Antenna for HDTV

[gary350]

I have built a pretty good antenna for my HDTV but I want a better one. I have an 8 element collinear array with reflector, 2 antennas in parallel. It has a good range and good bandwidth I can pick up signals 60 miles away. The signal is about 97% most of the time.

From time to time the signal sucks. It mostly has to do with the weather. In the summer when it is very hot 90+ degrees F every day when the sun is low on the horizon the signal drops to 25% for about 30 minutes. I don't have a problem with this because I don't watch TV until after dark.

Heavy fog, heavy rain, clouds and high humidity causes low signal too. Tonight signal is bad I can receive 7 channels out of 24 channels. TV was working fine until about 15 minutes ago it looks like a storm is moving in so there won't be much TV until the storm moves out of the area. I was watching a good movie when I lost the signal.

I know someone is going to say, get cable, or get satallite. Been there done that. I am tired of paying $$$ to watch the same shows they have been showing over and over and over for many years. I am especially fed up with paying money to watch advertisements. When pay TV started many many years ago there were NO advertisements I thought that was the whole idea, no advertisements. What am I paying for? I can watch this crap for free.

I watch very little American TV these days it all sucks. I check out Foreign movies at the public library for free. Its just like checking out a book you keep it for a week and return it. Foreign TV is good, they have a lot of very very good movies. Inspector Frost is one of my favoriate.

I don't watch much on TV anyway so its not a big deal but when I watch it I would like for it to work. Does anyone have any suggestion on how to get a better signal???

Sorry I should have taken a photo of my antenna but I can't go out in the rain and dark to take a pic now. Antenna is 20" wide 36" tall with 8 elements. Elements are 3/8" diameter 9" long. Reflector is 1/4" screen 4" from the elements. If you have Anateur's Radio handbook 1973 edition you can see a pic of my antenna on page 634.

I have tried other types of antennas but not many are suited for local TV where stations are scattered all over a wide area. I tried a beam antenna it pulls in a very strong signal but it is too sensitive it has to be aimed directly at the station like a laser beam. I can pick up TV stations several 100 miles away with a beam antenna but signal drifts alot. I would need 24 beam antennas each one aimed directly at each local station transmitter.

 

[kchriste]

I would need 24 beam antennas each one aimed directly at each local station transmitter.

Why don't you get a rotator for your beam antenna?

 

[Boncuk]

You might try to construct a "Hybrid Double Quad Array". It is said to be designed better than any commercial antenna.

It is also easy to construct with some wire and a strut to hold the assembly together.

Costs are very low. So why not give it a try?

Attached is an article in German language. If you need assistance translating that article (or parts thereof) you're welcome to PM me what you need translated. It's just the first page printed in German. The rest of the article is German and English.

Enjoy free advertisement.

Regards

Boncuk

 

[Sceadwian]

Boncuk, those are highly directional antennas, all high gain antennas are so gary is going to need a mast rotatory most likely anyways. One bit of information I've never found about quads like that is their bandwidth.

 

[Boncuk]

Boncuk, those are highly directional antennas, all high gain antennas are so gary is going to need a mast rotatory most likely anyways. One bit of information I've never found about quads like that is their bandwidth.

He could take care of a nice looking sky line of his home mounting 24 quads.

I guess the band width of hybrid double quad arrays is pretty narrow as seen in the construction drawings.

A rotary mast won't help much in every case. I know from experience as ham that a 2deg narrow (2m band) beam (four 22 element yagi antennas mounted as pairs on top of each other) started fading with the wind. The antenna doesn't have to turn, but mechanical instability of the carrier will get the antenna direction messed up by gusty winds.

For long range reception the antenna elevation must be considerably high at a position exposed more to the wind than close to ground.

The 2m beam was mounted 50m (~150feet) above ground level.

 

[mneary]

Elements are 3/8" diameter 9" long. Reflector is 1/4" screen 4" from the elements.

Sounds like you have a fairly narrowband antenna, tuned to 600 MHz. If I can believe Choosing the Best TV Antenna for Zip Code 37129 Area, you still have stations as low as channel 5.

9 inches (23cm) is waaaayyy too short.

 

[blueroomelectronics]

Figure out what sort of range you need first. tvfool.com can do that.

You can buy a 4 bay bowtie in Toronto for $20

 

[gary350]

Figure out what sort of range you need first. tvfool.com can do that.

You can buy a 4 bay bowtie in Toronto for $20

I tried one of those. Also tried many others. They all work but reception sucks. Signal fades IN and OUT the TV is basically unwatchable. I built my own antenna and it works great. Returned all the antennas I bought and got my refund.

 

[Space Varmint]

Well you can watch allot of good stuff on the internet like Hulu is pretty good. I'm still watching all the original Outer Limits. Great stuff! Anyway, why don't you try an rf amp? That will boost your signal considerably.

 

[blueroomelectronics]

Which antenna did you build? Where did you find the plans?

 

[JimB]

OK, a few random thoughts...

Are your home made TV antennas cut for the correct frequency? If you have copied a design for the 70cm Amateur Band, the frequency could be way off.

You say that there are two antennas in parallel, are both antennas pointing to the distant station which is giving you the problem?
If the antennas are paralleled but pointing in different directions there will be a signal loss of 3dB due to the power from the wanted station being radiated out of the other antenna.

There could be losses due to impedance matching problems where the antennas are paralleled.

What sort of coax cable are you using to connect to the TV? A cheap coax will have more signal loss than a good quality (and more expensive) coax.
How long is the run of cable? It may be worth considering a mast-head amplifier. A good low-noise amplifier mounted at the antenna will overcome the losses in the coax to the TV.

