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post #11731 of 17920 Old 09-30-2009, 03:37 PM
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[quote=ProjectSHO89;17273346]Nonsense. According to a little birdie, returns have been less than 2% and most of them were from people who didn't know what they were doing or self-selected the wrong antenna. About 1/4 of the returns were never even assembled.

Most posters here (on AVSforum) only come on when they have problems. You rarely hear the success stories. Station engineers who received samples of the C5 to try out have reported excellent results. One even reported good results with it on VHF-5 at about 25 miles, something that was unexpected.



While the c5 may be a great antenna, the c4 was not good at all. I actually took it out of the box, and mounted it 25ft above ground, and it still
was below SECOND rate.
I beleive most posters are looking for answers, and those who respond either say... I had good results with bla bla, or I had bad results with bla bla. I value the opinions of the posters on avs forums, and once in a blue moon will you get a station engineer to respond...

Tired
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post #11732 of 17920 Old 09-30-2009, 04:06 PM
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Quote:
Originally Posted by ray50 View Post

Just took down a huge HD8200P and added an 2nd XG91 (all stations I want are now UHF). I now have a vertical stack with the two XG91s about 4' apart. They are combined on the mast and feed a Winegard AP-8275. I expected a BIG improvement over 1 XG91, but see only a very small improvement (a few % maybe). I used equal length 6' RG6 to the combiner (http://www.directdepot.net/product_i...ducts_id=22826) to the preamp. Maybe horz. stack is better but vert. was easy because I had a 4' mast to add. Shouldn't I see a bigger improvement??

I can't get the link to work. Is your combiner one of these?:
http://www.directdepot.net/advanced_...&Submit=Search

The maximum theoretical improvement is 3 dB. When I combined two CM4221 UHF antennas for CH 15 I measured 2.5 dB gain using selected baluns. When two baluns are used they must be phased correctly. If you measure less gain then try reversing the 300 ohm connections on one of the baluns. I don't know what the feed connection for the XG91 is......I think it has an integral black balun box. Combining two antennas with a splitter/combiner is an "iffy" proposition. Sometimes it works; sometimes it doesn't:
http://www.hdtvtruckee.com/
http://www.hdtvtruckee.com/CombinerMeasurement.htm
http://www.hdtvtruckee.com/CombinerComparison.htm

You didn't say what equipment you are using to measure the percentage, but it's an arbitrary scale that varies according to the equipment used. When I calibrated the signal strength scale on my Apex DT502, using the method described in the Kelvin link in my signature, I got this (compare the 3 dB attenuator steps with the percentage change on the strength scale):
https://www.avsforum.com/avs-vb/showt...6#post15414426
https://www.avsforum.com/avs-vb/showt...0#post15790650

There is also a signal meters ... true lies? thread:
https://www.avsforum.com/avs-vb/showthread.php?t=1146498
Quote:


Maybe horz. stack is better

Horizontal stacking is more popular because it narrows the horizontal beamwidth (as in the 4228 vs the 4221). So, even if you don't end up with more gain, the narrower horizontal beamwidth often reduces multipath errors which makes it easier for the tuner to maintain lock on a weak signal.

Edit: ProjectSHO89 in the next post gives a link to some good ideas by Piggie about gain and other characteristics of antennas; don't miss it!

If you can not measure it, you can not improve it.
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post #11733 of 17920 Old 09-30-2009, 06:07 PM
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Quote:
Originally Posted by Don F. View Post

Quote:
Originally Posted by ProjectSHO89 View Post

Nonsense. According to a little birdie, returns have been less than 2% and most of them were from people who didn't know what they were doing or self-selected the wrong antenna. About 1/4 of the returns were never even assembled.

Most posters here (on AVSforum) only come on when they have problems. You rarely hear the success stories. Station engineers who received samples of the C5 to try out have reported excellent results. One even reported good results with it on VHF-5 at about 25 miles, something that was unexpected.

