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-   -   One channel from same location pixelating (http://forum.tvfool.com/showthread.php?t=16275)

Bigbear 4-May-2017 3:16 PM

One channel from same location pixelating
 
http://www.tvfool.com/?option=com_wr...e6a403c11d2bb9

I got a new TIVO Roamio DVR and I'm having issue with WCAX-tv. It pixelates
while the other channels from the same direction do not.
I have an old antenna that came with the house. I have a pre amp on the antenna. I use 75 ohm cabling and a 4 channel in house amp as well. The cable to the TIVO also goes through a Monster power bar.
So far I have swapped the cable from the power bar to the TIVO, and switched the cable to the power bar.
So far nothing has helped. BTW with all the same cabling when using my old HD TIVO I did not have this issue.

Any ideas?

Thanks
Bear

ADTech 4-May-2017 3:49 PM

Eliminate one of the (unidentified) amps, for starters

One amp is usually more that adequate if properly selected. Two amps are only needed under very, very unique situations and, too often, cause new problems.

The Monster power bar is largely irrelevant for any reception concerns unless it happens to be defective. No evidence of that.

Multi-tuner Tivo's usually have their own internal amp prior to the splitter that feeds the individual tuner sections. That would make three of them (if incorporated) in your case....

Different receivers, including Tivos, have different capabilities. My suspicion is that your new Tivo is slightly more susceptible to strong signal overloading than was the old one. You'd have to contact Tivo and see if they would answer that question (doubtful).

Bigbear 4-May-2017 4:02 PM

Thanks AD tech, never considered that.

The 2 channels I mostly watch (WCAX and WPTZ) both display a signal strength of about 60%. With this signal can I still be over loading the signal? Then any reason why only one of my 2 favorite channels pixelate?

ADTech 4-May-2017 4:11 PM

Quote:

both display a signal strength of about 60%. With this signal can I still be over loading the signal?
Displayed percentage is largely irrelevant since it doesn't correlate to signal strength but rather signal quality. Excessive amplification degrades the quality of the signal.

Quote:

Then any reason why only one of my 2 favorite channels pixelate?
Because, according to your attached plot, those two stations are already your two strongest signals, both with calculated VERY, VERY strong signals.

Of course, assumptions are being made due to the lack of specifics (antenna, aiming direction, potential line of sight impairments, specific amplifiers in use, cabling, etc). The above is a generalization based only on the provided data.

Bigbear 5-May-2017 12:36 PM

I have an old antenna mounted about 20' on a pole with a rotor. The antenna is pointed to the NNW ( towards Montreal) as that is where the weakest signals come from. The local channels actually are received from the rear of the antenna. I have an Antenna craft (made by permacolor # 106212) mounted just under the antenna.
75 ohm cable goes down the pole to a grounding block, then into the house to the power tap for the pre amp. From there on to a Channel master 3044 distribution amp, then to 4 devices with about 20' or so of cabling.

The pre amp's gain setting is as low as it can go, and the FM tap is enabled.
Yesterday I unplugged the pre amp to see if the pixelation would stoop, but without power no signal is passed through.
I read somewhere that a distribution amp is preferable to splitters.


Do I need to go up and bypass my pre amp?

ADTech 5-May-2017 1:50 PM

Unplugging the power to a preamp typically turns it into a ~30 attenuator. Not a valid test unless you WANT to test reception with a 30 dB reduction of signal.

I can't find anything regarding the amplifier you identified but, based on my experience with all of the Radio Shack amps I'd accumulated back before I started working here, I don't have any confidence in them. All of them got chucked into the recycle bin when I tested them on my lab's gear a few years back, their performance was truly that abysmal.

The choice of preamp vs distribution amplifier isn't that simple, it requires some analysis and calculations. If a preamp is used, the a passive splitter is almost always the correct distribution device but, again, that decision should be based on the circumstances for each individual installation, got any general rules.

Amplification should be thought of as subject to the "Goldilocks" rule: Not too much, not too little, it works best when it's "just right".

Tower Guy 5-May-2017 4:59 PM

There are multiple issues happening simultaneously.

The antenna is misaimed when you are trying to pick up the US stations. This causes multi-path (ghosting). The Roamio is a bit fussy over multipath.

