Summer - Interference problems


Tablo Support guys help me understand some pixelation problems since the first week of june.

Problems seem from interference.

What should I do?

I made some searches and I think I could first try adding an LTE Filter like the CM-3201 or maybe go stronger with amplifier and the FM Trap of the CM-7778.

I am 8 miles from the Towers.



8 miles? The only reason you’d want any kind of amplifier is for handling a large number of splits. Just saying…

Do you have any trees between the antenna and the broadcast towers? Swaying leaves will cause interference with any kind of breeze or wind. Even a tree 50 feet from your house.

@cjcox: Well, the interference / pixelation problem is worst when connected to my Tablo 4 tuners than my TV Tuner. I thought that maybe the Tablo’s splitter could need some more power gain?

@MarkKindle: Yeah, I’m living in suburb. So there is a lot of trees in the path. I have 4 channels, 3 are ok (UHF) but the only one in VHF is the worst.

My problem doesn’t seem to be the signal strength, all channels are 80%+ according to my TV tuner. I’m looking for a way to improve signal quality (don’ t know how to check it). That’s the idea behind adding the 4G LTE Filter, see if it can helps or no, maybe just waisting 50 bucks…

You could try a distribution amp such as the Channel Master 3412 or 3414 which will not overload your tuners as these only add 4 to 8 db per output. I use the 3414 with strong antenna signals to smooth out the distribution across 4 ports to different devices.

The LTE filter is irrelevant to VHF - it only applies to the upper UHF frequencies. If anything can be disruptive of VHF it is close, strong FM radio signals. An FM filter can alleviate that problem.

VHF is the signal type most susceptible to noise and interference. As well a strong signal can be open to interference. Your problem can very well be the trees which come out in summer.

The VHF addon your antenna has is not the strongest VHF antenna type. You could try another VHF antenna separate from your existing one to penetrate the trees with more directors (such as a VHF Yagi). Or move the existing antenna high enough to clear the trees.

My post was just in case you’re overloading the Tablo (too much amplification). However, I live Texas where our mountains are best described as the overpass of the highway. So, for us 8 miles is incredibly close and there would be almost no interference.

Low VHF (Ch 2 - 5) are also highly vulnerable to sunspots, particularly in the summer. The lower the channel (ie: Chan 2), the higher the interference potential. Sunspots will not always affect all channels in the low VHF band. This problem will exist as long as a market still has channels on the low end of the VHF band. Most cities still with low-VHF signals will lose them during the upcoming “re-pack” in the USA.

I am in Canada (Quebec), the problematic channel is 8.1 (TVA).

@MarkKindle: I think I could try the CM-3412 with an FM filter. Any FM filter you would recommand?

For your info, here is the TVFool report:

Being in the US, I order them from AntennasDirect. Radio Shack used to carry them. Any one will do really - they’re all the same.

Looking at your antenna, the VHF portion can be strengthened. It appears to be an open rod. You could double its size by getting something like copper refrigerator coil, cutting it to match the size of the VHF rod, and inserting it at both ends to form a semi-circle. Like this:

Just out of curiousity do you get any Vermont channels?

No, Vermont is 300km from my home!

For some reason I thought you were in Montreal until I looked at the TVFool report and realized you weren’t getting any Montreal channels. My advice would be to get the CM-3412 and not get the FM filter. See if the signal strength is smooth from just the CM-3412.

TVFool also runs FMFool which would show you if there are any strong FM stations near you.

BTW are you pointed to the 4 stations closest at about 88 degrees? Or are you trying to get those stations also at 190 degrees?

@MarkKindle: The FM stations are probably in the same towers, here is the results from FMFool:

I pointed the antenna noth-west at about 90 degrees. I admit that I didn’t know which one I should use (azimut (true) or magn?

Thanks for your help, I really appreciate!

Try magnetic north (103 degrees). In an attic installation every degree counts. Also different places in an attic may give better results. Try not to point through aluminum ducts. I’ve used my cell phone using its compass app.

You can even try augmenting the VHF rod by adding aluminum foil to it. Sometimes that works to strengthen a VHF receptor… Another trick - put a long rod or pipe (40 to 60 inches long) behind the VHF rod to act as a true VHF reflector (this may add as much as 3 db to it). You can just tape it to the screen behind the director elements directly behind the VHF element.

Thanks, I will try it this evening.

Strange thing is that my VHF channel is the stronger (98-100%) according to my TV Tuner (frequency meter).

Will the foil help for signal strength or quaity?

The foil was to help with signal strength. However if the VHF signal is already at 90-100%, that is strong enough. Something else may be interfering with it. However you say the pixelation is only on the Tablo and not the TV tuner?

If it is OK on the TV tuner, then somehow the Tablo is either losing the signal strength or something is interfering with the signal WHEN it enters just the Tablo. Even if the Tablo splits the signal 4 ways, the initial 100% should be sufficient for a 4 way split.

If the cable goes directly into the Tablo and there is no split, does it still pixelate on the Tablo?

We’ve seen at this forum, when the Tablo isn’t sufficiently ventilated, as it grows hotter and hotter, it screws up the incoming signal. How hot is your Tablo?

I’ve seen pixelation from the TV Tuner too, but it is worst on the Tablo. That’s why I thought that maybe the splitter was part of the problem. But I know for sure that there is some kind of interference, I will check again the antenna position first.

The cable is directly into the Tablo. I tried putting the Tablo on blocks to help the ventilation, but no effect. Maybe I should try stopping the Tablo for a while and boot it again and see what happens.

Are there any metal structures such as pipes or air ducts or a furnace in the attic near the antenna that could reflect a signal and cause multipath?

Degradation of ATSC signal in summer is normal/expected.
Humidity in the air as well as live/wet leaves on the trees are contributors.

Amplifying is unlikely to help, especially at 8 miles from towers.

I’d say “just wait until late fall and the signal will be fine” but obviously that is not really a solution. You could try pointing the antenna horizontally a couple of degrees away from the troublesome transmitter. This will reduce multipath interference as well as overall signal strength - you may find a “sweet spot” . Additionally try pointing the antenna slightly upwards by a couple degrees - (same idea, try to find a sweet-spot).

I’ve tried all the above antenna pointing stuff in summer, as well as preamplification. Nothing solves the problem reliably for me, but I am about 50 miles from the troublesome xmitters. So my “solution” to this same problem since 2001 has been to subscribe to comcast TV service, without renting any equipment from them (they provide a cablecard for free).

At any time the signal strength may stay the same but the signal-to-noise ratio may decrease. As the signal-to-noise ratio deceases further below 20db the higher the number of uncorrected errors the tuner tries to handle in the OTA data stream.

Luckily I have a newer Sony that can display signal strength, signal-to-noise ratio, and errors.

I just moved my antenna a few degrees to get one channel’s hi-vhf signal-to-noise ration from 17db to 20db. Thus reducing the uncorrected error rate to almost zero. Of course this can affect the other channels.

ok guys, I am confused…

Antenna is pointing NW 103 degrees.

Now the cable is connected to a splitter and then in the TV and Tablo.

Watching the same VHF channel… TV is fine, Tablo has pixelation. Same thing on iPad, iPhone and Roku. But TV from antenna is fibe.

What should I do?