Avant-X Programmable 4 input distribution amp from Televes
I was intrigued by this since it is such an unusual device. While there are plenty of preamps, even some with more than one input, for the most part almost everything is 'set'.
This is NOT a "preamp" It's designed for indoor installation to combine up to 4 antennas with the option to use (what is labeled) a CATV input as a 5th input either for an antenna that doesn't need any 'filtering' or more likely, a modulator to add another signal source; CCTV DVR, Media Player, HDTV DVR, DVD or BD player).
It's not 'cheap'. But, what it does, or what it can do, if you price MATV equipment, even low end, it could be a bargain.
Conversations I have had between the three of us have enlightened all of us. There are details that really aren't documented in the very limited 'quick guide' Televes provides. Which brings me to here.
Links to this and it's software and the source of my purchase which I recommend very highly;
This requires Java RE v1.7.0 either x86 or x64 v1.7.0.51. This is not stated on their web site. I didn't find this out until I tried to 'run' the program!
It also requires M$ Visual C++ 2008 (which is installed from the program if the O/S doesn't already have it)
I did run into a problem in XP Pro in one of two Laptops that JRE didn't install properly with no solution.
Below are comments from Javier Runano General Manager for Televes US and Justo Rodal in Santiago, Spain describing the unit and it's setup.
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Javier Ruano
General Manager
Televes USA Norfolk Tech Center
16596 E. 2nd Avenue Aurora, CO 80011
Like any other processing device the Avant has certain dynamic range per filter. It is able to adjust and equalize incoming signals between -20dBmV to 40dBmV to a programmed output level between 30dBmV and 55dBmV (or 75dB margin). Outside of that input range there will be cases where the agile filter programmed for a particular channel or cluster may not have enough gain or attenuation available to bring the channel to the programmed output level. After the automatic level adjustment has been completed, the "adjust" tab allows for a +/-3dB gain adjustment of each individual filter.
It is possible in some scenarios that a fringe signal which is able to marginally be decoded when fed directly to a tuner may perform worse after processing, by the Avant or other device. This is entirely normal as indicated by a user earlier in this thread. Any RF processing of a very fringe signal is not going to improve it's quality. The main advantage of the Avant is to be able to individually process channels coming from up to four different antennas/markets/directions and provide a way to distribute them on a single wire combining them filtered, well balanced and amplified, avoiding co-channel interference and multipath, for further distribution. This is not possible by directly combining the antennas or without an elaborate processing headend. Like in any processing system, the incoming signals need to meet certain specifications.
It is important to note that during the adjustment process the main TV+CATV output be loaded with a 75 ohm termination load. The reason for this is that when the unit is adjusting the gain of each individual programmed filter, it reads the level on that output, and if not terminated, there will be a mismatch and the read value won't be correct, and neither will the filter adjustment as a consequence. During that process, the input signals need to be connected as well, of course. Best practices dictate for any unused ports to be terminated anyway.
Another common configuration mistake is for users to program filters in empty channel locations "just in case" something comes in. This should not be done because the Avant X will maximize the gain of that filter during adjustment, only to add noise to the aggregated signal. The Avant X is intended to acquire existing signals from a set of antennas, and process, balance, and combine them in the best way possible on a compact headend solution. The Avant features an FM input that will be adjusted according to the output level programmed in the unit, and a CATV mix input for when it is used to inject OTA channels in an existing cable distribution.
The North America version of the Avant X, P/N 532180, does not have automatic channel scan. It does require to manually program the channels or clusters desired per input on A-Suite or using the Televes handheld programmer.
Once the unit has been programmed and adjusted, it will establish a set of filters per input, and reject everything else, so if a new multiplex becomes available, yes, a filter will need to be programmed for that channel on the corresponding input, the unit readjusted, and any downstream tuners to be re-scanned if needed.
