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Old 22-Feb-2011, 3:36 PM   #1
RoCo2011
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Question Transmitter Location Same--Reception NOT

Can someone explain ???

I get reception from two channels, both of which are transmitting from the same location, but one Ch 23.1 drops out during the day. Interestingly enough its the higher powered one, but it also shows a higher nm of -8.2 db, which in theory I shouldn't be able to receive at all. GO FIGURE

Channel Info::

CH 10 (10.1) PBS Max ERP 30.000 kw--Effective ERP 30.000 kW
40.5 miles @ 86 degrees Mag N. nm of 5.4 db

Ch 23 (23.1) Fox Max ERP 390.000 kW--Effective ERP 104.325 kW
40.5 miles @ 86 degrees Mag N. nm of -8.2 db

I would like to get both stations 24/7 if I can. I had thought of two antennas with combiners and or a switch (which would be a pain) etc but perhaps there is a better way.

My current antenna (A DB8 Multidirectional from Antenna's Direct, is roof mounted apx 30' high and pointed SSE (160 degrees) to pick up the other majors (NBC CBS ABC) all of which work just fine.

Thanks in advance

RC
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Old 22-Feb-2011, 4:07 PM   #2
GroundUrMast
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The DB-8 is not designed to be effective receiving VHF, real channels 2 through 13. Per HDTVPRIMER the DB-8 has 14 dBd net gain on real channel 23. (-8.2 NM + 13 dBd= +4.8 NM) That suggests that you could well be able to get marginal reception of channel 23.

The same source provides estimated VHF performance for the DB-8... all based on computer modeling.

We can make an informed recommendation if you post a TV Fool report.
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Last edited by GroundUrMast; 22-Feb-2011 at 5:35 PM. Reason: Removed reference to CH-10 performance prediction.
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Old 22-Feb-2011, 4:39 PM   #3
RoCo2011
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Ok now I'm more confused and must admit know less now than I thought. The DB-8 I'm using seems to be working well picking up most of the Digital TV station in my area. I guess these are termed as virtual stations (ABC 8 (8.1), CBS 38(13.1), NBC(44) 6.1) all of which work. Channel 23 (23.1) is the one that drops out during the day. Channel 10 (10.1,10.2,10.3) all work fine all the time.

A quick look at the HDTV Primer link suggests my whole set up is wrong. What antenna or other suggestions to fix this would you have.
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Old 22-Feb-2011, 4:43 PM   #4
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I miss-read your OP. I thought you were saying you could not see real channel 10 and that real channel 23 was unreliable. So I understand correctly, CH 10 is received reliably, only CH 23 is unreliable.

Can you post your TVF report? I would like to see the path profiles.
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Last edited by GroundUrMast; 22-Feb-2011 at 4:56 PM.
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Old 22-Feb-2011, 4:51 PM   #5
RoCo2011
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TVF Report

Does this work?



http://www.tvfool.com/?option=com_wr...8e44e2b78b4c2b
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Old 22-Feb-2011, 5:02 PM   #6
GroundUrMast
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Thanks, I see a TVF report... though the NM's are quite different than those stated in your OP. With the antenna facing 160 I would be quite surprised to see weak stations from 85 Magnetic.

Do you have a rotator?
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Last edited by GroundUrMast; 22-Feb-2011 at 5:09 PM.
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Old 22-Feb-2011, 5:24 PM   #7
Tower Guy
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Quote:
Originally Posted by RoCo2011 View Post
Can someone explain ???

My current antenna (A DB8 Multidirectional from Antenna's Direct, is roof mounted apx 30' high and pointed SSE (160 degrees) to pick up the other majors (NBC CBS ABC) all of which work just fine.
A DB8 is not multi-directional. The statement on the web site is implausible: "This DB8 is the ideal antenna for use in locations that can pull long range signals from various directions and offers an attractive alternative to using a directional antenna mounted on a rotator."

According to the posted TVfool report, FOX is hopeless, but because you get it sometimes it should work much better if you add a rotor and a HDP-269 preamp.

You'd probably get PBS from WCBB if you added a real VHF antenna.
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Old 22-Feb-2011, 5:53 PM   #8
RoCo2011
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Thanks Tower Guy, buts its my understanding that all the TV stations here are transmitting on UHF freq's so a VHF antenna wouldn't help much. That's what I had before they changed evreything over to digital.
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Old 22-Feb-2011, 6:26 PM   #9
John Candle
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TV Antennas and Reception

WMTW 08 is VHF High Band channel 08 , W03AM 03 is VHF Low Band channel 03 , WCBB 10 is VHF High Band channel 10 . Read and understand this about , Real Digital Tv Channels , Virtual Digital Tv Channels , Analog Tv Channels. . http://forum.tvfool.com/showthread.php?t=695
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Old 22-Feb-2011, 6:35 PM   #10
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The Truth

Urban Myths are not the Truth.
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Old 22-Feb-2011, 6:54 PM   #11
John Candle
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The Truth

How many Tv's will be connected to the Tv antenna or Tv antennas?? . Due to the Extremely wide spread of the Tv transmitter locations , receiving the channels with 2 Tv antennas is a real stretch.

