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Yagi vs Bowtie/Gray-hoverman for long distance Rx?

post #1 of 16
Thread Starter 
If I have any hope at all to pick up any US stations here in London (ON), I'm thinking I'm going to need the best UHF antenna and the best pre-amp possible.

So I'm wondering what the general consensus is when it comes to yagi vs bowtie / gray-hoverman.

Is it possible to wire up 2 (or more) yagi's in parallel?

Is there such a thing as a 12 or 16-bay GH?

I'm looking at the Winegard AP 4800 (UHF 28 dB, Noise: UHF 2.7 dB). It's a UHF-only pre-amp. Is there anything better?
post #2 of 16
It doesn't matter how you get the beam pattern you get. Log-Yagis tend to be preferred for VHF because multi-bay bowties and Hoverman-style antennas get very unwieldy at those frequencies. The bowtie and Gray-Hoverman are preferred by do-it-yourselfers because they're much easier to build than a yagi/corner-reflector or UHF log-periodic.

You can certainly stack yagis, and you can make a 16-bay bowtie:

http://www.hdtvprimer.com/ANTENNAS/16bay.html
post #3 of 16
Quote:
Originally Posted by sumguy99 View Post

If I have any hope at all to pick up any US stations here in London (ON), I'm thinking I'm going to need the best UHF antenna and the best pre-amp possible.

I used Google Earth to find the latitude and longitude of a point in central London, and fed it to tvfool.com:

http://www.tvfool.com/?option=com_wr...bc2721178fac83

It looks like Detroit, Cleveland and Buffalo stations are all in the 105 to 120 mile range, in different directions of course. The noise margin (NM) starts at -15.6 dB which is very low, and goes downward from there. I can get a few stations at the -15 dB level, but only at night with suitable weather conditions. They are not stations that I can rely on. This is with a top of the line UHF antenna (91XG) and pre-amp (CM 7777).
post #4 of 16
I second jtbell's suggestion for an antenna and preamp. Anything better is in the exotic (expensive) category.
http://www.hdtvprimer.com/ANTENNAS/comparing.html
http://www.antennasdirect.com/91XG_HDTV_Antenna.html
Quote:


Is it possible to wire up 2 (or more) yagi's in parallel?

Yes, this is called stacking. Four is often called a "quad."
Quote:


Is there such a thing as a 12 or 16-bay GH?

There is an XGH (Extended Gray-Hoverman):
http://www.digitalhome.ca/forum/showthread.php?t=96624
http://www.jedsoft.org/fun/antennas/dtv/xgh.html
http://www.jedsoft.org/fun/antennas/index.html his antenna index
http://www.jedsoft.org/ his main page

But I think you are better off with the 91XG, the XGH has narrow bandwidth.

My biggest concern is the strong local signals that you have that will cause preamp and tuner overload when you use an antenna and preamp with enough gain to do what you want. You might need a CH 10 bandstop filter from Tin Lee to knock down CFPL. Your exact location in London might make a difference. If you enter your exact coordinates at tvfool.com you will be able to tell. The last digits will be blocked to protect your exact location if you post the URL for the results here.
http://www.tinlee.com/index.php

How high is your antenna and how long is the coax downlead?
post #5 of 16
Quote:
Originally Posted by jtbell View Post

I can get a few stations at the -15 dB level, but only at night with suitable weather conditions.

Correction: the two stations I was thinking of are actually around -10 dB NM. Right now I get them about 3 or 4 nights a week. During the summer they're more consistent, but still only at night.
post #6 of 16
Thread Starter 
> > Is it possible to wire up 2 (or more) yagi's in parallel?

> Yes, this is called stacking. Four is often called a "quad."

If I wire two antenna's in parallel, I suppose I should use 300-ohm twinlead - yes? And then would the effective impedance of the two antenna's be 150 ohms - requiring a 150-ohm to 75-ohm balun?

And BTW, is there any general consensus here as to what is the best UHF antenna pre-amp? Still looking for comments on the Winegard AP 4800.
post #7 of 16
I assume you are talking about two identical yagis pointed in the same direction.
How they are combined depends upon the feedpoint impedance.
Usually, if the 2 antennas have a 300 ohm impedance feedpoint, you would connect each of the 4 to 1 baluns to a 75 ohm splitter/combiner using equal lengths of coax. It is important that the two antennas be properly phased together. If you get less gain with two antennas than with one, reverse the 300 ohm connections at the antenna of ONE of the baluns.

Phasing together two yagis with 300 ohm twinlead is not a good idea because its impedance changes a lot when it gets wet or covered with ice and it flaps around in the wind which also changes its impedance as it moves closer and further away from metal objects.

I have no personal experience with the Winegard AP 4800, so I can't comment on it except to say that Winegard has a good reputation. I like my CM7777, but it has a tendency to overload with very strong signals. The Winegard HDP-269 has less gain, but resists overload better. The length of your coax feedline is also a factor to consider when you select a preamp. If you look at the tvfool results posted by jtbell in post #3 you will see that the CFPL CH 10 signal pwr is -4.7 dBm and marked in red which indicates possible overload.