While the c5 may be a great antenna, the c4 was not good at all. I actually took it out of the box, and mounted it 25ft above ground, and it still
was below SECOND rate.
I beleive most posters are looking for answers, and those who respond either say... I had good results with bla bla, or I had bad results with bla bla. I value the opinions of the posters on avs forums, and once in a blue moon will you get a station engineer to respond...


How ironic that I just came across this post on another forum: http://www.dtvusaforum.com/dtv-hdtv-...r-antenna.html

Must be a blue moon!
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post #11734 of 17920 Old 09-30-2009, 07:15 PM
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Quote:
Originally Posted by Don F. View Post

While the c5 may be a great antenna, the c4 was not good at all. I actually took it out of the box, and mounted it 25ft above ground, and it still
was below SECOND rate.
I beleive most posters are looking for answers, and those who respond either say... I had good results with bla bla, or I had bad results with bla bla. I value the opinions of the posters on avs forums, and once in a blue moon will you get a station engineer to respond...

I'm pretty happy with my C4. Despite being an attic mount, I get the Albany UHF stations pretty well even though they're over 66 miles away. Sure, there are better UHF antenna's out there, but for the size it's pretty hard to beat the C4. In fact on a good day, I've even gotten WYNE and WFUT, which based on my TVFool results is pretty impressive:

http://www.tvfool.com/?option=com_wr...8ecdbb879d1a14

Of course YMMV.
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post #11735 of 17920 Old 10-01-2009, 11:21 AM
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Thanks rabbit73 for all the information. I assumed adding another antenna would be a no brainer if I was careful to align them. Your correct the link doesn't work... it is a Channel Plus 2532. The XG91's have a black box balun with 75ohm output. I see the tilt is off a little but other then that they are directly vert. with the driven elements the same distances from the mast. I will do some more reading...I had just the upper one before which just could receive a CBS channel I wanted but with many dropouts. At the lower position it couldn't see CBS at all. Guess it makes sense that if I run the upper XG91 through a combiner my total signal for that channel will drop.
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post #11736 of 17920 Old 10-01-2009, 12:10 PM
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I got the WG 7697P up and running.



Used my laptop running Win 7 RC1 media center and the Pinnacle 800e usb tuner and a short run of coax to dial it in. Much better than running down the ladder and inside between adjustments.

I am a little disappointed, though I am not sure the antenna is doing anything wrong. I think I am in a worse area than I thought, at least as it pertains to the fringe channels I thought I would get.

In short, I think I have quite a few channels that aren't LOS, contradicting TV Fool. The reception results that I got did not correlate with antenna alignment, at least as far as my understanding that all of my channels were available LOS at 15 feet.

The Boston CW and ION that I wanted to receive, nay, expected to receive and why I purchased a high gain antenna like this, were too weak, even pointed directly at the Boston towers.

We tried clocking the antenna at as many discrete positions as we had time for, with the rapidly fading light last night. We let Media Center run through the signal strength loop each time we moved the antenna. The best overall reception seemed to be pointing at the only real open spot out of my neighborhood, or about 300°. As a refresher I was expecting to receive the strong RI stations @ 41° and the weaker Boston stations at 28-29° while pointed at ~32°. Well, how about 300? And surprisingly I get RI CW from 83° and ION from 258°. I think I have a multipath problem, no? I did get Boston CW best as LOS I think, but "best" was only 3 out of 6 bars which I know would never be reliable enough to bother with. And Boston ION never came up over 1 or 2 bars.

Do I need to add height? An amp? Experiment more with aim? Should I have gotten the 14 foot 7698P, after all that deliberation???

I think trees and maybe some roofs of houses may be in the way, but definitely big pines.

I know the Winegard antennas suffer during shipment (and possibly manufacture) and after doing some reading I am going to take a close look at the crossover/balun box and make sure the prongs are making contact with the wires. I am also going to straighten all the elements, even the ones only slightly bent.

