Question: Does this make sense?

#1

nbound-au

The Graveyard Shift
#2
:horse:


Yeah it will be fine for OTA TV

Satellite splitters usually go up about 2.4Ghz




It is possible that it could be needed for Cable TV, but i dont know the channel plans in use on Cable (they dont need to adhere to broadcast channeling rules). Someone else should be able to confirm/deny... (even still i think its a bit misleading)
 
#3
Follow up question on splitters

Thanks.

In shopping for a splitter, I sometimes see "EMI isolation" with a number in dB such as 120 dB or 130 dB. Also sometimes see RFI = 120 dB. I think these are ElectroMagnetic Interference or RF Interference (basically the same thing) from the outside world. Doesn't seem critical for antenna systems unless you plan to set the splitter on top of your computer, or whatever.

Am I correct in that interpretation?

I also see "port to port isolation" figures quoted, such as 30 dB or 31 dB. In fact, Channel Master claims:
Channel Master TV splitters have been designed to meet all of these stringent requirements, including low insertion loss, excellent return loss, excellent port to port isolation, and excellent intermodulation/second harmonic performance.
Whew! When using a reverse splitter as a combiner, would good port to port isolation guard against each antenna rebroadcasting the other's signals and causing standing waves and similar problems mentioned by Fringe in another thread? Seeeeeeeeeeems like it should, but whadoo I know?

Geez, maybe I should move this to the antenna theory forum. Getting pretty heady. :alien:

All answers gratefully accepted -- if you don't have an answer, make one up. :becky:

Rick
 
#4
It is possible that it could be needed for Cable TV,
Yes, I just looked it up, and CATV frequencies go up to 1000 Mhz. In fact, I get ClearQAM channel 158, because I kept internet service when I cancelled CATV, and they didn't install a fancy enough filter. Channel 158 is 999 Mhz. I bet they use it just to protect their frequency turf.

So the eBay seller is probly a cable user, and can't imagine HDTV would apply to that ancient OTA technology.

R.
 

nbound-au

The Graveyard Shift
#5
Yes, I just looked it up, and CATV frequencies go up to 1000 Mhz. In fact, I get ClearQAM channel 158, because I kept internet service when I cancelled CATV, and they didn't install a fancy enough filter. Channel 158 is 999 Mhz. I bet they use it just to protect their frequency turf.

So the eBay seller is probly a cable user, and can't imagine HDTV would apply to that ancient OTA technology.

R.
Thought so, thanks for looking it up :)

Thanks.
Whew! When using a reverse splitter as a combiner, would good port to port isolation guard against each antenna rebroadcasting the other's signals and causing standing waves and similar problems mentioned by Fringe in another thread? Seeeeeeeeeeems like it should, but whadoo I know?
This is my understanding also (But Im not 100% on it). Happy to be proven wrong :)
 

n2rj

Moderator
Staff member
#6
Cable systems go from 5-1000MHz, most aren't that high. Ours is 860MHz here.

Satellite is more complicated. You usually have a multiswitch and not a simple splitter because of L/R polarization of the signals.
 

scandiskwindows9x

Moderator of DTV Latino
#7
:horse:


Yeah it will be fine for OTA TV

Satellite splitters usually go up about 2.4Ghz




It is possible that it could be needed for Cable TV, but i dont know the channel plans in use on Cable (they dont need to adhere to broadcast channeling rules). Someone else should be able to confirm/deny... (even still i think its a bit misleading)
i use splitter for satellite dish in my over to air HDTV setup, 2.4GHZ or greater because the HD reception the dataflow can be greater than 1GHZ
also get less signal to noise patter and better interference isolation, my last one that used was a truspec and works good.

are you sure that clearqam channel is not cyphered? sounds rare because if you can not watch that channel then is not a channel in clearquam mode.

in Chile my cable company later of many complains of users that had the older televisions with the ATSC turner locked the channel 13 HD for be only watched in the paid HD service but later they unlocked the channel to be tuned by any tv with ATSC, we in those years were unsure of what HD system choose and Sony had a strong belief in that we would choose the ATSC system due the report of the engineers union about ATSC system , but well we use other stuff that is not good but well.
 