In a nutshell the Avant X is a filter > processor > amplifier. It allows the filtering of up to 32 individual channels or clusters coming off of four different antennas, and processing them to any frequencies desired, equalize the levels, and provide a programmed output level which is maintained over time. There are a number of applications for this feature set, for example to be able to ingest, filter, equalize and combine content from different markets/antennas in a clean fashion over a single coax feed. Since the Avant also allows to frequency-shift incoming carriers, an operator can receive same RF channels from different markets without co-channel interference.
The output level in the Avant X is programmable between 30dBmV and 55dBmV, and also a slope setting is available for larger cable distributions, such an MDU for example. The higher values will likely be too strong in many residential settings, so the Avant also features a -20dB output, on which the programmed value will range between 10dBmV and 35dBmV. So in practice, the output level can be adjusted between 10dBmV and 55dBmV, enough range to cover a wide variety of distribution scenarios.
The AVANTx has 4 independent input preamp stages (wideband up to 608 MHz) and then the set of 32 filters which are programmable with the different wanted channels. If a channel is blocked, it enters the input preamp, but it is blocked in the filters and it is not present in the output wideband amplifier, where all the signals coming from the 32 filters are boosted altogether.
The main CATV+TV output is the mixed output for the CATV mix input and what comes from the antenna side of the Avant. The way the Avant adjusts the filters is by reading the power level there as it goes through the frequencies and adjusts each filter width and gain. For this reading to be accurate and the adjustment to be satisfactory this output needs to be correctly adapted and loaded with a 75 ohm load, otherwise there will be impedance mismatches, the power reading will fluctuate wildly and the filters will be totally unadjusted.
See the attachment for the port configuration of the device
__________________
Keep OTA television alive. Streaming is 'all wet'..........
Last edited by videobruce; 4-Feb-2021 at 1:37 PM.
Reason: updated important comments about the software
Specifics;
The AVANTx has 4 independent input preamp stages (wideband up to 608 MHz) and then the set of 32 filters which are programmable with the different wanted channels. If a channel is blocked, it enters the input preamp, but it is blocked in the filters and it is not present in the output wideband amplifier, where all the signals coming from the 32 filters are boosted altogether.
The main CATV+TV output is the mixed output for the CATV mix input and what comes from the antenna side of the Avant. The way the Avant adjusts the filters is by reading the power level there as it goes through the frequencies and adjusts each filter width and gain. For this reading to be accurate and the adjustment to be satisfactory this output needs to be correctly adapted and loaded with a 75 ohm load, otherwise there will be impedance mismatches, the power reading will fluctuate wildly and the filters will be totally unadjusted.
My question;
How can the CATV be used with ATSC since they are two different modulations AND two different frequency tables?? IOW's no North American tuner would or could work.
Reply;
The CATV input could add locally generated content modulated in ATSC via encoders.
There is a different version of the Avant X we make for a very large hotel integrator that allows for the incoming OTA 8VSB carriers to be frequency shifted to QAM center frequencies. By having both the QAM and the 8VSB located in CATV frequencies, commercial TV tuners will pick up both and work.
My observation;
Regarding reassigning stations to other physical channel numbers.
I see a possible problem regarding devices when using outside party 'Guide data'. Namely TiVo recorders. Rovi (that owns TiVo and also supplies the data for their 'Guide') has their 'system' programmed to expect stations to be on predefined physical channel numbers. During the 'repack' when everything was in 'disorder', stations that 'moved' earlier than expected the 'Guide' data did not show under the new physical channel number. It still did show on the old allocation, but not under the new assignment.
IOW's you could not record a program on that channel without manually entering in the channel number, start & stop times, AKA 'VCR' style. They changed their regional data to now include stations in the market you are in. Of course there are many mistakes in this and many stations would be out of range for most owners given the lack of decent outdoor antenna(s) or just being in a poor location. I guess to make things easier for 'Joe SixPack' where an antenna scan almost isn't necessary (but still required).
Moving the station to a different physical channel number I would expect would do the same thing.
Attached are screen shots of the 'Custom User Guide'.
