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Old 15-Sep-2013, 8:10 AM   #1
GroundUrMast
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Basic A-B-C test to determine if an amplifier is needed

If you don't need an amplifier, why add one to your system? It's money and time wasted, and if the signal strength is already high, it may reduce reliable reception.

Step 1:

a) Connect a single known good 'test' cable, no longer than 50', to the antenna (which is presumed to already be mounted and aimed properly). (Also, see note 1)

b) Connect the other end of the 'test' cable to a known good tuner. (Ideally, one with a signal strength/quality meter function.) No amplifier, splitter or other accessory should be in line.

c) Perform a full rescan. Then, make a note of the channels received and the meter indication for each. Refer to your TV Fool report and rabbitears.info to convert virtual channel numbers to real channel numbers as you make your list. You only need to make one entry for each real channel, antennas, cable, splitters and amplifiers have no 'awareness' of virtual channel numbers.
Generally, if a desired signal is not received in this test configuration, the addition of an amplifier is not likely to result in reliable reception... Go ahead, try if you want to, but you'll likely be more successful if you use an antenna with more gain and / or relocate the antenna or adjust it's aim so that it has better access to higher quality signals.


Step 2:

a) Disconnect the 'test' cable used in step 1.

b) Connect the antenna to the existing cabling and splitter(s) and reconnect the TV(s) at their normal locations. (It's assumed that no amplifier is installed at this point.)

c) Compare the available signals with the recorded list of reception results from step 1c. If Reception is degraded, an amplifier is indicated.
Amplifier selection needs to take into consideration the strength and number of TV signals, possible interference signals, length of cables, splitter loss, and in some cases, presence of satellite or MOCA signals coexisting on the same system. If you need help or have questions, please post in the 'Help With Reception' forum with details of your situation.
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Note 1 - A 50' section of RG-6 will have roughly 3 dB of loss {at the highest UHF frequencies}. This will cause the signal noise margin to be reduced by about 3 dB which coincidentally, is about the same effect that the typical consumer grade preamp will have, presuming their NF specification is close to accurate. As a result, use of an amplifier on systems with total cable lengths under 50' is often a waste of money and effort.

Last edited by GroundUrMast; 10-Oct-2013 at 9:42 PM. Reason: Added antenna aim and rescan comments. Added 'no amplifier' caveat to 2(b), format
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Old 8-Oct-2013, 7:32 PM   #2
Hiker Dude
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Thank you, this is good advice. Sounds very basic, but can save lot of money, time and headaches just using this method
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Old 27-Apr-2014, 2:46 AM   #3
mulliganman
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Reception trouble shooting is best started at the antenna... This test, http://forum.tvfool.com/showthread.php?t=13646 is a great place to start, even if you aren't concerned about the question of needing a preamp, the test answers the question of whether the antenna is producing a usable signal.

Regarding the ABC test, what does "If reception is degraded, am amplifier is [B]indicated[B] mean? Not to hijack this thread but it seems pertinent to my own situation. Thought possibly the OP could possibly be confused as to its meaning as well.
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Old 27-Apr-2014, 4:28 AM   #4
GroundUrMast
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Quote:
Originally Posted by mulliganman View Post
...

Regarding the ABC test, what does "If reception is degraded, am amplifier is [B]indicated[B] mean? Not to hijack this thread but it seems pertinent to my own situation. Thought possibly the OP could possibly be confused as to its meaning as well.
If you have reliable reception with just: an antenna > short coax (50' or less) > TV, and then add the loss of a splitter and more cable, you may find that the reception becomes unreliable. If that happens, a preamplifier or distribution amplifier may help, by overcoming the loss caused by the splitter and longer cable.
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If the well is dry and you don't see rain on the horizon, you'll need to dig the hole deeper. (If the antenna can't get the job done, an amp won't fix it.)

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