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17cm would be approx 451Mhz by http://www.qsl.net/kd4sai/quad1.html quad calculator for the driver element. Have you ever tried a 7 element like from the calculator. the frequency range you mentioned are for a 400Mhz center, so Im wondering how you calculated 17cm?

I used www.tvfool.com to list channels in my area, took the real frequencies used google to list the real channel frequencies, and with the calculator my average should be 13cm per side.

Use the driver element, the 17cm per side is based on 547MHz as the center frequency from the calculator though the center frequency from the frequency range in post #46 is 400MHz. If you know the frequency of the specific station frequency you really want, you could use the calculator for that channel, and see what all comes in.

I have a larger outdoor antenna, wanted to create a portable antenna, so I charted the channels I get, and with tvfool.com and google I came up with the average frequency for my stations, and will use the biquad with the calculator and see what happens, still in the process of building it :)

still would like to know what frequency he selected for his antenna, and how he came up with the measurements.

I wonder if a 7 element cubical biquad was ever done before? Would be interesting to see the results.
 

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hkaye's 17 cm is for bi-quad antenna, which is completely different than the cubical quads antenna the calculator you posted is about.
a cubical quad well its driver element alone is a nothing more than 1/2 of the biquad or a quad on its own, given the frequency to ft or inches should be the same for the driver element itself, I calculated 13cm per side for 592 if I remember my notes, which is the center of what I am aiming for. I have the biquad built, and a channel test on the center station worked well. Going to menards to pick up pvc piping. my design is for a magnet mount for non motion automobiles. I wish I had a biquad calculator, but Im going on a hunch the driver element measurements are on target for the target frequency, then I just need to see if the antenna has enough bandwidth. any more on calculators, or if you have a better program that will calculate dimensions for this frequency for a biquad would be most helpful.
 

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or if you have a better program that will calculate dimensions for this frequency for a biquad would be most helpful.
4nec2 has quad model examples in the models/Equations directory. Use the Rescale feature in 4nec2 to your desired frequency and then tweak away.

http://home.ict.nl/~arivoors/
 

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FYI: User <florida_ham> wondered how well his 144-MHz Cubical Quad antenna would work for DTV reception,
so I modeled the dimensions given in the "simpleton" article, as well as different dimensions in on-line calculators
and ran some very wideband frequency plots:
http://www.digitalhome.ca/forum/showthread.php?t=125684

It was a very narrow band antenna, just barely adequate in the 2-m Ham Band, exhibiting extremely
high SWR and mediocre Raw Gain elsewhere. Even if rescaled for Hi-VHF or UHF, it would remain
mediocre for only one (Hi-VHF) or a few (UHF) channels. Hence, I relegated it to the "Not-For-TV" folder:
http://imageevent.com/holl_ands/notfortv
If the length of the Spiral is doubled, it should increase Gain by about 2.5 dBi, at the expense of bandwidth.

PS: K6STI analyzed something he called a "Cubical Quad" for the FM Band, which could be simply rescaled
to the Hi-VHF (half the size) or UHF Bands (about 1/6 the size). It provided good SWR and F/B Ratio with
about 5.9-7.8 dBi Gain. HOWEVER, it uses a Square, Tapered, SPIRAL driver and hence is a Circularly Polarized
(Square) HELICAL type antenna:
http://www.ham-radio.com/k6sti/cpquad.htm
If the Tapered Spiral continues, doubling the length of the antenna, the Gain should increase by about 2.5 dB,
although modeling should be used to determine the impact on bandwidth.....
 

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Discussion Starter #8
4nec2 has quad model examples in the models/Equations directory. Use the Rescale feature in 4nec2 to your desired frequency and then tweak away.

http://home.ict.nl/~arivoors/
Hi 300ohm,
Found the nec program, did not understand what file is for a biquad file to use. Found one from http://www.lecad.fs.uni-lj.si/~leon/other/wlan/biquad/index.html Changed the frequency to 589Mhz, The program said it rescaled. Have no clue on how to tell it Im using 10 gage wire, and no clue on what to do to find how long each side should be. Looks like a nice program, but looks lit it does why more then what I need it to, All I wanted was to find a calculator, or something less complex, to help find how long the sides of a biquad would need to be to have a center frequency of 589MHz.

Can anyone give me a hand on how to set this up, or if someone is more use to this program, can you please let me know how long per side to make this for 589mhz as its center frequency PLEASE!
 

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The program said it rescaled. Have no clue on how to tell it Im using 10 gage wire, and no clue on what to do to find how long each side should be.
By clicking on a wire in Geometry Edit, it will turn red to indicate thats the selected wire, and you can change the wire size there one wire at a time. It will also show you the length of the wire. Remember to save after changing.
 

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UHF Bi-Quad Multi-Diamond Antenna with NO and with 9 Reflector Rods:

Analysis and 4nec2 files for UHF Bi-Quad (DIMENSIONS per khaye post) can now be found here:
http://imageevent.com/holl_ands/multidiamond

In the build directions, khaye described all Diamond Sides as being 17 cm (6.7-in) long, which is a
good trade-off of the Raw Gain curve vs SWR for the NEW UHF Band (Ch14-51) using Reflector
Rods. In the NO Reflector configuration, the high SWR on Ch14 could be improved using about
10-percent longer side lengths: 18.7-cm (7.4-in).

