Aerial splitting for VHF/UHF/DVB-T

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Felicks

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#24803 3-Aug-2008 11:44

I did a quick search and couldn't find answers to my queries, but I would appreciate answers to the following. I'd say they are fairly simple.

I had a new terrestrial aerial installed about 6 months ago. Unfortunately the receipt just says its a 303 VHF and it doesn't say what cable was used. I asked for good quality as the aerial was going to be used for VHF and DVB-T connections. See pics:

Anyway, the single cable currently comes to the lounge (a length of distance of approx 10 - 12meters). It is split at that point using a 3 way ANTSIG splitter. One goes to the tuner on my media PC, one to the RF on the TV, and one to another PC in another room.

I am doing renovations and getting under the house (only when I have to as there isn't a lot of room!), and would like to route cables to two other rooms.

That would mean a total of 5 connections. The cables coming off the splitter would vary in length from 3 meters to 8 meters.

QUESTIONS:
1 - Is this too many connections and do I risk loosing analogue or digital signals?
2 - Are the lengths OK or should splitting occur closer to the earial itself rather than further down the line?
3 - What is a diplexor out of interest and what does the 'power ' reference mean on a splitter?

I am computer savvy but NOT aerial savvy. All references to cable types, diplexors, multiplexors, frequencies, powered splitters etc are all lost on me I'm afraid. My splitter makes reference to power on it via two of the connections but what the hell this is, I don't know. There isn't any power going either way as far as I know - is that for amplifier applications or something?

Any help, much apreciated.

cyril7

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#153774 3-Aug-2008 12:08

Hi, obviously without seeing your installation and signal levels all is reserved advise. Normally 4way split is no problems before amplication is needed, and often you can go a bit more without issues. I suggest you go with a 4way splitter, and split the feed where your TV and media PC is (I guess they are the same location) off one feed directly behind the TV.

The cable lengths you refer to are pretty trival and should not cause any real issues. Ideally you should use quad shield cable, however the most commonly available is duobond (two shields, fild and braid) and in practice I have not yet found any issues with using duobond. DVB-T's cofdm is prone to impulse noise issues, this is its primary failing compared to other modulation schemes, however overseas where VHF DVB-T transmissions are used the use of quad shield has proven more benificial. In NZ we use UHF and most man made noise sources that would cause issues are largely disipated, so less of an issue. Most noise still enters via the antenna itself. When running cables ensure you clear power cables by 300mm as the standard recommend (50mm for safety purposes, 300mm for interference). My guess is that duobond has been used by your installer, but without looking at the cable cannot tell.

Your DTT tuners in the media pc should report BER and signal level with enough of a rough guide to see if there are issues. Typically DTT tuners can get by with much less signal levels compared to analog, the BER or quality dropping off is the important one.

The DC pass port of splitters means exactly that, it will pass DC from the common port to the stated port, this is more used in LBand satellite to power the LNB but is also used with remote powered line amps in UHF.

Placing the splitter further down the line where you have indicated is not a problem. Ideally placed out of the elements.

A diplexer combines or splits two different frequency bands onto one cable, there are V&UHF ones for combining V and UHF antennas, and there are V/UHF & LBand ones for combining/splitting V/UHF and Satellite signals.

If you do need more signal to over come split losses, then I recommend going for a higher gain antenna before using an amplifier. Without knowing you location to the Tx or the signal levels you are getting I cannot comment futher. The antenna you have, Gizmo 303 is a lower to medium gain antenna, which is fine if you are in a good signal area, ChCh might I suspect?

Cyril

Brunzy

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#153780 3-Aug-2008 12:29

Your antenna suggests you have LOS to the Tx,so signal strength should not be an issue.
If it was you could easily swap it for one with more gain(UHF)
In that case I would be inclined to run a seperate quad up the mast(or leave it under the house until if/when needed)and you can use the existing ant for vhf only until Sw off.

Felicks

62 posts

Master Geek

#154112 4-Aug-2008 20:14

Thanks guys, appreciate the feedback.

Yes I do have LOS of Sugarload here in Chch. As I'm in Beckenham, its about a whole 3 km away so I suppose the low-med gain aerial is fine.

So a 4 ways splitter over those short lengths is fine by the looks, now I will just have to summons the strength and get under the house to grovel around in the dirt fixing things. The shielding terms you refer to Cyril is interesting. I'll have to pay closer attention to it next time I'm on/in the roof.

As for my signal stregnth, I'm running a Huappauge HVR2200 tuner with the standard drivers (WinTV disk) and Vista Premium O/S. I have yet to find a signal strength / quality meter anywhere. Is there any downloadable programs that'll do that for me? I'd be interested to see what I'm actually getting.

Cheers anyway.

richms

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#154170 5-Aug-2008 00:32

about the same distance in auckland, a friend with a new sony with integrated dvb was complaining about picture breakup on the digital channels on it. When I looked at it, they had the lead from the dvd player to the tv connected - at one end only, the dvd end puled out when they moved stuff around. So based on that, I think you will be fine with what you have.

Richard rich.ms

Dawg

233 posts

Master Geek

#157425 16-Aug-2008 15:23

Felicks: Thanks guys, appreciate the feedback.

Yes I do have LOS of Sugarload here in Chch. As I'm in Beckenham, its about a whole 3 km away so I suppose the low-med gain aerial is fine.

So a 4 ways splitter over those short lengths is fine by the looks, now I will just have to summons the strength and get under the house to grovel around in the dirt fixing things. The shielding terms you refer to Cyril is interesting. I'll have to pay closer attention to it next time I'm on/in the roof.

As for my signal stregnth, I'm running a Huappauge HVR2200 tuner with the standard drivers (WinTV disk) and Vista Premium O/S. I have yet to find a signal strength / quality meter anywhere. Is there any downloadable programs that'll do that for me? I'd be interested to see what I'm actually getting.

Cheers anyway.

Hi Felicks,

i'm looking at doing a very siimilar install - Just concerned about the cable I am going to use - What grade of coax have you used?
I have been given (Free) a reel of RG 59U - and from what I am reading should do the job - but RG 6 dual shielded is recomended.

I am in Barrington and have just mounted my Gizmo arerial.

Cheers Shane

Spyware

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#157435 16-Aug-2008 16:27

You shouldn't really use RG59 but in Barrington Street area it will probably be OK. One pain of RG59 though is trying to get F type connectors made for RG6 to fit as cable is smaller diameter. I have RG59 install with saddle clamp splitter in Belfast and DVB-T is perfect. I've only replaced fly leads wth RG6 so far.

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