The Official AVS Antenna and Related Hardware Topic! - Page 97

There aren't too many situations where a preamp driven by an attic 4-bay bowtie is going to get overloaded by transmitters that are 23 miles away, though Ronon_R6 probably doesn-t need one.

If Ronon_R6 is only concerned with receiving Washington market stations, but he favors attic installation, then he still probably should spend the extra $30 for the 8-bay bowtie, which will also give him a better shot at Annapolis WMPT, but realistically, the difference between excellent and poor reception will be just the roll of the dice, determining what obstructions are between him and the transmitters.

I am not really concerned about any stations other then the 4 networks, and maybe WB50.

But is it better safe then sorry? meaning should i just get the 8 bay to be on the safe side? its not like $30 is going to break the bank or anything.

Also what type of cable should i run? RG-6?

New Here! But Is There A Way To Combine 2 Uhf Antenna S Together Instead Of Using A Rotor ,my Chaneels Are In 2 Different Directions

Also I Am On A Hill And The Stations Towers Are On The Other Side,any Idea's Of Away To Pick Up Better Signal?

There are several ways to combine two UHF antennas pointed in different directions:

1. Standard RF Splitter/Combiner, which incurs about a 4 dB loss in sensitivity
(with optional Preamp on combined output).

2. Preamp for each antenna so don't lose sensitivity and then combine the two amplified signals
using an RF Splitter/Combiner that has DC PASS on both ports
(e.g. Zenith ZDS5010) in order to provide power to both Preamps.

3. Low Loss (0.2 dB) Stripline Antenna Coupler (with optional Preamp on combined output),
such as the $100 Lindsay:
http://hdtv.forsandiego.com/messages...html#POST15877
Some examples:
http://hdtv.forsandiego.com/messages...html#POST16670
http://hdtv.forsandiego.com/messages...html#POST18916
http://hdtv.forsandiego.com/messages...html#POST19479

A Preamp should not be used when broadcast towers are within about 20-30 miles
(and maybe less if you are behind a hill, or use indoor/attic antenna):
http://hdtv.forsandiego.com/messages...tml?1126998999

When you combine two antennas, you also pick up more undesirable multipath reflections
than a solitary antenna and increase the noise floor a few dB.
So not all people have been successful.

=======================================================
An inexpensive alternative that avoids these problems is to use an RF A/B Switch
(e.g. R-S 1968) and simply switch between two coax downleads:
http://www.radioshack.com/product.as...5Fid=15%2D1968
Of course, that makes channel surfing and PVR recordings much more difficult.

One more: if the stations are generally opposite each other (180 degrees +/- 30 degrees)
and not too far away, then the rear screen on a CM-4221 4-Bay Antenna could be removed,
turning it into a modest gain bi-directional antenna.

=======================================================
PS: A search for "Stacked Antenna" arrangements will yield additional solutions
if the antennas are pointed in the SAME direction, .

Does anyone know anything about the terk tv55 hd antenna? Can you hook it up to a d-vhs recorder or hi def hard drive recorder? The antenna is so small (46in long) that it doesn't seem like it would pull in a strong enough HD signal.It says you can mount it under your window seal.But i also see these HD antenna's that are like 5ft tall. I don't want an eyesore on my roof.

The thing is awful. Good antennas look like antennas have looked for decades.

Greetings all-

I am helping a friend in Eugene, OR finally jump into the HD world. According to antennaweb, he has DT stations locally all under 10 miles away, no major obstructions, but the channels are split - some are at 35 degrees and some are at 131 degrees. He has Dish with the 942 HD tuner and I was originally going to get him the Winegard SquareShooter but I cannot get any good info on whether this thing can deal with teh slip in direction of the stations. I like the squareshooter becasue it can attach to his dish. Suggestions?

Thanks!

Looks like MAX HD is at it again:
http://community-2.webtv.net/GregBar...TowerAntennas/
That VHF-hi horizontal stack is new, I believe.

SquareShooter beamwidth is quite wide: 68 degrees for lower UHF channels,
decreasing to 54 degrees for upper UHF channels.
But you would be working some of the channels on the back side of the antenna.

The CM4221 4-Bay Antenna with the rear screen removed would be a much better,
higher gain, bidirectional antenna.... and much less expensive.

The Channel Master StealthAntenna is also bi-directional, but with a lot less gain
than the CM4221.....actually it has about as much gain as the SquareShooter.

You could also consider a two antenna arrangement as was discussed just a few posts ago....

Well I was a little off. The spread of the DTV channels is less than 90 degrees so it seems if he pointed the squareshooter in the middle of them it's only looking just less than 45 degrees left or right for the signal.

