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4-Jul-2014, 10:58 PM
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#1
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Junior Member
Join Date: Jul 2014
Posts: 8
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Deep Fringe Madness
Hello and thank you. I live in Manchester New Hampshire, in what appears to be what is categorized as "deep fringe".
http://www.tvfool.com/?option=com_wr...e1c6365a0acd91
That is my tv fool report. I am interested in the Boston stations.
Currently, I using a channel master 2020 and a cm7777 preamp. Unfortunately the channels are hit or miss. I don't always get nbc or fox. I get channel 9 on Vhf from the back. My antenna is located on an exterior mast about 26 feet up. It is imperative that I get nbc, abc, cbs and fox. All the Boston stations are UHF so I ordered an antennas direct 91xg. Does anyone know if this will do the trick? I figure I could add a VHF antenna to get the nh stations later.
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5-Jul-2014, 2:41 AM
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#2
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Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,748
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Welcome to the forum.
Your tvfool report looks much worse than the generic Manchester report here:
http://www.tvfool.com/?option=com_wr...e1c6bfe6a63308
Your report is only resolved to "block level." Can you give us a more accurate tvfool report for your exact location? It is critical for an accurate analysis. If you can't enter your exact address or coordinates using the >> Click HERE << on the tvfool.com entry page, try using the interactive maps feature >> Start MAPS << and move the teardrop indicator to the exact location of your antenna. Then, generate a report, after entering antenna height, by clicking on Make Radar Plot at the upper right of the map.
Your choice of the 91xg is a good one for your needed channels from Boston because it has more gain than the UHF section of the 2020 according to the CM and AD documents.
http://support.channelmaster.com/att...Data+Sheet.pdf
https://www.antennasdirect.com/cmss_files/attachmentlibrary/Technical%20Data%20PDF's/91XG-TDS.pdf
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Does anyone know if this will do the trick?
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I can't really say for sure if it will do the trick, but it's your best shot without going to more exotic and expensive solutions like stacking 91XGs or a taller tower. The increased gain of the AD antenna should improve your NM, but 2Edge signals will not be 100 percent reliable. You will just have to try it.
It would be interesting to see how much difference there would be in your tvfool report by increasing the height of the antenna.
http://www.hdtvprimer.com/antennas/comparing.html
Please let us know how the testing goes.
Best regards,
rabbit
Last edited by rabbit73; 5-Jul-2014 at 3:06 AM.
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7-Jul-2014, 7:08 PM
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#3
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Junior Member
Join Date: Jul 2014
Posts: 8
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I would like to thank everyone for the time and response that you have given to my issue concerning reception.
I have generated a tvfool report using my longitude and lattitude instead of address. Whenever I use the address, the report always comes out as "block level". I will try to figure it out tomorrow.
Fox is at -6.4db and that is the "most difficult" of the network stations that are a must need. The other is NBC at at -5.3.
I am waiting on my 91xg. The tracking says it should be here by fed-ex tomorrow, but hoping that it exceeds those expectations and makes it here today. Once I receive the antenna, I will give a report as to its performance. If I do not get the Fox and NBC stations I don't know what to do from there.
Thanks again,
Joe
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8-Jul-2014, 12:09 AM
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#5
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Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,748
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Joe:
Thanks for posting your exact address report; not much different than the original one.
In theory, the new antenna has a good chance of bringing your NM above zero, which would make reception of your weakest desired signals possible.
Does your TV have a signal strength indicator? That would be a big help when aiming your new antenna, after first doing an approximate aim with a compass.
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If I do not get the Fox and NBC stations I don't know what to do from there.
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The next thing to try would be a slightly different location in a horizontal direction, especially if there are any trees in the signal path. Moving my 2-bay UHF portable antenna in a horizontal direction made a big difference in signal strength in this test setup:
On the table: 12v 125w Exeltech inverter, CM7777, preamp power supply, and Sadelco DisplayMax 800 signal level meter. The final adjustment of antenna aim and location was to maximize the pilot signal which is the peak at the left end of the channel scan. The tuner locks on to the pilot signal:
What TV are you using? Some TVs have better tuners than others, which can make a difference in areas with marginal signals. My SONY KDL22L5000 has a tuner that is about equal to the better converter boxes. The tuner in my more recent KDL22BX320 is a little better by about 2 dB. My best set is a new KDL32R400A. I like the SONY TVs because they have a diagnostic screen that gives relative signal strength, SNR, and errors; the last two being indicators of signal quality.
