Cell Phone Interference?
 

I am not too sure if this is the issue I'm having.

I can get many stations from Los Angeles pretty well, but occasionally a couple weak UHF ones the signal bounces from 50% to 0% during the day and sometimes NO signal at night.
Someone suggested possible cell phone 4G LTE interference and that I should try a 4G LTE signal filter.

Is this a common issue here in the USA now and what frequencies need to be filtered out?

I am behind a couple mountains and picking up transmitters from Mt. Wilson in LA county and also stations in the Inland Empire.

The ones I seem to be having issues are:

KTBN 33 (40.1)
KMEX 34 (34.1)



http://www.tvfool.com/?option=com_wr...e2cb74ea324603

Welcome, jerrymc

Where is your antenna located?

Those 2 channels are very weak and require a high gain antenna aimed at them. There is also a mountain in the way and your location is pretty much in a dead zone for them.
http://www.tvfool.com/?option=com_wr...ALLTV%26n%3d38
http://www.tvfool.com/?option=com_wr...ALLTV%26n%3d37

If your 7777 is the new 30 dB version, it overloads very easily with strong signals; even with a partial overload it will make it more difficult to receive weak signals.

Cell tower interference is possible to UHF channels. Their transmitters are moving into the frequencies just above TV channel 51. Different carriers use different frequencies.

https://www.google.com/?gws_rd=ssl#q=4G-LTE+Filter
https://en.wikipedia.org/wiki/4G-LTE_filter

frequencies
https://www.google.com/?gws_rd=ssl#q...frequency+band

http://www.wpsantennas.com/cellular-...formation.aspx

more filter info
http://www.avsforum.com/forum/25-hdt...l#post31466817

Filters are now becoming available, and some preamps have one built-in.

You could try one of the external filters to see if it will make a difference in your area.

The best tool to check for cell transmitters just above UHF TV is a spectrum analyzer, but most people don't have one.

Going from 50 to 75 feet doesn't seem to make a lot of difference for your problem channels.

You have some strong FM transmitters in your area. FM interference to TV reception affects the VHF-High channels before UHF channels. I not sure if the FM filter in the 7777 is sufficient.


http://www.fmfool.com/modeling/tmp/b...7/Radar-FM.png

You are allowed to have a 75 ft tower in that area?

Sorry, it's on my second story roof.
Second pic is view towards Mt. Wilson. LACO (to the left of that peak is 279W)

https://drive.google.com/open?id=0B6...jcyZ1pFY2lRSFk

https://drive.google.com/open?id=0B6...zRWNkxTTUhLSzg

I also have a CM-3410 dist. amp in the attic because I have 5 rooms hooked up and 2 splitters downstream. (I did try omitting the dist. amp, but I did notice some channels began dropping out (pixelating) even without ANY splitters.


I'm using a cheap RCA DTV/PVR to tweak the signals because all of my TVs have crappy signal strength meters...

https://www.walmart.com/ip/RCA-Digit...TSj14d5LWPSNOQ

Thanks for the interesting photos.

Do you get NBC and CBS?

It's a shame that you have to use an RCA DTA880 to tell you what the TV should tell you. I like the Diagnostics Screen on my Sony TVs that gives me signal strength, SNR and uncorrected errors.

I'm surprised that you can use a 7777 & a 3410 without tuner overload. I would have thought you would need a single channel bandstop filter to attenuate KVCR.

LOL...No. I just input different heights to see if it makes any difference, but it does not...

If only I lived up the street; those homes get a clear view of San Diego and Palm Springs as well as Mt. Wilson...

CA has been building homes so F%#$^ close to each other that each home blocks towers, the Clarke Belt, as so forth...

NBC and CBS come in very strong. 60~70%

KVCR is in the other direction, so the signal it very well even though I'm pointed away from it...