The entire Guide in OpenOffice (.odt) format is here (the upper right corner of the page has the 'Download" link for the file);
Taken from Justo Buffalo-Toronto plan
by Justo Rodal Santiago, Spain
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The AVANTx can accept signals in its input ranging from -40 dBmV to +20 dBmV, that is to say, 60 dB. The block diagram of the AVANTx, which is depicted as follows, is helpful to understand why the balancing cannot be achieved.
The AVANTx has 4 inputs. Each one of the inputs has a first block of analog filtering, VHF high&low and UHF, after which a high margin amplifier prepares the whole set of received signals to the digital filtering block. After these 4 amplifiers, and before the digital filters, there are 4 Analog to Digital Converters (ADCs), one per amplifier, that give off the digital samples of each input to the digital filtering block.
This digital filtering block encompasses 32 filters, which are programmed by the user depending on the channel map in the location. The AVANTx can operate without channel conversion (i.e. same output as input channel) or performing channel conversion, moving the output channel to a different frequency. The digital filters bandwidth depends on the presence/absence of adjacent channels to the wanted channel. If there aren’t channels, this bandwidth is wider.
The problem of this schema is that the AVANTx won’t be able to cope with input imbalances higher than 30 dB in the same input1, because input 1 receives signals from Buffalo and from Toronto. Due to the high level of the signals received from Buffalo, the amplifier attenuates input 1 instead of boosting, not to overwhelm the ADC. That makes that the low level signals received from Toronto are attenuated, which makes the balancing of the whole set more difficult.
Ideally, to solve the problem, we should be receiving the signals coming from NW from two different antennas, separating Buffalo and Toronto. However, this is not possible, as the beam width of reception is very narrow.
The solution to use traps to attenuate individual signals in channels 15, 16, 31 and 32 seems therefore the only option reasonable not to override the input ADC of the AVANTx. However, the frequency response of the traps (picture below) added to the fact that channels 15 and 16 are adjacent to channels 14 and 17 coming with low levels from Toronto affect the level of these latter, as the trap is not strictly speaking narrow band.
Therefore, the use of traps attenuates effectively the higher level channels, yet impairs the adjacent ones. In the scenario we have, the trap in channels 31 and 32 would be useful, impairing channel 30, whilst the use of traps in channel 15 and 16 impairs channel 14 and 17 from Toronto. There is a channel 33 in use, yet received by the second antenna pointing to SW. Therefore it would not be affected by the use of the trap 31-32, provided that this second antenna uses a different input of the AVANTx to process the channels.
(For the following, see the attachment)
Input 1 in AVANTx would process the channels from Buffalo with the highest received levels. If needed, an attenuator could be placed in order not to override AVANTx input, as the level could reach the maximum of +20 dBmV. The channels from Toronto are disregarded in this input.
Input 2 in AVANTx would process the channels from Toronto. It is necessary to attenuate the levels of the channels 15,16, 31 and 32 by using the traps. If possible, the frequency response of the traps could be modified in order to achieve a minimum impair in the adjacent channels. However, channel 30 is extremely difficult to process, as the imbalance regarding nearby channels is too high.
Input 3 in AVANTX would process the channels from Buffalo received by Antenna 2
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Attached is the proposed config plan for the 3rd input. Instead of using a 'splitter', I'll use a 16db 'tap' to offset the loss on the output for the weaker Canadian stations.
__________________
Keep OTA television alive. Streaming is 'all wet'..........
Last edited by videobruce; 20-Jan-2021 at 10:16 PM.
Reason: typo corrections
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;
--------------------------------------------------------------------------- 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.
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.
__________________
Keep OTA television alive. Streaming is 'all wet'..........
Last edited by videobruce; 8-Mar-2021 at 1:02 PM.
Reason: updated & clarified issues
The two main PCB components are as follows. Due to NDA and proprietary issues the Broadcom chipset, all I could find was a PR announcement for the 2015 CES (no less).
2015 Consumer Electronics Show (CES);
Broadcom announced a new low-power satellite device in its Outdoor Unit (ODU) portfolio. The BCM4554 addresses consumer demand for satellite services with support for North America, Europe and Asia-Pacific regions.