I did not know that by removing the back screen from teh bowtie antenna that it would make it a bidirectional thing but since we're at just less than a 90 degree split would that really work? I don't think two antennas is a choice.

What about the clip on ones that terk and phillips make? They seem to be omnidirectional and since he's so close as long as it's up high enough I think that would work. Plus they have the built in dual diplexer which is good for him. He's not yet ready to run another line into the house.

If I got something like the Channel Master 3014 or 3016, would he have to rotate it to get both sets of signals or would it pick them all up (assuming it's installed rooftop high enough without obstructions)?

What is the smallest antenna i can get that will still pull in good signals?

Simple piece of wire! If the stations are good and strong, you really don't need much. I have just a wire hanging on the back of my media center PC's HD tuner card and I get just about all the digital channels in Seattle area! But then we are on a hill with a direct view of Seattle towers....

Amir

Here is some info on antennas with wide beamwidths:

W-G SquareShooter: SS-1000 (no Preamp) or SS-2000 (with Preamp)
http://www.winegard.com/offair/s2shooter/WC-811.pdf
When I blow up the scale, I see that it uses a field polar plot (volts/meter),
rather than the usual dB scale.
So 3 dB down is at 0.707, i.e. 20*log(0.707) and 6 dB down is at 0.5.
At +/- 90 degrees, it's down about 5 dB from maximum gain for low channels,
and about 8 dB for upper channels.
W-G says the average UHF gain is about 4.5 dB, so you have about -0.5 to -3.5 dBd gain
in two desired directions and about 4.5 dBd gain in undesired direction.
Fol. is NEC Simulation for SquareShooter:
http://www.hdtvprimer.com/ANTENNAS/SquareShooter.html
It shows that +/- 45 degrees is about 6 dB down on the sidelobes.

W-G Sensar III: GS-1100 (no Preamp) or GS-2200 (with Preamp) is much lower cost.
http://www.solidsignal.com/manuals/WC-810.pdf
Note that at VHF it is bi-directional, whereas at UHF it is unidirectional.
This is also a field polar plot (volts/meter) rather than the usual dB scale.
At +/- 90 degrees, it's down about 5 dB from maximum gain
(give or take a little due to the skewed response and pointing inaccuracies.
W-G doesn't say what the maximum gain is, but it must be less than 3 dBd.
So the net gain is -2 dBd in desired directions and + 3dBd in undesired.

C-M StealthAntenna:
https://www.solidsignal.com/prod_dis...=&PROD=ANC3010
Gee, they don't say much...but antenna pattern is probably similiar to Sensar III.


Either of these antennas are much lower cost alternative to the SquareShooter
and all will perform about the same.

Note that omnidirectional antennas (e.g. W-G MS-2000 MetroStar and MX1405 Maxus)
will have about 0 dBd gain in all directions, but do not provide suppression of multipath in any direction.
Suppression of multipath being reflected into the "back" side of the antenna is highly desirable.

Simple piece of wire! If the stations are good and strong, you really don't need much. I have just a wire hanging on the back of my media center PC's HD tuner card and I get just about all the digital channels in Seattle area! But then we are on a hill with a direct view of Seattle towers....


What type of wire?Just standard coax cable,or special antenna wire?And will i be able to hook it up to a HD recorder to record HD?If i run a wire up the chimney, Do i have to expose the wire end?If it rains will it damage anything?

question for holl_ands below,

If i get the squareshotter ant. ,Isn't puting it in the attic under a roof going to block and sort of weaken the signal? Can i hook a squareshooter up to a HD recorder? I don't know anything about antennas,so forgive me if i sound stupid.

I am trying to get OTA HDTV set up, but I'm having some problems with it. I'm hoping that somebody here can help me out. I am in the Boston area, and according to antennaweb I'm located about 7 miles away from the broadcast towers (and they're all in the same direction too).

I bought an HDTV tuner for my computer, and I went to Radio Shack today and bought a simple rabbit ears antenna with modest amplification (model 15-1838) to test it out. Even if I don't turn the amplifier on, my computer reports that I am receiving a strong signal (between 90% to 100%, whatever that means), but every 10 to 30 seconds, the signal will go out. The disturbances can be momentary or they can last up to 5 seconds before the feed comes back.

After reading stuff online today about antennas, I am assuming that the problem results from multipath issues. Does that sound right to everyone else?

If so, I've read that the standard UHF loop does a very poor job of isolating a single direction. I would be interested to hear ideas from everyone about any antenna that focuses well on a single direction. So far I am looking at the Silver Sensor and also the Radio Shack model 15-1880 antennas, but I'm open to other suggestions as well.