JimB

 

[mneary]

Are your home made TV antennas cut for the correct frequency?

It sure sounds like he's using a narrowband antenna designed for around 300MHz (9" elements, 4" from a screen). I don't have the 1973 ARRL handbook, but without more detail from him, it's probably a variant of the "16-element" (8 driven elements) collinear array (1977 Handbook, fig. 22-17) using a screen instead of individual parasitic reflectors. His 23 local stations (see my post #6) include several on VHF. Three of them are less than 1kW.

Post #8: I built my own antenna and it works great.

Leaves me totally mystified.

He apparently wants it fixed without changing anything. I once had a manager like that.

 

[gary350]

I actually have 2 antennas in parallel. One is a bow tie antenna other is collinear array. Most of my good channels are in the UHF ranges. Channel 8-1, 8-2, 17-1, 28-1, 28-2, 28-3, 28-4 and 30-1 = 180, 488, 554 and 566 MHZ. I did some experementing and built one antenna for 554 Freq. range it picks up 488, 554 and 566 MHz great. The lower frequencies come in too but the drift a little. Bow tie antenna was designed for 180 MHZ now channel 8 reception is excellent and so is channel 17, 28 and 30. Channel 2-1, 2-2 , 4-1, 4-2, 5-1, 5-2, 5-3 come in 98% of the time but there is some drift problems. What I need now is another antenna just for the VHF range 54 to 76 MHz that would probably solve all the drift problems in the VHF range.

Amateur Radio Handbook shows a 432 MHZ coliear array that I copied. The book calls is an 8 element antenna. Elements are 12.5" long each space between elements is 3/4" so that makes it 25.750" tip to tip. Space between elements is 13 7/8". I got the formula for calculating the new frequency of 554 MHZ on the internet because it is no instructions in this book for this type of antenna. My elements are 9" long each space between them is 3/4" so they measure 18.750" tip to tip. I don't recall spacing between each set of elements without going outside in the dark to check. I have been known to make math errors I have not double checked to see if I made a mistake, maybe I should.

I don't know if the bow tie antenna is better or worse than the collinear array for this frequency range?

Do you know where I can find instructions to design the correct spacing for each element?

My bow tie antenna is a copy of one that I bought. The $75 factory made antenna had 4 elements and my $5 antenna has 8 elements. I have no idea if the elements on this antenna are correct I have never done the math the be sure.

4 years ago I bought a $200 antenna. It would not pick up much at all. I had it mounted on the roof on a pole. My house sets up on a slight hill so it was fairly easy to get the antenna 15 ft above all the other houses to the south west where that antenna was pointed. Returned the factory antenna for a refund. I put up a long wire antenna it worked better than that $200 antenna.

I just did a web search I still don't find anything that is much help in designing an antenna. I found a dipole antenna calculator it says elements are .84 ft long total or .42 ft each leg for 554 MHz. A collinear array is basically 8 dipoles in parallel. If this is correct my antenna is 293 MHz.

 

[Sceadwian]

I've always been confused by paralleling antennas, how do you do it without the applied field from one interacting with the one that isn't picking up a field?

 

[mneary]

I've always been confused by paralleling antennas, how do you do it without the applied field from one interacting with the one that isn't picking up a field?

There's some help on the subject from the ARRL Antenna Book, ISBN 0-87259-613-3. 728 pages plus CD, $30. The collinear array gets a few paragraphs and drawings on page 18-9.

 

[stevez]

I am going to consult with a very knowledgeable pal (he works at Harris) but I think a diplexer would isolate the two and prevent the interference (I agree with Sceadwian's concern). For my RV I did construct a great antenna - more or less a 1 meter square of chicken wire with an element that resembles a pair of zig-zag wires. It's excellent but quite directive. I would like to receive stations from two cities (Buffalo and Toronto) and need to point an antenna in each direction - but want one feedline. I think the diplexer will help with that

 

[mneary]

FCC (The Digital TV Transition: Reception Maps) says your location should only expect good signals from ten stations, marginal signal from WPGE and poor if anything from WCTV in Cookeville. Most of the transmitters are almost due North from Murfreesboro, not South West. You want Memphis stations 200 miles away?

I used proportions to calculate your antenna frequency. Since the Handbook's 12.5" elements make a 432MHz array, 9" elements make 600MHz. Basic math check: lower frequencies, longer elements.

As for 24 different azimuths, your primary stations are in 2 locations: Little Creek and Brentwood. There is one each in Charlotte Park and Lebanon. Cookeville is PBS and may have similar programming (except for pledge drives) to WNPT in Brentwood.

 

[Sceadwian]

I'm not spending 30 bucks for a paragraph =) I was hoping for links or understanding. Antenna websites are generall vague in the first place, I just want to understand antenna arrays and in particular parallleing of different types of antennas, and imepdance matching and the whole bit.

 

[kchriste]

Usually you make a multiband antenna with traps. Traps are tuned LC circuits which make the elements appear longer or shorter at different frequencies.
The OP should go to the DX zone:
https://www.dxzone.com/catalog/Antennas/Multiband/

 

[RCinFLA]

ATSC has more issues with multipath reception (ghosting in old analog terms). Putting multiple antennas pointing in different directions and combining them can really aggrevate multipath reception. Second most common issue is booster amps. If you use one make sure it has good high signal handling capability.

BTW, the % signal strength reading is not really signal strength. It is correlation energy at the demodulator. Multipath or intermod will lower the number even though true signal strength is the same.