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post #31 of 57 Old 01-03-2009, 06:29 PM
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High-performance Hi-VHF Antenna designs for use in the ATTIC.

I've been using (free) 4nec2 antenna modeling software for about a month now
and decided to analyze several Zig-Zag LPA (Log Periodic Array) designs.
I first heard about Zig-Zag Log Periodic Arrays in a magazine
article....but only kept my notes. (About 1966-67??? Anyone still have a copy???).

Back then, I constructed a Stacked Zig-Zag FM Band antenna in my parent's attic
while on spring break. I remember it was a dramatic improvement over a
twin-lead Folded Dipole, but not quite enough to pick up my favorite distant JAZZ
station I only picked up from campus location.
[This was LONG before the "smooth jazz" craze took over....And today, thank you
San Diego State Univ's KSDS-FM (88.3) for finally "graduating" to full power status.]

===================================
Zig-Zag LPAs and other "Frequency Independent" antennas date back to 1958+
when computers first modeled antennas. FI antennas used periodic structures and
symmetrical/mirrored construction techniques for extended frequency response:
http://www.ece.illinois.edu/about/hi.../photos.html#2
http://www.ece.illinois.edu/about/history/timeline.html

The (first?) Patent for a Zig-Zag Antenna was one of several Frequency Independent
Antennas developed at the Univ. of Illinois (mostly with U.S. Govt funding) filed by
Ray Du Hamel and Fred Ore in March 1958 & granted Feb 1965:
http://www.freepatentsonline.com/3079602.html

Patent for a foldable Zig-Zag Antennas was filed by J.W Carr in 1961 & granted Oct 1965:
http://www.freepatentsonline.com/3213457.html
Hmmmm, folds up like a baby-gate.....

Patent for other configurations was filed by P.E. Mayes in 1966 & granted Nov 1967:
http://www.freepatentsonline.com/3355740.html

FREE registration is required to see the *.pdf files with the figures.
Consult a patent attorney if you are into that sort of thing.....

====================================
A comparative analysis of various Zig-Zag Log Periodic Array construction
techniques can be found on W4RNL's (L.B. Cebik, RIP) website:
http://www.cebik.com/content/radio.html
FREE registration required. Search for "zig-zag" to find four part article.

=================================
To start with, I analyze the antennas found in "Wideband Antennas for the TV DXer",
an old article by ZS6BTE (no longer available on QSL.net), including a 14-Element
LPDA (Log Periodic Dipole Array) for Hi-VHF Band and a 45-Element (YIKES!!!!)
LPDA for the UHF Band...and beyond....

The 100-inch (8.33 feet) long 14-Element LPDA was the "standard" for comparison
purposes, although some viewers might want a shorter antenna (on my "to-do" list).

All of the antennas described here were OPTIMIZED using the 4nec2 modeling program,
although under the constraint of trying to match the LPDA's size and geometry.

Stacked Zig-Zag had 1-2 dB lower gain than the LPDA...but is REAL SIMPLE to
construct using a roll of your favorite electrical wire, BARE shielded braid cable
or relatively inexpensive copper tubing used to plumb refrigerator ice makers.

Wedge Zig-Zag was within 1 dB of the LPDA and I'm still working on a Boom-Wedge
Zig-Zag that should close the difference. The angle between the two Zig-Zags is
treated as (yet another) variable to see Gain, F/B and SWR tradeoffs.

Results are posted in a folder on my favorite HI-REZ image hosting website:
http://imageevent.com/holl_ands/zigzaglpa
If you have problems, such as "thumbnail" images being too big, let me know....

The 4nec2 simulation files and a couple figures are posted below.

 

Hi_VHF_14el_LPDA_ZS6BTE.nec.txt 2.6220703125k . file

 

Hi-VHF_14-el_ZigZag_Stacked_RG59_Zsep3_25.nec.txt 4.369140625k . file

 

Hi-VHF_14-el_ZigZag_Wedge Phi=18__Bare_RG59.nec.txt 3.4375k . file
LL
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Attached Files
File Type: txt Hi-VHF_14-el_ZigZag_Wedge Phi=18__Bare_RG59.nec.txt (3.4 KB, 205 views)
File Type: txt Hi-VHF_14-el_ZigZag_Stacked_RG59_Zsep3_25.nec.txt (4.4 KB, 178 views)
File Type: txt Hi_VHF_14el_LPDA_ZS6BTE.nec.txt (2.6 KB, 193 views)
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post #32 of 57 Old 01-05-2009, 09:54 PM
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holl_ands,

I think I understand the stacked construction in that each element of the zig zag is in parallel planes seperated by a distance but I must be missing something about the Wedge design. Are these elements in planes that are not parallel? Do they nearly share an axis? Could you elaborate further?

