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Old 20-Jan-2021, 10:39 PM   #4
videobruce
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Join Date: Feb 2013
Location: Western NY State
Posts: 27
Problems

From my experience tiring different DA's (distribution maps) in place of my long term Winegard DA1018 DA (18db gain, adjustable), fpr example, Winegard's 36db version was way too much to handle the excessively strong signals that I have had to deal with for well over 25 years. First with analog, then digital, now with a UHF spectrum that was reduced a THIRD time (originally 82, then 68, then 50, now only 35 channels) cramming everything much closer together.
Single channel tunable traps (filters if you prefer) are the only solution. To be clear, this has to do with stations coming from the same direction within say +,-20 or so degrees

The outstanding problems with this product are excessive amplification, inability to handle differences in signal level over 25db on adjacent channels and filter width. Some wer addressed here in one of his emails, the others were not;
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My point;
From page 5 of the “Product Sheet”;
Recommended input range....dBmV.. -20…40
Gain regulation................... dB......... 0…30 (auto)

That is not the clear, the term “Input” is not used in the line for "Gain regulation", assuming that line is the difference issue.

His response;
What the AVANTx cannot do is to balance a difference of 30-35 dB IN CASE OF ADJACENT CHANNELS. If the channels are not adjacent, there is no problem. The reason is because the filter, albeit digital, takes a vestige of the upper and lower channel. If the level is very high, spikes appear, as you saw in your graphs. See below channel 17 with a peak which is a vestige of high level channel 16. Notice that the level of channel 17 is lower than 18, 19 and 20, yet the power detected is the same, because of the peak of adjacent channel 16.
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1. Excessive gain:
Even at the lowest output which is 30db, with the three 'problem' stations (as I call them) still overload the Avant-X with my custom traps. Without the traps , I loose at least five channels. Period! The signal is there, but numerous factors prevent tuners from locking on to them.
If that was reduced down to 20db, I would be willing to bet most of that issue would go away. Putting a 10db 'pad' defeats the purpose of this in the 1st place. using the 'test port' doesn't solve the problem either since the 'damage' is already done before the output.

2. Filter bandwidth:

The Avant-X is based on European TV channels which is 8 MHz derived from PAL & SECAM systems (with some being 7 MHz).
This can cause problems with adjacent channels here that are overpowering the wanted channel due to (what I call) 'leftovers' that aren't attenuated enough affecting the neighboring channel. Level differences over say, 25-30 db can cause issues depending of the specific situation. Even with the single channel traps, which help, it's still not enough.

https://www.britannica.com/technolog...h-requirements (scroll to bottom of the page)

3. Non-controllable AGC (to a lessor extent) ;
I was never a fan of 'auto' anything, especially when it comes to electronics. There is always a compromise. While it can work, many times it doesn't, or doesn't work correctly. Not having control can lead to other problems. ALC, AGC, for audio or video, Auto-Iris, Auto White Balance Auto exposure for cameras (film or video) and AGC circuits in RF amplifiers. It's all a compromise and how the circuit was programmed.
Reducing some levels while amplifying others to 'flatten out' the spectrum sounds good on paper, but if that includes cranking a weaker station excessively or increasing a channel that was 'blocked with that 'left over' can cause issues.
While having a +_ 3db level adjustment is better than nothing, I don't feel that is
adequate enough.
.
Note,
Take a look at these attachments of ch 15 & 16 and the text in them.Then look at the last attachment; a single channel and it's width at the markers.
To put things in perspective, look at the 3rd attachment. That shows the level differences here.
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Last edited by videobruce; 8-Mar-2021 at 1:02 PM. Reason: updated & clarified issues
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