The preamp is not necessary for the US stations but critical for Canada.

The use of both a preamp plus a powered distribution amplifier simultaneously will cause problems due to the higher strength of the US stations.

That said, how do you fix it?

I'd keep the existing system aimed at Canada. I assume that it gets the two VHF stations, CFTM and CFCF. The CBC station from Montreal is not on the TVfool report, but CBMT is running lower power than the other UHF stations from Montreal that the radar report lists as too weak to receive.

Next I'd get a simple UHF antenna for WPTZ, WCAX, WFFF, and WETK. DB-2 or C2 are two possibilities. The UHF antenna will not want any amplification. Couple the two antennas using a UVSJ, but be careful to add the antenna after the preamp used for Canada. You may be able to get WVNY on VHF channel 13 off the back side of the existing antenna.

If that works OK, stop there. If not, replace the distribution amp with a four way passive splitter.

Bigbear 5-May-2017 9:07 PM

Thanks Tower guy.
I'm running an experiment now where I put a spliter before the distribution amp and sending the signal to the Roamio without the distribution amp.
Hope it works!

Tower Guy 5-May-2017 10:26 PM

That is easiest to try, but the least likely to fix the problem. The overload of the second preamp is most likely to occur when the antenna is aimed at Mt Mansfield. The Roamio is most likely to work when the antenna is aimed at Mt Mansfield. Note the catch 22.

Bigbear 6-May-2017 2:00 PM

Thanks
experiment inconclusive as it was very windy here the last day or so.

The thing that is still buggin me is the fact that WCAX and WPTZ come from Mt Mansfield. One has issues, the other not.

If I were to get a separate antenna to point at Mt Mansfield, when the 2 signals are combined wouldn't the over power issue remain?

Tower Guy 6-May-2017 3:20 PM

The trick is to pre-amplify the VHF signals from Montreal but not the UHF signals from Mt Mansfield. You do that using a seperate coax for each antenna and add them after the power injector for the RS preamp. The UVSJ will remove the UHF signals from the all channel antenna aimed at Canada.

Bigbear 6-May-2017 3:37 PM

So would something like this work? https://www.antennasdirect.com/store...Combiners.html
Or would I need to run another 75 Ohm lead into the basement and combine them there? Oh I guess you already answered that!

ADTech 6-May-2017 4:45 PM

Quote:

The thing that is still buggin me is the fact that WCAX and WPTZ come from Mt Mansfield. One has issues, the other not.
It is a common misunderstanding of how different frequency (channel) radio waves propagate over distance, terrain, and through trees to assume that they will all arrive at some arbitrary point in space (where your antenna happens to be planted) with adequate strength and quality. Also, we don't have any idea of what antenna you have or what its reception characteristics might be, especially from off-axis directions. The solution for such instances is to simply move the antenna and try again, repeating as needed.

Don't forget that there is also a VHF-13 on Mt Mansfield. If you can get it with the big antenna aimed at Montreal, then TG's idea will work. One other alternative is, if you can score a UVSJ made by Holland or Pico (SCARCE!), is to take advantage of those models' DC pass on their VHF side for VHF-only amplification. This would allow masthead amplification and avoid running a second coax. Note that the Antennas Direct UVSJ has DC pass on the UHF port and cannot be used for this alternative idea but it will work just fine with TG's suggested configuration.

Tower Guy 6-May-2017 5:36 PM

Quote:

Originally Posted by Bigbear (Post 57905)
The thing that is still buggin me is the fact that WCAX and WPTZ come from Mt Mansfield. One has issues, the other not.

You could ask it the other way around. Why are you lucky enough to receive WPTZ using a mis-aimed antenna?

rabbit73 6-May-2017 7:42 PM

2 Attachment(s)
Quote:

I have an Antenna craft (made by permacolor # 106212) mounted just under the antenna.
That is probably the 10G212 which has a gain of 30 dB.

http://www.solidsignal.com/pview.asp?p=10g212

Quote:

From there on to a Channel master 3044 distribution amp,
That has a gain of 22 dB.

https://www.amazon.com/Channel-Maste.../dp/B000GGFXW8

Waaaay too much amplification.