Overall I get more channels than before, but instead of the 24 I thought I'd get, I am down around 19 or so.
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post #11737 of 17920 Old 10-01-2009, 01:12 PM
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See that tree that the antenna is pointed right into? You don't need a bigger antenna or an amp, you need a STIHL! Make firewood out of it!

If you can, try re-locating the antenna towards the left (of the photo) so it isn't staring right into a nearby tree.
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post #11738 of 17920 Old 10-01-2009, 01:27 PM
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Quote:
Originally Posted by kevm14 View Post

I think trees and maybe some roofs of houses may be in the way, but definitely big pines.

I've got an 18" Husqvarna and a pickup.
PM me the details and I'll be over on Sunday to take down all those trees and haul away the hardwood logs.
And THANKS!!
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post #11739 of 17920 Old 10-01-2009, 02:15 PM
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I would try a low gain preamp and try with the computer a larger distance from the antenna. The next step would putting the antenna 6-10 feet above the peak of the roof.
John
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post #11740 of 17920 Old 10-01-2009, 02:31 PM
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Quote:


I think trees and maybe some roofs of houses may be in the way, but definitely big pines.

Thanks for the photo, Kevin. It gives us a good idea of what's going on.

I quote Ken Nist, KQ6QV, from his hdtvprimer site (which seems to be down at the moment, otherwise I would have given links):

Quote:


Trees as obstructions -

A tree has very little effect on VHF-low, but a significant effect on VHF-high. But the big problem is UHF. A tree with leaves blocks about 90% of a UHF signal. The space behind the tree is an overlap of the signal going through the tree and the signal diffracting around the tree. Such overlapping fields have an alternating pattern of strong and weak spots separated by only a few feet. An antenna in a strong spot might work nicely until the wind blows, deforming the tree and moving the spots. Thus, for DTV stations, you are likely to see dropouts when the wind blows. Even in a good-signal neighborhood it is inadvisable to put a UHF antenna behind a tree.

If the tree loses its leaves in the fall, reception behind it will improve dramatically. Many people get a TV for Christmas, and erect an antenna for it in January, and then wonder why it quit working in May. It’s the trees.

The farther away a tree is, the less of a problem it is. For far away trees, assume no signal penetrates the tree, and reception will be by diffraction around the tree. See Diffraction.

Trees block 100% of satellite signals.


If you can not measure it, you can not improve it.
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post #11741 of 17920 Old 10-01-2009, 06:06 PM
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Quote:
Originally Posted by SemiChemE View Post

I'm pretty happy with my C4. Despite being an attic mount, I get the Albany UHF stations pretty well even though they're over 66 miles away. Sure, there are better UHF antenna's out there, but for the size it's pretty hard to beat the C4. In fact on a good day, I've even gotten WYNE and WFUT, which based on my TVFool results is pretty impressive:

http://www.tvfool.com/?option=com_wr...8ecdbb879d1a14

Of course YMMV.

My problem with the c4 was not uhf, but it's claim to be a vhf antenna. Probably works los within 40 vhf miles...

Tired
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post #11742 of 17920 Old 10-01-2009, 06:51 PM
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I had picked out the Avermedia Duet since I want a dual tuner with internal splitter. Any thoughts on that one? It is fairly new as well. Newer than the other competing dual tuner on the market, the Hauppauge 2250 (which also does NTSC).

Yeah, the Avermedia Duet is really recent and should have 6th gen tuners in it as well.

Like everyone else says, those trees are a huge obstacle for you. When the leaves fall, will there be any clear line thru them ?

Quote:


The next step would putting the antenna 6-10 feet above the peak of the roof.