In order to compare tuners, I connect two sets to a splitter and reduce the signal before the splitter with a variable attenuator to see which set drops out last. I don't know of any published test results comparing tuners, so I must make my own tests to avoid wasting money by trial-and-error testing. It doesn't do any good to connect one set to your antenna, and then substitute another set, because OTA signals are constantly changing in strength, which would lead to false conclusions.
After that try more height.
What gives me hope is that you can get Fox and NBC some of the time with your present antenna.
Have you looked at this thread by kenj66. He is also trying the 91xg:
Difficult location 15 miles west of Seattle
http://forum.tvfool.com/showthread.php?t=14593
Take note of the tilt feature of the 91xg.
Last edited by rabbit73; 9-Jul-2014 at 1:54 AM.
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11-Jul-2014, 12:26 AM
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#6
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Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,748
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When I clicked on the WFXT callsign in your tvfool report based on coordinates, I got this profile. You can see the terrain in the signal path:
I then generated a coverage map for WFXT using the interactive maps feature and an estimate of your location:
I then generated this tvfool report from maps:
http://www.tvfool.com/?option=com_wr...e1c6c7168d178b
As you said, DEEP FRINGE.
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In very rough terms, the colors can be broken down as follows (not related to Antennaweb):
- White is extremely strong. Beware of signal overload on amps.
- Red-yellow-green are all quite strong. You can expect reasonable coverage with an indoor antenna.
- Cyan is where it's advisable to move the antenna up to the second floor or attic.
- Blue is where it's probably necessary to install a good antenna on the roof.
- Purple is quite weak and you really have to work at it for any chance of reception.
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Last edited by rabbit73; 16-Jul-2014 at 2:23 AM.
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13-Jul-2014, 12:02 AM
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#7
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Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,748
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Then I tried increasing the height of your antenna. Usually, the 2Edge changes to 1Edge and then finally LOS. In your case it stayed at 2Edge for a long time, but the NM improved to a positive value:
26 ft 2Edge NM -5.3 dB
50 ft 2Edge NM -2.8 dB
75 ft 2Edge NM +0.1 dB
100 ft 2Edge NM +3.3 dB
150 ft 2Edge NM +10.8 dB
200 ft 1Edge NM +16.8 dB
300 ft 1Edge NM +19.6 dB
350 ft LOS NM +43.2 dB
I then generated an elevation profile between the WFXT transmitter and your location:
As in the previous profile, the transmitter is at the left end and your location is at the right. It's obvious why the report stays at 2Edge when raising the antenna.
After looking at the elevation profile, using the tilt feature of the 91xg to tilt it up might help at your location because of the obstructions in the signal path.
Last edited by rabbit73; 16-Jul-2014 at 2:22 AM.
Reason: added results for different antenna heights
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14-Jul-2014, 12:12 AM
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#8
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Junior Member
Join Date: Jul 2014
Posts: 8
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The 91xg is a fantastic antenna compared to the Channel master 2020. I'm so close to WMUR and the New Hampshire PBS stations that even though they are vhf stations, I still get them on the 91xg which is a uhf antenna. FOX, NBC and WSBK from Boston are "flickering" all day. I believe that I am so close! I can only hope that with fall and winter, the signal will get better. Last winter, when I installed the 2020, I was able to get Fox and NBC but not consistently, and not for very long. I'm hoping now, as leaves fall, my viewing gets better.
I cannot move my antenna, because that is the only clear path to Boston. There are trees that block the view any other way. I would like to raise my antenna higher, but I don't think I can justify this to the wife as we just purchased the mast and don't want to fight that battle.
I use a vizio tv in both the living room and bedroom. Very disappointed with the tuners and features in those TV's. My big tv doesn't even have a signal meter. Guess they just expect people to use cable. Just for giggles, I used one of the apex digital converter boxes that the government gave every household for the switchover to digital. And just like one would believe, it is horrible. Didn't pick up half the channels that either vizio could acquire.
I've been reading a lot online and the only thing next for me I believe, is to horizontally "stack" or "gang" in groups of two. The reason for this is also financial, I don't think I could justify to the wife going in a different direction, say like a db8 or something. I picked the 91xg, so that is the antenna that I have to go with. But what an antenna! I've been dropping hints that that might be the direction we have to go.
All in all, I'm very psyched with the switch from cable. I am an AM dx'er. and enjoy "searching the signals". Shout out to the Panasonic rf 2200. Now I can just add the UHF band.
