EMI problems

Kill EMI

DTVUSA Jr. Member
#1
Hi All,I'm new here,glad to meet you.

System info-- 10yo Toshiba 50" projection tv-RCA DTA800B1 converter-CM 0747 amp-50' to 60' of 69B2 RG6 High Performance coax,split to single cable-antenna is 16' high,long range directional I think,it is about 8' long.

I receive 11 stations for a total of 30 channels,but,only 2 stations are reliable in all but the worst of weather,there are a few I would like to improve,the others I can live without. One problem I guess to be EMI,when a vehicle passes signal will pixelate or drop,push mowers and riders do the same. The cable is from an old Direct TV installation,I believe it is good but not as good as quad shield is claimed to be.

Should I upgrade to quad? I thought of inserting the existing cable into aluminum flex conduit for the outdoor portion of the run and wrapping the antenna connections with aluminum tape,would that be more effective than using quad shield? Is it likely to help at all? The cable shielding usually seems to be aluminum so I just thought "maybe".

I can shorten the cable run by half also but would like to keep it long so I can move the TV around without adding connections if ever I want to. I have no plan to rearrange and haven't for years though.

There is no filter before the power cord,just a plain old 6-way power strip. There is no ground block outdoors either but one is planned,maybe in a few weeks after I return from working on the road,I actually read the sticky here on that one! TY.
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#2
:welcome: Kill EMI,

My home was built and wired long before three-wire 'safe' power outlets and I have never had issues with electomagnetic interference/spark plug noise. Once in a while, an airplane flying by causes my tuners to loose their signal 'tracking' and I suspect that's part of your reception problem as well. You may be receiving the signal directly from the transmitter and a second signal is bouncing off a nearby car. That is an example of multipath (multiple-path) reception which was displayed as ghosts on your screen when TV signals were analog. Digital signals completely disassemble or disappear.

Your current antenna is suspect to me. Any 16 foot long television antenna was designed for deep fringe reception and it may the wrong or a poor choice. The amplifier may be making the impossible worse.

Please go to the TV Fool website and enter your street address and the maximum height above ground level you can mount your current or a much smaller antenna. Then return here and copy and paste the resulting URL for us to study so we can advise your next steps. The website will automatically conceal your personal information.

Jim
 

Kill EMI

DTVUSA Jr. Member
#5
TV Fool

The antenna is about 8' long and is pole-mounted at 16' high,I tried to post a pic I took today of it but the file was too big. It is the older conventional style with the two longest "arms" that form the point of the big "V" missing.The rest is there and I think in decent shape. It is about 10yo. It is pointed with the UHF end toward the west and to the southwest just a tad. There are two huge pines west within 100' and a huge maple to the WNW about 60' away,plus,another average sized pine directly north within about 30'. Topography has me down in a huge sloping "dish" of sorts with more trees and buildings from south around to north with only the ENE relatively open. The "dish" is maybe 1 mile across. Sorry if my tech terms are lacking.
 

Kill EMI

DTVUSA Jr. Member
#6
It is my guess the EMI is entering the cable outdoors,I mentioned not having a filtered power strip just to inform. I never considered gas engine's EMI getting to the house wiring then into the power cords! Yikes! I thought that was more from appliance noise like the fridge.

The signal interruptions most often occur when a vehicle passes by. It can happen on channels with a 40% signal or a 70% signal. KIMT and KTTC only have probs in pretty bad weather and KSMQ is just about as good. It is of course worse in summer when trees leaf out and traffic,mowing,etc all increase. If I can improve it for summer use then winter should be a fine.
 

dkreichen1968

Moderator
Staff member
#7
You have an interesting tvfool. You have two groups of medium strength stations almost 180 degrees from each other. KTTC is VHF, everything else in those two groups are UHF. If I was you I'd build a reflectorless Gray-Hoverman for the UHF www.diytvantennas.com/sbgh.html and join it to a high VHF antenna (AntennaCraft Y5-7-13 or similar) pointed at 286 degrees magnetic for KTTC using a UVSJ (UHF, VHF, Splitter, Joiner).
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#8
It is my guess the EMI is entering the cable outdoors,I mentioned not having a filtered power strip just to inform. I never considered gas engine's EMI getting to the house wiring then into the power cords! Yikes! I thought that was more from appliance noise like the fridge.
You know for certain you are experiencing electrical interference because this happens when your fridge turns on and off (POP! - electrical spark) or is there constant interference when its running? How about other appliances like a kitchen blender, microwave oven, etc?

