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Old 2006-02-25, 10:16 PM   #61
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Hey,
How do you know how much dB you are feeding the unit?
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Old 2006-02-25, 10:50 PM   #62
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Quote:
Originally Posted by dcorreia
How do you know how much dB you are feeding the unit?
Most antenna pros have signal analysis devices such as spectrographs that give a real time graphical view of the signal shape and strength coming from the antenna. The signal shape view helps identify multipath and other signal abberations. These units are the ideal way to peak an antenna's aim. They are not consumer items due to their huge cost but mostly due to their required knowledge of antenna technology and electronics.

For the consumer, you can look up the gain levels shown on the official web sites of the main brands (they are from lab tests but they're still useful) and then add gain addition from any amps or preamps and subtract the amount of line loss as well as insertion losses of splitters and other devices. With good educated guesses you might get within 2 or 3 dB of the actual levels. Here's an example of how you can justify having a preamp using published figures:

Antenna gain at desired channel + pre-amp or amp gain - line loss - insertion losses = signal strength in dB

So, let's plug in some numbers off the top of our heads: 14dB + 18dB - 6dB - 5dB = 21dB at the receiver. Therefore without your preamp you'd have only about 3dB at the receiver in such a situation. Now if you consider that your numbers might be a bit off plus-or-minus, you are still left with a guess of somewhere in the range between 3 or 4 to -1 or -2 dB at the receiver, so your best guess was worth it in order to decide on buying the pre-amp.
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Old 2006-02-26, 11:44 AM   #63
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I agree that most preamp that is used in a OTA system is a overkill, too much gain most people think more is better.

I do not recommend a preamp unless you are going to run more than 70' and intending to split the signal. I have been using at my office a Winegard AP4700 and going directly into the tv from a 4221 is fine.

This would be a better choice for those who need a milder boost becuase of cable or split signal loss.

I mean you really only need a preamp if you have long cable runs or intend to split the signal several times.

I know with my short cable runs less than 50' from my antenna that with my 7775 I have to reduce the signal going into all my tuners.

I have the premp in my bedroom and use a 3 way splitter 7db port to the LG with a 3db attenuator. if not I noticed Cbc pixelates at times.

Going into my Dish 811 receiver its down -25db if not Pbs would pilexate. Out of the other 7db port then into a 8, then 6 then 3 db attenuators.

The Samsung 451 rec wuld normally get 7db but had to add a 3db attenuator total 10.5db I found that Fox would pixelate at 7db.

The Jvc tuner in the tv is fine with output down 7db in total because of the way I distributed the signal. No problems with the signal there.
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Old 2006-04-09, 05:09 PM   #64
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Question CM Spartan vs Titan Preamps?

I can't find an answer about the ChannelMaster preamps.

What is the difference between the Spartan and Titan series of pre-amps?

Are the Spartan pre-amps for satellite usage? If so then why do they have VHF/UHF specs?
Titan such as CM7777 for antenna applications?

Thanks
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Old 2006-04-10, 02:01 AM   #65
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Quote:
Originally Posted by z0z0
What is the difference between the Spartan and Titan series of pre-amps?
The Spartan line goes back a long way and is a medium range solution. The Titan line also has its roots in tried-and-true gear but offers much more gain. Suit yourself, but I recommend the CM Titan 777X line, and so do many other DHCers. The CM7777 offers much better DXing opportunities, and is a better choice for the future when more and more Canadian stations go digital.
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Old 2006-04-10, 08:37 AM   #66
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Richard in Lockport recommends Wingard AP-4700 or AP-4727 pre-amp over the Channel Master lineup. He says:

The Chanel master 7777 is aproximately 22 db HOWEVER, if your using in the Toronto market most channel master amps overold bigtime!!! They have no overload protection. Wheras the ap4700 and 8700 amps will take up to 110,000 microvolts before overloading . The CMs are 35 to 40,000 . In Toronto thats not enough!! You get beeld over like nobodys business.


Winegard preamp specs
http://www.winegard.com/offair/pdf/Chart29.pdf

I can't find Max Input Voltage specs for the Channel Master line.

I have read many posts here about people experiencing overload conditions in Toronto. My thinking is that it is better to get a more powerful pre-amp just in case you need it and then tone it down with an attenuator if needed.