For best coverage of the OLD UHF Band, optimum size would be 16.3-cm (6.4-in) per side,
shifting indicated performance at 770 up to 806 MHz.

khaye assumed a Feedpoint Gap of 2-cm (0.78-in). However, the metal-to-metal gap on
the screw-type balun he used is much less. I assumed the infinitesimally smaller value of 0.75-in,
and may or may not do some additional runs to see the effect of different Gap sizes....
or leave it as an exercise for the 4nec2 student.....

=======================================
In 4nec2 files khaye posted, Outer Lengths=17.5-cm at 45-deg and Inner Lengths=16.8-cm at 47.4-deg
with a Feedpoint Gap=2-cm (0.78-in). The performance with these dimensions was slightly WORSE
than when they were all equal, so I didn't post any results for this "fictious" antenna.
=======================================

UHF Bi-Quad Raw Gain and SWR (300-ohms) with NO Reflector:




UHF Bi-Quad Raw Gain with 9 Reflector Rods (SWR under 2.0 up to 728 MHz):
 

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Discussion Starter #11
Thanks, I borrowed the input file below changed the frequency to 589MHz and saw the wire dimensions in the geometry edit did not change and is still for wifi, The wire size is in mm, but I am using standard 10 gage, can't figure out how to remove the reflector. not sure if its the SP SC entries.


CM NEC Input File Biquad for 2439 MHz, Pow 20020608 |
CM All data in wavelengths. Scaled to meters with GS |
CM --------------------------[ http://pow.za.net/ ]--'
CE
GW 1 1 0.6392126 0 0.03389764 0.6392126 0.87843307 0.87843307 0.02905512
GW 2 1 0.6392126 0.87843307 0.87843307 0.6392126 1.75686614 0 0.02905512
GW 2 1 0.6392126 0 -0.0338976 0.6392126 0.87843307 -0.8784331 0.02905512
GW 3 1 0.6392126 0.87843307 -0.8784331 0.6392126 1.75686614 0 0.02905512
GW 3 1 0.6392126 0 0.03389764 0.6392126 -0.8784331 0.87843307 0.02905512
GW 4 1 0.6392126 -0.8784331 0.87843307 0.6392126 -1.7568661 0 0.02905512
GW 4 1 0.6392126 0 -0.0338976 0.6392126 -0.8784331 -0.8784331 0.02905512
GW 5 1 0.6392126 -0.8784331 -0.8784331 0.6392126 -1.7568661 0 0.02905512
GW 9 1 0.6392126 0 -0.0338976 0.6392126 0 0.03389764 0.02905512
SP 0 1 0 -0.0738 -0.0615 0 0.0738 -0.0615
SC 0 -1 0 0.0738 0.0615 0 0
SP 0 1 0 -0.0738 0.0615 0 0.0738 0.0615
SC 0 -1 0.02829 0.0738 0.0615 0 0
SP 0 1 0 -0.0738 -0.0615 0.02829 -0.0738 -0.0615
SC 0 -1 0.02829 0.0738 -0.0615 0 0
GS 0 0 0.0254 ' All in in.
GE 0
EK
EX 0 9 1 0 1 0
GN -1
FR 0 1 0 0 589 0
RP 0 73 73 1001 -90. 90. 5. 5. 10000.
 

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Discussion Starter #12 (Edited)
Well here is luck that the 13cm is the right measurements to center the frequency close to 590mhz


this is the first build, with 13cm sides. The back support is 1/2 pvc with electrical tape to make it look more pleasant, the bottom has 3/4inch pvc to allow 1 inch magnets, that I did not get time to order from ebay, I tried this forum last week, but posts didn't make it and got splintered to its own section, mislabled. Still need to replace the screws and washers, as they come off too easy, for this weekend, and I don't think Ill have time to construct a 2nd since this post is a Thursday. I didn't have enough time to learn this nec program, all I needed was a measurement to better center the antenna.

If I figure this nec program out, or get help with better measurement, I try again, and use 1/4 PVC instead for a slimmer design. This is intended for a table top / top of a stationary vehicle with magnets in the bottom. At times my wife goes to these craft things, and I recently got a deal on 7inch portable digital TV and needed a better antenna than the original stick antenna that comes with the TV, so I don't get too board when my wife enjoys her crafts.
 

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can't figure out how to remove the reflector. not sure if its the SP SC entries.
Yes, its the SP and SC cards.

From the main screen, select Settings > NEC Editor and delete those lines and save.


That frame is just sooooo much overkill for that antenna, I dont where to begin.
 

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Discussion Starter #14 (Edited)
I tried my Modification of 13mm per side, and found out it works really well.

I was also surprised I was able to obtain a PBS on channel real 8 which is in the VHF High, a channel that I thought was outside my targeted channels. I guess I was being overly critical with the measurements for TV.

