The Official AVS Antenna and Related Hardware Topic! - Page 393

It's the trees. The signals can't go thru the trees, so they are diffracted around them giving you antenna aim that is not towards the transmitters. If you could somehow gradually increase the height of your antenna, you would begin to see your azimuth readings match the ones in the tvfool report. (Where's that friend with a "cherry picker" truck when you need him?)

Tvfool is sometimes wrong, but not in this case. It has to make some assumptions, one of which is that there are no trees directly in front of the antenna.

I think you are doing very well considering the location of the antenna.

Yes, you need to add height....as much as possible and away from the trees as much as possible.

A preamp will make up for the loss in the coax downlead (as 300ohm said) but it will not make up for a poor antenna location.

The aim experiments that you have already done have told you that the trees are in the way.

The 7698 is not the best solution for your problem. Its gain is only slightly more than the 7697 and it is a lot harder to handle up in the air. Actually, I initially imagined that you would end up with the 7696. An antenna smaller than the 7698 mounted up-in-the-air in an open location will out perform the 7698 in your present antenna location.

Many times I have measured a signal increase of more than 10 dB after moving an antenna to a better location.

Correct!

The hdtvprimer site seems to be working now. Take a look at the neat diffraction diagrams:
http://www.hdtvprimer.com/ANTENNAS/siting.html

That tree is killing your reception.

Can you relocate the antenna to the other end of the house (towards the far front corner looks like it would be better)? Try to get at least 6' above the roof peak (10' would be better).

I would think that vertical stacking would work better for you than a pre-amp.

The first link has the answers in pretty simple terms:
http://vk1od.net/antenna/dl6wu/EstimatingBeamwidth.htm
Fig 1 shows how Yagi Beamwidth can be derived from Gain (and vice versa).
Fig 3 charts the optimum separation Distance vs Antenna Gain, which will
VARY with frequency in most antennas....chose which freq or channel to optimize.

Gain vs Channel is given here (or in manu. specs):
http://www.hdtvprimer.com/antennas/comparing.html
Converting between Channel and Freq isn't even required.

Clear as mud.

OZ

For Ray50 or any XG91 users here's some links:

http://hdtv.forsandiego.com/messages/4364/5643.html

http://www.dbstalk.com/showthread.php?t=9676

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

Good luck,

OZ

Thanks for the interesting links. But, in the third link stampeder has it backwards about vertical and horizontal stacking vs beamwidth (unless he does an edit):
http://www.digitalhome.ca/forum/showpost.php?p=933732

He should have said that vertical stacking reduces the vertical beamwidth and horizontal stacking reduces the horizontal beamwidth. I hope he doesn't think that the DBGH has narrow horizontal beamwidth:
http://www.avsforum.com/avs-vb/showt...3#post14937123 polar plots DBGH VS CM4228

http://www.hdtvprimer.com/ANTENNAS/g...R.html#stacked
which says:

Narrower beamwidths shown here:
http://www.hdtvprimer.com/ANTENNAS/16bay.html

Ive always liked the venetian blind / horse blinders analogy found here :

http://www.kyes.com/antenna/stackluge.html

And I like that link.
Thanks.

Here are a couple of tests I conducted last year between a single XG91 and two Triax Unix 100s (almost identical to the XG91) horizontally stacked.
http://www.wtfda.info/showpost.php?p=6610&postcount=1
http://www.wtfda.info/showpost.php?p=6715&postcount=13

If you have multipath issues and plan to stack, stack them horizontally.
http://atechfabrication.com/tests/03...cking_test.htm

Great discussion here about stacking XG91s.
http://www.avsforum.com/avs-vb/showthread.php?t=1182277
MAX HD and cpcat have built and tested a number of various configurations with many different brands/models of antennas. My antenna setup came from MAX HD.

Steve

Actually, thinking it about it a little more, the pc tuner gets sound and video about a millisecond behind the regular tv (other pc tuners I played with do the same). So its really recovering from a drop out at about the same time.

