Questions About Digital TV Antennas

[martys]

I have tried posting a somewhat different post the RF/Ham forum, but I haven't gotten any reasonable/advice/help after several days, so I am taking a new approach, just trying to see if anyone here on this forum can help me learn as much as possible on how to make a DIY good TV antenna. If there is any problem with my latest approach to seeking knowledge, then gods that be, please delete my other topic post.

I need to DIY the smallest possible antenna that will allow me to view clearly some distant TV channels I am interested in.

Here are my the ideas I must pay attention to to achieve this goal and must govern my antenna's DIY design and construction:

1) I need to have a good understanding on how different TV antennas work to make a best choice as a DIY project.

2)Apartment rules demand I optimize a chosen antenna's esthetic footprint. I must not create an eyesore on the only place available for me to install an outside antenna, which must be within the area defined as the interior area of my small balcony.

3)Large, tech-ugly, roof-intended antennas are out of the question. I must create a smallest working design.

3)I can see that Apartment rules have obviously permitted some people to install small satellite TV microwave dishes, and I know I can subscribe to cable TV, but I am not interested in paying for subscription/fee-based TV. Besides, the local cable TV or satellite services do not broadcast at least one of the channels I want to receive and the others are only available buying a "premium" expensive monthly subscription.

4)I want to view some fairly hard to receive TV channels and I want  to view as many free channels  as I can. With a small indoor amplified TV antenna I can already receive well the free local channels I want, but there are 6 channels that are quite more distant that I can't receive well.

5)I am already using a good-quality, LTE-filtered UHF 13-dB antenna pre-amp mounted very close to the antenna I am using now, but this antenna is just a rather hard to find, but small, indoor TV consumer swept-wing looking gizmo that is horizontally polarized and is carefully horizontaly pointed towards the distant channels I want to receive.

6)There are nearby(100-meters away) 5-story buildings in my apt complex. I am on the first floor.  My antenna is therefore oriented to peek just over their top to receive a signal. What may be worse is that that is a large tree just feet away from my balcony that partially obstructs my antenna's point of view. What distant signals I am already able to receive at times(atmospheric conditions permitting) with my existing antenna are most likely due to reflections. I am able to watch all the channels I want..sometimes.


7)The hard to receive channels I am most interested in have broadcast freqs around 600-MHz.

Vertically constructed/mounted BowTie arrays would be too ugly to install on my balcony, so they are out of the question.

9)I have already tried out many small-sized antennas that are good looking, vertically mounted, flat, black plastic enclosed rectangular amplified indoor/outdoor antennas I can find and they all fail to receive the more distant channels I am interested in, although they can receive local channels well.

10)I know it is possible to receive the channels I am interested with rooftop-mounted antennas with amplifiers, but this option is not available to me.
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Ok, that being said, here is my first questions about DBT-T antennas:

Why is it that some horizontally-constructed antenna designs have parasitic elements mounted on their metal boom unconnected while other designs have all the elements driven(except for their reflector elements), that is, why is that some have all driven elements are interconnected by some type of metal strapping hard-wired connections? Which design is best for me to copy?
(I already know that the designs that do not connect parasitic elements are of the log-periodic or Yagi design..but what are the designs called that do connect them? Why are these interconnected element designs a better or worse design choice for me?

[hagster]

See answers inline. My suggestion is that you build a radome for a commercial antenna to make it less of an eyesore.

I need to DIY the smallest possible antenna that will allow me to view clearly some distant TV channels I am interested in.

Here are my the ideas I must pay attention to to achieve this goal and must govern my antenna's DIY design and construction:

1) I need to have a good understanding on how different TV antennas work to choose the best design to optimize as a DIY project.

TV antennas work in the same way as any other antennas. You won't be able to get a 'good' understanding of how they work from a forum post response. If you want to learn about antennas then I can recommend www.antennatheory.com .Worth looking at sections on gain and directivity.

2)Apartment rules demand I optimize a chosen antenna's esthetic footprint. I must not create an eyesore on the only place available for me to install an outside antenna, which is my small balcony.

Can add an RF transparent radome to conceal the antenna?

3)Large, tech-ugly, roof-intended antennas are out of the question. I must create a smallest working design.

Antenna gain is FUNDEMENTALLY linked to its physical size. Small = low gain. You have a choice as to what dimension you want to be big, so it could be say a big flat panel, or a long yagi, or something in-between.

3)I can see that Apartment rules have obviously permitted some people to install small satellite TV microwave dishes, and I know I can subscribe to cable TV, but I am not interested in paying for subscription/fee-based TV.

