Your Help Please

PacMan

Hello again. Good to be back on the boards after an absence of 8 months. Been away for work!!!
But I always did keep an eye on what was happining here.
Question.....
I purchased a dixplexer (Spelling??) which combines the satellite and terrestrial signal into one cable then splits them again at the outlet behind the tv.One to the TV for annalogue RTE/TV3 and the other direct to the Sky digibox.
Now the question.
Can I put the terrestrial signal through a booster in the attic, before I link it to the satellite cable, or will this cause interference??

DMC

Welcome back squire!

chernobyl

who are you? [i wanted a higher post count]
/wink

watty

The whole point of a diplexor is to put two signals on DIFFERENT bands down one cable.

The lowest Sky frequency when you are watching 2D is 979MHz.

The highest TV frequency is 890MHz (TG4 is Ch68 close to this some aeras).

This is a bit close for an average diplexer (i.e. not a €1000 part out of a repeater system) to separate.

But when you watch 2A/2B the 2D signals are still there so lowest Sky frequency is 129MHz!!!! Who knows how much filtering there is on the LNBs?

Pointing my dish at Astra 19 which has analog, I can pickup 3 or 4 channels on the portable TV by pointing the aerial at the Satellite coax 20 ft away (The AM video detector can receive FM video by slope on edge of IF filter).

If I connect a coax running in same duct under the ground to workshop with RF TV alongside the 3 Digital IF coaxs from LNBs all the TVs get noisier pictures from "leaking" digital signals when any receiver selects the high band. (as this makes the low band signals move down into the UHF).

Since a booster might overload a bit on one strong channel and double or triple (triple is more likely), then 600MHz UHF TV becomes 1800MHz, inside the Satellite IF band.


Diplexing Cable TV or UHF TV with Satellite LNB signal (satellite IF ) is a seriously flawed idea.

Diplexing BandII radio (88 to 108MHz) and Band IV/V TV (470MHz to 890 MHz) just about works. Even then some TV tuners can "react" to a high level of BAND II radio and make the picture noisy.

Since the TV band and satellite IF Band are side by side and even overlap with a "Standard LNB" or a "Universal" set to High band, you are asking for poorer TV pictures (noisy) and potentially "freezing frames" on Satellite.

Don't forget Terrestrial signals don't stop at Ch68 either, nor does your aerial stop there too. There are all kinds of strange signals some strong enough to be picked up by a UHF aerial between 750MHz and 2150MHz (tuning range of Satellite IF).

A domestic diplexor simply has not enough filtering to block unwanted inputs, nor fully separate the bands.

You can even use an existing cable as a "pull wire" to pull in two new CT100 cables.

PacMan

Phew:D
Thanks Watty. I appreciate the very detailed answer.
Two cables it is then........
BTW, I used to enjoy your postings on the old MediaUK site. Glad to see that you are now "Over Here" on ICDG.