difference between HDA-1000 and HCA-3086

Not from those links. Edit your post and add another 'w' at the beginning.

The HCA3086 has separate gain and slope controls, whereas the HDA1000 does not.

The HDA1000 has a bit better specs than does the HCA3086, and it accepts a lower input. The HCA3086 also comes in a wall mount version as well as a rack mount version.

I've used the HDA1000 for launch amps in a few headends and absolutely love them. If it's going to be located out in the distribution system, you need separate gain/slope controls.

You're right. I was going by what I have used in the past.

As far as the input level, your needs would be determined by what the signal levels actually are. Signal level could be calculated using the distance of the cable and any passive devices in the run. Of course, an inline attenuator (pencil pad) could be installed at the input of the amp to lower the level if it's too strong.

The input is a set level coming from the headend (modulators). Really, the system (which includes the headend itself) should be balanced every so often, say every 6 months. To properly do that would require a signal level meter as well as a modulator at 860MHz. Google ST-4000D

As I said, I have used the HDA-1000 and have been very pleased with it.

The signal levels of a system are not determined by the number of TV sets connected. Systems are typically designed to provide a signal level of 5-10dBmV at each outlet.

Oh, you can replace an HCA with an HDA-1000 without any worries. If you're really concerned about the input, you can always insert a 2-way splitter on the input of the HDA-1000 (be sure to terminate the unused port). That'll knock it down ~3.5-4dB. It's unlikely that you'd even need to do that, though.

Just some fine, horizontal lines on some, if not all, of the channels. The hotter the signal, the worse they become. It won't break, mainly annoying.

That's why I suggested taking a small TV set with you. There's a test port on the output you can connect to to see what's coming out of the amp..

There's not really any such thing as too many TVs on an amplifier. Systems are designed to provide a certain signal level at the tap. The signal level at any given tap is within just 2 or 3dB of the next (or previous) tap. Neither the amp nor the system even cares how many TV sets are connected. They put out what they put out.

If the system is designed right, you can have 1, 50, or a hundred TV sets connected and each will have the same quality of picture.

You can also think of it in terms of FM radio. If everybody tuned to the same station at the same time, would nobody be able to hear that station because too many people were tuned in?

The question there is what was the source for each of the amps? Was one to distribute the local CATV system and the other to combine local origination (such as CCTV) into the system? That's fairly common.

No -- I haven't seen that before. If it's stationary. If it rolls, that usually indicates a bad power supply.

Perhaps each amp fed a different building or floor or part of the system. That's the only thing that makes any sense at this point.

Are you saying you've combined several Over the Air signals with CATV signal and a locally modulated signal? Then yes, I know the 'black stripe in the middle of the image'. It's caused by having multiple sources for the 'same' signal.

Yes, could be. Hadn't thought about that.

There's no way of knowing what frequencies the cable company has stuff on. Even if there was nothing at, say, 470MHz yesterday doesn't mean they won't have something there tomorrow.

The -20dB test ports are merely connections that are 20dB lower in signal level than what is actually at the input or output port. For example, if you have a +10dB signal at the input port of an amplifier, the level you would read at the test port would be -10dBmV. If it amplifies the signal by 30dB, the output of the thing would be +40dBmV, while the level at the test port would be +20dBmV. Test ports are provided so that you can see what is going with that piece of equipment without having to disrupt anything.