Quote:


Stacked Zig-Zag had 1-2 dB lower gain than the LPDA...but is REAL SIMPLE to
construct using a roll of your favorite electrical wire, BARE shielded braid cable
or relatively inexpensive copper tubing used to plumb refrigerator ice makers.

Wedge Zig-Zag was within 1 dB of the LPDA and I'm still working on a Boom-Wedge
Zig-Zag that should close the difference. The angle between the two Zig-Zags is
treated as (yet another) variable to see Gain, F/B and SWR tradeoffs.

I look forward to also seeing your Boom-Wedge Zig-Zag design too.
Do you think these design would also be transferable to an outdoor antenna as well?

Thanks,
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post #33 of 57 Old 01-06-2009, 02:29 AM
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The imageevent link above contains images for Wedge Zig-Zags, but the small angle makes it confusing.

Here is a Wedge Zig-Zag with a 55-degree angle between the two Zig-Zags (opens like a book).
I captured a display with the antenna surrounded by the shape of it's antenna pattern.
I only picked the 55-degree example because it's easier to see the structure....at wide
angles the Gain is good, but the F/B Ratio isn't so hot.

I also attached a perspective look at a Boom Wedge Zig-Zag, which simply has an
additional wire (or rod or tube) down the center of each Zig-Zag....
which requires a bunch of solder joints.

Whether someone can build these for outdoor use depends on their construction skills
and whether they insist on sticking it on a rotator....within reach for a skilled HAM
antenna constructor who knows how to calculate wind loading....perhaps not
for your typical handyman....who should consider attic, garage overhead or roof-top.

Their strongest point is how easy it is to simply string some bare wire or bare shield coax
(no cable jacket) from point-to-point on some sort of (wood or PVC) frame.

Size of the high performance 14-element Hi-VHF antenna is about 100-inches (8.33 feet) long,
33-inches wide and 3.25-inches for Stacked and roughly 10 to 18-inches high for Wedges,
so all versions are relatively low profile.

Soon, I'll provide analysis for shorter, lower gain Zig-Zags.....
LL
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post #34 of 57 Old 01-08-2009, 07:51 PM
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Thanks I understand now and look forward to your results.

I am quite attracted to this design concept because the zig zag elements will be relatively simple to contruct for a DIY.

I am personally interested in what it would take in extra zig zags added onto the larger end to extend this concept down to include FM bands and specifically down to Channel 6 (WPVI) at +8.4 NM (dB) as I will have potentially 5 more HI-VHF channels from this noise margin down to Channel 12 at -4.5 NM. as I am located regonally to both Philadelphia and Baltimore markets see Zip 17603.

Others may be interested too in a more generic but directional 5-13 VHF antenna design if as some guess the FCC stops or discourages TV broadcast on the lower channels 2-4 in the future.

Do you know where can I find more information on the Log Periodic element progression?
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post #35 of 57 Old 01-10-2009, 09:39 PM
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Quote:
Originally Posted by fm234n5 View Post

Thanks I understand now and look forward to your results.

I am quite attracted to this design concept because the zig zag elements will be relatively simple to construct for a DIY.

I am personally interested in what it would take in extra zig zags added onto the larger end to extend this concept down to include FM bands and specifically down to Channel 6 (WPVI) at +8.4 NM (dB) as I will have potentially 5 more HI-VHF channels from this noise margin down to Channel 12 at -4.5 NM. as I am located regonally to both Philadelphia and Baltimore markets see Zip 17603.

Others may be interested too in a more generic but directional 5-13 VHF antenna design if as some guess the FCC stops or discourages TV broadcast on the lower channels 2-4 in the future.

Do you know where can I find more information on the Log Periodic element progression?

Lo-VHF Zig-Zags are on my TO-DO list...and I'll be looking at Lo/Hi-VHF as well.
One approach is to use a Hi-VHF Z-Z as the front end of a Lo-VHF Z-Z,
but the transition section may need some tweaking....

I have heard of NO proposals to vacate Ch2-4, but HAVE heard of proposals
to expand FM into Ch6 and perhaps also Ch5....