Before we give any more answers about your desire to receive US stations, we really need to see what your tvfool.com results are based on your exact coordinates. This is because London ON has some very strong transmitters near the center of the city. If you live North of the center of London your antenna will be pointed at these very strong local stations that will make it difficult to receive US stations. It would be a lot easier if you lived well South of the center of London because the back of your antenna would then face the strong local stations.

LL
LL
post #8 of 16
Quote:
Originally Posted by sumguy99 View Post

If I have any hope at all to pick up any US stations here in London (ON), I'm thinking I'm going to need the best UHF antenna and the best pre-amp possible.

So I'm wondering what the general consensus is when it comes to yagi vs bowtie / gray-hoverman.

Is it possible to wire up 2 (or more) yagi's in parallel?

Is there such a thing as a 12 or 16-bay GH?

I'm looking at the Winegard AP 4800 (UHF 28 dB, Noise: UHF 2.7 dB). It's a UHF-only pre-amp. Is there anything better?

To answer your question,Yes you can find commercial made 16 bay G-H antennas.Google in Summit Source amd look for the STACKED SUPER G .It's complete w/phasing harness Northeast Indiana has a huge presence of these antennas.Toying with the idea of replacing my 5ft. parabolic with one ,too narrow of beamwidth.
post #9 of 16
Please explain why this one (the stacked Super G)


has more gain than this one?
post #10 of 16
Quote:
Originally Posted by arxaw View Post

Please explain why this one (the stacked Super G)


has more gain than this one?

I don't think the pictures match the description. The $105 16-bay is 2 of the $46 8-bay Super-Gs mounted side by side, give it a 3db improvement in gain.
The picture accompanying the 16-bay is 2 4-bays side by side.
post #11 of 16
Thread Starter 
This is the report for my location from tvfool.com:

http://www.tvfool.com/?option=com_wr...bc273ef6dfa2aa

I entered 20 feet (above ground level) for the height of my antenna. My hand-held GPS tells me that the height (above sea level) of my antenna is about 905 to 915 feet. For what it's worth, lake erie water surface is 571 feet ASL.
post #12 of 16
Quote:
Originally Posted by arxaw View Post

Please explain why this one (the stacked Super G)


has more gain than this one?

The above pic has a second pair above it w/phasing lines and combiner.High gain wide beamwidth,light in weight very "rotor friendly"
post #13 of 16
sumguy99:

Thanks for posting your tvfool results. It gives us a good idea what your situation is at your location which seems to be only 1 mile WNW of the very strong CFPL transmitter (368.2 kW ERP) which most certainly will cause overload. Actually the first 3 are going to be a problem when you are trying to receive US stations which will probably require some fancy filters. But, you'll just have to try it to find out for sure. The difference between CFPL and WICU 101.7 dB! That's a problem that even the easy-to-talk-to talented engineers at Tin Lee Electronics Ltd in Toronto might not be able to solve. They might even be tempted to suggest that you move a little South to St. Thomas (just kidding), in which case your tvfool report would look like this:
http://www.tvfool.com/?option=com_wr...bc27ba7453e316

WICU is on CH 12 and will require a VHF-hi antenna with a lot of gain.

There might be some hope in the future because an application is pending for CFPL to go digital; see the attachment.

A few words about stacking two antennas:
Antenna theory says that the max increase in gain would be 3 dB, but I have never measured more than 2.5 dB from stacking two identical antennas aimed in the same direction.

Your first effort should be in finding the best location for one antenna, because I have often measured an increase in signal strength of more than 10 dB when moving an antenna from its initial location to the best location possible, which is more than stacking 8 would give you (3 dB each time you double the number of antennas).

Have you talked with the other guys in your area to see what works for them?
http://www.digitalhome.ca/forum/forumdisplay.php?f=129
http://www.digitalhome.ca/forum/show...115171&page=31esp. post #452 & 454
LL
post #14 of 16
Quote:
Originally Posted by rabbit73 View Post

very strong CFPL transmitter

I think that must be the Canadian station we used to get a very snowy signal from when I was a kid growing up about fifty miles south of Lake Erie, not far from Youngstown, Ohio. Channel 10 rings a bell in the back of my head.
post #15 of 16
Thread Starter 
Quote:
Originally Posted by rabbit73 View Post

Thanks for posting your tvfool results. It gives us a good idea what your situation is at your location which seems to be only 1 mile WNW of the very strong CFPL transmitter (368.2 kW ERP) which most certainly will cause overload. Actually the first 3 are going to be a problem when you are trying to receive US stations which will probably require some fancy filters.

Let me ask this question:

I have zero experience or knowledge of satellite receiver systems, nor of what is broadcast "in the clear" by any satellites (FTA or other-wise) that I might be able to pick up. Is it possible to pick up US network feeds that are not scrambled? ABC / NBC / CBS / PBS ?
post #16 of 16
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