Define SMALL? Most Sat dishes here are about 50cm

4)I want to view some fairly hard to receive TV channels and I want  to view as many free channels  as I can. With a small indoor amplified TV antenna I can already receive well the free local channels I want, but there are 6 channels that are quite more distant that I can't receive well.

5)I am already using a UHF 13-dB antenna pre-amp mounted very close to the antenna I am using know, which is actually a rather hard to find indoor TV consumer gizmo that is horizontally polarized and is carefully pointed towards the distant channels I want to receive.

Dont confuse the pre-amp with antenna gain. The pre-amp only compensates for cable losses(if the signal to noise from the antenna is poor this will not help). As your TV is probably fairly near the antenna I doubt that it will help much. You need antenna gain that can only be achieved by a larger antenna.

6)There are nearby 5-story buildings in my apt complex. My antenna is therefore oriented to peek just over their top to receive a signal. What may be worse is that that is a large tree just feet away from my balcony that partially obstructs my antenna's point of view.

7)The hard to receive channels I am most interested have broadcast freqs around 600-MHz.

What exact upper and lower frequency bounds do you need?

8)Vertically polarized BowTie arrays would be too ugly to install on my balcony, so there are out of the question.

Could you put it inside a radome?

9)I have already tried out many small-sized antennas that are good looking, vertically mounted, flat, black plastic enclosed rectangular amplified indoor/outdoor antennas I can find and they all fail to receive the more distant channels I am interested in, although they can receive the all local channels well.
These will be designed to be fairly wideband to account for the range of frequencies TV operates on. i.e. not tuned to your 600MHz. The Log-periodic you showed in the other post probably only has about 5-6dBi gain.

10)I know it is possible to receive the channels I am interested with rooftop-mounted antennas with amplifiers, but this option is not available to me.
------------------

Ok, that being said, here is my first question about DBT-T antennas:

Why is it that some horizontally-constructed antenna designs have parasitic elements mounted on their metal boom unconnected while other designs have all the elements driven(except for their directors and reflector elements), that is, why is that some have all driven elements are interconnected by some type of metal strapping hard-wired connections? Which design is best for me to copy?

Difficult to be certain what type of antenna you are talking about. Horizontal is a polarisation not a construction. Some antennas (such as the yagi) use parasitic elements that may or may not be connected to a central boom. Other use an array of similar driven elements to provide gain.

[martys]

Thanks Hagster, I will checkout the link you've posted.

Who can say for sure how many antenna experts there are that peruse this forum?

Building a radome is probably not an option. I don't have room or the knowhow to make something aesthetically good-looking and yet durable and such a thing would probably exaggerate the presence of the concealed antenna within. In some seasons there can be hurricane magnitude winds that would blow any such thing off my balcony and maybe land on someone's head, unless it was mounted so securely and made with the strongest construction design possible.
My balcony extends out from the building only approx 1.2  meters and is only 1 1/2 meters wide.  Anything I use must not extend much outside of its perimeter more than a few inches and thus become a techy eyesore. It must, for the very most part be contained and be modest in appearance, and obviously visible only within the area available of my balcony.

I already have small size, I have maybe enough room to make something bigger, maybe 2 to 3x the existing size.

What I have now working is almost working well most of the time, so some small antenna size/design improvement could mean I can solve my reception problem.

I can not receive at all the distant channels I want without using the quality antenna amp I've installed. It definitely makes it possible for my antenna to work at all.

What I mean by horizontally constructed antennas is that they lie within and are pointed in and are flatly orientated to a horizontal plane, just like a long roof-top horizontally-polarized log-periodic or Yagi.

The small satellite dishes permitted here are at the most, approx 50-cm in diam.

The channels that are the weakest and the ones I am most interested in receiving are centered around 600-MHz, UHF digital channels 37 to 43.

[C]

Need to think of what an antenna amp is
It makes all signals on the input X times larger. It has a max signal limit & min signal limit.
Your TV has a max signal limit & min signal limit
Your TV turner is built to amplify the selected channel and not amplify other channels and has limits on the difference.
The TV tuner also needs to create an output that has signal to noise ratio that will work.
At some point as you increase the antenna gain & antenna amp gain you have the  strong signals to larger then what can be handled and still have the weal signals with too small signal to noise ratio.
To get past this you need an antenna with more gain for weak channel and an antenna with less gain for strong channel.

Need to look at antennas for weak signal and not so good for strong signals.

C

[hagster]

The fact that the amp makes a difference suggests that you are absolutely on the edge of being able to receive the signal. It may have slightly better noise figure than the built in TV amp.

Hence you should be able to get away with an antenna that provides only slightly more gain than the current antenna.

