How to build a UHF antenna... - Page 159

Can you not get the 49 in the DTS that's closer to your location (in green)?

No, it's evidently much less power than it actually says. No signal.

I don't think their Single Frequency Network is working like they hoped it would. Not sure what to suggest for building a bidirectional antenna. From your TVFool, it looks like a reflectorless 4bay should work.

Well it could be the fact you have 4 channel 49s in your area for some reason. I suggest putting a reflector on that antenna and aiming it in the direction of all your other channels.

I've tried that, I'm telling ya 0 signal from 49, every other channel full strength. TVFool is wrong about how much power i'm getting from that 49.

When you add more than one balun to an antenna will that reduce the strength of the signal or is it fine? I've got like 5 TV's i'm wanting to connect to the antenna.

Never add more than one balun to an antenna. Use a splitter or distribution amp for that purpose.

The multiple 49s for his FOX affilate are a Distributed Transmission System aka Single Frequency Network.

http://en.wikipedia.org/wiki/Distributed_transmission
http://en.wikipedia.org/wiki/Single-frequency_network


.

Doesn't mean he still can't suffer multipath.

Good to know, I had like 5 hanging off of one the other day!

I am looking to purchase an antenna from http://m4antenna.eastmasonvilleweather.com. According to http://www.tvfool.com/?option=com_wr...36164469060718 would a 9 1/2" whisker elements and 9" element separation still be my best option? I am looking to pick up the tower that shows 18.1 miles away.

I need to connect 7 tuners in 4 different rooms throughout the house. Most of the channels I get (except for 49) show full 6 bars in media center. Trying to use splitters makes the signal way to weak. Should I go for a pre-amp or a distribution amp?

At first I was looking at this distribution amp

http://www.amazon.com/8-Port-Bi-Dire...656724&sr=1-19
but then I was reading and some people said that it's better to just get a good pre-amp and then use a few splitters. So I was thinking about this pre-amp



http://www.amazon.com/Channel-Master...pr_product_top

Am I close enough to any stations that a preamp would overload?



Note that the only one that I'm REALLY close to is the 49 in green (11.8 miles away) which doesn't actually come in at all.

That channelmaster amp would likely overload. And distance has nothing to do with it. Signal strength in the TVFool report determines whether certain preamps would overload.

Use the distro amp you posted a picture of. Terminate the extra unused port with a screw-on 75ohm termination cap, available at http://www.solidsignal.com
Termination caps look like this:

Thanks for the help, that's what I ended up impulse buying soon after my post. Glad I made the right choice.

UPDATE

Got the 8 port distribution amp today. It works pretty well even without the terminators on the unused ports. I went to get some at Radio Shack today and I couldn't find them and of course the "expert" there had no idea what I was talking about so I came home and ordered some on Amazon. Good signal on my ATI tuner and my Hauppauge tuner but my 2 tuner HDHomerun with the internal splitter gets a pretty weak signal. 2 TV's downstairs that had really weak signal with regular splitters both get channel 49 so I'm happy.

1 more question. Is there much signal loss if I use a barrel connector to connect 2 coax cables to a TV tuner? It will be a 50 ft cable to a 25 ft cable. I am wondering I need to buy 100ft or 50ft of coax.

Hi,
How far away can you pick up with it? What kind of parts do you need to get and how much does each cost? What measurement for the coat hanger and how far a part do they need to be to pick up uhf channels 65 miles and 100 mile ? What do the measurement have to be to pick up the higher vhf channels and what do the measurement need to be to pick up the lower vhf channels 65 miles and 100 mile? Email me back with photos.


Thanks,
Varian

@varian, go to http://m4antenna.eastmasonvilleweather.com/index.html to get plans for bowtie antennas. Don't rely on any other site.

It is impossible to say how far away you'll get with an antenna ahead of time. You need to know what signals actually reach you first. Use http://www.tvfool.com/ to figure that out. Read the signal analysis FAQ there for more information.

PRETTY




But Quads and Dishes are better bird catchers!

How critical is the horizontal spacing of elements in a horizontally stacked array? I plan on building a 4 bay horizontal (2x2) to fit a window that's only 44.5" wide x 19" tall. Using the 9.5" whiskers and 1.5" phase line separation I'm looking at 20.5" bay sections. I'm pretty sure the remaining 3.5" clearance isn't going to be close to a full wavelength. Probably closer to 25", right? Since horizontal real estate is a premium for this build, might I be better off using huge diameter elements, like copper tubing, or is just not feasible with these dimensions?

