View Single Post
Old 16-Apr-2013, 2:45 PM   #13
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 127
High Dynamic Range

Quote:
Originally Posted by Pete Higgins
...If it had received CBS on channel 43 (2.1) as well as it received NBC channel 36 (4.1)...
Initial thought:

You cannot receive Channel 43 very well because it isn’t there (that is; in the TVfool table)!

Then, after eliminating analog channels from the table, channel 43 shows.

That’s a difficult situation to receive such a weak signal in the presence of very strong signals.

--------------------
2nd thought:

When applied to your area, TVfool signal prediction algorithms (presumably based on Longley-Rice model) must not be as accurate as they usually seem to be.

1. It’s unlikely that an ordinary TV receiver can simultaneously process signals having a dynamic range of 106.5 dB (difference between KVCR, -15.6 and KCBS, 122.1).

Then, recalling that you used a notch filter to essentially remove KVCR, obviously improving the dynamic range situation, tho still very challenging for an ordinary TV receiver.

That’s not to mention the complications of two FM stations at –13.4 and –26.9 dBm, plus some more moderately strong TV stations.

2. The available antenna gain is insufficient to compensate for a noise margin of -22 dB.

-------------------
For many, receiving KNBC, at predicted noise margin =-16.8 dB, would be a challenge.

Do you receive both KNBC channel 36 (-107.7 dBm) and KCBS Channel 43 (-112.9 dBm) on their assigned antennas throughout the day (say most of 24 hours)?

-------------------

Regardless the accuracy of TVfool predictions for your particular location, you undoubtedly have a situation that challenges the dynamic range of amplifiers and tuners.

Pete, you have an interesting situation. From reading in other forums, you have worked out a good approach toward solving the problem (filters, high dynamic range drop amplifiers, and such).

Last edited by tripelo; 16-Apr-2013 at 3:05 PM. Reason: clarify
tripelo is offline   Reply With Quote