The new device adds support for up to 32 resident set-top boxes (STBs) on a single coaxial cable within a multiple dwelling unit, enabling operators to deliver additional services to more subscribers without requiring new satellite dish installations. These offerings also enable operators to improve services such as faster channel changing by assigning more channels to a single STB.
"Broadcom's newest addition to our low-power ODU portfolio allowsb operators to increase the availability of satellite services in single homes and multiple dwelling units across the globe," said Nicholas Dunn, Broadcom Vice President of Marketing, Broadband & Connectivity Group. "The BCM4554 enables operators to streamline the cabling, hardware and installation costs associated with supporting multiple set-top-boxes and ultimately simplify satellite distribution to their customers."
Among residential customers worldwide, access to free-to-air channels provided by a range of satellites has stimulated demand for satellite TV. In order to lessen deployment costs resulting from the need for separate coaxial cables for each STB, Broadcom's BCM4554 device simplifies installation for these additional service offerings.
Broadcom's BCM4554 offers a higher level of integration while consuming less power than the previous generation chipset. It also enables direct sampling of low-noise block (LNB) outputs across worldwide ODU satellite markets. The simplified design of Broadcom's new ODU chipset allows 32 DVB-S2 channels to be stacked on a single coaxial cable to service any STB in a home, simplifying and reducing satellite operator installation costs.
Broadcom's BCM4550 satellite channel stacker solution is a fully integrated satellite Outdoor Unit (ODU) solution to support Full-Band Capture (FBC) technology. Broadcom's BCM4550 with integrated Full-Band Capture digital-tuning technology minimizes satellite TV installation costs and complexity, delivering single-wire architecture into the home. Enabling design efficiency and scalable bandwidth to operators, Broadcom's ODU technology provides a TV-everywhere connected home experience with additional high-definition video streams, multiroom DVR and IP services.
Microchip PIC18F8750 64/80-Pin High-Performance, 1-Mbit Flash USB Microcontrollers w nanoWatt Technology
OVERVIEW OF THE PIC18F87J50 FAMILY USB CAPABILITIES
The PIC18F87J50 microcontroller is the “superset” device in the PIC18F87J50 micro-controller family. The PIC18F87J50 has the highest memory and pin count in the family, but otherwise shares an identical feature set (except features which require pins not present on 64-pin devices) compared to the other devices. All of the devices in the family are code-compatible with each other and share the same USB capabilities:
• USB 2.0 compliance
• Full-speed (12 Mbit/s) and low-speed (1.5 Mbit/s) operation
• Support of control, interrupt, bulk and isochronous transfers
• Support of up to 32 endpoints
• 3.9 Kbytes of dual access RAM for USB or general purpose use
• On-chip features for a single chip USB implementation, including:
- USB Serial Interface Engine (SIE)
- USB transceiver
- USB pull-up resistors
- D+ and D- driver output impedance matching resistors
-------------------------------------------------------------------------------
Separate subject;
That RJ45 jack on the device, it can only be used for their handheld programing unit. Of course I did ask about that also. The response was basically cost to implement it. They wanted to keep the cost down as much as possible, so that was passed by.
I don't know the protocol that is used, but I wonder if an outboard Network adapter couldn't be designed (if there isn't anything already) to 'adopt' it for Network use so one could control the functions from desktop or Laptop PC? That would be separate from the unit as an option.
.
__________________
Keep OTA television alive. Streaming is 'all wet'..........
Last edited by videobruce; 12-Feb-2021 at 3:24 PM.
Reason: minor typos
Thank you for the inner details of this amazing product. Having grown up in Wheatfield I know the advantages and problems receiving stations from multiple directions.
My brother still lives in WNY. An optimum array for his location is a small UHF antenna aimed at Grand Island, an 8 bay UHF antenna aimed at Colden (but aimed to put Grand Island in a null), and another 8 bay UHF aimed at Toronto (but aimed to put Grand Island in a null), plus a VHF antenna with UHF filtered out aimed at Toronto for CTV on channel 8.
