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It's amazing stuff, and much of it is over my head. Yes, you'll see simulations/comparisons of existing antenna's, and also much improved upon designs, plus a lot of new custom creations.

Filters? Are you referring to lc filters? For the designs I've been looking at on Holl's site, I don't recall seeing any filters, but I have used them long ago to tune in my antenna's (mostly to compensate for my errors). Pc's and antenna software weren't around then, and it was all trial and error if you tried to modify existing designs w/out all the fancy analyzers.
 

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Can a notch filter do anything for the below readings (20 foot antenna height)?

KSMI ch 30.1 nm: 45.8 sig power: -45.1
KDCU ch 31.1 nm: 64.0 sig power: -26.9

If the signal strength of the two stations are anywhere near what TV Fool predicts you should have no trouble decoding KSMI. It is only 18 dB weaker.

I've attached a couple of spectrum analyzer images of station situations I have here. The first images shows KTLN on 47 sandwiched in between KQCA on 46 and KSPX on 48. KTLN is about 20 db weaker than KQCA and 30 dB weaker than KSPX. I never have any trouble decoding KTLN as longer as it doesn't drop below the minimum strength that can be decoded.

The second image shows KUVS on 18 next to KOFY on 19. KOFY is hard to decode because of adjacent channel interference from KUVS which is 40 dB stronger. You might think that a very sharp notch filter on KUVS would eliminate the problem. It wouldn't. Notice that on the low side of KUVS you see the signal trail off into the top end of 17 starting at 40 dB down. That same amount of signal is present on the high side trailing off into 19. That destroys the SNR at the low end of KOFY making it impossible to decode. Even if you had a perfect channel 18 notch filter it wouldn't get rid of the signal that bleeds into the adjacent channels.
 

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Hi Cal,

Nice! I could spend days testing, playing, and learning with that frequency analyzer!

Thanks for the info, unfortunately for me, my signal levels are low. I'm 70 miles away in Salina, so I wouldn't have a chance of receiving ksmi, although I have no problem receiving kdcu at 100%, and kmtw at ~80% from atop Indian Rock Park. I didn't even see a hint of ksmi though. Adjacent 31 must be killin' it.

Looks like DavidEC may stand a chance of getting what he wants. Dave, let us know if those filters work for you.
 

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Good evening everyone. After several years of inactivity I find reason to reactivate and cruise back through here. Long story short, my girlfriend is having major difficulties getting any sort of UHF reception in her current apartment. With football season upon us, this is cause for major concern. As an upcoming weekend project we decided it would be fun to try building an UHF antenna rather than buying yet another off the shelf model and almost invariably returning it for ineffectiveness. I'm looking for suggestions of which kind to try building; having read through a half dozen plans and designs a little expert guidance in the right direction wouldn't hurt.

Presently we both live in the flat part of California and are only about a mile and half apart. While my place is surrounded by groves of large trees, there are no buildings over one story between myself and most of the transmission towers about 20 miles away to the NW. In my case, a directional antenna pointed WSW picks those up just fine along with VHF & UHF channels broadcast from even further away to the west. Her place, however, is on the first floor of a two-story building, and her line of sight to the important towers 20 miles to the NW is blocked by several two+ story commercial buildings just across the street. We've tried several omnidirectional antennas from various stores without much success. They find VHF channels, but no UHF. Signal amps/boosters help some with VHF strength but aren't helping with UHF. I've taken my antenna over and spent a few hours searching the sky only to find it performs even worse than the omnidirectional antennas in her location.

All this has led me to believe she needs something fairly sizable and omnidirectional. What type I'm not quite sure. It does need to be indoor, however, for practical reasons. We can set it up to face most of the towers to the NW through a sliding glass door to help minimize interference. Here's the TVFool report for good measure. KCRA, KOVR, and KTXL are the key channels. With that, any suggestions?
 

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; said:
Her place, however, is on the first floor of a two-story building, and her line of sight to the important towers 20 miles to the NW is blocked by several two+ story commercial buildings just across the street.
You're probably tilting at a windmill The UHF signals are likely getting blocked by the buildings and simply aren't making it to or into her apartment. Watch the games at your place.

Omni antennas are the poorest possible choice. A very directional antenna would offer the best hope for such an impaired location.
 