FYI: According to RabbitEars.Info after Feb, there will be only 42
Full Power Lo-VHF stations left:
Ch2: 7ea, Ch3: 7ea, Ch4: 3ea, Ch5: 16ea and Ch6: 9ea.
Of course, that does not include Low Power, Repeater, etc.
Ch6 would make the most sense to relieve overcrowding in the FM Band....
But don't expect anything to happen anytime soooonnnnn.....

================================
A Log Periodic Array consists of multiple "Cells", where the size of each "Cell" shrinks
by a fixed fraction in each subsequent cell. In the Zig-Zags, I chose to "match" the
dimensions of a conventional LPDA (Log Periodic Dipole Array), where the
apexes of the Stacked Zig-Zag match the ends of the LPDA dipoles elements.
To compare antennas with the same "boom-length", I projected this geometry
up and down to form the Wedge Zig-Zag (although I could have alternatively
matched along the plane of each Wedge, resulting in a different, shorter design).

So I'm simply using the geometry of a standard LPDA design (without all of the
complex metal construction):
http://www.physics.adelaide.edu.au/~...g-Periodic.pdf

Here is a simple LPDA calculator spread sheet:
http://www.ycars.org/EFRA/Module%20C/LOGPERIO3.xls
Leave SIGMA field blank to let the program calculate the optimum value.

LPCAD3.1 is more complex...but also much more powerful:
http://wb0dgf.com/
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post #36 of 57 Old 01-11-2009, 09:43 AM
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A regular LPDA tends to work at both the design frequencies and 3 times the design frequencies (which is how VHF LPDAs get both high and low VHF). Probably the same is true of the LPZA.
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post #37 of 57 Old 01-11-2009, 01:27 PM
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holl_ands, this is great information.

I'm thinking I'll prototype a 5-13 VHF (76-345 Mhtz) LP ZigZag boomed and eventually wedged. I don't understand yet the impedance issues but I'll work thru those later. If I stay near 8.28 feet and .8 Tau a regular LPDA would have 11 elements.

Quote:
Originally Posted by holl_ands View Post

I have heard of NO proposals to vacate Ch2-4, but HAVE heard of proposals
to expand FM into Ch6 and perhaps also Ch5....

If this happens then extending the antenna coverage down to 76 Mhtz. Ch. 5 makes more sense for those who like music. Channels 2-3 just get to big physically and I don't need them.

Quote:
Originally Posted by nybbler View Post

A regular LPDA tends to work at both the design frequencies and 3 times the design frequencies (which is how VHF LPDAs get both high and low VHF). Probably the same is true of the LPZA.

Since my plan will cover 76-345, I'll sample the results up into the UHF bands as well. logically a regular VHF only design starting at Ch7 (174 x 3 = 522) would add little to UHF before Ch 23.
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post #38 of 57 Old 01-18-2009, 10:16 PM
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I can't find a local source for RG59 so it is starting to make sense to use local RG6 instead - any problems aside from cost for this plan?
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post #39 of 57 Old 01-19-2009, 02:45 AM
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Bigger is better (see swept wire size charts) and small wire sizes (e.g. AWG10)
have less gain and higher SWR. Bare, non-insulated wire or braid should be used
to minimize loss. We only care about the SKIN EFFECT and NOT what is actually
INSIDE the braid....

At my local Home Depot in San Diego, I found BARE AWG8 copper wire 69cents/ft,
and 1/4-in O.D. copper tubing for refrigerators ($32/50-ft = 64cents/ft).
Either of these would work just fine.....but are rather stiff to work with....

Most RG-6 I've seen has a very fragile wire shield (usually not even braided)
around a mylar aluminum foil which I don't think will survive when you try
to strip off the outer insulation:
So avoid most typical RG-6 (and some RG-59) cables which have partial 60% shield
(plus perhaps a second 30% shield) with aluminum mylar foil:
http://www.cablewholesale.com/specs/...10x4-01150.htm
Click on the specs pdf...

RG-6 with 95% coverage, copper braided shield might be okay....if you can find any.

RG-58 and RG-59 (like these for 10-40cents/ft incl shipping) usually come with
a rugged BRAIDED shield after you strip off the outer insulation:
http://www.cablewholesale.com/specs/...10x1-01150.htm
http://www.cablewholesale.com/specs/...3-091th-20.htm
Note the spec says they have a copper braid with 95% coverage...what we're looking for.
[Note: Since I have an old roll of RG-58 in the garage, I haven't inspected any
of these cables....call direct to ask for pictures & details....]

