Signal Source

[Birddog]

I'm a Noob here and am a little perplexed.
Here is my report http://www.tvfool.com/?option=com_wr...27eed9df526c02

This a vacation property and I am located in a low area surrounded by Pine trees. My mast is only about 20' tall and is definitely below the tops of the surrounding trees many of which are in line of sight. I have a 20 year old UHF above a VHF antenna, not sure of brand, but probably best you could buy back then. I haven't much depended on a strong signal from the antenna, because I rely on Satellite. In the past, I've just done without locals.
I just switched over to an HD set and HD Satellite programming and thought I'd do a channel search and to my surprise I'm getting a very strong signal with excellent picture on 4 channels off air.
Here is the line up of off air channels.
2.1 KASA DT (FOX)*
7.1 KOAT DT (ABC)
7.2 KOAT ET (ABC) (Spanish programming)
13.1 KRQE DT (CBS)*
28.0 KNME NTSC (PBS)
30.0 KOB NTSC (NBC)
48.0 KOB NTSC (NBC)**
*= signal not always received sometimes mosaic
**= not really watchable unless desperate

I can't figure out the source of the strong signal and none of my neighbors know anything as they receive locals off satellite. I understand the 28 through 48 are coming off the translators, what could be the source of the others?
On another older set with converter, I receive only 2.1, 7.1 and 7.2.
TIA,
Birddog

[mtownsend]

Hello and welcome!

Your tvfool report was only resolved to a city level. Since your area is surrounded by mountains, it's really important to get a more accurate analysis for the location of your house. The generic city-level analysis might not show the same results as your true location.

Address lookups don't always work, so the best thing to do is to use the Interactive Maps feature (link is here). This will bring up a map of your area and allow you to move the point being analyzed. If you switch the map to "satellite" view, you can zoom in to see house-level details. To adjust the location being analyzed, just drag and drop the orange marker. You can also edit the value for antenna height to experiment with making the antenna higher or lower.

When you have the marker and height settings the where you want them, you can press the "Make Radar Plot" button to generate a radar plot report with the current settings. If you post the URL for that analysis, we can get a better look at your signal situation.



Just based on the city-level analysis, it does look like you have a handful of translator stations serving your area. The channels you picked up are probably one of the translator stations (channels with numbers in their callsign) rebroadcasting content from the major stations around Santa Fe and Albuquerque.

Not all translator stations have fully converted to digital signals yet, but most of them should be done sometime this year.

Each digital channel is capable of sending multiple sub-channels. That is, one physical channel (e.g., RF channel 33) might contain multiple sub-channels with different programming (e.g., x.1, x.2, etc.). All the sub-channels are carried on the same signal, so if you get one of them, you can get them all.

Just FYI, all the channels ending in .0 are analog stations, and the rest are digital.

The major channel number (the value before the decimal point) on digital stations is a "virtual" channel number. That is, even if a channel shows up on your screen as 7.1 and 7.2, it might actually be broadcast on a different channel number like 33. When you turn your TV to channel 7.1, it is actually tuning to the true RF frequency of the broadcast, which might be different than the major channel number you see. I suspect that the digital channels you are seeing (KASA, KOAT, and KRQE) are actually coming from some of the digital translator stations in your area (maybe channels 33, 38, and 23).

If you want to find out what real RF channel you are watching, most TVs have the ability to show you both the real and virtual channel numbers for the station you are watching. That option might be hidden somewhere in the menus, but there's a good chance it's in there. That will help you identify exactly which transmitters are active and receivable from your house.

[Birddog]

Thanks Mtownsend,
That already explains a lot. I was wondering if I was actually getting the signal from atop Sandia Peak (All albuquerque towers are there and it's about 130 miles away). That didn't seem possible, but I was wondering if digital could do that. I already knew the direction etc of the translators, it's just that these call letters didn't show on the chart and I didn't know the source. My location is such, that I can actually receive signals from both sets of translators.
I am curious as to why the digital signal is sooooo much better than analog has ever been, and also why sometimes I get no signal. I should point out that there is snow on the ground, and back in the old analog days it seemed like I got better reception when the ground was snow covered.

If I'm able to get a signal of this quality with my old set up, then I wonder what a new appropriate antenna on a higher mast would do?