I would go about 30 - 40 ft above the roof with guy wires to clear the trees. (or are they even higher than that ?) The WG 7697P doesnt look heavy or like it would have a lot of wind load.
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post #11743 of 17920 Old 10-01-2009, 07:10 PM
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I removed a few of the problem branches from the leafy tree closest to the antenna. As I also mentioned I had 4 very large white pines removed from my front yard only a few weeks ago. It was a very big job...I have those pictures elsewhere on my gallery if anyone is interested

Here are all the pictures of how the antenna is currently aimed. It is about 308 degrees. My signals of interest are between 28 and 41...so obviously something is going on. I took a picture at what I thought would have been my ideal aim, about 32 degrees. As you can see I did remove some of the problem leaves. I also plan to take the entire tree down but the rest of the trees are large white pines that are gonna cost probably $600 or $700 each to remove, and they're not mine.

http://kevinallenmoore.com/photo/v/misc/ATSC/
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post #11744 of 17920 Old 10-01-2009, 09:09 PM
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It is about 308 degrees. My signals of interest are between 28 and 41...so obviously something is going on.

Your stations at 41 degrees are very strong, above 47 NM for the most part, so no surprise getting those just about any way the antenna is pointed.
Can you get channel 9 and 26 at 265/274 degrees now ?
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post #11745 of 17920 Old 10-02-2009, 05:56 AM
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I don't think so. I recall 29 coming in while I was on the roof but I don't think the current aim is ideal for that.

I do get CW, 28.1 from 83° at 4/6 bars and ION 69.1 from 258°. My original plan was to somehow receive these. Unfortunately, I lost a Boston ABC 5.1, PBS 2.1 and independent 38.1, while aimed at my current 308°. If I aim towards Boston I get the channels back that I lost but then I get no CW or ION...boston or otherwise. The two Boston versions I thought I'd get.

I went back on the roof last night and tried to straighten the elements. I looked up at the antenna this morning and I could still do a better job.

I also removed the crossover box and bent the prongs inward a bit so they grab the wires a little better. That didn't seem to make a difference, though perhaps I should put the antenna back at 32° after I get that tree down and see what happens.

One more thing...is there any reason I should persue the exchange of 7697P for the 7698P? It has 1.6dB more gain at RF 32, which was the Boston ION that I had such trouble with. From RF 25 to 40 the 7698P provides 1dB or more of increase from 7697P. Should I bother or are my environmental and/or geographical issues much bigger?
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post #11746 of 17920 Old 10-02-2009, 07:20 AM
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Quote:
Originally Posted by kevm14 View Post

Wow that is a bad area. What is your antenna height?

Also I looked up those antennas. They are pretty high gain. How much do you think you lose by splitting? And do you have them pointed in the same direction? You have a lot of stuff at 90d but not everything.

You know what else I realized...you probably don't need a fancy band pass/cut combiner. You might even be able to use a splitter backwards. What do you use?

If this is a response to my last post, the uhf is at about 25 ft AGL and the VHF is mounted 4 ft below. I didn't use a combiner I wired the YA 1713 to the VHF terminals on the HD 9022 with quad cable and CM baluns and then the HD-9022 to the preamp. I wasn't worried about losses from the YA-1713 as we have no problem getting the VHF signals, just the UHF. I think the CM baluns have about 0.5 db loss, so I might have lost 1 db as it takes 2 to connect. I suppose I could have used shielded 300 ohm and had no loss, but it wasn't worth the trouble tracking down a couple of feet of 300 ohm. See the attached photo below.

I pick up the major Philly networks (including ch 6) as well as the NYC networks and the array is pointed at NYC. Lots of trees in the way plus 2 or 3 ridges. We are the only people in our neighborhood still using OTA. I may add another HD 9022 to improve WOR and WNYW reception and maybe eliminate the multipath interference we get when aircraft fly over as we are on a major flight path to NYC and Newark and probably Philly. But that's next year's project.