Although most CAT cable is unshielded or only comes with a mylar foil shield, if you can find
BRAIDED SHIELDED CAT cable, it might also be suitable....check the construction....

Any Radio Shack and most Home Depots should carry RG-58 or RG-59, preferably
by the foot so you can see the construction:
http://www.homedepot.com/webapp/wcs/...10000003+90012
Note the BRAID in Home Depot RG-59 coax (about 25-30cents/ft in short lengths).

I haven't cut into these (27cents/ft) Component Video cables, but they appear to be RG-59:
http://shop.willyselectronics.com/br...fm/4,1713.html
[Yes, our local Willy's has very good prices....]

Avoid the fol. which claims to be RG-59 cable, but it's more like cheap RG-6,
using partial aluminum braid with only 60% coverage and an aluminum mylar foil,
neither of which is in the RG-59 MIL-SPEC.
http://www.cablewholesale.com/specs/...10x2-01150.htm

Unfortunately the RG numbers don't mean a specific construction as they
were intended, so you have to either physically inspect the construction or
carefully check the specs.

From time to time, I also find 1/4-inch BARE braided grounding straps
in our local electronic supply houses (anything FAT and conductive will work):
http://www.allspectrum.com/store/pro...oducts_id=2663

BTW: In the VHF Band (unlike UHF), copper vs aluminum conductivity
differences are negligible....any ol' metal will work....
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post #40 of 57 Old 01-21-2009, 09:24 PM
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Quote:
Originally Posted by holl_ands View Post

... At my local Home Depot in San Diego, I found BARE AWG8 copper wire 69cents/ft, .... and 1/4-in O.D. copper tubing for refrigerators ($32/50-ft = 64cents/ft).
....

My Home Depot did not have any braided RG-59 on a spool or in the box available.

I picked up 1 foot of RG-6 "Quad shielded" at $.31/ft. to be able to cut it apart and verify the construction: Under the outer cover the outer braid was quite loose, open and fragil. Inside that was an aluminum coated mylar and then more loose wire braid over the dielectric. Unless this can be taped or tied together at regular intervals without destroying the "skin effect" and/or it remains in an attic area where it will not be touched, I will probably not be using this material.

Home Depot did have AWG8 copper wire at $.63/ft. (I bought 10 feet to use for wiskers in another UHF bow tie as I gave my first one away.)

They also had 1/4 OD copper refrigerator icemaker tubing at ~$13.6/20 feet which is about $.68/ft.

Given the closeness in cost and the larger swept wire size the icemaker tubing is looking more attractive to me.

If anyone already has a short piece of icemaker tubing and can test cold bend it 320 degrees around a small sewing spool to see it stays together and doesn't crack. I'd love to know the results.
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post #41 of 57 Old 01-22-2009, 01:27 AM
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Probably not....pretend you're a plumber and get a TORCH to heat it up....
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post #42 of 57 Old 01-22-2009, 07:19 AM
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Icemaker tubing can be bent very easily (I've got a bunch I removed from an icemaker -- it works for fishing wires through crawl spaces, too), and it doesn't crack even if you bend it double, but if you try to bend it that tightly it will probably crease.
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post #43 of 57 Old 02-01-2009, 02:30 AM
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I did some 4nec2 simulation runs with and without insulation on RG-59 for Hi-VHF Wedge Zig-Zag.
It didn't make ANY difference....so no need to strip off the insulation.

However, at UHF frequencies, insulation can be a problem....and perhaps other VHF antennas....
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post #44 of 57 Old 02-03-2009, 02:26 PM
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Quote:
Originally Posted by holl_ands View Post

I did some 4nec2 simulation runs with and without insulation on RG-59 for Hi-VHF Wedge Zig-Zag.
It didn't make ANY difference....so no need to strip off the insulation.

However, at UHF frequencies, insulation can be a problem....and perhaps other VHF antennas....

So if people do use simple coax to make a zig zag, what should they do at the "points" to keep them sharp enough? Should they score thru the inside of insulation at those areas to get a sharper bend ?
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post #45 of 57 Old 02-03-2009, 06:23 PM
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Me thinks you worry too much?????
Don't sweat details much smaller than a wavelength.
Won't affect Gain, although may be a very small perturbation to SWR.