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nbound-au

The Graveyard Shift
#8
i use splitter for satellite dish in my over to air HDTV setup, 2.4GHZ or greater because the HD reception the dataflow can be greater than 1GHZ
. Nope, it isnt... There is nothing happening faster than the carrier waves (which wont be up at 1Ghz for OTA), If you swap it with a 5-900Mhz type for example, it will still work fine. Try it.

also get less signal to noise patter and better interference isolation, my last one that used was a truspec and works good.
You could probably find similar splitter for just OTA frequencies, but a satellite splitter isnt going to hurt your system and is only marginally more expensive.
 
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Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#10
... I also see "port to port isolation" figures quoted, such as 30 dB or 31 dB. In fact, Channel Master claims:

Whew! When using a reverse splitter as a combiner, would good port to port isolation guard against each antenna rebroadcasting the other's signals and causing standing waves and similar problems mentioned by Fringe in another thread? Seeeeeeeeeeems like it should, but whadoo I know?

Geez, maybe I should move this to the antenna theory forum. Getting pretty heady. :alien:

All answers gratefully accepted -- if you don't have an answer, make one up. :becky:

Rick
Rick,

I'm old enough to remember being able to hear faint 'distant' conversations in the background on my land line telephones: that is called crosstalk. There was just barely enough energy from one subscriber to pass to a second (or more) phone line when the physical phone line ran parallel to each other, such as when bundled into a single (looking) wire from phone pole to phone pole back to the local Central Office.

I also remember 4-track (real-to-real) tape where tracks 1 and 3 gave you stereo and tracks 2 and 4 run in the opposite direction doubled the tapes' content and also gave you stereo. I recall hearing a similar 'leakage' of information (backwards audio) on many tapes I played. The same happened with cassette tapes. Broadcasters' real-to-real tapes (before carts) used the same identical tape but two-track: the machines read two tracks (stereo) that used twice the width of the tape run in only one direction. No chance of crosstalk.

That's not a relevent issue when combining antennas using a splitter that has been reversed to accept two inputs and combine them into one 'output'. They are electrically connected like a 'T' connector. Sure, the internal impedence matching causes a slight loss but as a 'T' it drops signals in half, like a 'T' fitting on a garden hose.

Antenna 1 sends what it captures and the signal is split between the TV set and the second antenna. The same goes for Antenna 2 in reverse.

Aside from internal losses, consider a standard splitter to be electrically similar to this 50 ohm Amphenol T fitting. Signals pass both ways. There is nothing present to stop the sharing of the signal in this 'T' nor in a splitter.

Jim

 
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nbound-au

The Graveyard Shift
#11
Scandisk, Try a different one then.It would be nice to know the frequencies though (aka. the REAL RF channels (and freq), not virtual channels/LCNs). Im sure someone else will back me up on this though. If it doesnt work with the 5-1Ghz splitter its due to some other reason, not the frequencies it passes.
 
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#12
are you sure that clearqam channel is not cyphered? sounds rare because if you can not watch that channel then is not a channel in clearquam mode.
It's not just one channel, and yes I'm sure. It's a complicated situation. The cable companies are required to keep some local stations unencoded for their subscribers, for emergency broadcasts. This is required by the FCC. I get a total of 10 channels, I think. I used to get (almost) the full Time Warner Cable lineup. Then I switched to RoadRunner internet service only. What they do, in that situation, is send a man out to put a filter on the line in the little green box outside the apartment complex. It's quite common for them to use a cheaper filter, and most people don't even know they can still get a few local channels with a QAM tuner, if they even have a QAM tuner.

I think the filter for no service is common, and for just basic service is common. After that, they generally take off all filters and rely on encryption to parcel out the different packages. But then they have those few channels they're NOT ALLOWED to encrypt. And wise guys like me, who just want internet, which uses a frequency band right in the middle of the whole mess. They can still filter it out, but they just don't have a lot of those exact filters laying around. Doesn't matter, cause technically I'd be quilty of theft of service, if I ever looked at those channels that the cable company sends into MY home. :censored: (It's different in Canada. In Canada, a man's home is his castle.)

