Mohu Leaf antenna questions

[OldStump]

I read a review that offered a discount code for the Mohu Leaf antenna. Just for grins I ordered one to see what my OTA reception would look like.

It's pretty amazing, but there seems to be one channel in my area that I can't access.

I live in the DFW, Texas area. Channel 8, WFAA is the ABC affiliate.

I can't get this station, while I can get most of the other stations.

On the dtv.gov site, it lists all the local stations with OTA reception in my area (75077). Here the band for WFAA is indicated as HI-V wheras for all other channels it is UHF. Might htis be the problem? I can't find anywhere the difference between the different bands are discussed.

Some help, links or advice would be appreciated. Thanks a bunch in advance.

Edit: Added a link to the TV Fool coverage info.

[GroundUrMast]

The Mohu Leaf is primarily a UHF antenna. UHF channels (real channel numbers 14 though 51) range from 470 MHz to about 700 MHz. As frequency is increased, antenna elements need to be shorter to match the signal.

Channel 8 on the other hand is a VHF range of frequencies from 180 MHz to 186 MHz. An antenna designed to receive this and other VHF channels needs longer elements to match these frequencies.

If you want to try another indoor antenna, consider these: http://forum.tvfool.com/showthread.php?t=2828

If you would like more accurate recommendations and advise, please read the Guidelines When Asking for Help

[OldStump]

Great, thanks, progress already.

From your site report for my location (added to my original post). I see that the other channels I do receive have real channels in the higher range. WFAA alone is in the lower range.

Where can I read up or go to understant the real channel vs virtual channels? how and where is that mapped?

For instance, channels 5 and 11 are virtual but the bands are in the UHF range, which explains why I can receive them.

If there is something specific (apart from the coverage link which I've already added to my first post) that I'm not telling you, please let me know.

[GroundUrMast]

Here is a starting point: http://en.wikipedia.org/wiki/ATSC_standards

Virtual channel numbers are like the address label on an individual envelope inside a bag of mail. The VC helps the receiving set identify the data associated with an individual program when there could be several other streams of data interwoven in the information transmitted by the station. Virtual channel numbers are added at the station during the MPEG-2 multiplexing process. Multiplexing is a method of combining unrelated data streams for transport or storage, in a way that each data stream can be later separated from the other data.

[GroundUrMast]

Based on your TV Fool report a Terk HDTVi indoor antenna would be worth your consideration if you were connecting a single set.

For even better reception reliability, I'd suggest a roof or wall mounted RCA ANT-751 or better yet, a roof mounted Winegard HD7010. The strong signal levels would be sufficient to drive a passive 4-way splitter and the coax runs in a single family home... no amplifier needed.

In either case, begin by aiming at about 160° compass, then fine tune by moving the antenna left and right to find the most reliable signal quality.

[OldStump]

Edit, sorry, this was in response to your link to the UHF/HI-V signals.

Holy cow, that went over my head by about 5 miles!

On an (un)related note. I recalled that I early in the days of HTDT had a different OTA antenna, I went to look on the top of the shelf and there, covered in dust was an RCA ANT-121.

I saw that in the link you gave you have a review for it.

Now I seem to recall that the cable for it was too short to reach my TV.

Would it be worth getting a cable extension and using this instead of the Leaf? I have very limited options in how to turn the "ears" sticking out from it. Basically I'm going to have them run parallel to the wall, since it will be on the shelf if I decide to use it.

Some friends has suggested I get a SiliconDust HD HomeRUn and put the antenna on that upstairs on my network. maybe that is something to do one day.

[GroundUrMast]

Sorry... think of the virtual channel as a way to keep the brand of a station. Many stations changed to different frequencies as they switched from analog to the new digital system. They want to continue to be known as to old channel number for marketing reasons.

An ANT-121 will serve well. you can add an extension cable if needed.

I own several SiliconDust tuners. If you're computer savvy I think you would find the product quite versatile. It is one of several products on the market which can make one or more computers in your home capable of watching and recording TV on... no TV set required. http://forum.tvfool.com/showthread.php?t=820

[OldStump]

Just a quick FYI. Tried the RCA antenna, still no channel 8. Bummer.

[GroundUrMast]

Did you re-scan for new channels?

And have you adjusted each of the two rods to about 15"?

[OldStump]

Originally Posted by GroundUrMast

Sorry... think of the virtual channel as a way to keep the brand of a station. Many stations changed to different frequencies as they switched from analog to the new digital system. They want to continue to be known as to old channel number for marketing reasons.

Ok, that's interesting. This part isn't strictly related to Reception, so feel free to split to a new topic if you so wish. I'm now interested to know a bit more.

a) what happened to the old VHF bandwidth? I believe spectrum is at a premium? (Edit. I see some of it has been reallocated.)

b) How is this applied in practice? (Edit: I see from a Wikipedia article that it is a tuner function.)