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A few suggestions to consider, listed in increasing SIZE and complexity. You might want to start with a NO Reflector version...you might get lucky...and if not add one of the various Reflector Options:

UHF Hourglass, which only requires stringing some Wire (size not very important) on a DIY Frame or Metal/Aluminized Tape on Cardboard:
http://imageevent.com/holl_ands/loops/uhfhourglassloop

UHF Quad-Trapezoid enhancement to Hourglass:
http://imageevent.com/holl_ands/loops/uhfquadtrapezoidloop

UHF FF4 or M4 4-Bay Bowtie, may use AWG12, AWG10 or Metal/Aluminized Tape on Cardboard:
http://imageevent.com/holl_ands/multibay/4bay
http://imageevent.com/holl_ands/multibay/4bayrefl
 

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Watching the games with her is the fallback option in case nothing seems to work. It will be plenty of fun until we want to watch different games on one TV. Until then it's simply a fun challenge to see if we can make something work. I know there are some UHF signals bouncing around in there, as we've picked up some before by aiming indoor antennas in odd locations (e.g. right angle to the distant towers, off at the ground, etc.). Only a few minutes ago it dawned on me her exterior is stucco, and usually that means metal grids. That should mean a fair shot at improvement just by positioning the antenna by her sliding glass door, which also happens to face NW towards the desired towers.

In regards to specific antennas:

  • I have some old, spare antennas leftover from previous wireless base stations (the joys of working IT), these are worth a shot, I'm assuming?
  • On the UHF hourglass loop, the center strands are just leads to the coax connector, correct?
  • On the UHF quad-trapezoid loop, are the top and bottom connected or is there supposed to be a gap there? The diagrams show a small gap and it's not clear if that's intentional.
  • Would reception on a bowtie be degraded significantly by enclosing it in canvas, fabric, or something else? When discussing this last weekend the estrogen took over and she started thinking about how to conceal antennas with fabric enclosures, or maybe even a canvas painting over a wood frame that would enclose the antenna. Overall she was most impressed with a bowtie design, even though it rankles her aesthetic sense.
 

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Stucco is a killer due to the chicken-wire behind it.

Low-E glass is a killer, clear glass isn't, so check the slider.

WiFi equipment and stuff is useless, wrong frequency.

Fabric and the like is transparent to RF energy, so she can decorate away to her heart's content.
 

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Small GAP at the top and bottom of the Quad-Trapezoid Antenna provides significantly MORE Gain than if they were connected together....and since the Gain drops as the GAP is increased, I assumed it would be only about 1/4-in wide, the smallest that I think can be fabricated without inadvertently touching. If desired a NON-Conductive material can be used to interconnect and hence maintain the Gap.

The Center Wire (marked with a Red Circle) represents where the two wires of a (300-to-75-ohm) Balun Transformer need to be connected and is the SAME for all three Antenna types. The output of the Balun is a 75-ohm Coax Connector that goes to the HDTV's input.

Fol. diagram explicitly shows the Balun connections:
http://rickviola.com/images/McLappConnectRJV021012.jpg
You can find other build examples in the fol. thread:
http://www.digitalhome.ca/forum/showthread.php?t=100137

Although the author probably intended to depict the M4 (9.5x9.0) size, he inadvertently ended up with a (10.5x9.0) instead, due to the extra 1-in connecting the Feedline to the Whiskers. In the (Whisker Length x Bowtie Separation) nomenclature, the Whisker Length is measured from the where the Feedline crosses the Whisker to the end of the Whisker. And I would recommend the M4 (10x9.5) size instead of M4 (9.5x9.0) if additional Gain is needed on the lower channels at the expense of the higher channels. All dimensions are described in the above posted 4nec2 Files.

And here is an example Grey-Hoverman explicity showing the Balun connection.....using Copper-Foil Tape on Cardboard:
http://macgyverisms.wonderhowto.com...ength-more-free-broadcast-tv-channels-0146459
 

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A bowtie antenna is a 2D representation of a 3D biconical antenna. So, wouldn't a biconical work better (be more unidirectional) then a bowtie? And why not a 4 bay biconical array?
It just strikes me as funny that 2,4,8, and even 16 bay bowtie arrays are so ultra directional and no one is making them 3D biconical and thus, I would think, much more unidirectional.
Do we loose anything making them cones instead of flat?
 

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A Bowtie improves SWR Bandwidth compared to a Dipole....a VERY FAT Dipole is needed to even come CLOSE to what a Bowtie does.
The FATTER Bicone (aka "Caged Dipole") may improve SWR Bandwidth....it does NOT significantly improve Raw Gain.

Expanding the "Fatness" into another Dimension (X-Coordinate) only provides a SMALL improvement in Raw Gain and the already sufficient SWR provided by the Bowtie (esp. when used with a Reflector which further improves SWR)....and chews up a LOT more metal....increasing cost and wind resistance.