The signal interruptions most often occur when a vehicle passes by. It can happen on channels with a 40% signal or a 70% signal. KIMT and KTTC only have probs in pretty bad weather and KSMQ is just about as good. It is of course worse in summer when trees leaf out and traffic,mowing,etc all increase.
The 'percentage' signal is related to signal strength, but it does not necessarily represent how 'clean' a signal you are working with. I know it is counterintuitive but in digital TV reception, a weak clean signal beats a strong dirty signal. So, the question is where the noise is coming from and a typical source is an antenna pre-amplifier or distribution amplifier. They generate their own 'noise' and they amplify noise your antenna and/or coax receives. If you bypass your amplifier, what happens to your reception?

To determine if that device is causing or contributing to your reception problems, you can use a double-female 'F' fitting in place of the amp. They are readily available at Radio Shack for about a dollar.

It is the older conventional style with the two longest "arms" that form the point of the big "V" missing.The rest is there and I think in decent shape.
From your description, your antenna was originally designed to receive VHF and UHF channels, however, the portion dedicated to UHF is gone, which means you have no antenna for channels 14-51! What UHF channels do you currently receive?

In some ways, VHF-HI reception can be more forgiving than UHF. If this was my project I would go after channels 7, 8, 9 and 10. I'd remove the amplifier and test, raise your existing antenna and test, then add the amplifier back into the system and test. Next, I would add a 4-bay UHF antenna joined into the existing single coax with a UVSJ as dkreichen1968 mentioned above. (Radio Shack Part #15-2586 -around $7.00)

Jim
 

Kill EMI

DTVUSA Jr. Member
#9
You know for certain you are experiencing electrical interference because this happens when your fridge turns on and off (POP! - electrical spark) or is there constant interference when its running? How about other appliances like a kitchen blender, microwave oven, etc?

I don't get much interference from appliances that I can tell anyway,I was just giving example of what I thought would come through the house wiring if that were happening.


The 'percentage' signal is related to signal strength, but it does not necessarily represent how 'clean' a signal you are working with. I know it is counterintuitive but in digital TV reception, a weak clean signal beats a strong dirty signal. So, the question is where the noise is coming from and a typical source is an antenna pre-amplifier or distribution amplifier. They generate their own 'noise' and they amplify noise your antenna and/or coax receives. If you bypass your amplifier, what happens to your reception?

I just tried hooking the cable to the converter,bypassed the amp,lost everything except KTTC.

To determine if that device is causing or contributing to your reception problems, you can use a double-female 'F' fitting in place of the amp. They are readily available at Radio Shack for about a dollar.



From your description, your antenna was originally designed to receive VHF and UHF channels, however, the portion dedicated to UHF is gone, which means you have no antenna for channels 14-51! What UHF channels do you currently receive?

KTTC is the only VHF,the rest are UHF.

In some ways, VHF-HI reception can be more forgiving than UHF. If this was my project I would go after channels 7, 8, 9 and 10. I'd remove the amplifier and test, raise your existing antenna and test, then add the amplifier back into the system and test. Next, I would add a 4-bay UHF antenna joined into the existing single coax with a UVSJ as dkreichen1968 mentioned above. (Radio Shack Part #15-2586 -around $7.00)

Jim
I can try all that at some point if needed Jim and dkreichen,TY both. To start with I think the ground block is 1st,then maybe a noise filtered 6-way on the power cords just for good measure. What I'm most curious about at the moment is the cable quality question from my 1st post as well as whether or not an aluminum flex conduit would act as a good shield.

I had planned to raise the antenna by now but have delayed because it is accessible where it is. If I can get it to work better without raising and/or spending hundreds then great,if not,well,these other little things can't hurt too much.
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#10
Kill EMI,

During freezing weather, overhead trackless trolley bus lines in my neighborhood become covered with ice and when a trolley passes by, the resulting sparking wipes out AM radio reception across the entire LF spectrum over a 5-6 block range (snap-crackle-pop!) but I have never seen a negative blip of interference on my TV screens since the digital transition. None of the appliances or power tools in my 2-wire non-grounded home bother my reception at all. I still wonder how you came to the conclusion you are receiving electro-magnetic interference.