Quote:

The 2 channels I mostly watch (WCAX and WPTZ) both display a signal strength of about 60%. With this signal can I still be over loading the signal?
Overload can cause gain compression that will reduce the signal strength reading on the Roamio Diagnostics screen. Pay attention to the uncorrected errors on that screen; it should be no uncorrected errors.

The Roamio signal strength will not go to 100; it will max out before that.

Forum member mulliganman was using a TiVo Roamio and also had strong local signals. See his report in attachment 2. His signal strength never went above 72%.

https://forum.tvfool.com/showpost.ph...6&postcount=21

Try following the advice by Tower Guy in post #7.

The difference between your strong local signals and your weak desired signals is too much for your present system to handle.

Also, CFCF on real channel 12 has adjacent channel interference from WVNY on real channel 13.

Bigbear 6-May-2017 9:34 PM

Thanks
I'm thinking of going with tower guy's suggestion, but a little fuzzy on where to combine the signals. If it's up on the roof, will water be a problem?

Could you give me a suggestion of a UHF antenna to use?

BTW this is what I am using now http://forum.tvfool.com/attachment.p...6&d=1402837984

rabbit73 7-May-2017 12:56 AM

Thanks for the photo of your antenna. That looks like a medium gain all-band antenna for channels on VHF-Low, VHF-High, and UHF.
Quote:

Could you give me a suggestion of a UHF antenna to use?
The antennas suggested by Tower Guy are suitable.
DB2E
https://www.antennasdirect.com/store...r-Antenna.html
https://www.amazon.com/Element-Bowti.../dp/B0074H3JCS

C2
https://www.antennasdirect.com/store...-Complete.html
Quote:

Originally Posted by Bigbear (Post 57908)
So would something like this work? https://www.antennasdirect.com/store...Combiners.html
Or would I need to run another 75 Ohm lead into the basement and combine them there? Oh I guess you already answered that!

That is a suitable UHF/VHF combiner AKA UVSJ.

Quote:

I'm thinking of going with tower guy's suggestion, but a little fuzzy on where to combine the signals. If it's up on the roof, will water be a problem?
The problem is with the preamp. You need the preamp for the weaker VHF signals from 342 degrees using your present antenna, but you must not use a preamp for your local strong signals from the UHF antenna. If you put the combiner outside between the antennas and the power inserter inside, then the combiner must be able to pass power to the VHF antenna preamp. But, that type of combiner is no longer available; only the ones that would pass power to a UHF antenna preamp, which you don't need.

That is why you need two coax lines coming down.

Code:

                DB2E > coax > grounding > coax >
                                block          \
                                              UVSJ > splitter > TV           
                                                /
VHF > preamp > coax > grounding > coax > power >
ANT                    block            inserter

The first thing you must do is to use just the DB2E to get the locals OK. Then, add the VHF antenna with the combiner.

Bigbear 7-May-2017 2:59 PM

Thanks rabbit for the diagram. Now the only problem is finding a UVSJ. All the links I find lead to discontinued products.

Bigbear 7-May-2017 3:06 PM

Is this a UVSJ?
https://www.radioshack.com/products/...itter-combiner

JoeAZ 7-May-2017 3:13 PM

Bigbear, Another option might be to use a new, compact antenna for UHF/VHF
for your locals such as:https://www.walmart.com/ip/RCA-Attic...enna/146879296 or https://www.amazon.com/GE-29884-Outd.../dp/B01MYMVPVX Those antennas should provide satisfactory reception of RF 13 as well as your UHF stations. For your Canadian stations on VHF, continue to use your existing antenna, aimed at Montreal. Unless your RG6 cable runs are over 50 feet, you should not need
any amplification except perhaps a distribution amp. Run the two cables of
RG6 and use an A/B switch to change between antennas. I do
not favor combiners as they cause more problems than they solve.
Not the most convenient way but after installing antennas for 30 years,
it works best...........

rabbit73 7-May-2017 3:22 PM

2 Attachment(s)
Quote:

Originally Posted by Bigbear (Post 57916)

Yes. The last time I measured one, it performed well.
Quote:

Thanks rabbit for the diagram. Now the only problem is finding a UVSJ. All the links I find lead to discontinued products.
They are getting hard to find. Solid Signal is out and mjsales.net is out. There are some on Amazon and ebay. Antennas Direct still has them:
https://www.antennasdirect.com/store...Combiners.html

