Interference Sources on OTA, Radio, WiFi Signals

[JamesK]

I believe the issue was interference to reception. Powerling induced "hum bars" haven't been an issue for a long time and that's also why NTSC was set to have a field rate matching the powerline frequency. By doing so, the visible effect of those bars was minimized. Also, the bars were a result of deficiencies in the set's power supply, not interference received via OTA.

[pshelston]

Hello,

I live in Toronto on a street with streetcar service and everytime a streetcar goes by I get some loss of signal on CFTO-DT (Ch 40) and also some fuzziness on CIII-TV analog (Ch 41).

Any ideas how I can reduce the impact of this interference? It doesn't appear to be affecting other channels (at least not that I notice).

[roger1818]

Originally Posted by pshelston

I live in Toronto on a street with streetcar service and everytime a streetcar goes by I get some loss of signal on CFTO-DT (Ch 40) and also some fuzziness on CIII-TV analog (Ch 41).

Any ideas how I can reduce the impact of this interference? It doesn't appear to be affecting other channels (at least not that I notice).

Looking at your previous posts I gather you have a hacked CM4221HD, Kitztech amp and a couple UVSJs to filter out VHF. Are the UVSJs between the antenna and the amp or the amp and the TV?

If the streetcar is producing RF noise directly on channels 40 and 41, there isn't much you can do about it other than move the antenna higher to get it further away from the streetcar.

More likely it is producing noise at a lower frequency and the amp is generating harmonics on UHF. That is the biggest issue with the Kitztech is I gather it only has one amp for both VHF and UHF so harmonic distortion from VHF signals can appear on UHF. Having a UVSJ before the amp should fix this problem, if you aren't already doing this.

Another option is it is generating noise on the powerline (though I would think it would be on a separate circuit). Making sure both your amp and your tuner are plugged into good RFI filtering power bars should fix it in this case.

[stampeder]

Just adding that you might want to ask in the Antenna R&D forum how to build a cheap, simple, small UHF Yagi antenna optimized only for channels 40 and 41, aimed right at the CN Tower with no amplification. The idea is to have an antenna that "sees" only straight forward but almost nothing from the sides or back. Mixing that in with your existing antenna is a topic we could help you with later if you want to go that route.

[Jase88]

I'm getting some low-VHF interference in the Toronto direction...it only seems to hit at night, so I'm starting to suspect street lights.

I may have to do some late-night target practice with a pellet gun to confirm (just kidding).

[Jase88]

@pshelton: You're probably close enough to the CN tower that you could angle your antenna up sharply. I wonder if this would provide enough front-back isolation to reduce/eliminate the interference?!

[pshelston]

Originally Posted by roger1818

Looking at your previous posts I gather you have a hacked CM4221HD, Kitztech amp and a couple UVSJs to filter out VHF. Are the UVSJs between the antenna and the amp or the amp and the TV?

If the streetcar is producing RF noise directly on channels 40 and 41, there isn't much you can do about it other than move the antenna higher to get it further away from the streetcar.

More likely it is producing noise at a lower frequency and the amp is generating harmonics on UHF. That is the biggest issue with the Kitztech is I gather it only has one amp for both VHF and UHF so harmonic distortion from VHF signals can appear on UHF. Having a UVSJ before the amp should fix this problem, if you aren't already doing this.

Another option is it is generating noise on the powerline (though I would think it would be on a separate circuit). Making sure both your amp and your tuner are plugged into good RFI filtering power bars should fix it in this case.

Actually, I didn't get any better results with the Kitztech or with the UVSJ so I removed everything to simplify.

All I have now is the 4221HD (mild hacks) -> ~40' -> grounding block (ground to water faucet) + surge suppressor -> 8' -> TV.

Is there any way to tell if I'm getting noise on the powerline? On analog ch 37 & 41 the interference manifests itself as a rapid flickering/dimming.