Another thought - are we comparing apples to oranges in that Richard is talking about input voltage overload going into the pre-amp from the antenna (causing problems in the preamp) while I am thinking of overload going into the TV tuner (causing problems in the TV)?

Thougts?
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Old 2006-04-10, 09:17 AM   #67
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z0z0 I have experience with both the Winegard AP4700 and Cm7775 preamps.

Not sure about the over load protection never had a problem with the cm7775 before. The titan and Iam sure the other channel master series of preamp has full lighting and surge protection.

I have found that the cm7775 can has too much signal gain that you have to add attenuators to reduce the receiver from being overloaded.
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Old 2006-04-15, 06:49 PM   #68
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Default Older vintage preamps

Does anyone know if there has been any technology improvements in Winegard preamps over the last decade?

My buddy wants to sell me a vintage 1996 AP4700.

I know that electronics are always improving and am wondering if preamps have been improved for HDTV.

Thanks
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Old 2006-04-15, 11:22 PM   #69
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Quote:
Originally Posted by z0z0
My buddy wants to sell me a vintage 1996 AP4700.
Actually my only concern about it would be its condition. Was it up on a mast for 10 years? If its clean and operational you can probably offer a bargain basement purchase price, but really a brand new one is not very expensive and you get a warranty.
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Old 2006-04-16, 07:37 AM   #70
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Actually - the AP4700 is still new in a box. He had it sitting in the basement for a long time.
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Old 2006-04-16, 01:13 PM   #71
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Then you are good to go, but lower your price offer because you won't be getting a warranty.
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Old 2006-04-19, 08:40 AM   #72
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Default Mast Mount VS In Home Amplifiers for OTA HDTV

Hello all,

After searching around for some info on this, I thought I had better ask outright.

Just installed the CM4221 and am missing a couple of channels with low signal. Am interested in adding an amp to help this - but am confused as to the type needed. Should I choose a mast mounted amp or one in my home of the type that I could get at The sourcecc.

Can anyone explain the difference to me in performance?

Thanks

Stu
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Old 2006-04-19, 08:47 AM   #73
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Follow Up -

I tried a distribution Amp from The Source CC and thought I noticed a slight decrease in the sharpness of the HDTV picture. Is this even possible??( It only had a range up to 1000Mhz) Removing it 'seemed' to restore the picture I was used to...

Didn't help me pick up any stations with lower signals either. Although with the CM4221 I am getting CBC, FOX, CBS, NBC and ABC already. City TV works here for a few minutes every little while, but mainly does not come in - was hoping to fix this with an AMP. WNED shows big signal but MCE won't tune it...like CTV! Weird.

Using MCE and Avermedia A180. Am in Oakville near Trafalgar and QEW.

Stu
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Old 2006-04-19, 09:23 AM   #74
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Tenstu

Ideally a mast mount amp is used to overcome long cable run signal loss, but it also helps with some signals that are on the edge. Hoever if a siganl is down near the noise floor, all the amp will do is amplify the signal with the noise (plus insert a bit of it's own noise), which will give you a stronger noisy signal. An antenna is also an amplifier of sorts, but due to the way it amplifies the signal, it doesn't amplify the noise with the signal, thus you end up with a stronger signal. A distribution (or in house amp) was designed to make up for splitting of signals. Now you're amplifying the atmospheric noise that the antenna has provided, plus the noise picked up during the cable run. Not an ideal solution as you're discovered. In the end you're best results will come from spending money on the antenna setup first, then a decent mast mount preamp.
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Old 2006-04-19, 09:24 AM   #75
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tenstu a mast mounted preamp will amplify the signal and push it down the cable to prevent the usual cable loss. Boosting a stronger and cleaner signal at the source.

A dist amp or booster at the end of the line will bosst what ever signal comes down, lower signal and noise gets boosted.

How long is your cable run from the antenna, and is your antenna mounted on the roof up high ?

From your location you are most likely picking up the Toronto from the side of the antenna if you pointed the antenna towards Buffalo.

CityTv itself is harder outside of the gta especially with low power.

What signal strength do you get on CFTO? Try using WatchHDTV software, for me this software gets all the stations. This is what I use on one my kids computer as I have a Ati HD tuner card and the Ati software does not work for Cfto.

Good luck.
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