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Old 31-Aug-2016, 5:41 PM   #1
jerrymc
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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)



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HD8200XL with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

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Old 31-Aug-2016, 6:03 PM   #2
rabbit73
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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.
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Last edited by rabbit73; 31-Aug-2016 at 6:52 PM.
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Old 31-Aug-2016, 7:03 PM   #3
rabbit73
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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
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Old 31-Aug-2016, 7:36 PM   #4
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You are allowed to have a 75 ft tower in that area?
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Old 31-Aug-2016, 9:41 PM   #5
jerrymc
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Quote:
Originally Posted by rabbit73 View Post
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.
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
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HD8200XL with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

Location Radar
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Old 31-Aug-2016, 10:24 PM   #6
rabbit73
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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.
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Last edited by rabbit73; 31-Aug-2016 at 10:28 PM.
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Old 31-Aug-2016, 10:31 PM   #7
jerrymc
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Quote:
Originally Posted by rabbit73 View Post
You are allowed to have a 75 ft tower in that area?
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...
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HD8200XL with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

Location Radar
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Old 31-Aug-2016, 10:37 PM   #8
jerrymc
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Quote:
Originally Posted by rabbit73 View Post
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.
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...
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HD8200XL with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

Location Radar
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Old 31-Aug-2016, 10:57 PM   #9
rabbit73
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Quote:
Well, I supposed I can climb in the attic and remove the 3410 again to test...
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.
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Old 31-Aug-2016, 11:28 PM   #10
jerrymc
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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
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HD8200XL with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

Location Radar
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Old 1-Sep-2016, 12:27 AM   #11
rabbit73
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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?

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





A Fade Margin of 10 dB is needed to allow for changes in signal strength, but those signals don't have it.
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Last edited by rabbit73; 1-Sep-2016 at 12:41 AM.
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Old 1-Sep-2016, 1:10 AM   #12
jerrymc
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Quote:
Originally Posted by rabbit73 View Post
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





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
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HD8200XL with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

Location Radar
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Old 1-Sep-2016, 3:01 AM   #13
rabbit73
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Quote:
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.
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:



Attached Images
File Type: jpg jerrymcTVFcovKTBN.JPG (107.8 KB, 777 views)
File Type: jpg jerrymcTVFcovKTBNcu.JPG (79.1 KB, 752 views)
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Last edited by rabbit73; 1-Sep-2016 at 3:31 AM.
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Old 7-Sep-2016, 6:34 PM   #14
jerrymc
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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?
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HD8200XL with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

Location Radar
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Old 8-Sep-2016, 2:34 AM   #15
rabbit73
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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.

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Last edited by rabbit73; 8-Sep-2016 at 2:40 AM.
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Old 8-Sep-2016, 2:28 PM   #16
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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.
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Last edited by rabbit73; 8-Sep-2016 at 2:45 PM.
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Old 8-Sep-2016, 2:56 PM   #17
jerrymc
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Quote:
Originally Posted by rabbit73 View Post
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!
RABBIT
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HD8200XL with RCA TVPRAMP1R pre-amp aimed at Mt. Wilson (Los Angeles) in Etiwanda area.
CM3410 dist. amp in attic for a 5 room hookup.

Located in foothills behind Mt. Baldy, and experiencing signal loss and pixelation depending on time of day.
Using RCA rotator motor now to tweak.

Location Radar
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Old 8-Sep-2016, 3:16 PM   #18
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Quote:
Is the HLSJ the same as this combiner?
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.
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Old 8-Sep-2016, 3:46 PM   #19
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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:

Attached Images
File Type: gif ADTechHLSJs3.GIF (22.5 KB, 1002 views)
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Old 8-Sep-2016, 6:20 PM   #20
rabbit73
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Quote:
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...
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:

Code:
ANT > 7777 > coax > grounding > coax > power > 3410 > splitters > TVs
                      block           inserter
or is it like this:
Code:
ANT > 7777 > coax > grounding > coax > splitter > power > 3410 > splitters >      
                      block                      inserter
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?
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Last edited by rabbit73; 8-Sep-2016 at 6:50 PM.
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