One of the main differences between indoor and outdoor aerials is that outdoor ones can be oriented permanently towards your local TV transmitter masts, whereas indoor aerials are designed to be uni-directional so that moving them around isn’t much needed.
Nevertheless, even in these days of digital TV this is never entirely true. Sometimes moving your antenna a little to the left or right will make the difference between getting a good grip on an already weak channel or losing it. Inside, and outside, your house, signals bounce around off walls or other obstructions so there will always be some spots ‘sweeter’ than others.
Generally speaking, locate your aerial as high as possible and preferably near a window where the signal can enter unobstructed. Also, remember to check that your cables are good quality and securely connected.
Signal strength meters
Your biggest problem is in being able to know when your aerial is in the best possible orientation. You need better feedback than constantly repeating lengthy channel scans. A few receivers incorporate signal strength displays, but most don’t or are too cumbersome to use while you’re moving around the room.
Hand-held meters are hard to beat and measure signal strength in NM(db) (noise margin in decibels), and also Pwr(dBm) (power ratio in decibels-milliwatts). The noise margin in decibels tells you how ‘clean’ your signal is and the second tells you its actual strength. You need to get both right for the best possible channel reception. You can find instructions on using one here: https://www.techwalla.com/articles/how-to-measure-a-tv-antenna-signal-strength.
You’ll find signal meters on Ebay for under a fiver but when you know that engineers use ones costing closer to £1000 you’ll appreciate why it’s worth hiring professionals. This Evesham TV aerial installation company offers free site surveys http://steveunettaerials.co.uk/services/satellite-repair-installation-evesham/.
Aerials and amplifiers
If you’re still struggling to find those channels, you’re bound to consider replacing the aerial but they’re all much the same, so you’ll probably waste your money. Aerials with built-in digital amplifiers can be poor economy because a low-quality amplifier can actually degrade the signal or prevent you benefiting from a good quality one bought separately. It’s best to go for a simple aerial and try a separate signal amplifier.
Buying new aerials, cables and meters may be more expensive than calling an expert.
