I have a DirecTV receiver with HD and DVR hookied in my room on the second floor in the front of the house and the satellite is in the back. The installation guy said that I needed two cables running to the receiver, one extra for tuning so that I can watch other stuff while recording, but that he would have to charge me the cost of extra cable length since they are ~$100 a box or something and DirecTV doesn't reimburse them after like 100 feet of cable is used. So I opted for one cable to save money. I haven't had any problems, but I was wondering/being paranoid if using only one cable could potentially affect performance or video quality of the HD received, even though the installation guy said it would make no difference.

Using one cable will not allow you to watch one channel and record a different channel. It will have no effect on the quality of the of the HD signal.

Using one cable will not allow you to watch one channel and record a different channel.This is incorrect.

DirecTV now has hardware that will allow use of a single coax cable to provide two sat signals for their HD DVR's; one to watch and one to record.

The SWM8 will allow you to run single coax cables to 8 different locations from the 5 LNB dish, and with specific DirecTV HD receivers & DVR's, and have dual tuner function.

Compatible with HR21 HD DVR Receivers, H21 HD Receiver, and H20 w/.2042 Firmware Update.

OTA antenna can also be used with the SWM8.

http://www.directv.com/DTVAPP/customer/downloadPage.jsp?assetId=1100066

In the HR21 manual, note PDF page 17 (numbered page 6 in actual manual). Note that it states that the SWM is connected to Satellite In 1, not both 1 and 2 and is labelled SWM-2. You do not need to split the feed from the SWM, only connect it once.

DIRECTV Plus HD DVR Rear Panel
Your equipment may not look exactly like the model illustrated.

1) SATELLITE IN 1 (SWM-2) – Use to connect the DIRECTV Plus HD DVR to a second LNB onthe satellite dish antenna, giving you the ability to watch and record up to two programs at once. If your installation includes an SWM (Single Wire Module), connect the SWM output to this input. SWM is a technology that allows multiple tuners to work with a single satellite input. (SWM support may require a software upgrade. Ask your DIRECTV Installer for details.)

2) SATELLITE IN 2 – Use to connect the DIRECTV Plus HD DVR to the satellite dish antenna.

Directv isn't installing SWM8's, you need to buy your own. They should be using the SWM enabled LNB's on new HD installs though, may be able to get one of those out of the installer if there are no legacy receivers in the house also.

Will two cables improve the speed of the TV guide or channel surfing? The HD receiver is very sluggish while the SD receiver I have downstairs is snappy.

# cables won't change the surf speed. Part of the sluggishness is inherent in the HD receiver since it has to acquire enough infor and then process it to make a functional picture. This has improved some with the more UTD firmware, but nowhere near the speed that the SD is capable of.

If you have "Native On" in the display settings this often slows things considerably though it does add a bit of potential quality -- a trade off that happens in many things. Turn off Native and I find surfing about twice as fast, but still not close to SD units.