If for example you want say 3dB more gain, this would generally require an antenna that is twice the size.

[martys]

Thanks C. but it seems impossible that an antenna good for weak signals would not also as well amplify the strong.

Hagster, that's what I have been saying over and over, but how who can tell me with electronic RF experience and know how to best make an antenna that is 2x better.

It is most interesting to note that anyone can find on youtube videos made by idiots, morons, hillbillies and other self-proclaimed experts who want tol show how to make the "best" TV antenna ever from egg mixer attachments, paper clips, cardboard, coat hangers, coke cans, fan faces, fractal fantasies, or even from your mother's bra.

The attached photos below show the construction of what I am using now. It is made from just two driven pieces, two mirror-image aluminum stampings (shown by the red and the black in my drawing)separated by a 1/2-in plastic boom and the feedpoint that works at all is connecting to the frontmost shortest elements.

I am using the best 75-ohm coax I can find, not using a balun to match the balanced antenna elements to the 75-ohm coax and I attach the industrial quality ant amp as close as possible to the antenna. This antenna has not been optimized for the small freq. spectrum of channels I am able to receive weakly.

[Ian.M]

Martys' previous topic with a lot more background:
https://www.eevblog.com/forum/rf-microwave/how-to-make-a-good-small-size-diy-dbt-outside-antenna-perplexed-and-pixelated/

Can you post a photo of the balcony, and also one looking in the direction of the transmitter so we can see what you are up against?  Please feel free to photoshop out any visible signs or highly distinctive buildings (but please at least leave the roofline outline) so you don't inadvertently disclose your location.

I hope you mean 'first floor' in the European sense of the floor above the ground floor, not in the US sense of the street level floor.  If you have to conceal the antenna from people walking past at the same level, its *MUCH* harder.

As the antennae is going to be aimed tilted up,  you should be able to keep it entirely within your balcony low enough so its barely visible above the railing if observed from street level.   Painting a roof antennae to blend in with the background using cellulose paints (avoid metallics) may help conceal it.   If the balcony railing is very open, adding a plastic mesh behind the railing cable tied to it may also help concealment.  There are probably other tenants with small children who have already added such meshes to prevent their children causing a hazard by dropping small objects.

Worst case: you may have to get a plastic garden tool storage container large enough to conceal the antenna, either a colour that's non-obtrusive or paint it to blend in, weight the base with paving slabs so it can withstand the winds, and mount the antenna inside it.

The balcony antannae will probably be unsatisfactory for local signals due to its direction and orientation, so you'll probably need a coax switch to change between it and an indoor one.   Its only possible to combine the local and distant signals into a single cable if the multiplexes carrying the desired channels are at well separated frequencies so you can filter out the unwanted signal from each antenna before the combiner to avoid multi-path and destructive interference, or so you can combine them in a frequency selective diplexer.

[martys]

Ian.M  Thanks for your camouflage help!  Many tenants are using 1-in sq. plastic mesh screening to either keep their cats from taking a plunge into their next remaining life, and some use the mesh just to discourage very messy pigeons that insist in making babies on a balcony. However, it is quite easy to see through this mesh.

I am on the second floor, not on the bottom floor which would be called the first floor in the US just above street level.

The antenna I am using now is a the only antenna for TV I am using and works well some to most of the time. Luckily, my balcony easily allows my antenna to face the direction required which is a pointing just slightly upwards(5-10 deg slant) towards a clear-view of the sky just over the unbroken string of 5-story apt buildings approx 100-meters away. The antenna only works best when pointing in the most precise direction that I have taken much time to find.  I attach it to the top of the corrugated metal 6-ft visual barrier(using large strong clothepins) that gives each and every apt balcony a one-sided attempt to provide privacy.  Because it is quite small and lightweight, my antenna is nonetheless quite stably stuck in place(has survived hurricane force winds) and I certainly would be able to make something more sturdy to mount a better antenna that is a tad bigger.

[David Hess]

A bowtie array is still your best bet because of its form factor; any log-periodic style antenna will be even more visually apparent and difficult to conceal.

Instead of using a traditional radome, mask the bowtie array with black fabric like would be done on the front of a speaker enclosure.

[martys]

David Hess: When I look directly up when out on my small balcony, the concrete bottom of an identical balcony floor for the apt upstairs is just 2 1/2 feet above the top of the corrugated barrier of my balcony, each balcony floor is separated by approx 15-ft vertically. This provides some visual shielding of anything placed upon my balcony. I might even be able to attach a longer antenna to the bottom of  the concrete floor of the apt. above, but mounting an antenna so close to concrete is not the greatest idea, likely would also attenuate the TV signal.