But hundreds of people in the U.S., with cable internet only, do look at the ClearQAM. That's how I knew about it. Read it on the internet.

Now, there ARE close to a hundred encrypted channels there also, according to the QAM tuner in my TV. But I gave up on trying to crack those. As I understand it, it MIGHT be possible, but you have to know somebody named Guido that did time in the big house, and it's going to be over a thousand bucks, and then it might stop working three months from now... :flypig:

Rick
 
#13
That's not a relevent issue when combining antennas using a splitter that has been reversed to accept two inputs and combine them into one 'output'. They are electrically connected like a 'T' connector. Sure, the internal impedence matching causes a slight loss but as a 'T' it drops signals in half, like a 'T' fitting on a garden hose.
Thanks Jim. So as you're describing it, it sounds like there's no electrical difference between the inputs and the outputs, right? In other words, you could hook up the TV and the two antennas to any of the three F connectors on the splitter, and result would be the same?

Rick
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#14
Rick,

I haven't disassembled a three-way splitter in many years but one I looked at was very similar in design to a 75 ohm antenna balun. There was a ferrite iron core "doughnut" that had three, rather than two 'wraps' of wire surrounding one third of of the iron core.

If you picture a simple transformer in your mind's eye, where there is a coil form and two different wraps of wire around the form on opposite sides like a balun (180 degrees) and then rethink it as a circle where there are three wraps of wire around a coil form 120 degrees apart, that's pretty close to how a splitter is mechanically built.

There are usually small (picoFerrad) capacitors involved as well, probably there to reduce Inductive Reactance, but I am guessing - I'm not an authority on this. The point is, signals are shared in both directions from all connectors and there isn't anything present to stop signals from connector A to being distributed to connector B AND TO connector C, or B to A and C or C to B and A. Instant 50% loss, an average of 3.5 dB including internal losses. The signals are divided and shared. The receiver (your TV set) is not contributing a signal, so both antennas feed the TV and both antennas feed each other.

Jim
 

scandiskwindows9x

Moderator of DTV Latino
#17
dish splitter for OTA, because in CHile is not a adequate digital television splitter

the normal ones are of 900MHZ, the "advanced cable system" ones of 1.200MHZ

i tried an splitter of 1000MHZ and got bad results so the right splitter is the one that i am using now
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#18
Francisco,

How high are the OTA TV frequencies in South America? Perhaps a better question is, what is the maximum frequency you want to receive? Just because a particular splitter is rated for 900 mHz and lower, does not mean it won't pass much higher frequencies: it means there is more attenuation at higher frequencies.

A clean low-level signal is all you need or what you need. I have not seen any splitters with diodes within the circuitry ever recommended for unamplified OTA reception. I may be wrong, but others here will either confirm or reverse me.

Jim
 

scandiskwindows9x

Moderator of DTV Latino
#19
we just use UHF for DTV, the VHF frequencies in chile will be unused when the DTV deployment be done, perhaps wants something else in VHF as the digital radio thing that are not defined what we will use.

14-69 channels except the 37 would be used and the frequencies would be fully used in a future in fact will be an tv channel in the channel 69

the better question or reason is perhaps ATSC with 8VSB do not work due the signal modulation, but our system uses an COFDM modulation which is like the same than the DVB-S and DVB-S2 modulations so perhaps that is why works here fine this. also do you remember this

http://www.dtvusaforum.com/dtv-hdtv-reception-antenna-discussion/46165-no-signal-one-television.html

that is what happened with an Splitter of 1GHZ for cable TV

best regards
Francisco
 
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nbound-au

The Graveyard Shift
#20
I have a local station on CH68 (809.5Mhz), Australia uses DVB-T, which is COFDM just like ISDB-T. 5-900Mhz splitters pass signals just fine or this station (which for the record includes a HD subchannel, and two SD subchannels), and pass it with no/negligible attenuation. But regardless of that, as I said earlier there is nothing happening faster than the channel frequency. If you system doesnt work with that splitter, its not due to the splitter (or that particular splitter is faulty).
 
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