Out of band signal rejection

I’m wondering if anyone has any experience from a technical standpoint on the out of band signal rejection on the tuners used with the Tablo. I often have commercial airplanes fly pretty much right over the house on approach to Phoenix and they will often key up their radios. Looking at the spectrum analyzer they become the strongest signal by far when they do this. My outdoor VHF Hi / UHF antenna loves these signals at around 120 Mhz.

Has anyone had any experience with how well the Tablo handles out of band signals? I can build a notch filter to drop these VHF signals from the airplanes way down, I just don’t really want to unless I need to. I’ve noticed some shows failing commercial skip due to poor reception and I question if it’s not related to glitches caused by air traffic. I don’t think they would be causing any multi-path reflection issues, but that’s also possible, just not highly likely based on the position of the aircraft in relation to the transmitting towers 17 mules (err Miles) away.

I don’t have any technical reasoning to it - don’t live anywhere near an airport. When small plane fly by - as determined because I can hear a plane. My TV signal at times will distort (digitally speaking) for a moment.

This has been happening virtually forever, NTSC days as well. I haven’t attributed any issues from it to my tablo - extremely rare do I have segmented recordings (I do sometimes) but can’t confirm nor deny there was a reboot.

This can be caused by the radio signal your trying to receive being bounced off the airplane and returned back to your antenna out of phase with the original signal. When this happens the out of phase signals cancel each other out. The amount of this effect will change based on the distance the aircraft is from your antenna and the wavelength (channel) being received. In the old days this would have looked like a pulsing in and out signal or ghosting. Literally receiving the same signal multiple times. Primitive radar if you will…

I live in an area where the U.S. Air Force has an AWAC plane flying overhead 24/7/365. This plane is full of electronics gear including a radar dome. They vary their routes, but generally fly directly overhead multiple times each day. In the days of analog TV, I could always see when an AWAC was flying overhead because I would see multiple images on the screen from multi-path interference. Today with digital TV, I don’t see multiple images, but it still may be a cause for degrading the signal quality enough to distort the signal. I replaced my old yagi antenna with an Antop AT 400-BV and since then I’ve experienced fewer segmented recordings and a higher rate of commercial skip processing properly.

To fully enjoy using your Tablo, a good antenna providing a clear and strong signal and a great SNR is extremely important. I believe that the reason many of the people on this forum are happy with their Tablo is that they have a good antenna and a rock solid wifi/ ethernet network. When rf or wifi signals are borderline, you can’t expect the Tablo to work perfectly all the time.

Isn’t 120 Mhz the band assigned to air traffic control?

The quad uses the newer MaxLinear tuner and demodulator. You might be able to find it’s specifications.

I would agree that a good signal is important and well WiFi most people have home grade routers that hardly work at all. Signal wise I’m on the other end, I actually may have to attenuate the signal a bit as I’m right on the edge of what Tablo’s website calls too strong. In some cases I’m seeing channels at -38 dbm which is pretty strong. This is from the spectrum analyzer which of course most people don’t have the luxury of using.

I’m actually thinking a good omni directional might be a good choice for me, at the moment I’m using one of these “RCA” outdoor antennas. They claim 70 miles in the actual details…whatever.

It’s complete overkill for only being 17 miles from the towers I care about. It’s line of sight based on tvfools report. Getting a bit off topic.

Yes, they are on approach talking to the tower. They love to key up right on top of my house for some reason. Do you happen to know the part number on that tuner? I failed to note it while I had everything apart and don’t really want to tare it all down again. New thermal pads and such all in place and would rather not have to disturb them.

You can probably google tablo/maxlinear for results. But I would suspect it might be hard to find an off the shelf filter for 120 since it’s in the band for the emergency radio channel.


“most people” are consumers, buying consumer grade - home routers - the several I’ve had worked, but I can’t account beyond that. This device is marketed for/to “most people” with home grade equipment. :neutral_face:

tvfool.com is severely out dated and aptly maintained image
When I enter my info there are stations missing and incorrect when compared directly with FCCs DTV Reception Maps. There are other sites offering credible, current information for antenna suggestions.

I can build one pretty easily that’ll do the job, probably go from 88 - 170 Mhz and just drop that entire area down 25db or more. Looking at the mxl608 specifications it appears to have really good out of band rejection, i.e. what your not tuned to. I didn’t find any details on the mxl603 specifically which it appears the quad uses.

I also thought about just making a band-pass for 170-600 Mhz. Bit more work component wise but not really difficult either. I can 3D print an RF shielded shell, or just reuse an old filter housing.

Can you make something to monitor the power line usage of the TV, and occupancy/audio sensor. So like if it can tell the TV has been left on, and there’s no longer any audio coming from it nor anyone in the room - send some alert reminding them to turn it off?

As difficult as it may be, figuring it out on their own is overly complex.

Yah it’s called turn on the sleep timer on the TV.

Something like that could be built, not that difficult. The problem is if you have a smart TV where the app is internal, would need to either capture audio from the SPIF optical out or HDMI ARC channel. Once you have the audio either a simple micro or just a basic long delay analog timer that’s reset via presence of the audio signal is pretty easy.

Really though, sleep timer is the simple solution.

Hopefully it will work.

I watched the documentary, “Close Encounters of the Third Kind”, and it seemed that large low flying objects can cause problems.

you would think…

I made a notch filter to drop out the FM band all the way up to 160 Mhz, It’s not the best however it’ll kill off 25Db. It’s a bit bumpy as well, still it’ll do the job. Funny thing is I housed it in a DirecTV B-Band converter.

This is a good web-page for designing such items. For tuning I used my SA with a tracking gen.