Also, since I haven't seen too many examples of 2x2 arrays, it appears I don't need a phase line crossover on either double bay section or feedpoint. Is this correct?

It's not too critical. Look how close they are in the 4221HD and the DB8:
http://www.google.com/search?q=4228hd&hl=en&tbm=isch&tbo=u&source=univ&sa=X&ei=gVoyUe2dAbTy0wHVzYCIDw&ved=0CF4QsAQ&biw=1001&bih=569
http://www.google.com/search?q=db8+antenna&hl=en&tbm=isch&tbo=u&source=univ&sa=X&ei=zVoyUZ2PAe2D0QHCm4DACQ&sqi=2&ved=0CEwQsAQ&biw=1001&bih=569

When the two arrays are that close, there is a slight loss of gain because the two apertures of the arrays overlap causing a duplication of coverage. If the two arrays are moved further apart, there will be a slight increase in gain but it might not be realized because both arrays might not be equally illuminated by the wavefront at the best location. Or, to put it another way, the hotspot might not be as wide as the antenna.
It doesn't need to be a full wavelength for adjacent tip-to-tip and it will be a little more than a fullwavelength centfer-to-center. Large diameter straight elements will be shorter for the same design frequency and will not take up as much vertical space as conventional fan-dipole whisker elements ><. How much broadbanding you get from the tubing VS the whiskers depends upon the tubing diameter. How valuable this advantage is will depend upon what UHF channels you want; the low UHF channels need longer elements. What channels do you want?


Why would you point your antenna at the Cuestra Grade? It is north toward Atascadero, and ABC is south at 127 degrees magnetic? KEYT-DT ABC on real channel 27 is a 2Edge signal from 65.7 mi away; it is too much to expect it to be reliable with an indoor antenna. Using a tvfool report based on your approx location this is what the profile for KEYT looks like:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d1dda57366885c2
KEYTsaf3rd profile.JPG 52k .JPG file

The coverage for ABC is very poor in your area:


Correct, if the feedpoint is between the two bays.

More theory here:
4-bay Using Metal Tubes Instead Of Bowties
http://www.digitalhome.ca/forum/showthread.php?t=154177&page=5

http://www.google.com/search?q=cm+4220hd&hl=en&tbm=isch&tbo=u&source=univ&sa=X&ei=LGIyUfDrBKTl0QGNrID4BA&sqi=2&ved=0CFgQsAQ&biw=1001&bih=569

http://www.google.com/search?hl=en&sugexp=les%3B&gs_rn=5&gs_ri=psy-ab&gs_mss=antennas+direct+db2e+&pq=antennas+direct+db2e+&cp=20&gs_id=a&xhr=t&q=antennas+direct+db2e&bav=on.2,or.r_gc.r_pw.r_qf.&bvm=bv.43148975,d.dmQ&biw=1001&bih=569&bs=1&wrapid=tljp136225670239520&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=QmMyUZP-L4Pn0gH7uYGYCQ

http://www.antennasdirect.com/cmss_files/attachmentlibrary/AntennasDirect_DB2e%20QuickStart_Rev.pdf

How are you planning to combine the two arrays? Will they have reflectors? A 2-bay with a reflector might easily outperform a 2x2 without reflectors.
Edited by rabbit73 - 3/3/13 at 1:10pm

UHF 2x2-Bay Bowtie (Narrower) with NO Reflector:

I spent the last few days working on this one as a good exercise in finding an OPTIMIZED Horizontal Harness, such as has been a (loss of low freq Gain) problem in 8-Bay Bowtie Antennas. Next up: Optimized 2x2-Bay Bowtie without any constraints....and then on to the Horizontal Harness in the similar 8-Bay Bowtie. Note that an unconstrained 2x2-Bay Bowtie looks like the MIDDLE FOUR Bowties in an 8-Bay Bowtie Antenna, but was TOO WIDE to fit your window (2x2-M4's without Reflector would be 40.5-44.5 inches wide). Bear in mind that whether the 44.5-in wide x 19-in tall window frame was wood or metal, I wanted to keep several inches away from the edges to minimize the perturbation as much as was feasible....

