One quick question. With my HR10-250 I only had 2 cable runs and used a diplexer, and I understand that I need a dedicated line for the HR20. My question is can I use a splitter on the OTA line and run one to the HR10 upstairs and run one line downstairs to the HR20? Or will this make the signals too weak?
That only depends on one thing: is the signal strong enough in the first place? I have mine split 3 ways with no preamp or distribution amp and my signals are (on my Sammy TV)
Maximize Your OTA Performance Primer (follows below)
Let's assume for a minute that your OTA signal is a bit weak, if so you can do this:
Option 1: (the best)
Put an antenna mounted preamp at the antenna, and split the signal as you asked about (in the house). You will have a BETTER signal after the split, than you had before you put the antenna mounted preamp on, and then split it. In other words, the antenna mounted preamp when split will give you a better signal than you had with no split and no antenna mounted preamp. (again assumes your signal is a bit weak to begin with...if it is strong at first, then don't use an antenna mounted preamp...it will overload the HR20 and your sensitivity will go DOWN, not UP.) Try good quality passive splitters first, then option #2 below if that isn't good enough.
Gain has ONLY ONE FUNCTION in an RF preamp....it sets or "freezes" the noise figure of the SYSTEM. Once you have enough gain to "set" the noise figure previously discussed, then no more gain helps at all...in fact, is likely to make it worse.
How much "gain" is enough?
Typically 15 dB is quite adequate
If your signal is moderately good to begin with, then use this same antenna mounted preamp in the house, set to its lowest gain setting (assuming a switch and not an adjustable pot), and split off of it...you are then using the antennna mounted preamp in the house as a signal distribution amp.
Why do I suggest using the antenna mounted preamp in both cases, instead of the typical el cheapo distribution amps that get used:
The design and performance of antenna mounted preamps is FAR superior to the typical distribution amps that you can afford or will have access to. The key variable in evaluating ANY amplifier for OTA is Noise Figure NOT GAIN. Again, I repeat NOT GAIN, NOT GAIN, NOT GAIN....Noise Figure is EVERYTHING for OTA!
If the device you are going to buy does not specify its noise figure ...then you can be pretty sure its noise figure is POOR. The noise figure should be no worse than 4 dB...and it would be much better if 3 dB or less. The lower the noise figure, the BETTER the sensitivity that preamp will provide. (Be sure you are looking at its UHF noise figure and not VHF...they are usually specificied separately in a decent RF amplifier.)
Keep in mind with this "in house antenna mounted preamp as distribution amp":
Any cable loss ahead of the preamp or distribution amp ADDS directly to the noise figure of the preamp/distr. amp. So, if you get a 2 dB noise figure preamp and put 4 dB of coax loss in front of it (the run from the antenna to inside the house where you install your preamp/distribution amp), you end up with a SYSTEM noise figure of 2 dB + 4 dB = 6 dB...which is NOT very good...then again, it may suit your needs, don't panic.
Option 3: (the worst, but may be better than nothing but a passive split)
A garden variety distribution amp with no antenna preamp. Gain: no more than 10 dB...and noise figure no worse than 4 dB
1. Put your lowest noise figure device as close to the antenna as possible in weak signal situations.
2. A 100' of RG-6 cable in front of a preamp/distribution amp DRAMATICALLY reduces system sensitivity.
3. Use antenna mounted preamps for distribution amps, and then split off of them
4. Don't use any more gain than necessary in any amp or it will make things worse rather than better.