Last edited by John Candle; 23-Feb-2011 at 11:13 PM.
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Old 22-Feb-2011, 6:55 PM   #12
Tower Guy
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Originally Posted by RoCo2011 View Post
Thanks Tower Guy, buts its my understanding that all the TV stations here are transmitting on UHF freq's so a VHF antenna wouldn't help much. That's what I had before they changed evreything over to digital.
Your understanding is not correct, evreything is not UHF.
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Old 22-Feb-2011, 7:26 PM   #13
Dave Loudin
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The digital versions of your stations may all have been UHF prior to the shutdown of analog broadcasting. Stations at that time either switched the DTV operations to the former analog channel, kept using the same digital channel, or moved digital broadcasting to a completely different channel.

Think about it. The FCC overlaid a parallel digital TV service over the existing analog service without causing much interference to analog while doing a decent job of replicating reception ranges. Many compromises were made to make the parallel service work that were no longer necessary once analog broadcasting stopped, so stations could try to maximize their service areas.

This was all supposed to be transparent to folks who already had antennas, thanks to part of the data that's encoded with the video as part of the ATSC standard for digital TV. That data is the "virtual channel," so a station's parallel digital service could be known by the same channel number as the analog broadcast (e.g., a digital broadcast on channel 48 encoded to identify as "4"). When analog shutoff happened, whatever the station did, you should have had the antenna for, so a re-scan of channels would have restored reception and you could see channel "4" again.

This, of course, breaks down for people who never had an antenna. The solution is to pay attention to the real channels listed in your report.

BTW, this is all explained in the FAQ that's linked near the top right corner of your report.
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Old 22-Feb-2011, 7:27 PM   #14
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It appears you are located in SW Maine, among rolling hills. The prediction models used by TV Fool are good but 'your mileage may vary'. The 'virtual channel' listed on your report is of little interest, the 'real channel' is what matters when choosing a UHF versus a High or Low Band VHF.

In your OP, you say the NM (noise margin) for channel 23 is -8.2 dB. The TVF report you posted indicates -17.0 dB. There is also a discrepancy of 4 tenths of a mile. All that says is, you will very likely get more signal if you can some how raise the height of the antenna or perhaps, move the antenna elsewhere on your property.

If I were building a new antenna system, I would go with an Antennasdirect XG-91 stacked over an Antennacraft Y10713. If I thought the programing on CH 3 was of interest (it appears to be a PBS translator station, a duplicate of WCBB) I would also add an Antennacraft Y526 which would be mounted with a fixed aim at 40 Mag. The other two antennas would be on a rotator. The two VHF antennas would combine via a HLSJ then into the VHF port of an Antennacraft 10G221 preamplifier. The XG-91 would connect to the UHF port of the preamp.

All of that subject to a TVF report that I could rely on.
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Last edited by GroundUrMast; 22-Feb-2011 at 7:36 PM.
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Old 22-Feb-2011, 7:48 PM   #15
John Candle
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TV Antennas and Reception

Here is a Truth , reception of television stations that have minus -10 NM(dB) numbers and lower may not be received , if the station is received fine , if not fine. Tv stations that are in the gray part of the listing require ever increasing measures to receive. A person can spend several hundred dollars and still not get the stations. The Tv stations that are in the gray are in the gray for a reason.
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Old 22-Feb-2011, 9:58 PM   #16
RoCo2011
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Thanks to all for your input and expertise.I now see where I was led astray and confused. Its clear what I need to do and am pretty sure with a little yankee ingenuity can get the reception I want with what I have. I apologize to GroundUrMast for the slightly inaccurate information, my lat and long positions were off a bit. Thanks again to all, when I get it set will let ya know.

RC
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Old 22-Feb-2011, 10:54 PM   #17
John Candle
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TV Antennas and Reception

This situation has Funny aspects. Give a person that is confused , some correct information , the person gets excited and runs off all happy , before getting the rest of the correct information.

Last edited by John Candle; 23-Feb-2011 at 11:14 PM.
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Old 22-Feb-2011, 11:10 PM   #18
GroundUrMast
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Quote:
Originally Posted by RoCo2011 View Post
Thanks to all for your input and expertise.I now see where I was led astray and confused. Its clear what I need to do and am pretty sure with a little yankee ingenuity can get the reception I want with what I have. I apologize to GroundUrMast for the slightly inaccurate information, my lat and long positions were off a bit. Thanks again to all, when I get it set will let ya know.

RC
No need to apologize... If anything, my tone may have been off a bit. As long as you are able to improve your reception, I'm happy.
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