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Old 2012-02-18, 01:03 PM   #2941
dullgeek
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What do you guys recommend for a distribution amplifier. I have an inexpensive one from Home Depot that does a fine job getting signal from my downstairs central wiring closet to both my downstairs TV and TiVo. But since I've installed a TV upstairs, there are several channels that I can't get on the upstairs TiVo that I easily get on the downstairs TiVo. I suspect the cheap distro amp to be at fault.

Recommendations? Should I be focusing on a pre-amp over a distro amp?

Thanks in advance.
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Old 2012-02-18, 09:33 PM   #2942
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A pre-amp is almost always recommended over a distribution one, for several reasons:

1) Most pre-amps are designed specifically for OTA reception. They tend to incorporate an FM trap (to reduce/eliminate interference on VHF), and only amplify the OTA bands*. Distribution amps tend to be designed for cable applications, and employ broadband amplification from 50-1000MHz.

2) A pre-amp, due to design for OTA, typically presents lower noise than a distribution amp.

3) A pre-amp will help overcome line loss from the antenna forward. Whereas a dist. amp cannot correct loss up to the installation point in your system.

4) Many pre-amps have separate input spigots for VHF and UHF. This enables a loss-less (or micro-loss) means of combining separate VHF and UHF antenna. Quality combiners/diplexers often present a 1-3dB insertion loss.

*note that many OTA preamps still amplify the 700MHz band, which has since been allocated to wireless carriers/data applications. Whenever possible, it's recommended that you shop for a pre-amp that doesn't amplify the 700MHz band, to prevent interference in the high-UHF channels.
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Old 2012-02-18, 10:50 PM   #2943
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Ok. That's good to know. Seems like many are fans of the CM7777 pre-amp. Good, bad, indifferent?
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Old 2012-02-19, 01:06 AM   #2944
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Read through this thread. The CM7777 is a good amp, but not the best solution for every application. It's a powerful amp, and this isn't always required. Too much signal strength is just as detrimental as not enough.
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Old 2012-02-19, 12:40 PM   #2945
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Default distros

I will be splitting to 4 TVs using a 2-way splitter, and then a 3-way splitter further down the line. I estimate 5 dbs loss at 1st TV, 14 dbs loss at 2nd, & 3rd TV, and 11 dbs loss at the 4th TV.

The line coming from the antenna to the 1st splitter is about 30 ft long.


should I be using a distro amp or just a pre-amp, if a distro amp where should I put it ? ( - I will not be rewiring to split all the branches from a single splitter...)

Thanks
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Old 2012-02-19, 12:57 PM   #2946
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Any reason not to just get a 4 way splitter, with 7 dB ins loss on each port?
Or is that just what ya have layin around?

u can use the spreadheets from Post # 1 to see ya got.
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Old 2012-02-19, 12:58 PM   #2947
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dullgeek,

The current CM-7777 is an excellent preamp if you:
  • Live more than 20 miles from the nearest transmitter tower
  • Have a long cable run and / or use a multi-way splitter
Pros: Low noise factor, higher gain, well protected from lightning, rugged metal housing, substantial power supply, reasonably priced

Cons: May overload if you live near a transmitter

Most preamps with lower noise factor specs than the CM-7777, are either much more expensive and/or prone to lightning damage.
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Old 2012-02-19, 01:06 PM   #2948
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Jase88,

Excellent advice to dullgeek.

Quote:
*note that many OTA preamps still amplify the 700MHz band, which has since been allocated to wireless carriers/data applications. Whenever possible, it's recommended that you shop for a pre-amp that doesn't amplify the 700MHz band, to prevent interference in the high-UHF channels.
For the majority of preamps that still amplify the 700MHz band, do you recommend a low-pass filter such as a Pico Macom LPF-700 or another brand?

Thank you
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Old 2012-02-19, 01:07 PM   #2949
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majortom,

thanks


the splitters and cabling were already in place, & thru walls, not interested recabling.

If I centralize a 4-way I will need to run new cabling....not sure im explaining clearly....

so I assume unless the splitter downstream is power-passing (I may have some eagle aspens which are power-pass all ports), a distro wont work.
so if using a distro, best option would need to put it at the 2nd splitter (3-way)
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Old 2012-02-19, 01:26 PM   #2950
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balm,
I think u can do what ya wanna do. does the 3 way splitter have two 7 db down ports, and one 3.5 db down port? If so, use the two way splitter at the output of the 3 way splitter's 3.5 db down port, and you'll have the same as a 4 way split, with each output at 7 dB down (net).
Regardless, Preamp at the antenna, or Distro AMP inside the house, I'd hook up my Splitters something like this
So each Drop has roughly the same losses.
If using a preamp, I wouldn't send the DC power thru any of the splitters. I would just use the manufacturer's DC Power Injector device
right at the Downlead where it enters the house. The Winegard AP 8700 for example, inside the DC Injector is a DC Voltage Regulator.
So bypassing that connecting to a DC Passive Splitter instead would degrade performance. Because now the Preamp would be on an Unregulated DC Power
supply.

Code:
/ \
 |                                      ---- 3.5
 |            |------- 3.5 -------------|
 |-----AMP----|------- 7                ----  3.5
              |-------7
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Old 2012-02-19, 01:49 PM   #2951
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your close, but the 2-way comes BEFORE the 3-way....thus I have bigger losses off the 3-way...

cant I put the pre-amp injector ANYWHERE if all splitters were power-pass ?

also isnt it cheaper to use a distro instead, (again assuming downstream splitter was power-pass) ?
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Old 2012-02-19, 01:53 PM   #2952
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Your plan/design is less than desirable planning, u'd want the 2 way where I put it.