I am quite sure that the footprint of a bowtie array would be so much an ostenatious insult to the aesthetic requirements since it would have to stand above the side walls of the balcony to work at all. Besides,when enjoying the priceless pleasure of eating watermelon in the summer on my tiny balcony, who would want to face a risk of being poked in the back by a bowtie element.
Space is at a premium in Europe and the area use overhead of an antenna on the balcony is best placed over the head.

I am also now quite sure that I am catching just a narrow beam of reflected signal, and a bowtie array would be spread out too much vertically to be able to best receive a tiny window of reflected RF TV signal, all the while a horizontal-plane orientated antenna would point directly into and be immersed in the signal coming through this small signal window.

[Ian.M]

Lets see a photo of the corrugated metal barrier with your existing antennae attached to it, from the opposite end of the balcony. + a dimensioned sketch of the balcony 'floorplan' with the arc of swing of any outwards opening doors etc. marked.  That will give us a far better idea of the constraints.   I suspect that an antenna on a magnetic mount  below the top of the 6' barrier right back against the apartment wall will be fairly inconspicuous, especially if the elements are relatively thin and painted to blend in with the wall and the barrier.

You are going to have to spend some time mapping the signal strength and quality with your existing antannae on a longish  stick so your body isn't near enough to significantly interfere,  in a 3D grid over the whole balcony.   Do a rough sweep for good spots, then map the maxima with 10cm resolution as the wavelength is about 50cm.  You'll need a STB that has signal strength and quality bars that update quickly and can be left running, or to borrow a DBT installer's signal meter if you know anyone in the trade.

If there's only one small 'sweet spot' and your antennae's already in it, you are going to be S.O.L. as a larger antenna than the 'sweet spot' will just pick up more noise.   OTOH there may be a better, larger, more stable 'sweet spot' that you haven't previously considered due to it being inconveniently placed for mounting the antenna.

If you know anyone who can provide authorised roof access to any of the five story apartment buildings blocking the line of sight, consider a passive rebroadcast arrangement - a stack of large high gain narrow beam antennas aimed directly at the transmitter, linked by a short low loss cable to a single high gain antenna aimed directly at your apartment.  Its fit and forget as there are no amplifiers so no electrical power is required.

[videobruce]

1. You failed to tell us where exactly you are located. Which means the TV market and the suburb you are in.
2. In miles, how far are the closest and furthest stations?
3. What directions are they from? All in one general direction or are they scattered?
4. What direction does this balcony face?
5. Adding a radome only makes the antenna larger.
6. Are all the stations UHF? (The physical channel number, not the confusing, idiotic old school analog number left over from 10+ years ago)

Lastly, antennas are NOT ugly!!!!! Bite your tongue. 

[rdl]

You should be able to use whatever antenna is needed to receive Television. Or for some reason, does the OTARD rule not apply to you?

https://www.fcc.gov/media/over-air-reception-devices-rule

As directed by Congress in Section 207 of the Telecommunications Act of 1996, the Federal Communications Commission adopted the Over-the-Air Reception Devices (“OTARD”) rule concerning governmental and nongovernmental restrictions on viewers' ability to receive video programming signals from direct broadcast satellites ("DBS"), broadband radio service providers (formerly multichannel multipoint distribution service or MMDS), and television broadcast stations ("TVBS").

The rule (47 C.F.R. Section 1.4000) has been in effect since October 1996, and it prohibits restrictions that impair the installation, maintenance or use of antennas used to receive video programming.  The rule applies to video antennas including direct-to-home satellite dishes that are less than one meter (39.37") in diameter (or of any size in Alaska), TV antennas, and wireless cable antennas.  The rule prohibits most restrictions that: (1) unreasonably delay or prevent installation, maintenance or use; (2) unreasonably increase the cost of installation, maintenance or use; or (3) preclude reception of an acceptable quality signal.

Effective January 22, 1999, the Commission amended the rule so that it also applies to rental property where the renter has an exclusive use area, such as a balcony or patio.

[MarkF]

I bought one of these from Amazon:
   https://www.amazon.com/gp/product/B017JEF126/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1

It works pretty good for me (even indoors) for stations in the 50 mi. away.  At least as well as my old analog VHF/UHF 10 ft. long antenna.

I also have plans I found online for the old style 4 butterfly UHF antenna with element length and spacing dimensions for lower freq. into the VHF band.

[videobruce]

That I might call "ugly".   

One more thing, I would forget about a preamp. Line loss in not a issue here and using one may caoyse a overlad situation from other than TV broadcast.

[martys]

I have by the best hillbilly means I have available, made the best conjecture about the reception sweet spot on my balcony.