I have been receiving signals straight through to Providence, RI., when I rescan in the early morning. That's over 70 miles away. One of these days, I'm going to point towards the Maine stations about 60 miles away to see what I get.
Here's what I believe to be my next step. I'm going to research how to horizontally combine two 91xg's and hope that Santa brings me one for Christmas, along with the necessary equipment to combine them, then tie them together in the spring. That, along with the rotator I want, will be fun. So that by this time next year, I will consistently get those pesky channels.
Be safe and be well and happy tv.
Joe
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14-Jul-2014, 12:14 AM
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#9
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Junior Member
Join Date: Jul 2014
Posts: 8
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I forgot to mention that I have tilted the antenna up one station. That appears to be the sweet spot for me.
Joe
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14-Jul-2014, 12:22 AM
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#10
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Junior Member
Join Date: Jul 2014
Posts: 8
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Oh, who am I kidding. I'm probably going to talk the wife into getting another 91xg and stack them together sooner than later. Depends on how much the A/C fix is going to set me back.
Again, I would also like to thank you all for giving me an opportunity to get some help and information concerning reception. I appreciate it.
Joe
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14-Jul-2014, 3:27 PM
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#12
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Junior Member
Join Date: Jul 2014
Posts: 8
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I've been looking online, but not sure what to use to combine two 91xg's. Would it be a uvsj or a diplexer? How do I take into consideration my mast preamp, the channelmaster 7777. Do I combine before or after the the preamp?
Thanks for your assistance.
Joe
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15-Jul-2014, 1:20 AM
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#13
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Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,748
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Using a Splitter as a Combiner
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Would it be a uvsj or a diplexer?
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A UVSJ is a diplexer. No, that is used to combine a UHF antenna with a VHF antenna.
You can combine the two 91XGs with a splitter used in reverse as a combiner. The two pieces of coax from the antennas to the splitter must be the same length. This is what works for two antennas, that are identical and both aimed in the same direction, that have built-in baluns with coax output.
Some people think that using a splitter as a combiner would result in a loss of 3.5 dB, which would make two antennas worse than one. When used as a splitter, the loss is 3.5 dB. When used as a combiner the loss is about 0.5 dB, giving you a gain of 2.5 dB for two antennas IF they are identical, properly phased together, aimed in the same direction, and the wavefront presented to the antenna array is uniform (which you might not have if there are trees in the signal path).
http://www.avsforum.com/forum/25-hdt...l#post12978153
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It needs to be remembered that if a splitter that measures 3.5 dB on the split ports is used as a combiner with identical and properly phased antennas, that the loss is only 0.5 dB. IOW, you'll get 2.5 dB gain by phasing 2 antennas, which is the number most typically quoted for phasing 2 antennas.
I have a pair of phased VHF antennas and a pair of phased UHF antennas using the ferrite splitters as combiners. The splitters measured 0.4 to 0.6 dB loss across the bands. I used a Fluke 6062A signal generator and a Boonton 9200 power meter for the measurements.
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also:
http://www.avsforum.com/forum/25-hdt...ml#post5768148
http://www.avsforum.com/forum/25-hdt...ml#post8101234
http://www.sandiegohdtv.org/discus/m...tml?1181781042 (Posted on Monday, March 26, 2007 - 05:03 pm)
For antennas that have 300 ohm output, you use a 4:1 matching transformer (balun) for each antenna and then run the two coax lines to the splitter. It is necessary to correctly phase together the two antennas so that they work in unison and their outputs are additive, so you have to reverse the 300 ohm wires on ONE of the baluns to see which way works the best. When the antennas are NOT correctly phased together you get two peaks as you rotate the antenna, one each side of the direction you want, with a null between at the center. Another way to say it: The main peak is split in two. Since your two 91XGs probably will have built-in baluns, you don't need to worry about this phasing test.
The output of the splitter/combiner goes to the input of the 7777.
