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The Official AVS Antenna and Related Hardware Topic! - Page 275

post #8221 of 16086
If you have access to a spectrum analyzer and a pre-amp you could measure the real world gain of any UHF antenna using the sun. That would take many of the local error sources like terrain and trees out of the measurement.
post #8222 of 16086
OMG!!!

I don't know if this has been mentioned before, but in the antennasdirect.com manual for installing antennas, it has this warning:

Quote:


WARNING
Do not attempt to install if drunk, pregnant or both.
Do not eat antenna.
Do not throw antenna at spouse.

Source: http://www.antennasdirect.com/pdf/ge...structions.pdf

Man I was taking those instructions seriously until the last minute..
post #8223 of 16086
Quote:
Originally Posted by NightHawk View Post

If you have access to a spectrum analyzer and a pre-amp you could measure the real world gain of any UHF antenna using the sun. That would take many of the local error sources like terrain and trees out of the measurement.

Local TV signals would swamp any signals coming from the sun....fortunately....
otherwise we would ALL be watching the "SUN" channel.
post #8224 of 16086
Wow, with all of this information overload, we should all be antenna design engineers by the end of the week.
post #8225 of 16086
Quote:
Originally Posted by DrLar View Post

OMG!!!

I don't know if this has been mentioned before, but in the antennasdirect.com manual for installing antennas, it has this warning:
Source: http://www.antennasdirect.com/pdf/ge...structions.pdf
Man I was taking those instructions seriously until the last minute..


HA HA HA HA HA!!!
post #8226 of 16086
Quote:
Originally Posted by DrBri99 View Post

Yes I would like to turn it by hand. I have the antenna eave mounted, and I can get directly beneath it by opening a window which leads to the porch roof. I guess I could make one by placing something on the porch roof to hold the mast.

That sounds like a good situation for "manual" rotor. What you need is something on the porch to serve as a pivot and a lock for the mast (or mast extension). Then you can loosen the eave mount clamps slightly so turning would be possible.
Good Luck.
post #8227 of 16086
Quote:
Originally Posted by holl_ands View Post

Local TV signals would swamp any signals coming from the sun....fortunately....
otherwise we would ALL be watching the "SUN" channel.

Not really. Unless the local signals are strong enough to saturate the pre-amp(s), with the antenna aimed at the sun, the choice of analyzer settings can prevent their interference. Specifically, attention to the choice of frequency and RBW on the analyzer is made to prevent this. Since the sun is a broadband noise source whose value is measured everyday it makes an excellent calibrated point source and analyzer RBW does not affect the results (other than mentioned to prevent interference). I perform this measurement often using UHF and VHF parabolas and it's quite accurate.
post #8228 of 16086
Quote:
Originally Posted by jsauser11 View Post

two of the locals are moving back to VHF High (channel 7 and channel 9). I am worried my DB-8 is going to have a difficult time picking them up noise free at that time.

How do the current analog signals look on ch 7 and 9?
post #8229 of 16086
Quote:
Originally Posted by jtbell View Post

How do the current analog signals look on ch 7 and 9?

Channel 9 analog looks fine. Channel 7 is just ok, with some horizontal noise bars across the screen.
post #8230 of 16086
My XG-91 is performing quite well... but in my situation, I'd like to get more signal and have things be more stable.... so I've decided to stack 2 of them. What is the criteria one uses to decide if you stack vertically or horizonatally?
post #8231 of 16086
Vertical stack will narrow the vertical gain pattern, while a horizontal stack will narrow the gain field horizontally. In most cases horizontal will yield a little better results. What will work even better, is to get you antenna in a position where there is more signal. That usually mean either higher, or a different location where the signal is hotter.
post #8232 of 16086
Can someone recommend an antenna based on the pic below? I want to be able to view all the stations, but am unsure which one I need..

Thanks,
Tony
LL
post #8233 of 16086
Tony,

What's your ZIP code? I'd like to plug it into TVFool since the AntennaWeb site tends to be way too conservative about what you can receive.
post #8234 of 16086
I tested it both ways, and horizontal stacking yielded better results. If you decide to drive forward with this, just shoot me a PM, and I can go over the process.

Go here:
http://www.avsforum.com/avs-vb/showt...3#post13898183


Quote:
Originally Posted by alphanguy View Post
My XG-91 is performing quite well... but in my situation, I'd like to get more signal and have things be more stable.... so I've decided to stack 2 of them. What is the criteria one uses to decide if you stack vertically or horizonatally?