Actually I'd say it's cheaper and cleaner to use a single 4 way splitter and a preamp.
A preamp is what 40 bux? 4 Way Splitter, 5 bux.
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Old 2012-02-19, 02:01 PM   #2953
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In order to suppress nearby cellphone transmitters on old Ch52-69, a so-called
"700 MHz Low Pass Filter" would need to provide BOTH of the following:
1) MINIMAL attenuation on channels below Ch52.
2) LOTS of attenuation starting on 698 MHz and above....

Pico Digital LPF-700 (and other similar, inexpensive CATV Tier filters) meet the
first criteria but it's very iffy on the second. The bandstop specs START
at 800 MHz and says NOTHING for attenuation between 700-800 MHz,
a [ridiculously high] 100 MHz Transition Region:
http://picomacom.com/_data_sheet/LPF-SERIES_DS.pdf
It it's anything like the below low pass filters, there is probably very
little attenuation on old Ch52-54, perhaps a bit more on old Ch55-57
and only reaches the full 50 dB of attenuation on old Ch69.

======================================================
Although not intended for DTV applications, the fol. Minicircuits 500-700 MHz Band Pass
Filter provides some idea on how much attenuation might be provided in a "typical"
700 MHz rolloff....only -3.6 dB at 740 MHz and -8 dB at 750 MHz and 46+ dB at 800 MHz:
http://www.minicircuits.com/pdfs/BPF-A600+.pdf
Very typical for multi-pole filters....not much attenuation near the roll-off point, with
most of the attenuation accumulating close to the STOP-BAND spec point.

Minicircuits also provides an Envelope Delay Curve....which can be important for NOT
degrading the Digital TV waveform. Yet another design constraint that inexpensive
CATV Tier filters usually don't have to worry about....

======================================================
Although 700 MHz isn't one of their "standard" models, Tin Lee can make the
LP7-700 as a special order, with a 30 MHz Transition Region to 730 MHz....finally
suppressing old Ch57 and above by 40 dB. But LESS EFFECTIVE against Ch52-56,
so it's only a viable candidate if local STRONG cellphone freqs are higher than
Ch56.....and will become LESS EFFECTIVE when Ch52-56 is activated in near future:
http://tinlee.com/CATV_MATV-LowpassGeneral.php?active=3

If there are STRONG old Ch52 and above signals coming from nearby cellphone
towers (verify with signal level meter), a better approach might be to use one
or more SINGLE CHANNEL STOP-BAND filters, such as Tin-Lee CR-7D (or equivalent)
or a custom BAND-STOP filter. [And add more as other channels are activated]:
http://tinlee.com/PDF/CR7-HT%20series%20info%20sht.pdf

=================================================
Taiwanese supplier Soontai Technologies announced a "LTE Filter" that is
specifically designed to suppress LTE Cellphone frequencies: 698+ MHz in
North America and 790+ MHz in Europe. But it's new, so they haven't yet
posted detailed specs...and you wouldn't want to use a Euro model for N. America:
http://www.soontai.com/LTE-filter.html

But to meet both criteria I mentioned above, it's going to have to perform
MUCH BETTER than their standard CATV Low Pass Tier Filters:
http://www.soontai.com/LPF.html
A 700 MHz Low Pass Filter would be a special order part, and they only provided
a detailed roll-off curve for their 480 MHz part with a 40 MHz Transition Region
from 480 MHz (-2 dB) to 520 MHz (-56 dB):
http://www.soontai.com/LPF480_fig.html

======================================================
It's been well over 2 years since I checked Ch52+ signal levels at my son's location
70-miles SE from Mt. Wilson (L.A.). At that time, Qualcom's Ch55 MediaFlo was 30 dB
stronger than signals from Mt. Wilson and 20 dB weaker than Ch27 (5-mi away...now off-air).
There was another Cellphone signal on Ch58 at about same signal strength.
I should do another check sometime in the near future to see what's new......

I've tried to correlate various on-line cell tower location reports with where I think
the Cell Towers are located....they're probably on the hills in BACKSIDE of the
CM4228's antenna pattern, which was keeping them from being a problem.
But if NEW Cellphone Towers are being co-located with Ch12 (old Ch27 location),
then I might want to retweak CM4228 to make sure they're still in the sidelobe NULL.
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Old 2012-02-19, 02:10 PM   #2954
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Thanks majortom,


I agree, but im stuck with what I have.

40 bux, wow wish we could them for that here in Montreal...

A decent quality amp, such as CM, will ship here or in-store here for over $80...


However, a good PCT distro goes for around $40 !

thanks
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Old 2012-02-19, 02:17 PM   #2955
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do u have amazon up there in canada?

Not to take away from local stores, etc. All for supporting Local Stores and what not whenever possible.
I'm not aware of anyplace local around here where I live. Though there probably are some shops around.
But I routinely see the Winegard 8700 for 40 bux, and the CM 7778 for ~ 55 bux online.
Not sure I'd wanna pay more for being more susceptible to Intermod & Overload with the CM but..whatever works I guess.

Of course u still have shipping, etc.
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