Holl_ands & srenger

While sitting here waiting for Rita to steam roller over the station (she didn't), I collated some antenna data that I took last week. The antennas were all tested at the same place, on the same day, at the same hight. This time I used averaging to optimize for the DTV channels because I was looking for multipath or, specifically, multipath reduction from antenna to antenna. In previous testing, I had used the 'MAX HOLD' function to capture the peak of the NTSC carriers so I could get more measurement points to graph. However, MAX HOLD tends to mask the multipath ripple because it captures the DTV peaks also. Unfortunately, my neighborhood does not lend itself to that kind of testing as multipath there seems to be minimal.

I wanted to get a new baseline on all of the antennas for this winters attic & antenna testing. I have two people that I have promised a visit and both are at the far side of the DTV reception for the station. One is in Winnie, TX (and I hope he is OK after the storm). The other is just west of Conroe, TX. I wanted to see how the new antennas performed against the old favorites.

If you want to do any calculations with this data, the actual DTV average power received at the STB is 17.61 dB above the measured (charted) levels. The levels shown on the charts are because of the 100 kHz RBW of the spectrum analyzer.

Bob Chase
KHWB-TV

 

Antenna Testing 09-18-2005.pdf 274.8447265625k . file

If I read it right, it looks like UHF antennas with highest gain were:
1. CM4248, C-M "Diamond", UHF Corner Yagi
2. CM4228, C-M UHF 8-Bay Bowtie with Reflector Screen
3. CM3671, C-M "Crossfire", Hybrid VHF LPDA, UHF Yagi

in the middle:
4. 91XG, Antennas Direct, UHF Corner Yagi with 22 Bowtie Elements
5. 1469B, Scala, UHF LPDA inside a Radome Enclosure

and those with the least:
6. CM5646, C-M "Super-V", VHF Forward Swept "V", UHF Corner Yagi
7. HD7210, W-G "Ghost Killer", VHF/UHF Classic Yagi
8. SS1000, W-G SquareShooter, VHF/UHF Spiral Log Periodic

with the SquareShooter separated by several dB below the group.
It also was a terrible VHF antenna, contrary to W-G published claims.
So why would anyone buy one, other than it "matches" their SAT dish???

As expected, the CM4228 8-Bay Bowtie wasn't as good a VHF antenna as a
purpose-build VHF antenna, but it was only a few dB below the VHF/UHF Combos
for upper VHF (CH7-13) and finally dropped off for CH2-6.

Of course, this only addresses the gain parameter and not F/B and multipath rejection,
but since gain is obtained by narrowing the antenna pattern, they are related.

=========================================================
PS: Note typos on first page: "HD7120" should be "HD7210".
and Antennas Direct usually calls their biggest antenna the "91XG",
(although their home page calls it the "XG91" ....go figure....)

Any explanation as to why Scala LPDA would have a significantly higher noise floor,
such as in Business Radio and other regions?

The amplifier in the R-S 15-1838 may be overloading, even when Low Gain is selected.
I would avoid using any amplified antennas that close to the broadcast towers.

The Silver Sensor mini-LPDA has a moderate amount of multipath rejection.
The similiar Terk HDTVi mini-LPDA adds a pair of collapsable VHF Rabbit Ears.

In the past, I've used 4-Bay Bowties (e.g. CM-4221, W-G PR4400, or Antennas Direct DB-4).
The CM-4221 is the ugliest, but I could hide it behind a big chair in the LR.

You need to tell us where you are located. Preferable zipcode and nearest cross streets.
You should also punch this info into www.antennaweb.org to see what kind of antennas/preamps they recommend.

Putting an antenna 20+ feet above your roofline is always "best".
After that, it's a compromise process, depending on how much excess signal you have to begin with.

There is an antenna height loss the lower you go.
There is also an indoor/attic loss that depends a lot on your house construction.
See Bob Chase's earlier post re Outdoor vs Indoor measurements in his very lossy attic:
http://www.avsforum.com/avs-vb/showt...32#post5410432

And indoor/attic locations suffer the third whammy of strong multipath with short delay echos
(the worst kind of multipath for most receivers).

SquareShooter??? Overpriced, underperforming, need I say more....
HDTVi and Silver Sensor, uhhhh.....they're small and cheap (see amazon.com).
But if you are close to the towers and don't mind fussing with the antenna.....

Up the chimney? You gotta be kidding.....
It's a Fire code violation, and your insurance co. won't cover your loss if you get hit by lightning.
See fol for installation guidance:
http://www.solidsignal.com/manuals/AntInstallGuide.pdf
Note that indoor/attic antennas do NOT have to have lightning arrestors, etc.

The television signal from the on-air antenna can be fed to both the HDTV and the antenna input
on a recorder by using an RF Splitter, which results in another 4 dB of loss.
See for example the R-S 15-1234, but look around for a better price.