The RCA box is pretty good for $40, and I've tested the HD recording with old SATA hard drives and it's crystal clear. I just don't like leaving the power plugged into the HD 24/7. The box even has a program guide! Something my Vizio LED, Panasonic plasma, and Sceptre 4K TVs do not.

Well, I supposed I can climb in the attic and remove the 3410 again to test... :confused:

Sorry, didn't mean to worry you. Your tuner will tell you if the signal is good enough. Your signals could be weaker than predicted in the report, which is only a computer simulation.

No worries.

I just was wondering why the signal jumps from 50% to 0% back and forth only on those channels.

The FM trap in the 7777 pre-amp has always been in the "In" or ON position. IE: I never opened the box where the switch resides...

Is it possible I have co-channel interference?
I noticed a Virtual 40.1 on Real 40 and it's rather close but at 59W.

I set up for a friend's mom in Ontario, CA this antenna a couple months ago.
http://www.solidsignal.com/pview.asp...u=700112818400

She now gets many more stations than I, but she doesn't live in the foothills. :(

http://www.tvfool.com/?option=com_wr...e2cb5ab3bd0e14

That antenna is primarily for UHF, but will receive VHF-High if the signals are very strong. Does she get Fox, MyN, and ABC on real channels 11. 13, and 7?

OTA signals constantly vary in strength. Since they are so close to the "Digital Cliff" it doesn't take much change for them to drop out.

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

http://forum.tvfool.com/attachment.p...7&d=1465958114

http://forum.tvfool.com/attachment.p...8&d=1439497644

A Fade Margin of 10 dB is needed to allow for changes in signal strength, but those signals don't have it.

Very interesting! I will study these charts.

She does get EVERY single station and channel from the VHF-H range and when I tweaked the antenna, she gets many at 100%.
I did install an RCA pre-amp that I had used at my place a year ago.

She mostly speaks Spanish so she's thrilled that she no longer has to pay Verizon/Frontier $200+ for local channels, local phone, and FIOS.
I set her up with Free Google Voice and a $40 obi200 device and got her down to $45/mo. TOTAL :p

Yes, but only with the channels on real channel 40. KPCD and KRMV will not interfere with KTBN on real channel 33. However, there is a red C next to the KTBN callsign indicating co-channel (same channel) interference from another 33, but I don't see it listed.

You are on the edge of a dead zone for KTBN coverage; no color, no signal:

http://forum.tvfool.com/attachment.p...9&d=1472699920

http://forum.tvfool.com/attachment.p...1&d=1472700580

Hello Rabbit73:

Thank you for your help...

I am having weird dropouts during the day around 2-5pm when the sun in beginning to set, even though the stations have plenty of signal strength.
(This is something new AFTER I relocated the antenna from the ride corner of the roof to the left side. The reason I relocated it was because after my neighbor recently made an addition to his house, I noticed I got weaker TV signals. Maybe his new roof was reflecting the signals away from my antenna..?)

I created a video to show what it's actually doing.

https://youtu.be/TlSgsIUh-bw

Do you think this is LTE interference?

Thanks for the video showing three channels and signal quality, which looks more like signal strength.

KCAL real channel 9, NM 6.4 dB, weak signal on RCA and pixilation
KNBC real channel 36, NM -10.2 dB, strong stable signal
KABC, real channel 7, NM 8.6 dB, weak signal on RCA with pixilation and dropout

Is KTTV Fox affected? Is KCOP affected?

I don't think it is cellular transmitter interference which is more likely to affect UHF before it would affect VHF reception.

In your video VHF reception is affected, but not UHF. There might be another reason why VHF is affected but not UHF that is still unknown.

You should consider possible sources of VHF interference.

If the antenna is outside, the coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge, but the system will not survive a direct strike.

Notice that reject interference is in bold type. You might have a local source of interference like power line noise, strong FM signal overloading preamp, strong FM signal not sufficiently attenuated by FM filter in preamp, or EMI from a neighbor's solar system inverter.