 

The Bracket.pdf 423.40625k . file
post #8235 of 16086
Well, Tony, the color coding is described at the antennaweb site
http://www.antennaweb.org/aw/info.as...more_info#mark

You then have to look for UHF vs VHF stations and find that VHF only needs yellow, but UHF needs red. That's about all you get from antennaweb - small multi-directional VHF plus a small directional UHF antenna outdoors. All antennas have the little color wheels, and you can make a choice based on that.

If, however, you posted the results from TVFool.com, you'll find a lot more detail and precision because the modeling is more sophisticated. It doesn't sell antennas, it gives you a rational basis for choosing one.

Frank
post #8236 of 16086
Midwest users, this will be a great weekend for some DX'ing. I have not seen the map light up like this in years.

Check here: http://www.dxinfocentre.com/tropo.html

And by the way, it was a night and day difference using the Funke 1922 over the Winegard 1731. Holy Cow, I might buy another one from Greg!
post #8237 of 16086
Quote:
Originally Posted by ziggy29 View Post

Tony,

What's your ZIP code? I'd like to plug it into TVFool since the AntennaWeb site tends to be way too conservative about what you can receive.


My zip is 79416. I went to the tvfool website, and all of my channels are green or yellow. It said something about a medium gain antenna would get these channels. The antenna will go outside the house, attached to the eve of the house or the fireplace. It is a single story house. Do I have to worry about zeroing in an antenna to the tower, like you do with a satellite dish?

Thanks for all the help!
Tony
post #8238 of 16086
Quote:
Originally Posted by Turbulent View Post

My zip is 79416.

We should all have it this easy!

I think a small to medium directional antenna that gets high VHF and UHF, with no amplification, would be enough. Get one with a relatively wide beam width (30-40 degrees or more) aimed at about 130 degrees and you should be good to go.
post #8239 of 16086
Quote:
Originally Posted by ziggy29 View Post

We should all have it this easy!

I think a small to medium directional antenna that gets high VHF and UHF, with no amplification, would be enough. Get one with a relatively wide beam width (30-40 degrees or more) aimed at about 130 degrees and you should be good to go.

Got any recommendations for a good antenna that fits this? How do I aim it at 130 degrees?
post #8240 of 16086
Quote:
Originally Posted by Turbulent View Post

Got any recommendations for a good antenna that fits this? How do I aim it at 130 degrees?

I don't know too much about this class of antenna from personal experience, so I'd leave that for others who do. I think a single medium directional antenna that gets both UHF and high VHF is fine in your case, since these signals are strong enough that you don't need to maximize gain. I'd start by keeping it as simple as possible in your case; I see no need to spend a LOT of time and money on getting the "just right" setup when your information indicates that an adequate single UHF/VHF antenna pointed in the right place with no preamp is likely sufficient. In your case, don't let pursuit of the perfect be the enemy of the "good enough." You have a lot of strong signals, all of which are in the same general direction.

"Aim it at about 130" means that you point the antenna in the direction where front of the antenna points to 130 degrees azimuth. 0 is north, 90 is due east, 180 is due south and 270 is due west, so you'd be basically pointing it to the southeast.

All of your signals are between about 111 and 141 in azimuth (see the TVFool output), meaning they are all to your southeast. That's a 30 degree band. So if you get a medium directional with more than 30 degrees of beam width (that is, it's good at picking up a signal within a 30 degree arc or more) and point the antenna toward somewhere in the middle of the 111-141 range, you should be able to get just about everything listed in green and yellow. Fine-tuning it in that general direction, preferably with a helper to shout out the signal strengths from various directions and for VHF/UHF) will make it much easier.

You don't really need a compass to aim it exactly at 130 or anything else. But if you know generally which way is due southeast, you'll be close and can swivel it a little bit until you have good digital reception on everything. It's not nearly as exact as aligning a satellite dish.
post #8241 of 16086
Thanks for the help Ziggy. Ive had cable/satellite all of my life and have never used an antenna before.

Ive been eyeballing this antenna http://channelmasterstore.com/Channe...B000BSFK7Y.htm with this new information. Does anyone have an opinion on this and my specific area? Or would this be a good matchup?
post #8242 of 16086
Hi All:

Just found out that I will have a future digital VHF channel 6 about 51 miles away over rather flat land. I have two identical 25-year-old Radio Shack FM-only yagi antennas (the larger of the two long-discontinued models, 10 or 12 elements, I think). They are essentially brand-new, as they have always only been used in the attic, and they provided good FM reception (prior to digital FM hiss splatter) for stations 75+ miles away.