Log Periodics are Frequency Independent mostly due to the repeating structures,
not so much the SHAPE of those structures. Hence they can be rods (LPDA),
trapezoidal wire teeth, solid rectangles (Silver Sensor), zig-zag wire teeth,
solid triangles, et. al. (Refer to patents in Post#31 for examples)
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post #46 of 57 Old 03-07-2009, 09:43 PM
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I just went through similar hassles trying to come up with a decent antenna for HD FM. Let's be blunt: almost every indoor VHF antenna on the market is junk. Commercial manufacturers are far more interested in appearance than performance, so if you want something better than a simple dipole/rabbit ears, you're forced to DIY.

If you want something compact for VHF-Lo, a square loop, fed at the bottom center for horizontal polarization, is probably your easiest option. It'll have a width of four feet, vs. eight feet for rabbit ears, and theoretically will perform slightly better, although impedance mismatch will probably erase any improvement unless you can build your own balun. (A square loop will have an impedance around 120 ohms - not exactly a standard value.)

Luckily VHF-Lo will be rare post-transition. VHF-Hi antennas can be much smaller, and I'm surprised there's nothing decent on the market yet. I built a 2-bay UHF with a wide reflector which works reasonably well at VHF-Hi also. If you don't need UHF, a 3-element Yagi and a cubic quad are both reasonable indoor VHF-Hi designs, especially if you're interested in one particular channel.

Most TV stations use horizontal polarization, but a few use circular, so if you're lucky a circularly polarized antenna might be an option. They aren't terribly hard to build: just mount two dipoles at right angles and connect them with a 1/4-wavelength feedline. If the transmission is circularly polarized, the antenna will be directional, so you may have to turn it around so the "correct" side is facing the transmitter. The antenna should also work with horizontally polarized signals but won't be any better than rabbit ears.

Oh; as for my HD FM quest, I made a circularly polarized antenna from two cheap twinlead dipoles I picked up for $2.49 each at Fry's. Circular polarization is much more common in FM than TV, so that ended up working better than anything else I'd tried.
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post #47 of 57 Old 05-27-2009, 03:55 PM
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Yagi antennas are reportedly limited in bandwidth--but I wanted to know by how much.
Commercial "Single Channel" Yagi's are typically described as covering only one channel
in the Lo-VHF (Ch2-6) Band, 2-3 channels in the Hi-VHF (Ch7-13) Band and perhaps
5-12 channels in the UHF Band (fewer for low channels, more for higher):
http://www.hdtvprimer.com/ANTENNAS/WadeSCY.html
http://www.blondertongue.com/media/p...eption/bty.pdf

Using K7MEM's Javascript calculator (with DL6WU spacings) and 4nec2 antenna simulator,
I calculated the bandwidth for several 8-Element Yagi antennas (nearly 100-in boom length).
Performance plots for a Ch8-10 Yagi (suitable for San Diego), as well as a Ch11-13 Yagi
(the rest of the band) are presented here:
http://imageevent.com/holl_ands/yagis

Above the limited, three channel passband, the response took a steep dive, due to not only
a drop off in Raw Gain, but also a steep increase in SWR. Below the three channel passband,
the response was steadily decreasing at such a rate that it is likely to cause reception
problems. But YMVM.....if you're lucky...

Net Gain and Front-To-Rear Ratio Plots compare the Hi-VHF 8-Element Yagi's to the
14-Element LPDA (see post #31)....plus plots for Stacked Zig-Zag and Wedge Zig-Zag:
http://imageevent.com/holl_ands/zigzaglpa

The 8-Element Yagis had "good" (~15-20 dB) F/R Ratio performance on the
center channel, but dropped to only "moderate" (~12 dB) on the adjacent channels.

In comparison, the 14-Element LPDA had 2 dB lower Net Gain than the Yagi's max Net Gain,
but it maintained a flat Net Gain response across the ENTIRE Hi-VHF band. It also had
"exceptional" (20++ dB) F/R Ratio performance across the entire Hi-VHF Band.
The very low SWR is also advantageous to avoid the ADDITIONAL EVM (Error Vector Magnitude)
loss due to signal reflections up and down a long coax run (minimal for Preamp users):
http://www.tvantenna.tv/papers/PFactorsV.pdf
http://www.tvantenna.tv/papers/dtv%2...prediction.pdf

Note that I intentionally chose (not quite) 100-inch boom length because it the about
the SAME as a Winegard YA-1713, the 14-Element LPDA and 14-Element Zig-Zag designs.

CONCLUSION: Unless you only need to receive 3 adjacent channels, these Yagi designs
won't provide adequate performance throughout the Hi-VHF band.