I suggest you listen for electrical interference on an AM portable radio tuned to a vacant frequency first at the low 550 kHz end and then at the high 1600 kHz end. A portable radio tuned to FM doesn't work as well, but a portable radio that can tune VHF aircraft control frequencies will work because that is AM.

http://forum.tvfool.com/attachment.p...9&d=1441917363

There is one experiment that might be worth trying. Insert a HLSJ, common and high ports, between the antenna and the input of the preamp. This will block signals below channel 7, including the FM band.
http://www.solidsignal.com/pview.asp?p=zhlsj

Even if your antenna is aimed away from KVCR, I still think it might be too much signal for a 7777, assuming your tvfool report is an accurate prediction of the signal strength arriving at your antenna.

Is the HLSJ the same as this combiner?

https://www.walmart.com/ip/Channel-P...2-Way/19622660

I need to properly ground everything because the only thing grounded currently is the coax and that's in a box on the side of the house where I have a splitter to send feeds to 2 rooms. (Leftovers from TWC)
The other splitter is in the attic for the other 3 rooms...

Once again thank you for your expertise Rabbit! :D
RABBIT

No. The CP-2532 is a simple splitter. The HLSJ, is a frequency-selective splitter/joiner where each port admits only a certain range of frequencies while rejecting others. The HLSJ allows for combining different-band antennas without interference and minimal loss and may also serve as either a high or low pass filter when used as prescribed.

Ha, Ha; thanks for the link to the Bugs Bunny Broomstick Bunny video.

ADTech is correct. The high port of the HLSJ is a high pass filter that will only allow signals above a certain frequency to pass.

Take a look at the high port curves of these two HLSJs:

http://forum.tvfool.com/attachment.p...1&d=1473349418

It is probably OK to use leftover coax, but anything else might introduce a problem. I'm wondering what exactly is connected to what in your antenna system? Is it like this:

or is it like this:
I'm confused by your description.

KCAL real channel 9, NM 6.4 dB, weak signal on RCA and pixilation
KNBC real channel 36, NM -10.2 dB, strong stable signal
KABC, real channel 7, NM 8.6 dB, weak signal on RCA with pixilation and dropout

Are KTTV Fox 11 and KCOP MyN 13 affected the same way that KCAL and KABC are affected?

Which way is the antenna aimed in the photo?

Is it aimed at the solar panels?

Does the photo show the new location?

Is the left side on the NW or SE? Maybe you could send me a satellite image of the antenna location in a PM, or I could send you an image with my guess marked.

Does the corner point to the east?

Thank you for the clarification by PM. I have a better understanding of your antenna location; not as close to the solar panels as I thought.

If you are wondering about my concern with the 7777, here is the math:

your report for reference:
http://www.tvfool.com/?option=com_wr...e2cb74ea324603

KVCR Noise Margin is 61.2 dB + antenna gain of 13 dB = NM 74.2 dB, which is overload when the antenna is aimed at KVCR. When it is not aimed at KVCR, the strength of the signal depends upon the antenna pattern.

http://forum.tvfool.com/attachment.p...6&d=1471824123

Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html

KVCR has a signal power of -29.6 dBm = 19.4 dBmV

Max input of the 7777 = 15 dBmV
http://www.channelmaster.com/TV_Ante..._p/cm-7777.htm
Even without adding ANY antenna gain, KVCR will overload the input of the 7777.

KVCR signal power = -29.6 dBm

-29.6 dBm + ant gain 13 dB + preamp gain 30 dB = +13.4 dBm; tuner overload

even without adding antenna gain
-29.6 dBm + 30 dB preamp gain = +0.4 dBm; tuner overload

This calculation assumes that the tvfool report is accurate for your location, which isn't always true. But, it is necessary to be aware that a small amount of overload will affect the reception of weak signals even if the strong signals are not affected.


