VHF VS UHF
One of the things we know about VHF signals is that they do not penetrate walls as well as UHF. If you have even one wall between your antenna and the NPT transmitter, it may be enough to weaken the signal to where you see nothing. That’s the other thing we’ve learned since the DTV transition; whereas one used to be able to view a weak “snowy” signal, with digital TV it’s either crystal clear or not there at all, there’s very little middle ground. In cases like this, amplification does not always help, since a weak signal has a low signal-to-noise ratio, and amplifying the signal also amplifies the noise, which continues to block reception.
There are many popular “DTV” antennas that lack the long rabbit ears, such as the flat panel antenna. They look high tech, but they’re really just the old metal loop UHF antenna of old in a nice plastic case. The reality is that even though broadcasters were required to switch from analog to digital broadcast, the transmission and reception technology did not change at all, and in spite of all the cool looking antennas manufacturers came out with, the traditional ones work best.
Locally, channels WNPT and WSMV are broadcasting on VHF, which requires the old “rabbit ears” style indoor antenna or the outdoor antenna with the long splines that used to be atop everyone’s roof. It’s best to avoid those “flat panel” antennas that are so popular now, because they are designed for UHF only. You’d be better off with a $10 antenna like this one (https://www.walmart.com/ip/RCA-Basic-Indoor-Antenna/10983714) than the flat panel, if an indoor antenna is your only option.
Manufacturers say that that flat panel antenna is "tuned" to receive VHF and UHF, but if you remember the old antennas we used to have on our TVs, you'll remember that there were long sticks or "rabbit ears" and a loop. The loop was to receive UHF, the rabbit ears to receive VHF. Digital TV did not change the physics of TV reception, so VHF still comes in best with rabbit ears, and UHF still requires a loop type antenna. As you might imagine, there are no rabbit ears in that flat panel; it basically holds a loop type antenna.
NPT (and WSMV) broadcasts on VHF, while the rest of the Nashville stations broadcast on UHF channels. What we’ve learned since the digital transition is that VHF does not penetrate walls as well as UHF does. So, if you’ve got multiple walls between your indoor TV antenna and NPT’s broadcast tower, your signal strength can be cut so far as to make NPT not show up in a scan. NPT’s transmitter is located due south of the city, about two miles west of where I-65 intersects with Old Hickory Blvd. If you place your antenna in front of a window facing NPT’s tower and scan again, you may be able to receive NPT that way. That will confirm that the issue is signal loss through walls.
Locally, channels WNPT and WSMV are broadcasting on VHF (channels 2-13) while other local stations broadcast on UHF (channels 14 and above). To receive all Nashville channels best with an indoor antenna, you are better off with an inexpensive antenna like this one (http://www.rcaantennas.net/indoor-hd-antenna/?sku=ANT111F) than the more expensive flat panel.
Indoor vs Outdoor Antenna
Another issue that arises with indoor antennas is RF interference. There are so many electrical devices and motors in our houses these days (computers, microwaves, refrigerators, etc) that any one of them could be generating radio frequencies that interfere with one or more channels. I recently read an article where an engineer discovered that the new LED light bulb he purchased blocked one of his channels when it was on. I don’t know if that’s what’s happening in your case, but it’s one more reason why I highly recommend an attic or better yet, an outdoor antenna for best reception. 99% of the reception issues I get contacted for are for indoor antennas, enough to make me lose faith in them as a whole.
Another problem with indoor antennas is RF interference from appliances. Electrical motors (such as those on your refrigerator or dish washer), computer monitors and even LED light bulbs can emit RF that blocks out certain channels.
The “flat panel” DTV antennas are basically a loop antenna encased in plastic. They are very popular, but not very good, in my opinion. You might be better off with a simple rabbit ears/loop combo like this one for $10.
Another problem with indoor antennas:
Reception issues are not always due to weak signal with indoor antennas. Often the problem is RF interference within the home. Electrical equipment such as computers, routers and even cell phone chargers can generate interference. Appliances such as refrigerators, washing machines, dryers and microwave ovens can also cause problems that block out certain channels. Even LED light bulbs can cause interference. For these reasons, you’ll get the best reception with an attic or outdoor antenna.
What antenna should I buy?
I found many quality and inexpensive outdoor antennas at vendor sites like http://www.solidsignal.com when I purchased my antenna. If you go this route, make sure you get one that states clearly that it receives BOTH VHF & UHF. There are a lot of supposed “DTV antennas” that only receive UHF. I do not recommend going to a big-box store for an antenna, as I’ve found the sales staff in these stores woefully ignorant of reception issues in Nashville. They always seem to steer customers to $150 indoor UHF antennas that work no better than a $10 rabbit ears antenna like you’re using now. I’ve tried many of these “DTV antennas” and a $30 outdoor antenna like this one (http://bit.ly/1TLpq2p) works better.
I’m reluctant to recommend a specific antenna because I don’t have a lot of experience with a wide range of antennas. I usually explain why it’s necessary to make sure they get a VHF/UHF antenna for our market and how many of the “DTV” antennas they see in Walmart are UHF only. I also explain that the reception technology hasn’t really changed, so the old style rooftop or attic antenna are often best.
If pushed, I will mention solidsignal.com or antennasdirect.com, and give them the following links as examples:
These are all from $70 - $100
Where should I install my outdoor antenna?
High up on your roof is best if that’s possible. You may want to go online to search “antenna installation” to find professionals to do the job for you, as they are experienced working on roofs. If you live in a neighborhood that prohibits rooftop antennas, they can be installed under the eaves.
If these are not options, you may want to install your outdoor antenna in your attic. This will reduce signal strength slightly, but will still be better than an indoor antenna.
Will an Amplifier Help?
Not always. A weak TV signal has a low signal-to-noise ratio, and amplifying the signal also amplifies the noise, which continues to block reception. An amplifier may also boost the signal strength too high, which will also cause reception problems.
There are situations where an amplifier does help solve weak signal problems, but it’s best to start with a good antenna pointed in the right direction before resorting to amplification.