Which is why you'll very rarely come across them....except in "Calibrated" EMI/EMC Measurement Antennas. The fol. is fairly "typical", with a fairly narrow bandwidth range where SWR is acceptable:
http://schwarzbeck.de/Datenblatt/k9116.pdf
http://schwarzbeck.de/Datenblatt/s9116.pdf

When specifically designed to minimize SWR, they CAN provide a small improvement in performance....just don't expect much more Raw Gain than an equivalent FAT Dipole:
http://glendash.com/Dash_of_EMC/Modeling_Antennas/Modeling_Antennas.htm
 

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Hello All,

Was hoping someone could recommend an antenna configuration given that I am located right in the middle (or pretty close to middle) between two adjacent city transmission towers. I'd like to get signals from both towers.

I want to either get:

A) one DB4 antenna without a reflector (I'm thinking this may have one tower's signal interfere with the other)

-OR-

B) two back-to-back DB4s separated by a reflector (thinking that the reflector will prevent interference from each tower's signal )

Attached is my TV Fool Radar signature/details and an illustration detailing my two options.

Thanks.
 

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I made a bow-tie antenna like this


It's about 12 or 13 inches wide. I can pick up some channels but not all the channels I know are out there. I live about 50 miles south of Chicago and I'm getting about half of the channels. If I were to build the same thing but larger, maybe 2 feet wings instead of the 1 foot wings, would this increase reception? The antenna works pretty good, but it's hit or miss depending on which side the reflector is on (signal side or opposite). Does a larger antenna guarantee better reception for such a long distance?
 

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I made a bow-tie antenna like this

It's about 12 or 13 inches wide. I can pick up some channels but not all the channels I know are out there. I live about 50 miles south of Chicago and I'm getting about half of the channels. If I were to build the same thing but larger, maybe 2 feet wings instead of the 1 foot wings, would this increase reception? The antenna works pretty good, but it's hit or miss depending on which side the reflector is on (signal side or opposite). Does a larger antenna guarantee better reception for such a long distance?
This another antenna thread question, not about building a UHF antenna. Please start a new thread following the sticky at the top including your TV Fool report and then maybe we can help you.
 

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MODELING is the only way to know what works and what doesn't.....and those very WIDE Feedlines may also be a problem, since the Transmission Line Impedance is MUCH different than thin wires. Unless you actually MODEL a proposed design and then OPTIMIZE the Dimensions, you should pick a design that is KNOWN to work.....

For example, when forming a Bowtie using SOLID FLAT TRIANGLES, it turns out that 17-in Total Width is OPTIMUM for UHF BAND for assumed Tip Vertical Separation = 12-in, whereas when forming a Bowtie using a WIRE OUTLINE INDENTED BOWTIE, Total Width of only 10.5-in Total Width is Optimum for assumed Tine Separation = 5-in.

BTW: Simply increasing the Total Width will usually improve Gain on the Lowest Channels.....at the expense of the Higher Channels. But without modeling it, I have NO CLUE whether it is already TOO LARGE or TOO SMALL...or whether the SWR is even in the right ballpark...
 

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Greeting all, another newbie here.

I have only moderate success with my store-bought attic mounted antenna, so I'm looking at the various DIY ideas.

I'm considering something different than the preassembled antennas I see in this forum. What if I were to string copper from stud to stud, creating the horizontal Vs employed in most designs? In my attic (upper crawlspace actually, not intended to be used for storage and filled with blown cellulose) I could create something that is ridiculously large. The more wire there is to capture the signal, the better...right? I'm sure it's never that simple, which is why I'm asking. I understand that the orientation would be fixed, but maybe that's not an issue if it's big enough.

Is uniformity and ratio important in the sizes of the various components? For instance, should the Vs all be a multiple of a particular length with a particular spacing?


Thanks for your thoughts,
Chris
 

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I have only moderate success with my store-bought attic mounted antenna, so I'm looking at the various DIY ideas.

This is another antenna thread. Please read the sticky at the top of this forum and put your location in the title and supply a link to your TV Fool report and start a new thread. You should include exactly what you've done so far; i.e. make/model of your purchased antenna so we know your starting point.
 

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...I have only moderate success with my store-bought attic mounted antenna, so I'm looking at the various DIY ideas.

I'm considering something different than the preassembled antennas I see in this forum. ...
Pre-assembled antennas on a DIY forum??? Where?

Read some of the early pages where we were just starting to figure this all out for answers to your question. As soon as you proposed that you "string copper from stud to stud" it was clear you need a primer on antenna design.

Antenna elements are each designed for a specific function. In a Yagi, some are directors, some are reflectors and one is usually a dipole that's benefitting from the directors and reflectors.

In a bowtie dipole, size determines frequency of maximum gain. Double the size, you halve that frequency. Also, element spacing and polarity are carefully controlled so multiple elements work together to increase antenna gain. Same with reflectors. Element size (wire gauge) is also a factor.

The better approach is as Calaveras suggests; get us some signal strength data (TVFool) and tell us about the antenna you have, where it's mounted, etc. There may be an easy solution.

HAve fun,
Frank
 
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