Signal Amplifiers (Amps, Preamps, Distro Amps) - Page 2 - Canadian TV, Computing and Home Theatre Forums

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post #16 of 4296 (permalink) Old 2005-06-29, 04:40 PM
 
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It was my understanding that you should be using a distribution amplifier to bring your signal back up, and not a preamplifier

preamplifier for weak signal area
distribution amplifier for weak signals to multiple sets

Am I wrong?

kw................
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post #17 of 4296 (permalink) Old 2005-06-29, 05:18 PM
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I told you you will need an amp

Now get a Rotor Motor too.... it will make things more easy to aim and fun.
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post #18 of 4296 (permalink) Old 2005-06-29, 05:26 PM
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Quote:
Originally Posted by kwtoxman
It was my understanding that you should be using a distribution amplifier to bring your signal back up, and not a preamplifier

preamplifier for weak signal area
distribution amplifier for weak signals to multiple sets

Am I wrong?

kw................
An Amp is an Amp... but with an antenna the best place for the amp is right at the antenna.... this is why we have the amp mounted right at the antenna.
These amps are powerful with up to 28dB gain... more then enough to compensate for long cable runs and splitters. Splitters typically case a 3 dB loss when inserted in the line. Distribution amplifiers are more for cable TV signal boosting and when you have an Amp on your antenna to also have a distribution amplifier too will most likely overload and give poor results.
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post #19 of 4296 (permalink) Old 2005-06-29, 06:34 PM
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Yes, HDTV you are right. Roto oh no me don't want to go back on the roof again.

Can the new rotor be programmed the ones I remember was a dial that you turn and when the ghost images went away on analog channels you stop.

I have seen customers tape number on them to let them know where to stop.

I can get all Buffalo stations fine, and Rochester runs the same as Buffalo on prime time tv if Iam not mistaken. There is no real need for a roto unless I get bored and just want to have more channels.

The Titan 2 7775 pre amp is rated for UHF only and 26 DB gain at only 2FB noise.

CM4228/9521/7775;F.RmJvc70FH96/8300HDPvr/Dish 612;B.Rm LC52LE810UN/8642HD;Study LG50PK550/Xbox360;
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post #20 of 4296 (permalink) Old 2005-06-30, 01:31 PM Thread Starter
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Quote:
Originally Posted by kwtoxman
It was my understanding that you should be using a distribution amplifier to bring your signal back up, and not a preamplifier
You are correct, but... Yaamon is located quite a distance from the Buffalo NY stations so going for the solution that injects the least amount of noise (the preamp) was sensible. Heck with his initial signal strength its entirely possible that somebody could run a distribution amp alone and love the results, but I sure do not recommend it. If Yaamon had specified that he was going to drive several TVs then we would be looking at adding a distribution amp below the preamp. Check out the preamp posts in this thread:

http://www.digitalhomecanada.com/for...ad.php?t=26857

As for the rotator, I hate to say "I told you so!" but I did!
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post #21 of 4296 (permalink) Old 2005-06-30, 02:53 PM Thread Starter
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Testing a Preamp and/or Distribution Amp for more than one TV

If your antenna signal drops below satisfactory levels when you add a second or third TV, DVR, VCR, FM Tuner, etc. to the downlead, you can add a preamp and/or a distribution amp, depending on whether you have a preamp already installed, but you will have some tests to run because you need to see if there is now a risk of the newly amplified signal overloading one or all of the tuners that are downstream. Overload can cause damage. Please read the previous posts in this thread about Preamps and Distribution Amps before going further.

You'll need a pencil and paper to write down the name of each device we'll add and its signal strength results. Drawing a schematic of your antenna, gear, and cabling layout with the distances and signal strength results added can be helpful. For these tests lets assume that TV #1 is your main ATSC television and that we have installed a 2-way, 3-way, or 4-way splitter in the antenna lead just above that TV, depending on how many devices you want to run off that antenna.

1. disconnect all devices from the splitter except TV #1 and the antenna lead. If you have F-connector terminator caps for the empty splitter sockets put them on, but we'll be fine if you don't have them.

2. install the preamp directly to the antenna lead above the splitter as close as physically possible to the antenna itself on the mast, but make sure that the preamp's power source is not yet plugged in.

3. on TV #1 tune to the strongest DTV station you can find

If during step 3 the signal strength meter jumps to 100% you have a possible overpower situation. Imagine if the preamp had been powered up first: there is nowhere to go past 100% except overload, and it isn't pretty. If you have a possible overload situation don't worry yet, its not the end of the road. Its just a point to remember that your preamp could cause problems with your ATSC tuner(s) so you need to test further.