Even then there may be adjacent channel issues that the filter cannot fix. I wonder if frequency translation to channels without adjacent channels could bury the problem?
For instance, a station with a strong station below it could be shifted to channels 2, 5, 7, or 14. A station with a strong station above it could be shifted to channels 4, 6, 13, or 36.
Back to plan A, it's a 'no go', it's not the 'silver bullet'
What looked good on paper, wasn't in the field. After experimenting with this on my bench, not where the device would be placed, I finally did install it in place. Results overall were about the same except for a few 'variables' due to the additional 25 or so feet of additional cable between inside locations.
Splitting that one antenna feed via a 16db 'tap' to limit loss of the 'wanted' stations, then reduce the overload of the unwanted 'problem' stations using the 'Tap' out, apparently just added more complexity.
It made the one wanted station somewhat worse. So I went back to just using 2 inputs, but that just got me to where I was before this entered the picture.
This gross signal difference (around 40db between adjacent channels off the antenna) is way too great for this to handle, even with the 20db reduction of that after my traps. Compounding that is the 'slop' left over of the offending adjacent channel from their filters too narrow filter 'shape factor'. (There is a 'wide' and 'narrow' shape factor that is based on if there are adjacent channels active or not)
The Avant-X filters have a tighter 'Q' factor then my custom 'PAR' 'traps' I have (which is good), BUT, the incorrect width doesn't get rid of enough of the adjacent 'haystack', or lets too much empty spectrum in.
Now, having said that, there is a fine line (almost literally) between just how tight a filter/trap is. Frequency and cost come into play. The 'math' is above my pay grade, but since I have 20+ years of tuning traps (as I call them), it's not just a 'art', but a major math problem in design. It's a classic case of "Robbing Peter to pay Paul" between attenuating an adjacent channel while trying to persevere the wanted channel. It really can't be done fully, it's all compromises.
I have proved it more than once, without my custom traps, this would of been completely un-usable, as I stated earlier mostly due to excessive gain and filter width. I LOOSE channels including one VHF (which I can only guess it's because of noise, but that is just an educated guess), not because of any adjacent channels or excessive signal strength. That alone is a deal killing as those custom traps were almost the cost of this.
When I went back to my existing setup (the Winegard DA), two of the stations that were missing, locked back in. That was enough and the two months of fighting with this to get it to work. It was returned. I just couldn't justify the cost in spite of the time I put into this.
Attachments;
Below are pics of the testing, then the final setup in the attic, (not a crawl space) and a scan of the 'traps' that allow to Winegard DA-1018 DA to work where the Avant-X didn't. (The double trace was the traps flipping the order to see if that mattered, the 'dips' are ch 15 & 16 then 31 & 32)
Last edited by videobruce; 8-Mar-2021 at 2:30 PM.
Reason: final conclusions & determinations
Wow, Science is so, so scientific and technology is so um, technical.
As is the case with most, if not all, tools, it's how it is used.....
The TELEVES AVANTx is an excellent tool but how it's used is also
important. The Buffalo area and canadian signals reach well into
WNY and Grand Island, in particular, so that were it not for adjacent
channel interference, there would be little to no issues. Has any of
the braintrust used the roof/home to block or null the offending signals???
Simply mounting antennas on the roof and pointing them is
insufficient to insure good reception in many cases..........
Then to sum it up you are 40 & 50 miles from any of the xmitters with high gain antennas with no real overload conditions. Is that correct?
If so, then the Avant-X would be able to handle that. How about what the spectrum looks like directly off the antennas? Also, how about narrowing up the spectrum for 'groups' of channels?
Separate question, can you confirm a software glitch where the 11th channel position on each page (the one furthest to the right) can NOT be manually adjusted + - 3db?
__________________
Keep OTA television alive. Streaming is 'all wet'..........
Last edited by videobruce; 12-Feb-2021 at 3:27 PM.