Challenge to Yagi Designers: Come up with a much wider bandwidth design.....
LL
LL
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post #48 of 57 Old 05-29-2009, 09:23 AM
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holl_ands,

How about a folded dipole like the one I made?

https://www.avsforum.com/avs-vb/showt...2#post13785312

I also used K7MEM's guide and built this one for CH9. I only targeted ~6dB of gain since I am close to the towers. Does the lower gain widen the bandwidth? I'd like this antenna to still work at CH13.

David
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post #49 of 57 Old 05-29-2009, 02:57 PM
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Can you provide accurate dimensions so I don't have to guestimate off the photos???

Folded Dipoles are next on my list of things to model....incl. Bandwidth vs Element size.
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post #50 of 57 Old 05-29-2009, 08:49 PM
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Quote:
Originally Posted by holl_ands View Post

Can you provide accurate dimensions so I don't have to guestimate off the photos???

Folded Dipoles are next on my list of things to model....incl. Bandwidth vs Element size.

Here is a screen shot of what I have...

http://i301.photobucket.com/albums/n...-P/Antenna.jpg

David
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post #51 of 57 Old 05-30-2009, 01:04 PM
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It only provides good Net Gain on Ch8 and Ch9, although Raw Gain extends through Ch10.
Raw Gain is falling across Ch7. SWR is excessive on Ch10-13.

Here are detailed 4nec2 results for your 4-Element Folded Dipole Yagi (vs "Regular" 4-Element Yagi):
http://imageevent.com/holl_ands/yagis/4elyagi
LL
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post #52 of 57 Old 05-30-2009, 08:05 PM
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holl_ands,

Thanks for that! bit disappointing, though. Looks like I'll be back to figuring out something else in a month or two.

Question, though... It looks like it falls off like a ton of bricks above the design frequency, but if I design it for CH13, do I still have decent gain at CH7? An additional plus might be that the antenna gets even smaller. I really like this design since it is rugged enough for long term outdoor use and has an end launch from the pole.

David
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post #53 of 57 Old 07-03-2009, 03:34 PM
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More Hi-VHF Antennas Analyzed...and Tested:

I analyzed and found "optimum" sizes for Hi-VHF Folded Dipole, Square Loop and Circular Loops:
http://imageevent.com/holl_ands/yagis
I also analyzed K6STI's 5-Element Yagi which is very compact and provides exceptional F/B Ratio.

Surprise!!! Folded Dipole (1/2-in Pipe) received CH7, 9, 11 and 13 from Mt Wilson (70-miles in L.A.):
http://imageevent.com/holl_ands/smart
It beat out the DX Antennas DTA-5000 and RCA ANT2000 Smart Antennas...but overall winner
was YA-1713.

In the attic (with lots and lots of metal in the way) the big YA-1713 and even bigger Stacked Zig-Zag
could only receive CH7 and CH9, but we're still searching for better attic locations...after it cools off some...
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post #54 of 57 Old 07-04-2009, 08:37 AM
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Anybody looked at loaded antennas, particularly for VHF low? I have a center-loaded folded dipole I'm using for VHF (low and high). But there don't seem to be too many available; mine's a neutered Terk HDTVo.
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post #55 of 57 Old 08-06-2009, 11:12 PM
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For a Log periodic zigzag can you have each zigzag connected to a metal boom like done with LPDA's? (I am playing around with an 8 element prototype for 180 - 692 MHz after building a decent aluminum LPDA version for my TV.) I am attracted to the zigzag geometry (with booms) because the resulting triangles are much stronger than cantilevered dipole elements. I also like the idea of having one continuous piece of aluminum or copper form the zigzags.
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post #56 of 57 Old 08-07-2009, 09:03 AM
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Zig-Zag with boom has perhaps 1 dB more Gain than no boom per Cebik's analysis:
http://www.cebik.com/
Free site registration, search for "Zig-Zag".

I analyzed Hi-VHF Zig-Zag LPA's with and without Booms vs LPDA's here:
www.imageevent.com/holl_ands
I didn't particularly care for the Boom version (presuming braided coax), since each
and every crossing point would need to be soldered, which seems like a lot of extra work
for only a silly, little 1 dB Gain....but if you're up to it, go for it....
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post #57 of 57 Old 08-07-2009, 06:43 PM
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Great! I am thinking of design for outdoor using aluminum where the booms support the zigzags. The connections to the booms would be rivets.
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