UHF 2x2-Bay Bowtie (NO Reflector), NARROWER WIDTH with Bay-Bay Separation = 10-in (vice 12-in) and 2-in Vertical Spurs on Whiskers (so Whisker Lengths are hopefully shorter), analyzed using 4nec2. See 4nec2 Files for complete description and dimensions (Text File Format). This smaller version is about 2 dB lower Raw Gain than an Optimized full-size version without Vertical Spurs:
http://imageevent.com/holl_ands/multibay/uhf2x2bay/uhf2x2baynarrownorefl

a) UHF 2x2-Bay Bowtie (Narrower) with Two Transmission Lines (must be 450-ohm, 300-ohm degrades SWR) from a common SOURCE Wire was Optimized (using nikiml's Python Scripts). Bowtie-Bowtie Separation was FIXED at 9.0-inches, with all FIVE other parameters as VARIABLES. Maximum constraints were imposed on Whisker Length and Feedline Separation to also limit overall antenna width. Optimum Transmission Line Length is 11-in per side, but up to about 12-in is also acceptable, simplifying the very tight interconnections. Open Ladder construction is advised to avoid Velocity Factor's physical line shortening due to dielectric material between the lines. Width=38.5-in, Height=14.0-in.

b) UHF 2x2-Bay Bowtie (Narrower) with Horizontal Harness from a common SOURCE Wire was Optimized (using nikiml's Python Scripts). Bowtie-Bowtie Separation, Whisker Length & Tine Separation was as determined in para a) above. Harness Separation between the two Transmission Lines (determines Impedance), distance BEHIND Bowties and (retweaking) Bowtie Feedline Separation were VARIABLES. Width=38.25-in, Height=14.0-in.


Substituting thinner AWG12 (without re-optimizing dimensions) will slightly increase SWR (from under 2.0 to under 2.6), with no change to Raw Gain.

Raw Gain is about 2.5 dBi higher on the broad maximum across the higher frequencies than it is on 470 MHz. This is frequently desired to overcome higher Balun, Coax and (if no Preamp) RF Splitter Loss on the higher frequencies. Note that Horizontal Harness is acting as a REFLECTOR, with more Raw Gain Forward than to the Rear. But instead of INCREASING Forward Gain, it's simply SUPPRESSING the Rearward Gain....which is why it is important to make sure that it is on the BACKSIDE of the (NO Reflector) Antenna. With a Reflector, it MAY turn out it needs to be on the FRONT (like CM4228/CM4228HD):


Minimizing SWR wasn't easy....changing SOME dimensions by more than about 1/4-inch can change SWR:

Edited by holl_ands - 3/3/13 at 3:07pm

That's a relief. I built a mockup with the elements 19" apart and the outer elements are almost completely outside the window frame. I was, incorrectly, thinking that a full wavelength spacing would keep the signals from cancelling out instead of adding gain. Just goes to show how much I still have to learn.



In January 2013 KEYT began broadcasting from their repeater, K57BC, at the top of the Cuesta Grade. The TVFool database must not have been updated yet. You can see the RF shadow that 1200' Madonna Peak is throwing right at my location.



Thank you for the links. I enjoy filling my head with all kinds of knowledge. This is fascinating stuff and perhaps I may even learn a bit from it. Maybe.

I haven't quite worked out the harness yet but holl_ands has provided some really helpful data in the previous post. I was thinking of bending and soldering lines so that, let's say, the left phase line connected in the center of the left bay section, bend a 90 degree at 3/4" and pass that under the right phase line to a center section where the balun will be positioned. Reverse the setup for the right side except the 90 degree bend will take the line over. Basically trying to maintain 1.5" clearance all the way until the balun while keeping the length of each line as close as possible to each other. I need more "open a beverage and stare at the problem" time before I'll have the physical connections worked out.

Up until this point I haven't thought of making a reflector as the two antenna farms are 113 degrees apart and the target window I'll be hanging this in is almost exactly pointing toward the farther CBS/FOX stations. There is a 1200' hill right between me and the nearer NBC/ABC/KCET stations. Multipath is a fairly big issue for my location but I think I've found the sweet spot which is in this window where I am able to pick up everything except the ABC station and the airplane overhead drop outs only occur on the KCET stations. This is with a RCA hoop and ears currently. In my bedroom 10' above this I am using my old DIY 4bay bowtie in a window and am able to pick up the ABC station but the signal is unreliable. I'm hoping a better built one may help up there.