Reason: minor typos
With this or the Televes dual input one could one combine say two small RCA 751 antennas pointed in the same direction and get a signal on all VHF and UHF stations that
is twice as good?
What you are talking about is "stacking" antennas which is a science it itself, not for beginners or even intermediates.
There are specifics that have to be followed, starting with a decent antenna in the first place. That or any like that is not. It's a low cost, small, short range model which there are 3 or 4 other similar models like it out there. Now if you were talking about different directions, that maybe different.
Without knowing your exact situation, no one would or should make any recommendation other than, based on your question know that apparently isn't the correct choice.
If all your stations are in the same basic direction (within +- 20 degrees (or so) get a 8-bay 'bow tie' antenna (the former CM HD4228) or a high gain Yagi if the separation of degrees is more like +-10 degrees.
__________________
Keep OTA television alive. Streaming is 'all wet'..........
Thanks just thought Id ask.. I tried a Stellar Lab 2475 and it was able to pull in only my two strongest VHF stations reliably...other vhfs were marginal. With all the trees around me Im looking at the largest antenna possible and extreme measures to get the rest of my stations (mix of vhf and uhf). I'm finding it not right but I cannot be surprised I guess surrounded by so many trees. I'm thinking to wait for ATSC 3.0 (many years ) and try again...
He wanted to put the antenna in the arttic. He could try that, but it would work better outside. The best reception would be with a tilt-up, crank-up tower to get above the trees.
Is that azimuth based on True North or Magnetic North?
Channel 15, CHCH, is 476 to 482 MHz, 291.4° True, 301.9° Magnetic
Channel 16, WNYO, is 482 to 488 MHz, 324.1° True, 334.6° Magnetic
Channel 17, CIII-41, is 488 to 494 MHz, 330.9° True, 341.4° Magnetic
Quote:
Originally Posted by videobruce
The outstanding problem is differential in signal level.
His response; What the AVANTx cannot do is to balance a difference of 30-35 dB IN CASE OF ADJACENT CHANNELS.
The 2nd problem is the width of their electronic channel filters.
On adjacent channels, the width is the narrowest of the two widths presently available. Take a look at these attachments of ch 15 & 16 and the text in them. Note, This is the 'vestige (residue, so to speak) that is 'left over' from the carriers of those two channels.
To put things in perspective, look at the last attachment. That shows the level differences here.
Now, having said that, there is a fine line (almost literally) between just have tight a filter/trap is. Frequency and cost come into play. The 'math' is above my pay grade, but since I have 20+ years of tuning traps (as I call them), it's not just a 'art', but a major math problem. It's a classic case of "Robbing Peter to pay Paul" between attenuating an adjacent channel while trying to persevere the wanted channel. It really can't be done fully, it's all compromises.
At the present time, are you able to receive 17 that is adjacent a much stronger 16? That would seem impossible for a TV tuner to handle.
Quote:
The receiver should meet or exceed the thresholds given in Table 5.2 for rejection of first adjacent-channel interference at the desired signal levels shown above the columns therein.
Wouldn't it be difficult to design a filter to attenuate 16 without doing damage to 17?
TV Bandstop available for ch.14 to 69, NTSC or ATSC
Highly Selective stopband with 20-45 dB attenuation can pass adjacent channel (3-4 dB loss at 1.5 MHz from stopband)
CR7D-HT contains 4 notches which can be combined for deep and wide notch or 4-6 MHz stopband. Example graph 2 shows video carrier notch, 1 Mhz wide. Example graph 3 shows 6 MHz stopband. http://www.tinlee.com/PDF/CR7-HT%20s...info%20sht.pdf
Ignoring cost, would that work, or is there still too much difference in strength between 16 and 17?
Filtering adjacent channels can be done, but it’s expensive. A cheaper approach is to stack two yagis horizontally so that the first null occurs on the adjacent channel. In this case the stacking distance is wider than normal at about 8 feet. The antenna should be aimed to null the unwanted channel, not peaked on the desired channel.