Inside the Antennas Direct UVSJ housing:

http://forum.tvfool.com/attachment.p...1&d=1494170120

MCM also has one, but I have received mixed reports about its reliability. Maybe I'll have to order one and test it.
http://www.mcmelectronics.com/product/33-2230

http://forum.tvfool.com/attachment.p...1&d=1494251768

If it gets any worse, we will have to make one like in the GE 34792 Attic Antenna:

http://forum.tvfool.com/attachment.p...9&d=1494003888

http://forum.tvfool.com/attachment.p...0&d=1494003908

I have used the conventional terms for top and bottom of the board. The top is where the components are mounted and the bottom is where the ground plane is located. In actual use, the coax connector faces down.

The GE 34792 Attic Antenna includes a REAL UVSJ, not shorting stubs, to keep the UHF and VHF signals separated before combining. Each section of the antenna has its own balun. The UVSJ and the well designed reflector are responsible for the good performance of this antenna.

Here is a circuit of a UVSJ by SM0HX (amateur radio callsign for a ham in Sweden). The UVSJ UHF/VHF Separator-Joiner belongs to the filter family of Diplexers. All UVSJs are Diplexers, but not all Diplexers are UVSJs; Diplexer is the more general term. A HLSJ is also a Diplexer, but for VHF-Low and VHF-High.

http://forum.tvfool.com/attachment.p...1&d=1494003982

The UHF highpass filter section has 3 series capacitors and 2 shunt inductors. The VHF lowpass filter section has 3 series inductors and 2 shunt capacitors.

Here are the curves for the Radio Shack UVSJ:

http://forum.tvfool.com/attachment.p...2&d=1494007033

Original post in RCA ANT751 thread:
http://forum.tvfool.com/showpost.php...1&postcount=40

ADTech 7-May-2017 5:34 PM

Quote:

Originally Posted by Bigbear (Post 57916)

Yes, it is. It passes power on the UHF port.

If you happen to have a RS store still open in your 'hood, you might be able to score one locally. Do call ahead, though, inventory is pretty spotty in the remaining retail stores.

Our UVSJ is still in production and is available. ;)

rabbit73 7-May-2017 8:25 PM

1 Attachment(s)
Here are the curves for the Antennas Direct UVSJ:

http://forum.tvfool.com/attachment.p...1&d=1494193827

Bigbear 8-May-2017 7:27 PM

thanks AD tech. but any idea where I can score one of your UVSJ's in NW Vermont?
Will the UVSJ allow me to install it at the pole ,connecting my existing antenna to the VHF side, and the new antenna to the UHF port, and run one cable into the house.

Very important question. Will sending a signal boosted by 30Db do physical harm to my Roamio?

ADTech 8-May-2017 9:11 PM

Quote:

thanks AD tech. but any idea where I can score one of your UVSJ's in NW Vermont?
You would have to order it, it is not stocked in any stores. Amazon, Solid Signal, our website, etc.

Quote:

Will the UVSJ allow me to install it at the pole ,connecting my existing antenna to the VHF side, and the new antenna to the UHF port, and run one cable into the house.
Yes, BUT you will only be able to amplify either the UHF-only signals from the UHF-only antenna or amplify everything. This is an important constraint and will not allow you to amplify ONLY the VHF as recommended.
Quote:

Very important question. Will sending a signal boosted by 30Db do physical harm to my Roamio?
No, it will not cause any harm to the tuner. Worst case, it will simply not work very well, if at all, as long as the overload condition persists.

Bigbear 9-May-2017 11:46 AM

Thanks
How do I order from your website? It's not obvious as to how.

Update: After removing the Roamio from the distribution amp, the issue with WCAX is lots better so I am thinking of leaving things as they are. If the over load were harming my DVR, then.....


Thanks for everything all

ADTech 9-May-2017 11:51 AM

Quote:

How do I order from your website? It's not obvious as to how.
Well, one would click on the button that says "Add to Cart", then "Checkout" on the next page that loads. ;)

Bigbear 9-May-2017 11:58 AM

Thanks I see that, but can't find a UVSJ, or where it may be located. The only combiner I can find is this https://www.antennasdirect.com/store...Combiners.html

I think I need the UVSJ to combine the signals in my basement after the power injector for the antenna pre amp.

