No, I put it after the tee that splits the signal between the TV and the cable modem. It only boosts the signal to the cable modem.
But I suppose it would be possible to place it upstream of the tee, so it would boost both signals, or on the TV side so it would only boost the TV.
However, unless you've got a digital cable TV converter, there's no need to spend $80 for a cable modem compatible drop amp like this to boost the TV signal; you should be able to use a cable TV signal amplifier from Radio Shack. I think these cost about $25-40.
It doesn't affect the upload side; it only amplifies the download side. It's an amplifier; it can't increase the basic speed of your connection, which is only as fast as your ISP allows it to be. All it does is increase the strength of the RF signal.
However, if communication between your cable modem and the ISP's equipment is poor, you can lose packets or even lose the connection entirely (this is called "losing block sync"). If you lose a lot of packets, it will have a significant impact on your throughput.
It's much the same as an analog modem connection to a dialup ISP through a poor phone line. Instead of getting the rated 56k of your analog modem, you might get only 42k, 36k, or even less. The same thing happens when a cable modem has a poor connection to the cable ISP.
In my case, the drop amp improved the download speed by virtually eliminating dropped packets - and I was dropping a lot of them before I got the amp!
Inside the house, between the cable entry point into the house and the cable modem. It's an indoor-only model, although I'm sure someone must make outdoor models.
I would guess that it's best to place it as close to the entry point as possible, so it's starting with the strongest signal available and boosting from there.
Yes, it requires a grounded outlet.
It's a Motorola Signal Booster Broadband Drop Amp, part number 484095-001-00. Cost was $80 from Best Buy.