4. leave TV #1 on that same station, connect TV #2, and note the signal strength on TV #1

5. repeat step 4 one-by-one for each piece of equipment (TVs, DVRs, VCRs, FM Tuners, etc.) sharing the splitter, making sure to stop and note the signal strength after each addition.

If after all of them have been connected you still have very high signal strength on that station (like being a few blocks away from the CN Tower) you are very much in danger of the preamp overpowering the system if it is ever powered up. This poses a real problem if you need the preamp to receive some weak stations. Keep your signal strength notes and call a professional or come back here to DHC so we can discuss options such as attenuators, variable strength distribution amps, and other ideas.

If, on the other hand, you find that the signal strength drops accordingly with each device added to the splitter, its time for some further tests:

6. disconnect all TVs & equipment from the splitter except TV #1 and the antenna lead.

7. on TV #1 tune to one of the weakest DTV stations (lots of pixellation or dropouts, or not able to lock on but showing some signal strength)

8. display the tuner's signal strength meter on the screen

9. power up the preamp and note any signal strength difference

During #9 if you notice a sharp jump upwards on the meter to 100% on such a weak station (highly unlikely!) you are possibly at risk of overpowering your receiver: imagine stations that were already at 100% now getting that power boost and you start to see the danger. Disconnect the preamp's power and either call a professional or come back here for advice.

If, on the other hand, it doesn't jump to 100% but the signal strength seems very high, don't worry too much yet. Lets add some more connections to see what happens.

10. connect TV #2's antenna feed and note any signal strength difference

If you have a nice balance of good signal strength by adding another TV but if TV #1 on its own would be in an overpowered situation, don't just accept things as they are. Install an in-line attenuator directly on the back of TV #1. This will lower the incoming signal just to TV #1, so that in the future if TV #2's lead is ever disconnected for more than a small amount of time you will avoid overdriving TV #1's ATSC tuner. Attenuator strength is usually shown as something like "-3db" so you can try a couple of different ones since they're relatively inexpensive.

11a. repeat step 10 as necessary for adding any other TVs, DVRs, VCRs, FM Tuners, etc. that will also be using the splitter located above TV #1, and observe the signal strength meter after each addition, checking to see if an attenuator is needed on any of them. Odds are you probably won't need attenuators for them. Odds are you might now need amplification, but we'll get to that in a bit.

11b. there is a cheap and quick way to lower the strength of TV #1's input signal if you are going to add other devices. Splitters cause predictable signal loss (usually 2 or 3 db per splitter but at the risk of adding signal interference) so we can sometimes use that predictable signal loss to our advantage. Splitters are relatively cheap and much easier to find than attenuators so they are a poor man's bandaid and not a proper solution. Nevertheless: run a lead from the antenna to a splitter to TV #1 as usual with no attenuator, but then before it gets to TV #1 split it again into a 3 or 4-way splitter. Then add a DVR, a VCR, an FM Tuners, etc. and TV #1 to that new splitter and you will accomplish the same effect as an attenuator at that end, without lowering the signal as much on TV #2's branch (see why I draw schematics? ).

I do not recommend step 11b. without checking the signal strength on TV #1 one-by-one for each piece of equipment added because you could unwittingly lower the signal too far! Maybe only 2 devices are needed to achieve the attenuation effect. Maybe 3 should go in alongside TV #1 and 2 should go above it... only testing will tell. Test until you see a suitable compromise solution in which all devices get relatively equal signal strength no matter which branch they are split from. As I say, by that point you are probably in need of amplification.

If after adding TV #2 and especially after adding other devices your signal strength even on the strongest stations starts to drop unacceptably low, its time to add a Distribution Amplifier below the preamp. Think of it as a "powered splitter". Testing it is easy, just follow all the same steps as above. The goal is to get a good balance of signal strength across all your devices. You should be able to tell from your schematic drawing which branches of your system might need amplification or attenuation.

By the way, professionals use signal strength meters and spectrum analyzers so they don't have to do all this stuff unless abolutely necessary!
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post #22 of 4296 (permalink) Old 2005-07-04, 06:06 PM
 
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Winegard AP-8275 troubles

OK, I'm kind of ticked off. I just bought a Winegard AP-8275 pre-amp for a $100. I plug it in and I LOSE both KCPQ and KING (both usually stable at ~66%) and KBCB (which I can get anywhere) goes from 88% to ~70%.

I've messed around with the setup a bit trying to find the source of the problem. I noticed that having only the power supply in the loop (turned off) gives me my usual signal strength while having only the pre-amp in the loop weakens the signal. Is this normal, or is there something wrong with the pre-amp?