Yes, great link and it even has the most direct answer to my particular problem , multipath from aircraft:

"Vertical stacking improves both gain and vertical directivity. This helps reduce airplane flutter and attendant picture roll"

This may also be the original source for the post I read somewhere about vertical stacking 1 wavelength apart:

" 0ptimum and minimum spacing is 0.94 and 0.60 wavelength, respectively, at the lowest frequency received. Spacing exceeding one wavelength reduces the performance of the stack."


After wading through all these new links I remembered this one:

http://www.wtfda.org/index.php?optio...d=24&Itemid=43

Read the link to Stagger Stacking, it takes things to a whole 'nutha level 8^)

OZ

QUANTUM-FX ANT-101(ANT101) UHF/VHF Indoor TV Amplified ANTENNA or Winegard SS-3000 Amplified Indoor UHF/VHF Antenna

I'm about 13 miles form NY city on Long Island and the Monoprice antenna can't get 7, and now 11 and starting to drop 13 for some reason. Been looking for a new indoor antenna that will not cost much so thinking of one of these.

Cut down two trees and aggressively limbed the big white pine. I played the aim-game again with the laptop on the roof. I ended up at about 50 degrees which is almost exactly where the old antenna was aimed. Seems like the best overall trade off. I get a Boston CBS, ABC and FOX. And I get the off axis RI CW and RI ION. Boston 38 is intermittent but all of this is better than the 300 degree aim I said I was using earlier.

I know I need to raise it and I will. But something still confuses me. I mentioned I get Boston Fox 25. I also get another channel, 46. Well, the Boston ION and CW that I just can't get at all (not even a little) are supposedly stronger than these other two channels, according to TV Fool. And specifically 38, which is somewhat intermittent, is supposed to be stronger than Boston CW. What's up with that?

Keep in mind that the terrain modeling and signal power forecasting software has limitations that affect accuracy.

Two things in particular may apply:

1) Terrain resolution. The TVfool software divides the terrain into 100 square meter blocks and averages the terrain within that block and between adjacent blocks. That makes the resultant estimates highly variable for the "last mile" or so of the signal path. Other online modeling, notably at the FCC's website, is 10 times coarser in its resolution.

2) TVFool's (and any other forecast based on the LRI model) software assumes that you have clear line-of-sight to the horizon. No trees, no buildings, etc, can be forecast. if you have these, then the accuracy of the forecast becomes poorer very quickly

In other words, don't expect the forecasts to be 100% accurate....

I don't expect total accuracy but I did expect consistency. When the towers are in the same general area I figured I could at least reference tv fool on a relative level.

You could have an issue with the proper location of the antenna height to RF wavelength wave peak.

Follow this link "Erecting a TV antenna" at http://www.hdtvprimer.com/ , then follow this link "Choosing a mounting site."

I experience similar anomalies here in southern NH. 38 (WSBK) and 44 (WGBX) are much worse then stations modeled weaker. Channel 7 (WHDH) and 25 (WFXT) come in all the time even though they model 5 and 10 dB lower then WGBX.

http://www.tvfool.com/?option=com_wr...befb1d6ecdfd6f

We have a similar situation antenna is about 30 feet AGL which places it below treetop level.

Even signals from antennas on the same tower might vary significantly in actual signal quality due to variables related factors other than power.

Additionally, TVF uses FCC license and permit data, If a CP has been issued, TVF uses the to-be-built data as soon as the CP is issued. In real life, stations actually have a lot of time to build the facility that is permitted leading to a falsely optimistic forecast for that station.

IOW, take it as a guide, but not an absolute.

In my own case, my TVF isn't too bad: http://www.tvfool.com/?option=com_wr...befb2e2ee8e241

However, in real life, my signal from KETC is dismal and KDNL isn't much better off my 4-boom 91XG at 35' AGL. KMOV, however, is very strong compared to most of the others.

That 101 is a cheep indoor antenna ($14), the Winegard 3000 is a well made bidirectional indoor unit that goes for about $40. No comparison.

However, I don't know if either will solve your problem, without seeing a chart on you location. Give me your ZipCode, or attach a TVFool Chart for your Stations and we'll go from there.

Yep, and the stations do testing and tweaking right after the transmitter is operational, which can drive you nuts for a while, heh.

....and they don't tell the public what they're doing so the frustrated user is left thinking it's a problem with the receiving equipment.....

