View Single Post
Old 1-Sep-2020, 10:43 PM   #14
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,747
Back on topic
From PM:
Quote:
Originally Posted by verder
I'll use Spectrum Spy across the UHF band and take a screen capture of what I see. I've only looked at individual channels using SDR#, and that was after tweaking the gain for each.

This makes me wonder how the Tablo tuner operates. "How do it know" that it needs to crank the gain for some channels but also not crank it as high for channels that are coming in loud and clear? It's got 4 separate tuners, so it presumably should be able to dynamically adjust the gain based on whatever channel each tuner is being tuned to. Obviously, gain doesn't mean much if there's a lot of noise or interference that is distorting the original signal.

As always, thanks for your insight!
I assume that there is an internal amp to compensate before splitting to four tuners like in the TiVo. Each tuner should have its own AGC in use for the particular channel used by that tuner.

Ideally, the AGC shouldn't alter the SNR of the signal unless it is extremely strong or extremely weak; IOW, within its operating range.

Your additional tests should give you more clues.

Since your two directions are almost 180 degrees apart, you will need a bi-directional antenna or 2 separate antennas. The ANT 751 is not bi-directional, but your AD 4MAX is bi-directional since it doesn't have a reflector. I have some concern about the 4MAX because of its narrow beamwidth. If its aim is optimum for one direction, it might be off for the other direction.

A DB4e without a reflector would have a wider beamwidth, but perhaps not quite as much gain.

It looks like your present antenna location can "see" in both directions, but the antenna might not be high enough for the signals to clear the trees. Trees can seriously affect the incoming signals, especially when they are wet. Also, when the wind moves the branches it creates multipath problems.
http://www.hdtvprimer.com/ANTENNAS/siting.html
scroll down to Trees and UHF

You mentioned earlier that when you moved the antenna higher, you lost a channel. This seems counterintuitive, but is caused by layering:



I'm presently living in a retirement facility on lockdown. My previous room was on the first floor and an indoor antenna did quite well. When I was moved to the 2nd floor, I thought the additional height would help, but there is a tree in the signal paths.



and when the wind blows, it really messes with the signal:
https://www.dropbox.com/s/8gsw9t1zsr...Path2.mp4?dl=0

https://www.dropbox.com/s/8gsw9t1zsr...Path2.mp4?dl=1

this is what the signal looks like with a strong wind:
https://www.dropbox.com/s/ig3va499k2...Path4.mp4?dl=0

https://www.dropbox.com/s/ig3va499k2...Path4.mp4?dl=1
__________________
If you can not measure it, you can not improve it.
Lord Kelvin, 1883
http://www.megalithia.com/elect/aeri...ttpoorman.html

Last edited by rabbit73; 2-Sep-2020 at 1:53 AM.
rabbit73 is offline   Reply With Quote