Here's the new plot http://www.tvfool.com/?option=com_wr...27ee1be993ec5c

Thanks,
Birddog

[mtownsend]

Originally Posted by Birddog

Here's the new plot http://tvfool.com/?option=com_wrapper&Itemid=90

Sorry, but your report did not come through. You'll need to press the "Make Radar Plot" button to generate a report that can be shared with others. The web address of your report should look something like: "http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%xxxxxxxxxxxxxxxx"

[Birddog]

This should be it.
http://www.tvfool.com/?option=com_wr...27ee1be993ec5c

[mtownsend]

Originally Posted by Birddog

I am curious as to why the digital signal is sooooo much better than analog has ever been, and also why sometimes I get no signal.

It is because of the digital signal format. The content of a digital OTA broadcast is similar to the content of a DVD. As long as your receiver is able to lock on to the digital data stream, it can decode a perfect picture. If some of the data gets lost (like watching a scratched DVD), then you might see some video artifacts (pixellation, macro-blocking), hear audio glitches, or have the picture go away completely.

The cross-over point between a decodable signal and a non-decodable signal happens over a very small range. In other words, once the signal quality gets above a certain threshold, the digital data stream becomes 100% decodable, and when the signal quality is a little bit below that threshold, the data stream becomes 0% decodable. Since there is such a quick fall off from a perfect signal to a completely unusable signal, this is sometimes referred to as the "digital cliff".

If you have signals that sometimes show pixellation, or comes and goes when the weather changes, then it means that your signal levels are dancing around that "digital cliff". In a typical day, there are going to be natural fluctuations that cause signal quality and strength to vary. Things like temperature/humidity changes, heating/cooling of the Earth, blowing trees, weather fronts, seasonal changes, ground covering, and dozens of other factors can cause random ups and downs in your signal.

Choosing a good antenna and pre-amp will help improve your signal and thus give you more margin for error to deal with random signal fluctuations. If you have more signal margin, then you are less likely to see any pixellation or drop-outs.

I wonder what a new appropriate antenna on a higher mast would do?

It sounds like some of the translators in your area are already operating digitally, but some are still running analog (channels 28, 30, and 48). I can see in the FCC database that channels 30 and 48 have already been granted permission to build digital transmitters. I believe that they are in the process of getting a permit for a digital version of channel 28.

Since you are currently experiencing some pixellation on two of your digital channels, then it's quite likely that you'll be able to clean that up with an updated antenna setup. A mast-mounted antenna on the roof usually works best (antenna about 5~10 feet above the roof). There's minimal benefit to going any higher than that.

At present, you only have one VHF station to consider, K09AK (owned by Eagle Nest TV Association). You did not report seeing this channel, so I'm not even sure if it's on the air. Eagle Nest TV Association also owns the transmitters for K48AX and K35BZ. I'm not sure if they have any plans to apply for a digital version of K09AK.

If your area has no more VHF stations in its future, then you can choose to use a UHF-only antenna. If you think there might be VHF stations returning to your area, then you can either use a combo antenna now, or plan on adding a VHF-only antenna to your setup later.

Your antenna choice will depend on how you want to deal with VHF.

[Birddog]

Wow great info, thanks a lot. This gives me a much better understanding. In the analog days, I would have to say I was a little more over the cliff than on. Now in the digital, I'm a little more on the edge.

The Pine trees blocking the line of sight to the translators are many and dense. I'd say I would have to get up around 50' to see over them. I could either place an antenna a little up the slope and higher than the treetops at a distance of around 100' from the house, or keep it where it is and maybe raise it to 25' or 30'. That would make it about 15' above the metal roof but still lower than the nearby treetops.

I would not need a VHF antenna, only UHF. What antenna and extras would you recommend?
Thanks,
Birddog

[mtownsend]

It's probably not necessary to shoot over the trees. Your signals seem reasonably strong, so they may be good enough to pick up through the trees. There's no good way to estimate how much signal loss trees will cause other than trying it, but most people can successfully get their signals this way.

For a good UHF-only antenna, I'd lean toward the Channel Master 4221, Channel Master 4228 (for a little more gain), or the Antennas Direct 91XG (this is a Yagi style antenna as opposed to a bowtie style).