ADTech 9-May-2017 12:19 PM

UVSJ stands for "UHF/VHF Signal Joiner" Same device, you have found the correct item. Marketing decided to call it what they did, we've been using the common acronym for it. Sorry for any ambiguity. ;)

Bigbear 9-May-2017 1:44 PM

Thanks
I was looking for a smaller one to mount in the basement. I was lead to believe that the Antenna Direct would not pass power to my antenna pre amp.
I think I was told to mount the UHF antenna pointer to my local channels and run a separate cable into the house and combine the cables "down stream" of the amps power tap. Is this not correct?

Thanks
Bear

ADTech 9-May-2017 2:18 PM

Quote:

was lead to believe that the Antenna Direct would not pass power to my antenna pre amp.
Please re-read my previous statements, they address this question.

Quote:

I think I was told to mount the UHF antenna pointer to my local channels and run a separate cable into the house and combine the cables "down stream" of the amps power tap. Is this not correct
That will work PROVIDED your existing VHF antenna also picks up the local VHF channel, even when aimed at Montreal. If it does not, then that station will be lost unless extraordinary measures are taken (custom components).

Bigbear 9-May-2017 6:45 PM

Thanks, I'm getting a little lost in the technology. I understand analytical chemistry instruments, but your world is foreign to me.
I have one local VHF channel that I currently can get ( quite well via the back side of my antenna). In looking at my signal analysis chart I notice that CTV channel 6 from Montreal is not shown. It comes in quite well with my current set up.
So this proposed setup using an un powered UHF antenna pointed at 111 degrees true azimuth will work.
The remaining confusion is regarding the power pass diagram for the signal combiner. It indicates the power will not be shunted to my existing antenna, correct? My assumption is that my existing antenna will be connected to the VHF input of the combiner. Am I way off base?

Thanks for your patience.

Bear

rabbit73 9-May-2017 8:11 PM

4 Attachment(s)
Many years ago TV sets had separate inputs for VHF and UHF. The UHF/VHF Separator Joiner was developed to separate the UHF and VHF signals coming from the antenna to feed the separate inputs for two tuners. There were also UVSJs that would combine two 300 ohm antennas for a 75 ohm input TV. Some TVs had two 2-screw 300 ohm inputs, and some had a 75 ohm coax input for VHF and a 2-screw input for UHF where you could mount a UHF loop.

Separate tuners for UHF and VHF. To tune to a UHF channel, you would set the VHF channel selector to U, and then rotate the UHF dial. The output of the UHF tuner was sent to the input of the VHF tuner:

http://forum.tvfool.com/attachment.p...1&d=1494355873

The 2 screws in the center are for VHF and have the internal antenna connected. The 2 screws on the right are for a UHF antenna:

http://forum.tvfool.com/attachment.p...1&d=1494356524

This UVSJ combines a UHF and a VHF antenna for a 75 ohm coax input TV:

http://forum.tvfool.com/attachment.p...1&d=1494355873

This UVSJ separates the UHF and VHF signals from a 75 ohm all-band antenna for a TV with separate 300 ohm UHF and VHF inputs:

http://forum.tvfool.com/attachment.p...1&d=1494355873

The common use these days is to combine a UHF antenna with a VHF antenna for the single input of current TVs, but the UVSJ is a reciprocal device that can be used to combine UHF and VHF signals OR separate UHF and VHF signals.

The UVSJ UHF/VHF Separator-Joiner belongs to the filter family of Diplexers. All UVSJs are Diplexers, but not all Diplexers are UVSJs; Diplexer is the more general term. A HLSJ is also a Diplexer, but for VHF-Low and VHF-High.