If you want to record the HD DTV signal, you need a recorder that will record HD signals:
http://www.avsforum.com/avs-vb/showthread.php?t=508907
What equipment do you have now?

Any bare wire (inexpensive "rabbit ears" are a good choice).

Any wire intercepting a radio wave will generate a bit of electricity (at a matching frequency) - thats how antennas work.

To get a basic understanding of this, check out this link.

Holl_ands
I have yet to find a measurement method for multipath that I would feel confident putting on the web. For FTB, just turning the antenna around and measuring is not sufficient. (I made that mistake already.) The reflections from the surrounding environment cause too many errors. So it would take a day (a morning at least) and another truck to cut patterns against a fixed transmit antenna. The transmitter, fed into a channel cut dipole, at the same height, located close by, with enough power to swamp out any reflections that the receive antenna would pick up. In the end, we would have a table similar to the CM & WG FTB tables. Do you think it is worth it?

The Scala data was taken in the morning at 1138. Then I did some CM7777 overload testing. In the late afternoon, between 1500 & 1700 I flew the antennas. The only reason I can think of for the variance is that the noise floor changed from the morning to afternoon. It doesn't seem likely, but I can't think of any other reason for the variance.

Normally, I take a Scala measurement 1st & last during testing to compare them. This day, the final measurement was taken with the wrong input attenuation, so the last measurement incorrectly shows the Scala with significantly less noise than the rest of the field. All of the measurements were taken at 100 kHz RBW, 30 kHz VBW, and 0 dBm reference level. What you see on the chart for the Scala is the 1st measurement of the day.

The square shooter has a very high WAF (Wife Acceptance Factor). When I have been invited to customers' homes for antenna testing, she always asks 'won't that one work just as well as the rest?'. They will even ask this as I unload the truck, way before I ever run one up the mast. The runner up for WAF is the CM5646/CM3016. By the way, the SS1000 is the only antenna I have that consistently shows measurable multipath in the signals.
Bob C

Yep,it's a recent arrangement and I'm glad it was in the air when I picked up KMBC-DT-7 in KCMO.There were at least four other CH 7's that had to be nulled! This is the most load I've had on a CM rotor(2 8lb-13ft ants 6ft apart),but it seems to be handling it just fine.

With the crank-up/tilt-over tower and the swing-up mast it only takes a couple of minutes to get things down and change stuff around.There's no end to it :-)

BTW,if someone wants to do a UHF Quad that lives in the middle of nowhere,I've got a Lindsay combiner that I'm not going to put back in the air.It will produce maximum gain hands-down,but not good for Dxing.Pm me if interested,or send an email from my webpage.

Greg B

This has been mostly answered. But just to be clear... No, you don't need to run the wire anywhere. You just need a few feet of it behind the set. Move it around until it works and then tape it to something so it doesn't move.

The wire must be unshielded so coax does NOT work. If you do want to use coax (which you probably have to since you will have a hard time inserting anything in the center pin of the tuner input), then just solder 4 to 6 feet of any wire you have sitting around to the center pint of the coax.

Some equipment used to come with spit wire (T shape) antennas that you served the same purpose. You may want to see if you have one sitting around from an old TV or VCR....

Note that the above is a poor man's antenna (I can just see the RF experts here cringing after they read the above explanation ). You are really better off getting a small indoor antenna. I just said mentioned the above choice since you said you are very close to stations....

Amir

[quote=holl_ands]...
Of course, this only addresses the gain parameter and not F/B and multipath rejection,
but since gain is obtained by narrowing the antenna pattern, they are related.
...
QUOTE]
I think Bob Chase's test was showing net gain not raw gain so a low signal level measurement does not necessarily mean a poor antenna pattern; it could also mean a poor impedance match (high VSWR) which is the reason most UHF antenna's have much less signal than a dipole in the VHF band.

Anyone try/using this new antenna, which is new on the market?

Supposed to be at Best Buy, but I can't find one in my local store.

Any feedback?

Just ran across the fol DIY TV antenna: it's a narrowband UHF Yagi:
http://mysite.verizon.net/vandeb/hdtv_web/hdtv_ant.html

Back to Greywolf on grounding (I was sidetracked from this project by Rita - fortunately no damage)

Thanks for all the help. I thought I was ok, until I saw the part about the lead in not running close to the physical ground. Unfortunately mine does. This may be a tough one to get right because I am in a townhouse and the ground lead is running under the gate to my patio to get over to the single point ground rod that the electrical box and phone are tied to.

I could add another ground rod (not easily) to avoid this, but then I don't get the single point tie in.

Sorry for all the questions. Youv'e been a great help.

Just use a copper wire for the ground lead. Only aluminum is to be kept away from the earth.