Quote:
Originally Posted by Sev
The units have 3.0 and 2.2 dB in noise.
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Yes, plus.
Channel Master and some other manufacturers have not provided accurate noise figure numbers.
Numbers often provided are quotes from transistor manufacturers specs.
There is more to noise figure than transistor specs, for example:
- The excellent input filtering of the 0264/0064 and other older CM preamps, contribute to the noise figure.
- The loss in the ferrite balun adds to the noise figure.
Quote:
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I wonder if it would be possible to determine and optimize the components creating the noise.
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The VHF amplifier is a BFG198.
The first UHF transistor is a BFG67
(1st transistor is usually main active source of noise)
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The 0064 & 0264 are good and reliable preamplifiers.
The design, except for input baluns, is virtually the same as for the old CM7778.
The old CM7778 was cloned to the RCA_TVPRAMP1R.
http://forum.tvfool.com/showpost.php...76&postcount=2
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