FWIW: This window and frame are wood but the entire exterior is stucco.

Thanks for the update; I missed that with my initial analysis of your reception problem. Yes, tvfool doesn't have it yet. After a little more searching I found that the repeater (I also call it a repeater, and so do hams, but the FCC calls it a translator) has a new callsign: K31KE-D. I found more info on wiki:
http://en.wikipedia.org/wiki/KEYT-TV
Scroll down to Rebroadcasters to find it.

Rabbitears.info also has it:
http://www.rabbitears.info/market.php?request=print_station&facility_id=60638

http://www.rabbitears.info/market.php?request=station_search&callsign=K31KE

http://www.rabbitears.info/search.php?request=zip_search&zipcode=93405&miles=60&address=&lat=&lon=&dbtype=dBm&height=
Click on K31KE to see networks
Cick on Historical Ownership to see callsign history That's pretty bad. The transmitter profile doesn't look any better:


That 113 degrees is a very wide azimuth spread for any antenna. Your two goals are mutually exclusive. Your horiz stacking of two 2-bays will have a narrower beamwidth than one 2-bay, which will make such a wide spread unlikely. But your multipath problem will be helped by a narrower beamwidth. The CM4228 8-bay has a much narrower beamwidth than the 4221 4-bay; it handles multipath problems better inspite of the fact that it doesn't have much more gain than the 4221 because of harness losses when combining the two horiz 4-bays.

I'm going to stick with my first suggestion of a 2-bay with reflector for wider beamwidth than the 2x2. You seem to understand that there is no free lunch and probably think that adding a reflector will make the horiz beamwidth too narrow. The extra gain comes from eliminating the pick-up from the rear of the antenna, not making the forward beamwidth narrower. That would be true of a yagi and adding more directors, because it already has a reflector.
Stucco is usually applied over an expanded metal lath, so you probably don't get much signal thru the walls. Exactly what direction is the window looking at where you will have your antenna? Does it face NE, East, or SE? What is the azimuth (true or mag) that is perpendicular to the window? I'm confused. If the window (front of the bldg?) faces in that direction (SE?), how can the antenna "see" NE which is around the front corner?

Some people bend the reflector so that its concave side faces the elements and bend the elements forward to match. This gives a little more gain but makes the beamwidth narrower. It is also possible to bend the reflector back so that its convex side faces the elements and bend the elements back to match. This, and a reflector no wider than necessary, can give more gain and a wider beamwidth. If that doesn't work to allow you to receive both directions, then you will need to rotate the antenna or have two antennas and an A/B switch. But don't take my word for it, try some experiments yourself. That's how I learn.

Do you have a signal strength indicator on your TV to tell if your experiments are making the signals stronger?
Edited by rabbit73 - 3/7/13 at 7:45pm

UHF H4 2x2-Bay Bowtie - NO and 10 Refl Rods:

I uploaded 4nec2 results for a UHF Horizontal 4-Bay (H4), aka 2x2-Bay Bowtie with either NO or 10 Reflector Rods. Optimized Dimensions were determined by running a series of nikiml's Python Optimization Scripts, adjusting the Target Levels and esp. Target Function "weights" as necessary to find the desired balance of Raw Gain, F/B & F/R Ratio and SWR (Mismatch Loss). Each trial run takes 3-5 days on my Intel i7 (8 threaded) Alienware Laptop, so it's been a slow slog. Similar Horizontal Harness design for 8-Bays is in the works...."soonish"....

In preliminary Optimization searches, it became apparent that the lowest SWR performance was being found when there was either two Reflector Rods centered behind each Harness Wire. Or a Reflector Rod directly behind each Harness wire...as was designed into the below models.

Horizontal Harness interconnecting the pair of 2-Bay Bowties was specifically designed for EQUAL length in each wire by setting the end points precisely in the Center of each Bay and then connecting from there diagonally to the Feedline wires. The overall Harness Wire Length is changed in the Optimization Scripts by moving the Harness closer or further away from the plane of the Bowties and the Impedance is adjusted by the separation between the two Harness Wires.

