Cannot keep all channels on tv
When you say you "lose" channels, you probably mean there's no signal there anymore but they are still in the channel memory. This is normal if you have a rotatable antenna. You need to mark the rotator (or just keep a chart nearby) with the heading for each channel.
If you mean you're losing channels from memory when rescanning after turning the antenna, the only solution I can offer is to record the channels found (and their signal levels) after scanning a direction. Then change directions and rescan. See what new channels have been found, what have been lost, or how signal level has changed on common channels. Then you can manually add whatever you need, and you'll know what direction is best for each. It's tedious, but you should only need to do it once.