Let's assume this: I have already found the best sweet spot that where an antenna could be best placed, and a larger and  greater gain antenna could be best placed there and work better, since this spot is already a location that works well most of the time.

The 1/4 wavelength of 600 MHz for the weakest channel is about 4.98-in and 600-MHz, so also is it the reception freq of most interest.

All TV is digital, all signals are UHF channels.

[Ian.M]

@all:  Martys' country flag does *NOT* match his apartment's location.  Its not even the same continent.  See other topic for details (linked from reply #6 above).

[martys]

Special thanks to MarkF, for allowing me to accidentally discover another ant design on Amazon that maybe will work for me even better!

Interesting, found this one on Amazon, almost identical in design as my existing gizmo antenna but:
This gizmo uses a folded dipole to feed an internal ant amp, allowing a 4:1 balun match for 75-ohm ant amp build into it.

 My antenna has no rear reflector and no dipole and I am attaching unmatched coax to the front most elements. The one attached has to work better.

What if I attempted to remake the same style of swept-wing elements made out of metal stampings, but instead cut all the elements of of a piece of galvanized roofing sheet, so all the elements would be of an optimal length at the freq. of my interest, 600 MHz?
I would keep my existing ant amp but feed it through a coax fabricated 4:1 balun immediately under the ant  and then I achieve a perfect impedance match from ant to amp.

I looked at the other gizmo antenna promising me the world, but can't find any reason theoretically why it should work well or even begin to match the specs published on its homepage. Seems to be just a much-too-short array of nearly useless identical fractional wavelength (half dipoles?) too closely separated to work best? More BS than antenna, probably works a little better than nothing just because of the dipole at the end feeding a built-in ant amp, combined with the added benefit of a reflector element and a rotor.
Problem is, you can  rotate it, with wireless remote, but you don't know where you are pointing and where you are next then pointing too!

I think I will first give the my dipole-enahanced existing antenna idea a DIY try.

Thanks to everyone for their antenna input.

[Ian.M]

Galvanised steel sheet would be much worse at UHF than aluminum due to its much higher resistance and skin effect, enhanced by its ferrous nature, restricting the current to a very thin surface layer further increasing the losses.

[martys]

Thanks Ian.M

I could also find some aluminum or copper stock, but isn't just a few max ohms of skin resistance not a problem considering the wide area of the elements that effectively parallels resistance? After all, this is not a transmitting high-power antenna where skin resistance would cause zinc-plated material to develop high temperatures.

I am ready now to to build a DIY better antenna.

What about cutting element strips from double-sided FR4 PCB stock with  a few large diam (12 AWG) shorting "vias" between the two sides of the stock at one end? Could coat the copper PCB made elements after construction with neighbor-friendly camouflage paint that would also protect the copper from corrosion.

[videobruce]

You still haven't answered my other questions. Build all you want, but without knowing where you are and what and where everything is, makes this a waste of time.
You might as well asked what kind of cars should you get with nothing else stated..................

[BrianHG]

Here is a minimalist toy... Note that this is BS, don't buy...
https://skywiretvantenna.com/orderint-mod-nv/vsl1.php?s1=1873&s2=&s3=41473522&s4=

[Ian.M]

Copper clad FR4 blank PCB could work nicely.   Chemically tin plate it for added corrosion resistance.    I don't think you can get the right spacing for folded dipoles etc from a single double sided PCB. but you can always cut a slot and solder in an offcut at right angles to link two boards separated by the desired spacing + epoxy in more offcuts without copper on as mechanical spacers.   Rather than cutting right through the board to form the elements, mark them out carefully and score round the copper you need to remove with a sharp craft knife and peel it off.  Heat helps - either a >100W soldering iron or a pencil flame blowtorch.

However DON'T start *any* construction without a good idea of the antennae gain you need and full plans from a radio amateur site, that have been correctly scaled for your desired frequency, and checked for sanity by the experts here, or you *WILL* be disappointed.

[tomato]

Building a radome is probably not an option. I don't have room or the knowhow to make something aesthetically good-looking and yet durable and such a thing would probably exaggerate the presence of the concealed antenna within.

It is most interesting to note that anyone can find on youtube videos made by idiots, morons, hillbillies and other self-proclaimed experts who want tol show how to make the "best" TV antenna ever from egg mixer attachments, paper clips, cardboard, coat hangers, coke cans, fan faces, fractal fantasies, or even from your mother's bra.

I've never met your mother, but there may be an easy solution to your radome problem.

[LaserSteve]

Google WA5VJB log periodic. 24$ and shipping.
I find it very useful for TV and wireless microphone use in the 500-700 Mhz band.

Steve