Thread: 91XG or DB8e
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Old 12-Aug-2017, 2:21 PM   #22
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,451
Quote:
FWIW, the power supply and inserter shipped with the Juice is more than capable to supply two of them simultaneously. The amp usually pulls 120-140 mA at 12 volts and the supply is rated at 400 mA output.
Thank you for the clarification.
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I happen to ALWAYS view these installations as experiments with no expectation as to the outcome.
A good way to view them.
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He pointed out a factor I hadn't considered.
I couldn't get my head wrapped around what he said:
Quote:
Originally Posted by Tower Guy View Post
There is still a sensitivity problem if a splitter used as a combiner after both preamps. It occurs because any front end noise contributed by the preamp connected to the mis-aimed antenna adds to the noise of the preamp of the marginal signal.
Is he talking about "noise" that is from the internal NF of each preamp, or he is talking about other "noise" that is added to the NFs of the preamps from the mis-aimed antenna?

I am inclined to believe Tower Guy because he has extensive RF experience and knowledge, but I would have to demonstrate it to myself to see what would happen and I don't think I have the necessary equipment.

If one antenna and preamp was receiving channel A with an SNR of 18 dB, and the second antenna (aimed in a different direction) and preamp was receiving channel B also with an SNR of 18 dB, would the SNRs of both signals then be 15 dB after combining because of the NFs adding together, or would the result be difficult to predict because of the contribution of other "noise" from the antenna not properly aimed at the desired channel?
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Last edited by rabbit73; 12-Aug-2017 at 6:02 PM.
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