ATSC Recommended Practice:
Receiver Performance Guidelines
Document A/74:2010, 7 April 2010

RECEIVER PERFORMANCE GUIDELINES

5.1 Sensitivity

5.2 Multi-Signal Overload

You should not need to use the 7777 AND the 3410 with your signals, which is why I asked about how your equipment is connected.

When the antenna is aimed at KCIO:
-57.7 dBm + ant gain 13 dB + 30 dB preamp + 15 dB 3410 = +0.3 dBm; tuner overload

Looking at your FM signals, KDEY-FM has a signal power of -23.6 dBm:
http://www.fmfool.com/modeling/tmp/b...7/Radar-FM.png

The 7777 says FM trap >15 dB

-23.6 dBm - 15 dB trap +30 dB preamp + 15 dB 3410 = +6.4 dBm at the tuner input

KDEY-FM is on 93.5 MHz; its 2nd harmonic is 187 MHz which falls on channel 9 (186 TO 192 MHz), which makes interference possible.

Testing for DTV Interference
http://www.tvtechnology.com/expertis...ference/202503

Hi Rabbit:

A couple years ago I had the RCA ANT751 antenna with the RCA TVPRAMP1R pre-amp. I had decent signals from Mt. Wilson, albeit many upper UHF stations barely came in.

I decided to get the larger antenna and better/stronger pre-amp and I do get many more stations from Los Angeles.

KVCR is not a station we watch. If that's the issue with all the other stations, can I block KVCR's signals? (91.9Mhz) AND The FM signals in that range?
(I cannot tell you how many times I climbed that steep roof just to tweak the antenna!)

I just received my LTE filters from the UK but I do not think this is the correct range here in the US.
(Frequency range : VHF 5 - 300MHz (400Mhz trap)
Frequency range : UHF 470 - 790MHz)
LTE TV Filter

Many Youtube videos I see regarding LTE and OTA TV interference are from Australia and Europe. I read that US LTE will soon be utilizing the 600Mhz range which seems to cut into many stations here in the So. CA area. :(

I am going to remove the 3410 dist. amp and try out the LTE filter this weekend. I already grounded the coax, but still need to purchase and ground a new shorter 18 galvanized pole.

Does the 7777 pre-amp have a sufficient FM trap?

I will study the reports you sent this evening and once again, thank you very much for your help! :D

Thank you for your reply with further background information.

It is not necessary for you to quote my whole post.:)

Your present antenna has much more gain than the RCA ANT751, and it is larger because it has more gain and it also covers real channels 2-6 VHF-Low, which may or may not be important to you.

The HLSJ will block everything below TV CH7 including the FM band and CH 2-6, but it will not block KVCR. That would require a custom band stop filter for real channel 26 from Tin Lee Electronics (expensive) or from Jan Jenca (less expensive) in eastern Europe who sells on ebay.

http://www.tinlee.com/index.php
http://www.tinlee.com/NotchTraps.php...ategory=offAir

http://forum.tvfool.com/attachment.p...1&d=1473471644

If you want to experiment, you can try a notch filter that removes 24-29.
ChannelPlus ModelNF-471 Notch Filter
https://www.amazon.com/Linear-NF-471.../dp/B000J3AEYA

The Jan Jenca ch26 filter would probably be about the same price, but is a custom order from Slovakia.
http://www.antenne-komponenty.eu/eng...zlucovace.html
they also sell combiners
http://www.avsforum.com/forum/25-hdt...l#post37732809

When the aim is that critical for the 277-281 degree LA channels, that might be an overload symptom.

