Note: Skip this whole post if you're aren't concerned about an exhaustive reply to the following quote ;-) :
Originally Posted by ybsane
It's really not an issue except for excessive plant noise, the CMTS auto ranges the level back on the return for modems and MTA's, same goes for the de-mod. for the boxes. So its really a moot point about the amount of return amplification.
Yeah, you'd be surprised how much it drops in some places I have been. For the most part I've never had an issue. Lately, since moving around Santa Barbara lot, I've found some places that have some traits of poor line quality (whether it's due to long runs or truly poor quality lines I can't say). Admittedly, I'm making that statement largely based on the cable modem's S/N & power levels, but they're enough to infer quite a lot. The fundamental principle I'm appealing to is that auto-ranging or not, it's easier to read the signal (& auto-range etc) if the transmission power on the far end (in this case, my house) is higher.
Replacing a passive-return amp with an active-return amp has pushed my x-mit power levels down (I know, "pushed" has the wrong connotations). I have done some very simple testing to verify this:
Condition 1: plug CM straight into drop, measure values
Condition 2: put CM behind electroline (which is plugged straight into the drop), measure values
No surprises there. This simple test has also verified, in multiple houses/locations, that I am indeed able to fix [upstream] connectivity issues with the amp. I have stuck with my IT background as data service and PPV/digital cable are the only heavy upstream services. I don't know enough about how PPV/digital cable handles poor upstream performance and I don't know how to measure its effects reliably whereas raw data performance gives me a means by which to conduct reasonably reliable experiments. (I use several servers at different clients' offices that are also located on Cox to get average measurements).
...and I test connection quality like so:
1) Cable modem behind 1 splitter = poor upstream performance (easily measurable **) + high upstream power level.
2) When I put the modem straight on the drop: works great, no more upstream packet loss. Downstream is fine as well.
3) Put the cable modem behind the FT8100, see identical performance to #2 (from what I can see/test).
Note: This was always done after trying it with the Motorola Signal Booster first, to ensure it wasn't a downstream/downstream-only problem. The weak (3db) downstream amplification on the dropamp isn't enough to cure most downstream problems so I am attributing its success to the active return.
Poof. Problem solved. Many. Many. Times ;-)
So, point taken ybsane, but I needed to ensure that people understood that your caveat ("...except for excessive plant noise") is not worth brushing off without doing a simple test or two to ensure it truly isn't an issue. Well, I guess w/o an active-return amp it isn't so simple... *sigh*. What can I say? Borrow a friend's? Leave me one if you're in SB? I don't know ;-)
** measurable via split ping/bandwidth tests originating at either end -> I measure, with a custom app & a packet monitor, icmp (ping) echo request and echo reply packet travel times to establish one-way loss/delays. This could be done almost as easily by running packet monitors on both ends and pinging each other several times.