Originally Posted by stampeder

Just adding that you might want to ask in the Antenna R&D forum how to build a cheap, simple, small UHF Yagi antenna optimized only for channels 40 and 41, aimed right at the CN Tower with no amplification. The idea is to have an antenna that "sees" only straight forward but almost nothing from the sides or back. Mixing that in with your existing antenna is a topic we could help you with later if you want to go that route.

That's an idea... I'd hate to have to deal with this during the olympics. The only part I'm wouldn't be looking forward to is the mixing

Originally Posted by jase88

@pshelton: You're probably close enough to the CN tower that you could angle your antenna up sharply. I wonder if this would provide enough front-back isolation to reduce/eliminate the interference?!

Wouldn't that affect my Buffalo reception, though? Right now the CN Tower is on the right side of my antenna and Buffalo is straight ahead. The street car line is right between me and Buffalo.

[intravino]

Hi,

I been having the short interference on my UHF channels since about 2 - 3 weeks here at my location.

My setup is an outdoor original cm4228, cm7777 and TiVo HD. Everything is grounded.

I ran the TiVo signal meter during the short busts of interference and you see on the meter that signal goes way down for less then a second. It's random but it occurs every 15 minutes on average.

On the strong channels like WCAX 3.1 (R 22), WPTZ 5.1 (R 14) and WCFE 57.1 (R38), you just see a minor spot on the screen.

On the weaker channels like WFFF 44.1 (43), you see a major pixelization on the screen.


Where do I start to test this?

Electrical noise?

Ground problem, something that got loose?


Thanks,

[ProjectSHO89]

Without a spectrum analyzer, it will be pretty tough to isolate the source.

Turn off all communications in equipment in the home first. Cell phones, two-way radios, everything. Park the cars down the street a ways.

You can start in your own home by switching off every circuit breaker except the one required to operate your set. If it's still there, switch the receiver system to a different circuit and then switch off the original. If the problem is still observed, it's coming from outside your home.

[intravino]

If the problem is still observed, it's coming from outside your home.

Thanks for the infos.

If it's coming from outside, can I try a filter?

Should I try one that cuts the lower frequencies or upper frequencies ( on top or low then then TV frequencies ) ?

I going to try the electrical or home frequencies test first.

Can this come from the receiver itself (defective tuner) ?

Thanks,

[KRToronto]

Hello,

Is anyone experiencing complete disruption with the helicopters over the city (Toronto)?

I think it may be due to the Occupy Toronto demonstrations...but it is constant and rendering my TV blacked out or broken up for much of the afternoon and early evening as I write. This is so frustrating!!

thanks... don't know if anything can be done frankly!

[majortom]

it's kinda like the chicken and the egg,
Can't really propose a solution, until you find the source.
But if ya can find the source, there may be no need for a solution
Cause if ya could find it, u'd eliminate it

Did it just start recently? Been kinda windy in the northeast lately.
Could it be Electrical powerlines blowin in the wind?
What happened when ya tried the kill all breakers except the one powering your TV tuner???


Recently I found a bad porcelain light fixture in my basement. Replaced it
because the pull chain switch was broken. Low and behold one of the wirenuts
had a loose wire, occassionally arcing. Fixing that didn't solve anything here,
but it certainly eliminated one potential source.

[intravino]

Did it just start recently? Been kinda windy in the northeast lately.

2 weeks ago about. It's not the forced air furnace and it's not the fridge.

I just noticed it on UHF. I have to do tests but my wife is recording 4 hours per day with the TiVo so I cannot do it in the evening.

Thanks for your info and I will report what I find.

[Jase88]

KRToronto, I live near a hospital which routinely has helicopters arriving and departing, often flying over my home. Can't say it's ever impacted my reception. Though these are medical helicopters, and not likely broadcasting TV signals like the ones near your home are.

I'm not aware of which frequencies are used by news helicopters to carry their TV signals, nor what sort of strength they operate at.

It's possible the frequencies are near those used for conventional television, and thus it's overloading your tuners. Perhaps someone that knows more about these systems aboard news helicopters can comment...

[JamesK]

^^^^
Remote links are on microwave bands. Take a look at the antenna on the mobile trucks the TV stations use.