Diplexing and splitting

Forums › Home Theatre (incl HTPC) › Diplexing and splitting

buzzy

217 posts

Master Geek

# 20327 21-Mar-2008 19:17

Hi all,

I've just bought a new house and I'm in the process of sorting out the TV. I've done some reading, and I *think* I know what I need to do - which usually indicates I'm about to do something stupid, so any advice would be appreciated.

I want to get standard analog (UHF) signals to two Hauppauge PVR cards installed in a PC in my lounge.

I have both a dish and a UHF aerial on the roof, each with its own coax feed into the basement. The two coax feeds go into a diplexer. The output from the diplexer goes to a two-way splitter which sends one coax run to the lounge (where the PC lives) and the other to the back room of the house (which will be unused). Both coax runs terminate in what I'd call "satellite type" wallplates (a screw thread poking out from the wall plate). There's no RF-type sockets in the wallplates.

So, what I think I need to do is install a diplexer near the lounge wallplate to split the satellite and UHF signals, then
replace the satellite-type wallplate with an RF-type wallplate.

Alternatively, as I'm not planning to use the signal from the dish anytime soon, I could remove the existing diplexer, and have a single run of coax from the UHF aerial straight to an RF wallsocket in the lounge. Would this possibly be a better answer than diplexing and then splitting off a satellite signal I don't plan to use?

Cheers!
Richard

injuised

256 posts

Ultimate Geek

# 117946 21-Mar-2008 21:15

I think you just answered your own question

Take the IF out of the system and run uhf straight to the f-type wall plates

If you do decide to use the dish, then use the diplexer in the basement and then use another diplexer behind the tv to split the UHF and IF

hazza87

348 posts

Ultimate Geek

# 117949 21-Mar-2008 21:20

The current F type wall plate will be fine for using after you have taken out the satellite from the equation. The f type connectors (Screw thread sticking out on wall plate) provide better connections than simple rf ones. You can then get a flylead that has a male f connector on one end and a normal belling lee one on the other.

buzzy

217 posts

Master Geek

# 117965 21-Mar-2008 22:27

Thanks for the replies guys, most appreciated. As you said, I probably answered my own question, but having confirmation is much better than taking the suck-it-and-see approach :)

BarTender

2846 posts

Uber Geek

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# 117990 22-Mar-2008 07:21

Buzbar!, The one thing you will need to make sure is you run good quality RG6 Dual or Qual shielded Cable from the underneath of your house to your wall points and properly terminate it as well!! otherwise you won't be able to carry the Satellite (or TCL Cable) properly. Preferably use Quad Shielded RG6, so then you can run TCL Cable TV or Internet over it.

buzzy

217 posts

Master Geek

# 118486 25-Mar-2008 10:41

Hi fellas,

All sorted with a couple of in-line connectors. I'll be properly rewiring the lot as part of a greater project to wall-mount the TV etc, but that's not gonna happen until later in the year

Cheers
Buzzy

buzzy

217 posts

Master Geek

# 119327 28-Mar-2008 12:03

Right, time for an update. Apologies in advance for the long post:

A single feed into the TV or a single PVR cards works, but using an amp/splitter is causing horrible pictures. My overall objective is to get a good feed from the roof aerial (UHF/VHF) into two analog PVR cards and ideally the TV too. No DVB at this point, although that'd be nice down the track.

I've removed the diplexer and splitter under the house, and replaced them with F-type inline connectors. I now have one run (three pieces of RG-6 cable with the inline connectors) from the roof antenna, under the house and up into an F-type wall-jack in the room.

As a very temporary measure, the wall-jack had a convertor from F-type to Belling-Lee screwed onto it, then three pieces of el-cheapo flylead connected one to other the with in-line connectors. Reception is ok for most channels when plugged into the TV and acceptable when plugged into a PVR card (good on TV1,2,3, ok on C4 and prime). I'm guessing the difference here is simply that the tuner in the TV is much better than the ones in the PVR cards.

To replace the flyleads and enable use of an amp/splitter, I bought a 6m run of RG59 cable with F-type on one end and Belling-Lee on the other. When connected soley to the TV this actually resulted in a slightly worse picture than the el-cheapo flyleads, so it's gone back to the store for a refund today.

While I had the 6m cable present, I fed it into a 3-way distribution amplifier/splitter, taking the feeds from the amp into the two PVR cards and the TV. The result was a noticeably worse picture on the TV, and all-but-unsuable pictures on the PVR cards. As soon as the gain was turned up on the amp, the picture got worse and was mostly just snow.

I'm trying to work out where exactly the problems are. From reading other posts here (specifically one in the DVB forums), I'm not sure which of the following would be best:

- A higher-gain roof antenna. I'll post a pic of the existing one if that's useful
- A masthead amplifier
- Better cabling from end to end, which is a medium-term plan anyway
- Ditching analog/DVB-T and going down the DVB-S route with the satellite dish mounted on the roof
- Disconnecting power to the house and sitting in the dark reading books with a candle

Any advice appreciated

Cheers
Buzzy

mentalinc

1752 posts

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# 119348 28-Mar-2008 14:07

where in the run is the amp remember it will amplify everything it receives so if the signal is weak with noise in it it will also make the noise "louder".

Move the amp as close to the UHF as you can.

CPU: Intel 3770k| RAM: F3-2400C10D-16GTX G.Skill Trident X |MB: Gigabyte Z77X-UD5H-WB | GFX: GV-N660OC-2GD gv-n660oc-2gd GeForce GTX 660 | Monitor: Qnix 27" 2560x1440

buzzy

217 posts

Master Geek

# 119354 28-Mar-2008 14:49

Mental - the amp's at TV end of the cable run. I can certainly move it to the roof, but that will involve a fair amount of recabling and changing of connectors. Might have a go at that next week.

Cheers
-Buzzy

richms

22518 posts

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# 119459 28-Mar-2008 23:03

The 2 amps have different purposes. The masthead is go get a low signal up to a usable one, and a distribution is to take a good signal and make it really loud to send to multiple places. If you don't have an excellent picture with well balanced levels then a distribution amp will make it worse because they will only go to about 95dBµV typically - some will say 120dBµV on them but that is questionable.

Anyway, if you are putting that much gain in the system it will be amplifying all the out of band crap that it is picking up, cellphones are right above the UHF band covering what was once ch 64or so upwards, there is loads of stuff at the bottom end of the UHF band in the 400s like PRS and FRS radios - these will cause the amp to clip unless you have checked and filtered them appropriately, and that will cayse noise all over the place and herringbone patterns.

If the signal at the bottom of the cables is crap, no distribution amp or amplified splitter or whatever you want to call it will fix it on all channels all the time.

I would suggest you get it working on a single tv or whatever on the cable, then put the dist amp onto it and play with its gain and tilt to see if you can get it driving some splitters and multiple outputs properly.

If you are getting overload of the amp, then you really need a spectrum analyzer to see what freq it ois on, and then get a notch filter to get rid of it. Making a MATV system is not for the weak walleted unfortunately.

Of forget the analog, get some dvb-t tuners and enjoy its sensitivity to weak signals which will prob mean no need for an amplifier.

Richard rich.ms

buzzy

217 posts

Master Geek

# 119844 31-Mar-2008 11:15

Thought I'd replied to Richms already, but I it must have got lost in the post.

Rich, you say that DVB-T has better sensitivity to weak signals. I thought DVB-T was *worse* when it came to weak signals, so you needed a good signal before using DVB-T. If it'll handle the weaker signals better, I might give it a go without the amp and see how it works.