It is balancing act, between the strongest and weakest desired channels, which is called the dynamic range. You went from a low gain antenna with a medium gain preamp to a high gain antenna with a high gain preamp. The best compromise might be a high gain antenna with a medium gain preamp, but it might require further experimentation by you. I suggested the HLSJ because it is an inexpensive and fairly easy first step.
Your thinking is correct, passing up to 790 is too high. TV channel 51, our present highest channel, is 692 to 698 MHz. The Channel Master LTE filter seems more like what is presently needed in the US, but only if there are cell transmitters just above CH51 in your area.

http://www.channelmaster.com/TV_Ante..._p/cm-3201.htm
https://www.google.com/?gws_rd=ssl#q...ter+lte+filter
Yes, the FCC will be selling off even more UHF TV channels to commercial interests, which will again squeeze the TV broadcasters even more. That bothers me a lot. I consider those frequencies a natural resource that belongs to all citizens, not for the enrichment of a private business.
It does have an FM trap with an attenuation stated as at least 15 dB, but they don't give any further details, like an attenuation vs freq curve. I don't really know if it is sufficient, that is why I have suggested tests.
http://www.channelmaster.com/TV_Ante..._p/cm-7777.htm

The Antennas Direct Juice preamp has a 4G LTE filter built in, but no FM filter.

Hi again:

Is there a site that displays all stations' frequencies, in short of Googling every single station?

I've searched TVFool and other antenna sites, but not one shows the actual frequency channels these are using...

UPDATE:
Nevermind; I found this spreadsheet on RabbitEar.Info

http://www.rabbitears.info/ss/DTV-Channels.xls

A frequency list of real broadcast channels is quite easy to find.
http://www.csgnetwork.com/tvfreqtable.html
Most of the current confusion is caused by the use of virtual channel numbers.

Thanks, but I was looking for something that had more of a channel list for an entire region with all frequencies in order from lowest to highest...

IE: KCBS 2 = UHF 43, Virt. 2.1, Freq. ?
KNBC 4 = UHF 36, Virt. 4.1, Freq. ?
KABC 7 = H-VHF 7, Virt. 7.1, Freq. ?

I suppose I could tune each and every station just to see what their analog broadcast signal really is...? :confused:

I don't think there is a list that gives real channel, virtual channel and frequency of real channel. If you know the real channel number, then you can look up the frequency of that channel in the link that I gave in post #28.

by zip code
http://www.rabbitears.info/search.ph...pe=dBm&height=

http://forum.tvfool.com/attachment.p...1&d=1473618890

click on callsign to see subchannels

http://forum.tvfool.com/attachment.p...1&d=1473619272

The display channel is the same as the virtual channel; the physical channel is the same as the real channel.

You can do it here:
http://www.rabbitears.info/search.php

If you enter just the zip code, the distance and direction will be off. If you add your street address, it will be more accurate. If you also check Strength Search (optional), it will generate a report similar to a tvfool report. I will not give a link to that result because it will show your street address.

http://forum.tvfool.com/attachment.p...5&d=1473620632

Why do you need to know the actual frequency of the channel?

The only time I need it is to design an antenna for a certain channel, to calculate the specs for an interference filter, or to know if the second harmonic of an FM transmitter falls on a VHF-High channel.

Thanks. I'm not sure how I missed post 28.

I'll add to my spreadsheet the real frequencies of local stations.

The reason I wanted the real frequencies is because my TV tuner has a "Partial channel scan" where it asks for the frequency to find more stations.
It's much quicker than doing a Full Scan and, more importantly, it doesn't delete the current channel list! 😁

Excellent reason. Which tuner are you using to do that?

My Sony can also add a channel after scan, but I don't have to enter the freq.

the Diagnostics Screen shows the center-channel freq:

http://forum.tvfool.com/attachment.p...1&d=1473623660

Solar Panels?
 

Hi again:

Well, I haven't been able to swap everything out yet because I'm waiting for WM and HD orders to arrive... (18 ga pole, dielectric jelly, more coax connectors, etc...)

On another reply you spoke of Solar Panels possibly interfering with the OTA signals.

It just so happens that my other neighbor, 2 doors down behind us, has panels and this is directly where I am pointing my antenna towards Mt. Wilson ( ~280 degrees west)
(see attached pic)

https://drive.google.com/open?id=0B6...VF0UXNROHlodUU

I notice that signals drop on many stations late afternoon, no matter how many times I tweak my antenna, and then great signal after about a couple hours....

