000 8.141429 -0.165000  0.165000 8.141429 0.009525
GW 16 13 -0.165000 -0.165000 8.047143 -0.165000  0.165000 8.047143 0.009525
GW 17 13 -0.165000 -0.165000 7.952857 -0.165000  0.165000 7.952857 0.009525
GW 18 13 -0.165000 -0.165000 7.858571 -0.165000  0.165000 7.858571 0.009525
GW 19 13 -0.165000 -0.165000 7.764286 -0.165000  0.165000 7.764286 0.009525
GE 0
FR 0 1 0 0 550.0 0.0
EX 0 1 7 1 1.0 0.0
XQ
RP 0 1 360 1000 90 0 0 1 5.000E+03
RP 0 360 1 1000 -90 0 1 0 5.000E+03
RP 0 91 120 1001 0 0 2 3 5.00E+03
XQ
EN
 

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Im confused as to the output you want ?

Do you want the runs based 165 ohm input impedance ?

Where did you get a 2.2:1 balun ?
 
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