OZ
LL
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post #11747 of 17920 Old 10-02-2009, 07:23 AM
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Hmm that makes me wonder if I end up having to raise mine, if I should relocate it to the chimney or just put a longer mast on where it is now.
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post #11748 of 17920 Old 10-02-2009, 07:32 AM
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Quote:
Originally Posted by ray50 View Post

Just took down a huge HD8200P and added an 2nd XG91 (all stations I want are now UHF). I now have a vertical stack with the two XG91s about 4' apart. They are combined on the mast and feed a Winegard AP-8275. I expected a BIG improvement over 1 XG91, but see only a very small improvement (a few % maybe). I used equal length 6' RG6 to the combiner (http://www.directdepot.net/product_i...ducts_id=22826) to the preamp. Maybe horz. stack is better but vert. was easy because I had a 4' mast to add. Shouldn't I see a bigger improvement??

4 feet is too far apart, they should be 1 wave length apart - ch 14 is about 25 inches measured from boom to boom. Also your connecting cables have to be exactly the same length and your baluns have to be in phase with each other. Its always good to test your antennas on the ground before putting them up. I drove a section of rebar into the ground and slipped the mast onto it for my testing, worked great.

Good luck,

OZ
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post #11749 of 17920 Old 10-02-2009, 08:50 AM
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"Optimum" separation for Horizontal Stacking is a function of the antenna's
boomlength (or beamwidth) and would be MORE than one wavelength:
http://vk1od.net/antenna/dl6wu/EstimatingBeamwidth.htm
http://vk1od.net/antenna/dl6wu/
http://www.ifwtech.co.uk/g3sek/stack...ing2.htm#DL6WU
http://www.grantronics.com.au/docs/StkYagis.pdf

Of course, bear in mind that wavelength for Ch14 is much larger than Ch51,
with lower gain and higher beamwidth. So decide where to optimize....
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post #11750 of 17920 Old 10-02-2009, 09:57 AM
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Quote:
Hmm that makes me wonder if I end up having to raise mine, if I should relocate it to the chimney or just put a longer mast on where it is now.

What you should do is to experiment with the height, looking for the sweet spot. At UHF, even 6 inches can make a difference. And experiment with the height at the time of day you do most of your viewing, probably early evening, like when you took the picture.
Also, what condition is your coax in ? Also, maybe try another balun.
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post #11751 of 17920 Old 10-02-2009, 10:17 AM
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Quote:
Originally Posted by holl_ands View Post

"Optimum" separation for Horizontal Stacking is a function of the antenna's
boomlength (or beamwidth) and would be MORE than one wavelength:
http://vk1od.net/antenna/dl6wu/EstimatingBeamwidth.htm
http://vk1od.net/antenna/dl6wu/
http://www.ifwtech.co.uk/g3sek/stack...ing2.htm#DL6WU
http://www.grantronics.com.au/docs/StkYagis.pdf

Of course, bear in mind that wavelength for Ch14 is much larger than Ch51,
with lower gain and higher beamwidth. So decide where to optimize....

Very nice links the last one in particular as it has a good explanation of phasing. My choice of 1 wavelength came from much searching and a couple links basically said start at 1(reflectors can't touch) and adjust as needed. I can't find the link though so I can't post it.

Your references seem to be all related to HAM radio, and I am not sure if it is absolutely applicable to UHF antennas, especially if someone is stacking the bow-tie types. Here's some more links:

http://www.digitalhome.ca/forum/show...t=41102&page=2

http://www.digitalhome.ca/forum/showthread.php?t=107432

http://www.hdtvprimer.com/ANTENNAS/ganging.html#TAT

Hope this helps.

OZ
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post #11752 of 17920 Old 10-02-2009, 10:23 AM
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The statement from the grantronics.com stacking link of "you should stack at a distance in wavelengths of 57 / 3dB beamwidth in degrees." applies to any antenna at any frequency.
John
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post #11753 of 17920 Old 10-02-2009, 10:37 AM
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Quote:
Originally Posted by 300ohm View Post

What you should do is to experiment with the height, looking for the sweet spot. At UHF, even 6 inches can make a difference. And experiment with the height at the time of day you do most of your viewing, probably early evening, like when you took the picture.
Also, what condition is your coax in ? Also, maybe try another balun.

