[opendtv] Re: Test in New York
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sun, 12 Jun 2005 20:27:46 -0400
Bob Miller wrote:
> I am not an engineer, wish I was, so I tend to
> test like a typical Joe Sixpack.
Which is perfectly fine. Actually, it's refreshing to
hear someone who doesn't pretend to be something he
is not.
> From memory the numbers were between 27 and 32 dbu
> for the channels that were solid at 100.
That's perhaps dBuV, which means dB values referenced
to 1 uV. Not terribly useful numbers, in part because
they are hard to correlate between boxes. They depend
on the input impedance of the receivers being
identical, if you expect to compare power levels
received by each box.
A 27 dBuV measurement means you're seeing 0.501 mV at
the antenna input. Sounds reasonable for NYC. Assuming
the receiver's antenna input in 75 ohm impedance, as
it nominally would be for consumer TV antennas, that
would translate to -24.8 dBm received power. A good
strong signal.
> They were in the 24-26 dbu range for channels that
> showed a dip below 100 and for channel 53 it was 31
> dbu at 100 and 5 to 8 dbu when it showed 25%.
Assuming they are dBuV values, then a 5 reading would
mean you're seeing 0.0031 mV at the input, which
translates to -68.8 dBm, if the input impedance is 75
ohms. A weak signal for most boxes.
A value of -75 dBm received would translate to 1.875
dBuV. And a 0 dBuV value corresponds to -78.8 dBm,
which is getting down to the difficult reception
region.
Looks like the percent numbers are related to
received power.
Bert
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