So as a matter of practice, if the TV hasn't scanned for channels, it will, for instance, find virtual 5-1 on channel 41? (For my area).

As for the rest, I have a longer response that I will submit in a while.

[GroundUrMast]

The VHF spectrum (low band, CH-2 through CH-6 and high-band, CH-7 through CH-13) is still reserved/allocated/assigned to broadcast television. Because there is more RF interference in that spectrum, many broadcasters elected to move their operations to UHF assignments as they switch to digital operation. Not all chose to do so though.

Because the low-VHF channels are subject to the most interference, you'll find few full service broadcasters electing to use real CH-2 through CH-6. Still, a few exist. Most stations using the low-VHF spectrum are low power stations, either fill-in translators or small independent broadcasters.

Back in the 80's, the cell phone industry started operation on the frequencies formerly reserved for UHF channels 70 through 83. Then in the recent transition from analog to digital TV broadcasting, the FCC re-allocated UHF channels 52 through 69 to various services including cell, broadband wireless and others.

So, back to real vs. virtual channels, a digital TV needs to keep a list of real channels that have an active signal available, and, the TV also needs to keep track of the separate programs available in each real channel. Digital broadcasting technology now allows a broadcaster to send up to five video channels in standard definition.

When you punch in "4", "-", "2" on the remote here in Seattle, the TV has to look in the table created during the channel scan. It finds an entry for virtual channel 4-2 and sees that the real channel is UHF CH-38. The tuner is then set to real channel 38 and the data associated with the desired program can be filtered out of the rest of the data and set to the video and audio decoding process.

Many sets will not tune or display a channel without performing a channel scan... to create the table data that is used to control the tuner.

Some of my sets will accept manual entry of the real channel number. If there is a valid signal present, the set is smart enough to add the new information about the real & virtual channels so that in the future, I can channel surf or punch in the virtual channel number.

[Dave Loudin]

The virtual channel concept was also important during the transition from analog to digital broadcasting. I don't think many people appreciate the job the FCC did in overlaying a new TV broadcast service over the old one that minimized interference between the two while managing to essentially, not completely, replicate coverage. A little history:

Digital broadcast television was the first case where a new technology applied to a broadcast service was not backward-compatible with current recievers. Color TV and FM and AM stereo had to work on black-and-white TVs and mono radios. For digital TV, it was no longer a matter of adding extra information in a clever way to the existing signal. A whole new transmitting scheme was required.

Therefore, to implement DTV, broadcasters had to fire up a parallel broadcast on a separate channel. At the time, there was much wailing and gnashing of teeth about "giving away" spectrum to broadcasters. Those folks never had to equip a studio for digital, nor had to pay for erecting antennas and feed line up tall towers.

One question that came up was, how to tell people where the new channels are and make it simple to use. Since DTV is all-digital, adding additional information to describe what is in the stream, like a programming guide, channel identification, etc. is trivial. So, the idea of the virtual channel was born. This allowed labelling the digital channel with another number that corresponded to the analog channel number. You could then, with the digital tuners of the day, go from analog to digital with a single click on the remote (e.g., "4" for analog 4, then a click up to "4-1" which is RF 48 in my area.)

When analog went away, stations had three choices: continue with the existing DTV channel, move the DTV to the analog channel, or start completely over on a third channel. No matter where they ended up, the virtual channel allowed them to keep the same "identity," and you did not have to learn a third channel number for a station. (Note also that when analog went away, the TV spectrum went from 2 - 69 to 2 - 51.)

When we're working with antennas, we are dealing with, of course, the physical frequencies, so you have to figure out what those frequencies are. Enter tools like this one.

[OldStump]

Originally Posted by GroundUrMast

When you punch in "4", "-", "2" on the remote here in Seattle, the TV has to look in the table created during the channel scan. It finds an entry for virtual channel 4-2 and sees that the real channel is UHF CH-38. The tuner is then set to real channel 38 and the data associated with the desired program can be filtered out of the rest of the data and set to the video and audio decoding process.

Many sets will not tune or display a channel without performing a channel scan... to create the table data that is used to control the tuner.

Some of my sets will accept manual entry of the real channel number.

Do you know how if I can find out if my Samsung UN55B7000 might allow direct tuning without a scan? I've looked around, but that's not mentioned in the manual.

I'm suspicious that I may miss out on weak signals that does not appear at the precise time I scan.

That might explain why last night I could not get channel 8-1, which I can get today, while the situation is reversed for channel 5-1. Manual tuning might allow me to add entries to the table without removing existing entries.

@David Loudin: You and GUM are an amazing source of fascinating information that 90% of the population wouldn't need or care about - just the kind of stuff I like!

If you have more, keep it coming.