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View Full Version : anyone know anything about tv splitters?



reven
2005-09-12, 05:58 AM
does any one know anything about tv antenna splitters? just plain old vhf/uhf channels. the only one i could find in nz that also amplifies the signal is
http://www.dse.co.nz/cgi-bin/dse.storefront/432513ad0cca758c273fc0a87f990744/Product/View/L4207
and well i dont know anything about this kind of stuff, so i was hoping someone could tell me (from the specs) if it was worth the price or a waste of money. my signal is pretty crappy (a couple of channels are black and white on my 150, the 350 is much better).

TIA

KiwiKid
2005-09-12, 07:01 AM
Hey reven,

Do you really want to amplify the signal, or just split it out to another location?

To split it out to another location you can get a splitter from "Cory's" who are electrical wholesalers. They probably have amplified versions as well. Don't know the costs, but a basic splitter shouldn't be too expensive.

I've personally installed heaps of splitters, but never an amplified one - never needed to as the signal was always clean even with multiple splits.

Are you sure its a weak signal? Could be poor/corroded connections at the aerial, (could be the aerial itself), and it could also be the incoming coaxial cable. Check to see the plug on the end of the incoming coax isn't shorting to the inner conductor.

reven
2005-09-12, 07:19 AM
i want to boost it aswell and split it.

and yeah its a weak signal, its split about half a dozen times before it gets to my room, i get prime good and sky good. the rest are pretty bad.

csy
2005-09-12, 08:14 AM
Splitters are based on 2-way splitting where the incoming signal is split in 2 directions with 50% of the power going to each drop (3dB loss), plus an additional 0.5dB inefficiency loss within the splitter itself, resulting in 3.5dB loss to each drop. A 3-way splitter takes one drop and again splits that 2-ways, resulting in 7dB loss on those 2 drops and only 3.5dB on the 3rd drop. 4-way splitters take the 2 outputs from the initial split and splits both outputs to give four 7dB drops.

Amplifier/splitters usually incorporate a flat-gain pre-amp to compensate for the splitter losses to give zero loss through the unit. The Hills unit advertised at DSE also incorporates additional gain plus slope-gain to compensate for transmission losses through the ether and coaxial cable (higher frequencies are attenuated more than lower frequencies).

A tuner expects nominal 60dBuV (+60dB micro-volts, or simply 1mV) signal level input on each TV channel carrier frequency, and usually has an inbuilt automatic gain control (AGC) pre-amp to allow for lower signal levels. The AGC amplification range differs from tuner to tuner.

The objective is to get the RF input signal level to 60dBuV on all splitter outputs across the frequency range of TV channels (VHF-low, VHF-high, UHF).

The most critical component is the aerial. If the aerial outputs a poor quality signal at its terminals, then amplifying this will simply produce a bigger crappy signal. All aerials are not equal for signal quality and gain (yes aerials are quoted as having gain referenced to a simple dipole), so if you are intending on generating losses through splitters, then aerials with high gains are very desirable as a general rule of thumb to compensate for the splitter losses. It is also critical that the aerial electrical terminations are clean (not corroded), inclusive of the balun, and silicone grease used to stop future corrosion.

The coaxial cable is also very important as it attenuates the signal by "x" dB per meter length and this loss is worse at higher frequencies (sloped). Coax "type" determines how much dB loss per metre occurs. Most professionals recommend RG6 which provides relatively low loss at a reasonably budget price.

Noise is also an important factor with such low signal levels, therefore highly recommend "F" type connectors and splitters which shield the signal and provide optimal impedance matching (less chance of reflected power, therefore reduced ghosting).

In conclusion, I highly recommend a high quality aerial with good gain, in combination with RG6 coax and F-connectors/splitters. If the signal level is still too low then use amplified-splitter with unity gain.

Caution - If you feed a too high signal into the tuner, then you will overload the tuner input stage and get distorted picture/sound. The Hills amp/splitter has 20dB flat gain plus 5-12dB slope gain which is high but if your aerial signal is low anyway, then it is probably ok.

Best of luck!

reven
2005-09-12, 09:19 AM
well u appear to know what u're talking about :)

i primarly want to boost the signal before i split it four times to my tv, pvr cards and vcr and not lose any (well lose very little) signal quality. changing the aerial isnt really an option, and yeah we dont have any of those F type connectors. and the the frequencys im having most trouble with are VHF ones, UHF are good enough. so given all that the splitter mentioned before is worth the buy? and chances are when i finally move out of home and hook some crap up well (last semester at uni, so hopefully not far away) i still should use this booster thingy when i split the signal, right? (i read over at the beyond tv 6 pvr beast thing, that you should always boost the signal before splitting it.... or so i remember).

cheers for your help.

csy
2005-09-12, 09:49 AM
I would view the Hills amp-splitter as a "Rolls Royce" model because it has dual slope amplification which you don't need because you already have good UHF reception, but in general this unit should work ok for you. I had a look at some cheaper units but noticed they are only marginally cheaper ($99) so you may as well buy the Hills one.

Yes, you should amplify before splitting, and place the amp as close to the aerial as possible with the least amount of coax from the aerial. This means you have the bigest possible signal going into the amplifier (best signal to noise ratio). Try to place the amp ahead of any other splitters you may have (if possible).

reven
2005-09-12, 10:59 AM
cheers csy, ill get it when i get some money (students are usually poor). :)

johnburton
2005-09-12, 07:42 PM
Just a comment to add to this is from my experience when installing splitters either install them somewhere easily accessible, in daylight etc even if you need to run a few extra meters of cable to do so. Invariably splitters get installed in roof areas, you are probably holding a torch, balancing on ceiling beams and trying to screw/crimp cables in a hurry and end up with a second rate job. A bad connection or even a poorly terminated branch can wreck a good signal.
Try and use F connectors if you can - some shops find people buy crimp tools etc use them and take them back for a refund - surplus to requirements.

reven
2005-09-12, 08:28 PM
yeah im going to install it right behind my tv, which is accessible enough :), we already have a booster in the roof, but once it gets to my tv its pretty weak. i cant wait for hdtv to get to nz, this would no longer be a problem. or internet tv, now that would be something....