ADTech 9-May-2017 8:24 PM

Quote:

In looking at my signal analysis chart I notice that CTV channel 6 from Montreal is not shown.
Click on the "Pending" button. Industry Canada never fully updated their records that transfer into the FCC's system (which are subsequently picked up by this site's data gathering), apparently, when the Canadian digital transition took place

Also, make sure you are not confusing the virtual (displayed) channel number with the real channel number. For antenna purposes, we have to use the "real" channel number. CBMT-DT, for example, is operating on channel 21, not 6.

rabbit73 9-May-2017 9:01 PM

1 Attachment(s)
Quote:

In looking at my signal analysis chart I notice that CTV channel 6 from Montreal is not shown. It comes in quite well with my current set up.
CFCF CTV from Montreal is on real channel 12, virtual channel 12.1, unless all my research resources are wrong.
https://en.wikipedia.org/wiki/CFCF-DT

http://www.rabbitears.info/market.ph...&callsign=cfcf

https://en.wikipedia.org/wiki/CTV_Television_Network

http://forum.tvfool.com/attachment.p...1&d=1494360023

rabbit73 9-May-2017 9:40 PM

4 Attachment(s)
Quote:

So this proposed setup using an un powered UHF antenna pointed at 111 degrees true azimuth will work.
The remaining confusion is regarding the power pass diagram for the signal combiner. It indicates the power will not be shunted to my existing antenna, correct? My assumption is that my existing antenna will be connected to the VHF input of the combiner. Am I way off base?
You are not off base, you are correct. If you can not find a UVSJ with power pass on the VHF side, you must use two coax down leads like this:

Code:

                DB2E > coax > grounding > coax >
                                block          \
                                              UVSJ > splitter > TVs           
                                                /
VHF > preamp > coax > grounding > coax > power >
ANT                    block            inserter

If you can find a UVSJ with power pass on the VHF side, this would be the setup:

Code:

DB2E > coax >
              \
            UVSJ > coax > grounding > coax > power > splitter > TVs           
present      /              block          inserter
VHF > preamp >
Ant

If you look closely at the Radio Shack UVSJ, you can see the DC pass arrow going to the UHF port. This would allow you to insert a preamp between the UHF antenna and the UVSJ to amplify the UHF signals, but not the VHF signals, which is not what you need.

http://forum.tvfool.com/attachment.p...1&d=1494369089

The power pass for the Antennas Direct UVSJ is also to UHF.

The label on the Radio Shack pkg is misleading:

http://forum.tvfool.com/attachment.p...1&d=1494370999

It is described as a splitter for two components, which is not correct.

The Holland UVSJ passes DC to the VHF port, but there is no arrow:

http://forum.tvfool.com/attachment.p...1&d=1494470497

Notice that it says Separator so that it doesn't get confused with a splitter, as happened here on this thread, creating a heated discussion:
http://www.avsforum.com/forum/25-hdt...-combiner.html

Inside:

http://forum.tvfool.com/attachment.p...1&d=1494470497

I will try to find a UVSJ with power pass on the VHF side. If I can find one I will send it to you. Meanwhile, do a test with temporary coax lines and a second antenna for UHF to see if the plan will work.

Bigbear 12-May-2017 12:00 PM

After reading other posts about poor reception, how much does being surrounded by trees contribute to my issue? There are lots of trees between me and Mt Mansfield.

ADTech 12-May-2017 1:26 PM

Quote:

Originally Posted by Bigbear (Post 57938)
After reading other posts about poor reception, how much does being surrounded by trees contribute to my issue? There are lots of trees between me and Mt Mansfield.


That would have been good to know much sooner. I did point out (twice) that we didn't know any details about your signal path (among other things).

If trees are in the signal path, take any prediction made by the simulator and throw it out the window. Then, go outside and stomp on it a few times. For good measure, dig a hole and bury it. Then put a really big rock on top of it. The simulator's predictions are dead and buried since they are useless and no longer apply.

I've personally visited a location what was less than 5 miles from a million watt UHF tower, and measured a >50 dB reduction in signal power when moving a mere 50 feet from a spot with LOS to one behind a mature wet silver maple tree. When the wind blew, the signal looked like it had gone through a shredder and reception failed.

Bigbear 12-May-2017 2:29 PM

Ok, I'm sorry that I omitted the thing about the trees. Most of them are not mine so there is nothing to do about it other than to install the antenna on a 200' tower.
It must still be an issue with the roamio as the issue is with it only, and not the other 2 TV's in the system.
Guess I'll monitor for a while as by taking the Roamio off the distribution amp things have gotten better.

Again sorry, and thanks for all your help.

Tower Guy 12-May-2017 2:54 PM

the combination of trees and a mis-aimed antenna is killing you. One or the other by itself only works sometimes.


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