CM-4228 antenna ---> Tuner (normal signal)

CM-4228 antenna ---> AP-8275 pre-amp ---> AP-8275 power supply ---> Tuner (weaker signal, but this is how it should be plugged in)

CM-4228 antenna ---> AP-8275 power supply (unplugged) ---> Tuner (normal signal)

CM-4228 antenna ---> AP-8275 pre-amp ---> Tuner (weakear signal)

I've also tried changing the cables, but that has no effect. Is there anything I'm doing wrong? Please help.
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post #23 of 4296 (permalink) Old 2005-07-04, 06:45 PM
 
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Hmm... I plugged the pre-amp in on the tuner side of the cable (how you're NOT supposed to do it) and now I'm getting KING at from between 66% to 80%, while KCPQ is still below normal jumping from 0% to 50%. It makes no sense to me.
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post #24 of 4296 (permalink) Old 2005-07-04, 07:43 PM
 
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It might be a cable problem after all. I decided to use my regular TV cables instead, and they work better. With the preamp by the antenna, the power supply by the tuner (like they're supposed to be), using my TV cables I get KING at ~85%, while KCPQ is between 30% to 50% and sometimes droping to 0%.

If I remove the pre-amp and power supply I get ~66% on both straight away. It still doesn't explain why KCPQ is worse with the pre-amp. Could it have something to do with KCPQ's lower frequency?
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post #25 of 4296 (permalink) Old 2005-07-05, 03:11 AM
 
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4DTV HD told me I might have an overload problem, and I think he hit it right on the head. That's why my old and lower quality cables worked better than the new ones, they reduced the signal and prevented the overload.

I've now hooked everything up with the new cables and pre-amp by the antenna and such, like it's supposed to. However, from the pre-amp power supply I have hooked up my longest weakest cables with a cheap splitter in the middle. PERFECT!

Funny how things work out in the end? I posted my results in the OTA Results in the BC Lower Mainland and Vancouver Island.

Thanks again 4DTV HD!


Now, does anyone know if there's a better way of doing this? That is, not use long loops of crappy cable and splitter, but something like a overload switch or some kind of resistor?
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post #26 of 4296 (permalink) Old 2005-07-05, 03:35 AM Thread Starter
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Quote:
Originally Posted by Sarke
Now, does anyone know if there's a better way of doing this? That is, not use long loops of crappy cable and splitter, but something like a overload switch or some kind of resistor?
My guess is that the splitter and the old cable are knocking about 5 or 6 db off the signal, so I'd ask him about an attenuator in that range. Then you can go back to using the great new cables without the splitter.
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post #27 of 4296 (permalink) Old 2005-07-05, 03:38 AM
 
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Quote:
Originally Posted by stampeder
My guess is that the splitter and the old cable are knocking about 5 or 6 db off the signal, so I'd ask him about an attenuator in that range. Then you can go back to using the great new cables without the splitter.
Awesome stampeder, I'll ask him that, thanks! I had to look up what an "attenuator" was though, sounds like it's what I need.
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post #28 of 4296 (permalink) Old 2005-07-05, 03:46 AM Thread Starter
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Quote:
Originally Posted by Sarke
Awesome stampeder, I'll ask him that, thanks! I had to look up what an "attenuator" was though, sounds like it's what I need.
Here's another good read about how attenuators fit in with your situation:

http://www.hdtvprimer.com/ANTENNAS/basics.html

They make a good point in there that you should probably set the FM Trap on your AP8275 to IN for a little added insurance against overload.
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post #29 of 4296 (permalink) Old 2005-07-05, 04:50 AM
 
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Quote:
Originally Posted by stampeder
Here's another good read about how attenuators fit in with your situation:

http://www.hdtvprimer.com/ANTENNAS/basics.html

They make a good point in there that you should probably set the FM Trap on your AP8275 to IN for a little added insurance against overload.
Thanks, great read stampeder, it was very helpful. I've bookmarked it. The FM trap was set to IN by default, but it does have a variable switch that I can't set because it's so damn small.
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post #30 of 4296 (permalink) Old 2005-07-19, 10:45 AM
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Cm 7775

Hi Yaamon

I am in Markham, have a CM 4228 installed, but Toronto 1 and CFTO did not come out at all, the current amp I have overload easily and I want this 7775 as it only for UHF band, so it looks good to me.

Wondering if possible let me know how to order one in Canada as well. PM me or email. Try to PM you but your inbox full

I live at HWY7/9th, which area do you live.

Thanks,

Jason
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