How likely, in your opinion, would solar panels be the culprit?

Ahh, yes. I see the green signal lines pass just to the right of his panels in the photo I sent to you by PM, but I didn't want to post it on the forum without your permission.

It is possible that you might be picking up EMI from his inverters. Some inverters produce more interference than others.

case history:
Would solar panels interfere with attic antenna?

http://www.avsforum.com/forum/25-hdt...c-antenna.html

I remember using Tripp Lite 12V inverters back in the 70s, before the car audio industry was producing anything larger than 24WPC.
The Crowns I was using, had ample filtering, but even being in the trunk, that noisy square wave, was still leaking into the system through the line level components.
The only point I'm even close to making, is that regardless of proper grounding, EMI may be entering through an unshielded wall wart, or other plastic component case.
Most filters may be capable of blocking 60HZ hum and ripple, but can't deal w/ the sharp transients of the higher frequency square waves. Or maybe at best, even not the newer modified sine waves.

I was afraid that those panels being in the line of sight for Mt. Wilson would cause some sort of interference.

On another note, I was reading some Australian TV antenna forums and discovered that the loooong elements on VHF antennas are for stations 0-5 and could possibly cause more FM and other low-band interference. Many stations here are now H-VHF and UHF, and this HD-8200XL is more of a broad spectrum design. (FM, L-VHF, H-VHF, UHF)
I was thinking of folding in the longest elements to test that theory out.
Any input on this?

Maybe a good start, but there's also the possibility of signal induction, when running them parallel to your phasing lines.
Not to mention, shorting out against the boom, or other elements.

Forgive my ignorance, but I'm not very radio savvy. :confused:
When you mean "shorting out" are you saying the frequencies would go bonkers and no signal would be possible?
Or would it pick up more interference than before?

By "shorting out", I mean that any signal present on the longest elements that seeped over from the elements that are being used , could be shorted directly to ground when you fold them, resulting in almost zero signal.
Similar to a garden hose that's kinked.

Hey guys:

I did some experimenting this weekend:

I ran one coax directly from the large antenna (No splitters, pre-amps, or dist. amps) and all stations came in pretty well during the day.

I relocated the cable run from the opposite corner of eve to the closer corner of the roof eve. (Left side)
https://drive.google.com/file/d/0B6w...ew?usp=sharing

I tried bypassing the dist. amp, (Pre-amp only) but the picture was pixelating pretty bad. Without the pre-amp, the 5 TVs in the house got only a couple stations.

I re-installed the CM dist.amp and also closed/folded in the 3 longest elements and increased my KABC (177Mhz, the lowest frequency station) by about 6%. (see pic)

We also experimented by raising the antenna to the top of the pole, but it decreased the signal, so I lowered it as far as I could so it would clear the tile roof if I rotated it via the rotor motor.
I also replaced the pole with a Winegard 18 gauge steel one.

I need to remove the 2 splitters and try to combine them somehow, but the difficulty in this is that the 2 wired-in cables (Downstairs living room and master bed) are inside a TV box on the side of the house. (3 other TVs are connected to a splitter in the attic.)

Here's how it's all connected:

1. Antenna to CM pre-amp (exterior)
2. Pre-amp to CM dist. amp (attic)
3. Dist. amp to 4 port splitter (One goes to each of 3 other bedrooms.
The 4th goes to the TV box on side of house.
4. TV box connection has one 2-way splitter for both master bed and downstairs living room.
5. Coax is house grounded; pole is not grounded yet.

I'm pretty sure the coax is all dual-shielded RG6 only.
Would replacing the short coax between the antenna and pre-amp with quad shield have any significance in gain?

And do you think that a 5 port splitter would be best for our situation?

Thanks again for your expertise. :D