My own experience is with stacking two original CM4221 antennas side-by-side. They were 300 ohm output, so I used two baluns and a splitter in reverse. I got a gain of 2.5 dB (over one antenna) as measured with my Sadelco signal level meter. Theory says max possible gain is 3.0 dB, but there are losses in the combiner. It is possible to build a lower loss combiner, but I don't think it's worth the trouble, unless you need every 1/10 of a dB you can get. Lindsay used to sell one for about $100. This is what the combiner would look like. These are for 50 ohms, but could be made for 75 ohms by changing the size of the inner conductor:
http://www.gare.co.uk/6m_antenna/divider.htm
http://www.qsl.net/dk7zb/Stacking/splitter.htm
http://home.teleport.com/~oldaker/power_dividers.htm
http://www.packratvhf.com/power_di.pdf
I took another look at the Calaveras antenna diagram:
http://images.aa6g.org/AVSForums/Antennas.jpg
I'm guessing, but it looks like he is using an ingenious way to reduce combiner loss. Just before the preamp you see the notation 1/4 Wave Matching. If he has connected the two coax lines from the antennas together in parallel, you get 37.5 ohms. If you use a 1/4 wave section of coax between that point and the input of the preamp, it can convert the 37.5 ohms to 75 ohms. Calaveras didn't make a housing for his combiner, he just joined the coax lines together in a "Y" configuration with the center conductors soldered together and the braids soldered together.
The proper impedance for that matching section is given by this formula: the square root of the product of the two impedances to be matched. In this case it is the square root of 37.5 times 75, which is 53 ohms, close enough for 50 ohm coax. The disadvantage of this matching technique is that it is narrowband.
http://www.antenna-theory.com/tutori...nsmission5.php
http://www.qsl.net/w4sat/qtrwavtr.htm
Last edited by rabbit73; 20-Jul-2014 at 8:03 PM.
Reason: Added links for splitter VS combiner loss
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20-Jul-2014, 4:05 AM
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#14
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Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,748
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Additional reading
If you want to learn more there is a whole thread at DHC on the subject:
Stacking, Ganging, Combining TV Antennas
http://www.digitalhome.ca/forum/showthread.php?t=95148
You have to login and refresh to see all the images in posts on that forum.
Sometimes they use slightly different terms there. One above the other is stacking; one beside the other is ganging. That is the purist definition. I'm a ham. Most hams use the term stacking for either.
DHC has a thread you should read:
OTA FAQ & Knowledge Base
http://www.digitalhome.ca/forum/showthread.php?t=41102
In that thread there is a post (#15) about stacking:
Can I Use 2 or More Antennas For Better Reception?
(Just to make it even more confusing, in that post intravino uses the term ganging instead of horizontal stacking for two Delhi 10Y13s.)
http://www.digitalhome.ca/forum/show...3&postcount=15
They have two other threads that might interest you:
Antennas Direct 91XG Hardware Hacks
http://www.digitalhome.ca/forum/showthread.php?t=111398
Antennas Direct OTA Antennas & Gear
http://www.digitalhome.ca/forum/showthread.php?t=41076
Final Comments:
I consider stacking to be a last resort. Horizontal stacking gives a narrower beamwidth which makes aim more critical. Before doing it, I try every possible location for just one antenna. Sometimes I measure an improvement of 10 dB or so when I find a "hot spot," and often the increase is more than stacking would give me.
Granted, it's easier for me because I watch the reading on my signal level meter when moving the antenna.
You stated that you couldn't move your antenna in a horizontal direction because of the trees. But, it is also possible to move it in a vertical direction. The general rule is Higher is Better, but the increase in signal strength is not uniform as you increase height because there are hot spots. Sometimes a foot higher or lower for UHF can make a difference.
Stacking requires extra effort and expense, but a dedicated DXer can make it work.
Best regards,
rabbit
Last edited by rabbit73; 26-Jul-2014 at 4:59 AM.
Reason: Separated reading and comments from combiner explanation
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30-Jul-2014, 3:06 PM
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#15
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Junior Member
Join Date: Jul 2014
Posts: 8
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Moved the antenna up and down the mast at six inch intervals, but could not get a better signal. So I bit the bullet and purchased another 91xg, and yesterday I was able to install the stacked arrangement. It made a world of difference. I am now getting NBC and FOX pretty consistently and WSBK (mostly, it flickers during the day). I'm pretty psyched because I now get NBC, CBS and FOX, the three channels one needs to watch ota NFL football broadcasts.
I cannot recommend the 91xg enough. Even though it is a UHF antenna, I still receive the two local VHF stations. I did not believe that I would be able to get NBC and FOX, but last night I was flipping back and forth between both.
Thanks for everyone's help, and happy tv viewing.
Joe
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30-Jul-2014, 11:20 PM
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#16
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Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,748
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Joe:
Thanks for the report about your stacked 91XGs.
Glad to hear that I didn't lead you astray and that it works well for you.
Any chance you can show us a photo of it?
Best regards,
rabbit
Last edited by rabbit73; 30-Jul-2014 at 11:22 PM.
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