Ill be changing the back support for 1/4 pvc to slim down the project. As I figured one of the screws loosened and fell off, due to the wire size of 10 gage, will have to see about a fix for that.

The Attached coax was a 3ft quad shielded that I had laying around, Will be attaching a 6 to 12ft cheep coax to it, to keep the cable short and thin for the 7inch portable TV, It should not put much loss into it. Just need it more flexible and less cumbersome for portability.

This design is still much more portable then a 2 to 4 bay folded antenna like on youtube coat hanger antenna, But still puts a small bit of gain then the included telescoping stick from the tv manufacturer.
 

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Ill be changing the back support for 1/4 pvc to slim down the project. As I figured one of the screws loosened and fell off, due to the wire size of 10 gage, will have to see about a fix for that.
Really all you need for indoor support on that antenna is a fiberglass electric fence rod (about $1.29) stuck into a relatively heavy/broad base (enough to keep it from tipping over). Copper flattens easily, and you could flatten the connection points and drill small holes and use small brass bolts and washers to attach the balun. :)

Just need it more flexible and less cumbersome for portability.
For utmost in portability, you could build a foldable SBGH. It would fit in your pocket. :p

http://www.digitalhome.ca/forum/showthread.php?t=97216&highlight=foldable
 

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Discussion Starter #16
Really all you need for indoor support on that antenna is a fiberglass electric fence rod (about $1.29) stuck into a relatively heavy/broad base (enough to keep it from tipping over). Copper flattens easily, and you could flatten the connection points and drill small holes and use small brass bolts and washers to attach the balun. :)


For utmost in portability, you could build a foldable SBGH. It would fit in your pocket. :p

http://www.digitalhome.ca/forum/showthread.php?t=97216&highlight=foldable
Ok now you got me thinking, how would you make a fold-able SBGH or a foldable bi-quad I am familiar with the GH design sbgh300ohmplanzl5.jpg one thing is I would like to stay away from wood frame. Have not worked with fiberglass electrical fence rod, Ill check when I go to menards, I am assuming it would be used for the actual antenna itself, and not a support frame.

The original idea was to use a single antenna that has the ability to be tossed into the back of a truck without being broke, be placed on the top of the truck (with magnets), but also portable enough for a table or floor, does not stand out like a sore thumb.

As in switching to the GH design style, I do like the size of the bi-quad more compact style it may not have the gain of a GH but its not too tall / wide and easily carry from place to place by grabbing the top quad, and store in the truck, when not in use. I am not crazy about the 1/2 inch pvc support I used but it was the first try, my wife has another "pirl party" this weekend that I will be tagging along with. The support is a bit too thick but it will withstand abuse if something is placed ontop of it.

I am actually nicely surprised at the signal increase in comparison to the retractable stick that came with the TV. I was impressed that the bi-quad was able to get in VHF high, There are only 2 stations within that band, and I was not expecting to achieve coverage, The main use is portability, with a TV that has 2hr battery supply if no mains are available.

I may use the SBGH design for in house only that does not need to be mobile. I can see using it just like the bay style in a more of a stationary setting. So at this time Im going to stick with the 13CM sides bi-quad style, I wanted to get some nice 1'inch round magnets from e-bay for the bottom, at the time I was thinking of only using 2 pvc to stand up with, but then decided to use 4 as in the photo.
 

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Have not worked with fiberglass electrical fence rod, Ill check when I go to menards, I am assuming it would be used for the actual antenna itself, and not a support frame.
No, FOR the support frame as its non conducting. Just a single straight piece stuck in a base that wont tip over. Then just wire tie the antenna to it. For holding the feed point in place, just use a piece of plexiglass, with small brass bolts for connectors. :p
 

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Discussion Starter #18
Just read the fold-able antenna, great for camping, I can see that perfectly. Thats a little too portable for what I had in mind, for this project. More in the order of low profile, pre-assembled, protected from being tossed in the truck, able not to break if items may be placed on top of, and ready to go. Still have to go to menards and check into the size of the fiberglass rod's, and if there are connectors for them, or other means to secure them together, similar to my first attempt.

Btw it was my wife who requested the black electrical tape around the white pvc pipe, to make it more eye pleasing.
 

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MOBILE ANTENNA:

Here are some photos of Bob_K's Roll-Up DBGH Antenna:
http://photos.imageevent.com/holl_ands/files/hidden//Bob_K - Rollup DBGH1.jpg
http://photos.imageevent.com/holl_ands/files/hidden//Bob_K - Rollup DBGH2.jpg
Same principal could be used for a large number of other antennas, simply copy the dimensions.
You could also lay out another Roll-Up for the Reflector Elements....and perhaps a take-a-part PVC frame.

Note that for modeling purposes, 3/4-inch Metallized Tape is equivalent to round 0.4-inch O.D. elements:
http://www.digitalhome.ca/forum/showthread.php?p=1145329
http://www.digitalhome.ca/forum/showthread.php?p=1093615
 

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Btw it was my wife who requested the black electrical tape around the white pvc pipe, to make it more eye pleasing.
99 cent black spray paint on the frame would have been much easier. :p
 
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