The Optimization Script does a random search of ALL applicable variables to find the "Best" set of Dimensions which will maximize Raw Gain, F/R and F/B Ratios with an "acceptable" SWR level. In preliminary runs, slightly higher Raw Gain was found as separation between Left and Right 2-Bays was increased....however, forward sidelobe levels also increase to what I believe are unacceptably higher levels. Hence final Optimization search was limited to Center-Center 2-Bay Separation between 20-24 inches, with "best" result at my imposed maximum: 24-inches. Even better forward sidelobe suppression is found when Optimizing with 20-inch constraint (not shown).

a) UHF H4 2x2-Bay Bowtie - NO Refl Rods:
http://imageevent.com/holl_ands/multibay/uhf2x2bay/uhf2x2baynorefl

UHF Raw Gain Max = 12.8 dBi
UHF SWR (300-ohms) Max = 2.3

Note small amount of F/B Ratio on lower Channels due to Harness acting as a REFLECTOR.






b) UHF H4 2x2-Bay Bowtie - 10 Refl Rods:
http://imageevent.com/holl_ands/multibay/uhf2x2bay/uhf2x2bayreflrods

Locating the Horizontal Harness BETWEEN the Bowties and the Reflector Rods provided 1.4 dB
MORE Raw Gain acting as a DIRECTOR than when placed in FRONT of the Bowties (since inferior,
will not be shown).

UHF Raw Gain Max = 14.8 dBi
UHF F/B & F/R Ratio Min = 20 dB
UHF SWR (300-ohms) Max = 2.4
UHF Beamwidth = 30 to 20-degrees, about half as much as an M4 4-Bay.

Hi-VHF Raw Gain Typ. 6.5-7.3 dBi
Hi-VHF F/B & F/R Ratio Typ. 7-10 dB
Hi-VHF SWR (300-ohms) is Excessive [Which may or may not be a problem in any given situation....]






Edited by holl_ands - 3/21/13 at 1:25pm

I haven't abandoned this thread and I really appreciate the advice and data provided so far. The dusty part of my garage is on standby while some paint and cure projects are finishing up. So far it looks like I'll be building and testing 3 designs; standard 2 bay with and without reflector as suggested by rabbit73, a holl_ands 2x2 narrow with 2" spurs and holl_ands latest 2x2 with reflector rods. It's a modular build so I should be able to swap out parts and test the different configurations fairly quickly once the modules are built.

I joined the forum and have been reading avidly for about two weeks. This project started when my brother-in-law (good with tools, but not into electronics) heard I was having trouble getting my channels after I dumped sat tv. "I made it from coat hangers." he said. I thought, "yeah, right!" Well, he brought it over and it was the basic youtube DB4 design except that he had fractal curves in the whiskers. It worked much better than my $50 GE Futura (the Futura is on the roof). After a storm, the Futura was damaged Homemade TV Antenna 001.JPG 498k .JPG file

I joined the forum and have been reading avidly for about two weeks. This project started when my brother-in-law (good with tools, but not into electronics) heard I was having trouble getting my channels after I dumped sat tv. "I made it from coat hangers." he said. I thought, "yeah, right!" Well, he brought it over and it was the basic youtube DB4 design except that he had fractal curves in the whiskers. It worked much better than my $50 GE Futura (the Futura is on the roof). After a storm, the Futura was damaged somehow, I lost a bunch of signal and I built a youtube DB4. Better, but not all my channels. I built a Mclapp 10x9 using stripped 12 gauge copper wires and PVC pipe tees for standoff insulators. I also I followed his instructions concerning the 1 inch air gap between the phase lines at the crossovers! On the ground outside it was looking good but the neighbor's house was blocking Ch 19. I put it on the old unused sat mount and now have all my channels!! Oh, and I didn't use any sort of reflector. I am 17 miles from all my transmitters and they are all SSW of me. I am a happy man! Next project will be the same antenna, but with all soldered connections and PVC pipe to handle the outdoors better. Many thanks to everyone on the forum for all the great info!

Homemade TV Antenna 001.JPG 498k .JPG file

Homemade TV Antenna 001.JPG 498k .JPG file