High-VHF and an indoor antenna is often a recipe for frustration.

High-VHF doesn't penetrate structures as well as UHF does.

Try a simple VHF rabbit ears from Radio Shack for $10 to see if you can find a decent spot for the signal. Try different locations inside to see if you can find a "hot" spot.

Someone else posted that link before and I looked through it. Very illuminating.


Mine is actually only 15 feet and I have a fairly close and tall tree line. So I suppose I should be happy with what I have. Many of them will lose their leaves over the next few months so we'll see what happens. Could be very interesting.

Interesting about 38 and 44. They both have troublesome reception for me, as well. 7 sometimes gives me good signal strength numbers but doesn't want to actually work...could be interference. 25 works nicely now. How about your Boston CW or ION, 56.1 and 68.1?


I find TV Fool fairly accurate other than a couple of anomalies toward the fringe end of my list. I suppose that's why I was frustrated when it turned out to be less than 100% accurate.

Your reception discussion prompts my question.
I have a Wineguard PR-8800 and a CH3 only joined by UHF/VHF only connector/Joiners. Then thru a Wineguard HDP 269.
All Ch were UHF and one CH 3. all was well.
This week CH 34 switched to CH 13 and Reception dropped from 100% to 76% (on a DTV PAL DVR an over the air only HD DVR). The old analog from 13 could be picked up with a paper clip antenna.
My local Forum (Roanoke VA) had a comment that covering the small space between the two identical 11 step lader like reflectors with a 'mesh' would improve CH 13 reception on the PR-8800.
Any theoritical basis for this?
Also do I
1. lay a small strip over the approx. 1" gap
2. or cover the total two reflectors
3. Just connect each of the 11 ladder steps to its mate.
It is in the attic- easy to modify.
Thanks, I am not on here often but follow it every day.
Bernieoc

56 (WLVI) and 68 (WBPX) are problematical but not as bad as bad as 38 and 44. 56 comes in most of the time 68 about 50%. WLVI and WBPX both have DT-APPs to increase power so they ought to get better if that happens.

WHDH (RF 42) comes in all the time. I'm really glad they are staying on UHF. We have sperate VHF and UHF antennas. With WHDH on UHF we have no need for rotor. UHF points to Boston and VHF aimed at WENH. WMUR is a little off axis but it so strong it doesn't matter. We even get WMTW (RF 8) out of Maine on occasion.

The other stations WMUR (RF9) WENH (RF11) WGBH (RF19) WCVB (RF20) WBX (RF30) WMFP (RF18) WHDH and WFXT (RF31) all come in fine.

WPXG (RF21) the ION station out of NH comes in great but it requires use of rotor so we typically don't bother.

Here is a link to my setup:
http://www.tschmidt.com/writings/Des...%20antenna.htm

Wow you documented everything! Very nice job. I ought to follow your example...

I hope that, combined with raising my antenna a few feet, will allow me to receive them. Though right now it is not looking like I need WLVI as I get the off axis RI one. And I get the REALLY off axis ION but only Boston's WBPX promises some HD content (68.1 says 720p). But no such thing as too many channels, especially free HD OTA ones.


Ah, so are they RF 42 then? There is some weirdness associated to WHDH from what I've seen. First, both my Vista and Win 7 Media Centers say 7.1 is not the main channel...something about temp authority. And like I said, 7.2 shows signal but no picture. When I look at my Silicon Dust lineup, it shows a conflict for WHDH. Suggests RF 42 OR RF 7. And TV Fool says RF 42 for WHDH but lists no vChan ID!! So perhaps my problem is I need to manually tell my media centers what the deal is then it may work.

I'm looking for a longer mast and I'd probably get another 3 feet or so with this. I can't find anything longer and there is just not much out there overall. Am I looking in the wrong places?

I used a chain link fence pole from home depot. Maybe not the best solution, but it worked for me. There are various diameters depending on if you get railings or posts so I made sure it was sturdy enough for my length of mast. Some are obviously too thin and flexible but others are quite sturdy.

Yeah that is a good point. It's just hollow tubing. It doesn't have to be "antenna mast" pipe, which is really no different from any other kind of tubing.