I realize that the FM band (88-108 MHz) is a little off from VHF channel 6 (82-88 MHz), and of course it will depend on the power of the digital channel 6. But with no other VHF-low channels coming to my area, I was wondering if an FM-only yagi of this sort could possibly work well as a single-channel antenna for this future channel 6.

Thanks in advance...
post #8243 of 16086
Quote:
Originally Posted by gcd0865 View Post

I realize that the FM band (88-108 MHz) is a little off from VHF channel 6 (82-88 MHz), and of course it will depend on the power of the digital channel 6. But with no other VHF-low channels coming to my area, I was wondering if an FM-only yagi of this sort could possibly work well as a single-channel antenna for this future channel 6.

Most likely an FM yagi would have some gain for channel 6. But my concern is that FM interference would overwhelm channel 6.

If there was a chance to return it if it didn't work, it might be interesting to get a VHF preamp with an FM trap for this one. You might need a preamp from 51 miles out anyway, depending on the gain of the antenna, and maybe the FM trap could attenuate the signals from 88-108 MHz. I don't know how well it would work, but it would be an interesting experiment...
post #8244 of 16086
100% agree with ziggy...
post #8245 of 16086
Brian Breezley (K6STI) NEC simulation results for FM Antennas:
http://ham-radio.com/k6sti/curves.htm
http://ham-radio.com/k6sti/index.html
[Also includes HD Radio Receiver reviews, et. al.....]

Since an FM antenna has already been optimized to cover the 20 MHz wide FM Band,
VSWR and hence gain are gonna nosedive as you try to go down yet another 6 MHz.
So try to extrapolate where you think the gain curve will be a couple inches to the left...
Some are pretty good....others are really bad....

PS: In addition to gain loss, VSWR mis-match can result in ADDITIONAL DTV sensitivity loss
(in below papers, Oded Bendov calls it an increase in Noise Figure):
http://www.tvantenna.tv/papers/dtv%2...prediction.pdf
http://www.tvantenna.tv/papers/PFactorsV.pdf
post #8246 of 16086
Quote:
Originally Posted by holl_ands View Post

Since an FM antenna has already been optimized to cover the 20 MHz wide FM Band, VSWR and hence gain are gonna nosedive as you try to go down yet another 6 MHz. So try to extrapolate where you think the gain curve will be a couple inches to the left...Some are pretty good....others are really bad....

Right, and agreed. But unless we know the specifics of this antenna, we don't know if it's one that plummets quickly below 88 MHz. So I still say if someone felt confident that they could return a preamp with FM trap if it fails to work and they don't mind the labor, it's worth trying, most likely. If it's an antenna with significant gain from 82-88 MHz, it may work well. If it's one that drops off sharply below 88, maybe not. Without knowing the specific antenna, it's hard to say.

[Edit to add: Plus, there's a decent chance between now and 2/2009, some low VHF stations will be reassigned elsewhere since pretty much all stations now assigned to low VHF are trying to move. I wouldn't spend much money or effort trying to get stations that *might* be on low VHF next year until I knew it was a done deal. If we get to December and the channel hasn't changed, it might be time to make the investment.]
post #8247 of 16086
If you already have the antennas i would see how they worked out.
I wouldnt put a ton of effort into them.. but hey see what you got.

If not then get a VHF low band yagi.

John
post #8248 of 16086
A couple of years ago, I had a FM yagi that I wasn't using so I had the same idea, only I was looking at receiving a channel 5 from 70 miles away. I thought that since Yagi antennas drop off in gain more gradually below the design frequency that above, it might work. It didn't. Reception of that channel is usually fairly good here with a wide band VHF antenna, but the FM just didn't produce anything on channel 5.
post #8249 of 16086
Or, spend some time on the antenna making thread
http://www.avsforum.com/avs-vb/showt...798265&page=10
and find some neat ideas for cheap-but-effective VHF bowtie antennas.
Frank
post #8250 of 16086
Quote:
Originally Posted by holl_ands View Post

You could also try a simple UHF loop:http://www.cnaweb.com/index.asp?Page...OD&ProdID=1843

Holl_ands, what would be the technical difference as an indoor aerial between a UHF round loop, a UHF rectangular loop, a UHF flat-panel array, and a UHF outline bow-tie?

UHF round loop examples: RCA ANT110, CNA 72-121

UHF rectangular loop example: RCA ANT111

UHF flat panel array example:Philips SDV2210/17

UHF outline bow-tie example: Radio Shack 15-234
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