You're correct. I didn't think it through (and honestly didn't read your entire post). Bottom line, an amplifier may not be needed.
Which amplified ota signal splitter do you recommend?
- Thread starter sktrus
- Start date
- Latest activity Latest activity:
- Replies 38
- Views 7K
Thanks everybody. Glad we have some intelligent and knowledgable people here. Big help to nontech people like me.
Her family should perhaps take baby steps. A 4 way splitter first. Not satisfied, they use an amplified distributor. They will find a solution. The very worst case they all huddle in the same room and watch only one tv!
Her family should perhaps take baby steps. A 4 way splitter first. Not satisfied, they use an amplified distributor. They will find a solution. The very worst case they all huddle in the same room and watch only one tv!
Using a 30dB gain preamplifier is ludicrous, it can only create more problems than it might fix. Things like a digital cliff have been mentioned, which is when the receiver is simply starved for signal and the signal level has dropped below what the receiver can make use of. But you also have to consider signal to noise ratio which is completely different. You can have a signal thats so strong its about to overload the receiver but if the signal to noise ratio is say 4dB, you have no picture because there is not enough signal to deal with, its all amplified noise. This is why you want to put a preamp at the antenna and not at the TV.
I'll just pick a number here, so lets say you have 8dB signal to noise for a particular ATSC TV station right off the antenna and that's good enough to give a reliable picture. But you have 5dB of cable loss to the TV leaving you with a 3dB signal to noise ratio and the TV won't lock. Stick a preamplifier at the TV and you still have a 3dB signal to noise ratio, actually a tiny bit less depending on preamp noise figure, but the signal and noise are now amplified by whatever the gain of the preamp is. TV still won't lock.
Now place the preamp at the antenna and you will have the original 8dB signal to noise ratio minus a tiny bit due to preamp noise figure and the signal and noise are amplified enough to overcome cable loss and probably some splitter loss and the signal to noise ratio at the TV is near 8dB and the TV locks fine. Bravo!
However, there are several other specs that are very important when choosing an antenna preamp. The 1dB compression point, IP3 which is a calculated number and noise figure. If you buy a cheap preamp that has a lousy 1dB compression point of 0dBm or even 5dBm it can be easily overloaded by all the TV and FM signals plus police, fire, paging, ham radio operators, etc. All these signals picked up by the TV antenna can add up to a huge number and easily overload a preamp where it will create Inter Modulation Distortion or many sum and difference "ghost signals" of all the stuff clogging the spectrum with more junk. This raises the noise floor considerably covering up weak TV signals your trying to receive and there is no dynamic range left in the preamp because its saturated or near saturated.
The more gain a cheap preamp has the less signal levels it requires to trash it out and create IMD. Then you have noise figure and modern preamps should have noise figure numbers under .5dB, that's under a half dB for the VHF/UHF TV bands and enough gain to make up for cable and splitter loss plus maybe a few dB more. That coupled with a 1dB compression point of 20dBm or up to the 27dBm range should give you problem free performance in most cities.
But most TV preamps are 15 to 30dB gain, 3-4dB noise figure and a 1dB compression point of 10 or 12dBm at best, which is junk. Most TV preamps don't tell you any of these specs because you would cringe and not buy them. Many preamps are built into active splitters designed only to amplify cable TV signals, which are delivered at a higher level and with a finite number of carriers (maybe 100) in a very controlled RF environment where they can work fine. Put that same active CATV splitter on a TV antenna with some very weak signals mixed with thousands of other signals of extreme level and they spew out crap and your TV won't lock. CATV is not off air TV and those are two very different RF environments with different needs. That's why I originally recommended a known good performing off air TV preamp and then feed a passive splitter.
I'll just pick a number here, so lets say you have 8dB signal to noise for a particular ATSC TV station right off the antenna and that's good enough to give a reliable picture. But you have 5dB of cable loss to the TV leaving you with a 3dB signal to noise ratio and the TV won't lock. Stick a preamplifier at the TV and you still have a 3dB signal to noise ratio, actually a tiny bit less depending on preamp noise figure, but the signal and noise are now amplified by whatever the gain of the preamp is. TV still won't lock.
Now place the preamp at the antenna and you will have the original 8dB signal to noise ratio minus a tiny bit due to preamp noise figure and the signal and noise are amplified enough to overcome cable loss and probably some splitter loss and the signal to noise ratio at the TV is near 8dB and the TV locks fine. Bravo!
However, there are several other specs that are very important when choosing an antenna preamp. The 1dB compression point, IP3 which is a calculated number and noise figure. If you buy a cheap preamp that has a lousy 1dB compression point of 0dBm or even 5dBm it can be easily overloaded by all the TV and FM signals plus police, fire, paging, ham radio operators, etc. All these signals picked up by the TV antenna can add up to a huge number and easily overload a preamp where it will create Inter Modulation Distortion or many sum and difference "ghost signals" of all the stuff clogging the spectrum with more junk. This raises the noise floor considerably covering up weak TV signals your trying to receive and there is no dynamic range left in the preamp because its saturated or near saturated.
