[opendtv] Re: Transition report
- From: Doug McDonald <mcdonald@xxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 17 Jun 2009 07:39:44 -0500
Cliff Benham wrote:
Manfredi, Albert E wrote:
I also question the bandpass response of the signal displayed on the
spectrum analyzer. Could this be caused by their CH 6 analog antenna?
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That's a classic problem case.
The tilt is probably caused by you antenna, or by its location.
The antenna, if close enough to metal, could be seeing its response
tilted, or it could just be not flat enough.
But the classic problem is that big FM carrier just above it.
That's your big problem. It is overloading the receiver.
Nothing will fix that problem except getting rid of it.
It may be impossible, or maybe a trap will work. Remember
however that traps cause phase problems outside of their
reject region. A better solution would be a pro quality
bandpass filter for Ch. 6.
Ch. 6 should never have been used for ATSC DTV.
I have two adjacent DTV stations on Chs. 41 and 42 ...
both 1 MW on 1300 foot towers ... one 14 mi away, one 69,
in opposite directions (however, they are co-owned and transmit
identical programming except local news.) They are typically
40 dB different in power even with a 16 element Yagi
pointed at the weaker. The weak one varies in signal level:
when it is higher than -30 dB, it comes in fine. Otherwise,
no.
Doug McDonald
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