Wow 6 inches huh?

The coax is all brand new quad shield with compression F connectors installed by yours truly. The only variable is the way I made the connections. The foil would slide back and get crushed down. But comparing to the 8 footer I was using on the roof that was terminated by a cable guy, there is very little signal loss, including the fact that the run probably approaches 60 or maybe even 70 feet.

I bought a balun for my old antenna when I upgraded to the coax from the 300ohm. But this Winegard balun includes crossover circuitry to combine the VHF and UHF sections of the antenna, so I don't know if I could use a conventional balun.
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post #11754 of 17920 Old 10-02-2009, 10:46 AM
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Quote:
Originally Posted by 300ohm View Post

Yeah, the Avermedia Duet is really recent and should have 6th gen tuners in it as well.

Well if I am really lucky it will have better sensitivity and performance than my single USB tuner. But I dunno if I feel lucky.

Quote:


Like everyone else says, those trees are a huge obstacle for you. When the leaves fall, will there be any clear line thru them ?

The only leafy tree in close proximity to the antenna is the one in the first picture. I have limbed it since and will get rid of it soon enough. The rest are very large white pines, mainly trunks.

Quote:


I would go about 30 - 40 ft above the roof with guy wires to clear the trees. (or are they even higher than that ?) The WG 7697P doesnt look heavy or like it would have a lot of wind load.

Whoa, above the trees? I don't think that is going to happen. If that's what I need then I will have to say goodbye to certain channels. I never meant for this project to get that complicated and expensive.

It's not heavy, though I am wondering if I should upgrade to the 14 foot version, the 7698P. I just don't know if it's worth the hassle. I think getting the antenna in the path of the signal is worth a lot more than a little higher gain antenna placed sub-optimally. Then again, I could do both...
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post #11755 of 17920 Old 10-02-2009, 11:17 AM
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At UHF, even 6 inches can make a difference.

Absolutely!! I've seen only 6 inches make a huge difference with UHF.
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post #11756 of 17920 Old 10-02-2009, 11:53 AM
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It's not heavy, though I am wondering if I should upgrade to the 14 foot version, the 7698P. I just don't know if it's worth the hassle.

Hmm, I think your better off spending the money on a quality low noise preamp to make up for the 60 - 70 feet of cable (plus the inevitable splitters, heh).
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post #11757 of 17920 Old 10-02-2009, 01:03 PM
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The statement from the grantronics.com stacking link of "you should stack at a distance in wavelengths of 57 / 3dB beamwidth in degrees." applies to any antenna at any frequency.
John

"you should stack at a distance in wavelengths of 57 / 3dB beamwidth in degrees." This may be true, but WTF does it mean to us poor non-engineers? It's wonderful to have highly trained people adding their knowledge here, but when you do why not lay it out in terms anyone can understand? Like in the case of the XG-91 question why not just give the guy the calculation's results? And then maybe go step by step with that antenna as the basis.

Just a thought.

OZ
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post #11758 of 17920 Old 10-02-2009, 01:57 PM
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The only info I could find on the XG91 BW is a statement that it is about 23 degrees. If that is at the old channel 69 near 800 Mhz, a wavelength is 37.5 cm. The spacing would come out 93 cm.
John
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post #11759 of 17920 Old 10-02-2009, 04:17 PM
 
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The only info I could find on the XG91 BW is a statement that it is about 23 degrees. If that is at the old channel 69 near 800 Mhz, a wavelength is 37.5 cm. The spacing would come out 93 cm.
John

That seems too close to me. The middle of the UHF band is now channel 33 at 599 MHZ. That sets the spacing at about 4'.
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post #11760 of 17920 Old 10-02-2009, 05:24 PM
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You also have to take into account the beamwidth which will usually be wider at a lower channel. In fact for most UHF antennas if you calculate the spacing for one channel, it will be the same for other channels.
John
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