The more gain a cheap preamp has the less signal levels it requires to trash it out and create IMD. Then you have noise figure and modern preamps should have noise figure numbers under .5dB, that's under a half dB for the VHF/UHF TV bands and enough gain to make up for cable and splitter loss plus maybe a few dB more. That coupled with a 1dB compression point of 20dBm or up to the 27dBm range should give you problem free performance in most cities.
But most TV preamps are 15 to 30dB gain, 3-4dB noise figure and a 1dB compression point of 10 or 12dBm at best, which is junk. Most TV preamps don't tell you any of these specs because you would cringe and not buy them. Many preamps are built into active splitters designed only to amplify cable TV signals, which are delivered at a higher level and with a finite number of carriers (maybe 100) in a very controlled RF environment where they can work fine. Put that same active CATV splitter on a TV antenna with some very weak signals mixed with thousands of other signals of extreme level and they spew out crap and your TV won't lock. CATV is not off air TV and those are two very different RF environments with different needs. That's why I originally recommended a known good performing off air TV preamp and then feed a passive splitter.
I have my antenna split 4 ways through a powered distribution amplifier. No preamplifier is used. I tried one but the signals actually got worse. I had too much signal loss with just a 4 way splitter. Distribution amplifier works great for me.
Sent from my iPad using Tapatalk
Sent from my iPad using Tapatalk
It’s an Antronix MRA4-8. I got it on Amazon. Before I had this one I had a cheap GE that I got at Home Depot. It worked fine for a couple of years but the power supply failed so I upgraded. I think the cost on the Antronix was around $48 but I’m not positive on that.
Sent from my iPad using Tapatalk
Sent from my iPad using Tapatalk
I didn't know you could do that. Does it work better? When I used my AirTV adaptor on my Wally, I was so disappointed, I just put it in a drawer and used the built-in on my 211. It just worked a lot better.
I think it works at least as well as my VIP receivers, if not better. But I changed too many things simultaneously during that upgrade, so I can't make a real comparison.
With any dual tuner receiver, the signal must be split to each tuner and is therefore 1/2 the signal strength (-3 dB) that a one tuner receiver would have.
I would expect if you have marginal signals the 211 single tuner box might outperform the dual tuner USB adapter - get a 3-5 dB pre-amp to make up the difference.
I would expect if you have marginal signals the 211 single tuner box might outperform the dual tuner USB adapter - get a 3-5 dB pre-amp to make up the difference.
You might want to post this in the OTA forum. People there are more familiar with OTA equipment.
Thanks Geronimo; we are slowly narrowing our choices to get the right stuff. It will be either Antronix MRA4-8 or Channel master amplifier from Amazon.
The Antronix MRA4-8 is not an off air TV amplifier/splitter, its designed for CATV systems. Look at the lousy 3dB noise figure and "return band" from about 5 to 40MHz for cable box 2-way communication.
I checked some Channel Master reviews at Amazon. Some people are complaining that they don't answer phone calls. I was thinking about asking them what they suggest.
Inclined Orbit, is there any web site (or reputable company) that sells ota products? Talking to an expert and getting some information could really help.
Inclined Orbit, is there any web site (or reputable company) that sells ota products? Talking to an expert and getting some information could really help.
Finally got around to getting on the roof to mount a pre-amp. What a difference! Signal strengths are 100 on all my local channels now using the AirTV adaptor/Wally. Great advice, thanks!
AGREED! My OTA set-up is DA in all rooms that serve multiple OTA inputs that include the TV, Dish DVR's, TiVo DVR's, and a few others PER 5 separate rooms. DA's are well suited for such demands. I first start with a GOOD Yagi antenna placed OUTSIDE at a sufficient HEIGHT and at best position possible. That is THE SOURCE of a great signal to begin with because without that, amplification may not help much. I don't use any pre-amps either because I deemed them unnecessary for the signal I was getting and I was going to HAVE to amplify them in each room anyway.
Then I just drop the line from the OTA into crawl space into PRIMARY DA, then each output goes into each room where it enters that room's DA, and then into the devices. EXCELLENT signal strength with high reliability. In fact, it has only been the rare, occasional movement of the outside antenna due to high winds that loses Line of Sight. I have since secured it better and have NO--I mean ZERO problems, and get even some difficult stations. However, it is correct as others have stated that one only needs to be sufficiently away from the "digital cliff" and not get too obsessed with the highest possible signal strength. However, one must also be far enough away from the "digital cliff" that you don't start having problems in in-climate weather.
While it is generally true that amplification, and especially pre-amplification is best set closest to the antenna (especially the in the analog era), in practice--in the digital age--as long as you start with a good enough signal, just using good quality DA's placed further down the chain can actually be highly effective and the preferred way of dealing with distributing the signal to multiple devices/inputs, and even DA's themselves introduce some signal loss, which can sometimes prevent over-amplification, but the real key is all about the antenna itself (yagi best and avoid those pretty new fangled antennas because they often are the worst at getting signal), its location, height and position that is going to make all the difference in the world where getting the MOST signal to begin with is key, and then amplify when necessary, but I do stress QUALITY Amps and DA's.
Is it wise to rescan ota channels thru Hopper 3 to eliminate weak signals (also from Guide) and/or catch more sub stations? I remember some recommend that, mostly in the evening or very early in the morning. I hate to make it worse.
