Join Date: Jul 2010
Location: Lake in the Hills, Illinois
If you don't have a Sencore or other field strength meter...
You can still fine-tune the antenna location in the attic, but you will need to do some prep work.
I like to use a laptop computer and a USB tuner stick. It's not too hard to get the laptop up to the attic, and with this setup you can use a freeware program called TS Reader. TS Reader will give you a lot of information about the quality of the signal (which is usually more important that quantity, especially in the attic). I have found that, in the attic, very small spatial adjustments (up/down, right/left, clockwise/counterclockwise) can make a HUGE difference in reception quality.
If you don't have a laptop, you can also use a small portable LCD ATSC TV; I found one for only 30 bucks (7" screen), but unfortunately the signal meter is not very helpful on that model. So I have used it with a CECB, which at least has a somewhat better signal meter.
If you don't want to drag electronics up there, you can use a CECB that has a audible signal meter. If you set it up on a TV that is within earshot of the attic, and crank up the volume, you can fine-tune the antenna by sound. The downside is that you would have to go back down and change the channel in order to make sure that you have them all.
About cable routing: You might find that your vent stack has firebreaks installed in the wall, which will stop you in your tracks. Cold-air returns are fine as long as you are routing the cable OUTSIDE of the duct. If you put the cable inside the duct, the force of moving air could cause it to bang around inside the duct, which would be very creepy. If you find that running the cable inside the house is going to cause a lot of headaches, it may be best to cut your losses and go outside the structure. If you do a good job of securing the cable along corners and break lines, and paint the cable to camoflauge it, it shouldn't look too tacky.
Attic installs work very well as long as the signal is strong enough to overcome your home's material loses. You have year-round access to the antennas (ironicaly, it's a lot nicer up there in winter than in summer), you don't have to weatherproof everything, and your equipment will last forever. I have also found that the right attic location can better combat co-channel interference compared to an outdoor mast, which will be fully exposed to the interfering signals.
One more thing- if your attic is small, or has a lot of trusswork in the way, it might be better to go with a panel-style antenna instead of a Yagi. Yagis generally like to have a lot of empty space around them, and don't perform as well if there are two-by-fours getting up in their business.