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ChrisF_1

Dvb-t Reception Issue - Mt. Wellington, Auckland

45 posts in this topic

Chaosmaster,

Impulse noise energy drops as the frequency rises. On analog TV the band 1 channels of 0 -2 always suffer from a pair of horizontal bands from arcing on HV power lines. This problem is much less noticeable on channels 6 - 12. This is the reason why the ACMA states it is not allocating any DTV to RF channels below channel 6.

So if it is strong enough it can cause intermodulation distortion in masthead amplifiers making out of band noise become inband noise. Hence the need to put the filter at the input of the amplifier and not on the output. I am not suggesting you are doing this.

The higher the gain amplifier the greater the likelyhood of the impulse noise will cause the output voltage to reach near to that of the power supply, the greater the likelyhood of intermodulation distortion.

Chris has his gain turned right down to prevent intermodulation distortion, however there is insufficient gain for his very weak DTV signals.

AlanH

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That is correct, Alan, however sometimes the impulse noise itself may have considerable energy in the UHF band (ie. not simply due to distortion in the amplifier), especially if it is a strong source, and if this is indeed the case, then filtering will be useless, as the signal has been irreversably corrupted before even reaching the amplifier.

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I used to have this huge one that did everything I found it was just too intense for me, and too big!

Really?

Around here,

Long & thin, goes right in;

Short & thick, does the trick. :hyper:

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You are, of course, talking about the various types of F connectors and which type of coax is best suited to them?

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