You can hunt for many noise sources using a hand-held AM transistor radio tuned off-frequency to a vacant channel. Hover it around the appliances in your home as well as lighting dimmer switches, bathroom and kitchen fans, aquarium pumps, standard and CFL fluorescent light bulbs and fixtures.

Take the radio outside and check the telephone and power poles in your neighborhood. Years ago I participated in a 'hunt' to find a noise source and we found a guilty pole-mounted transformer. Quite recently in Seattle, a dog was electrocuted by an aluminum street lamp standard that was not properly wired. After a threatened lawsuit, City inspectors were motivated to check other lamps and they discovered nearly 100 others that were improperly installed. All were possible noise sources but the lesson is: never relieve yourself on an aluminum lamp standard!

Also, tune a 110 VAC AM radio off-channel and you may be able to hear powerline 'noises'. If you know someone who has an oscilloscope, they can 'look' at your AC power line for noise, up to the frequency limits of the scope. If an electrical device makes 'noise' in the AM radio band, that does not guarantee it creates noise at television frequencies.

Is this the coax you are using? Eagle Aspen 69b2 Dual Rg6 Solid Copper Coaxial Cable & Messenger With 60% Braid - 69B2 - RitzCamera.com

Please tell us more about the splitter you mentioned in your first post: its type, where it is located, how and why it is in your system. Yes, in theory putting your coax inside grounded rigid or non-rigid conduit would have a shielding effect. I use RCA RG-6 and my longest run is 105 feet from a dedicated 'cut-to-channel 35' Yagi. It receives a station at 75 miles range, split 4-ways using no amplifiers or pre-amplifiers. I receive no RF EMI from four, million-watt TV transmitters nor any of the dozens of ancillary transmitters on the same towers which are about a mile away from me. I hope this helps.

Jim
 
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MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#11
The am radio trick - for sure! Walking around the house with a radio may help pinpoint sources.

I recall building an AM "transmitter" for morse code using a noisy DC motor as a kid. It had a range of about 50 feet.
 

Kill EMI

DTVUSA Jr. Member
#13
Kill EMI,

During freezing weather, overhead trackless trolley bus lines in my neighborhood become covered with ice and when a trolley passes by, the resulting sparking wipes out AM radio reception across the entire LF spectrum over a 5-6 block range (snap-crackle-pop!) but I have never seen a negative blip of interference on my TV screens since the digital transition. None of the appliances or power tools in my 2-wire non-grounded home bother my reception at all. I still wonder how you came to the conclusion you are receiving electro-magnetic interference.

Example- Neighbor lady comes home,drives past my place,from the time she is within 150' or so mt tv signal has problems. When she shuts her engine down my signal problem stops,at least until another car goes by. I've seen it so many times over the last few years,happens every day unless I watch only the strongest channels all the time.

You can hunt for many noise sources using a hand-held AM transistor radio tuned off-frequency to a vacant channel. Hover it around the appliances in your home as well as lighting dimmer switches, bathroom and kitchen fans, aquarium pumps, standard and CFL fluorescent light bulbs and fixtures.

Take the radio outside and check the telephone and power poles in your neighborhood. Years ago I participated in a 'hunt' to find a noise source and we found a guilty pole-mounted transformer. Quite recently in Seattle, a dog was electrocuted by an aluminum street lamp standard that was not properly wired. After a threatened lawsuit, City inspectors were motivated to check other lamps and they discovered nearly 100 others that were improperly installed. All were possible noise sources but the lesson is: never relieve yourself on an aluminum lamp standard!

Also, tune a 110 VAC AM radio off-channel and you may be able to hear powerline 'noises'. If you know someone who has an oscilloscope, they can 'look' at your AC power line for noise, up to the frequency limits of the scope. If an electrical device makes 'noise' in the AM radio band, that does not guarantee it creates noise at television frequencies.

Is this the coax you are using? Eagle Aspen 69b2 Dual Rg6 Solid Copper Coaxial Cable & Messenger With 60% Braid - 69B2 - RitzCamera.com

Looks to be the same,mine isn't stamped "Eagle Aspen",it is stamped "Direct TV".

Please tell us more about the splitter you mentioned in your first post: its type, where it is located, how and why it is in your system. Yes, in theory putting your coax inside grounded rigid or non-rigid conduit would have a shielding effect. I use RCA RG-6 and my longest run is 105 feet from a dedicated 'cut-to-channel 35' Yagi. It receives a station at 75 miles range, split 4-ways using no amplifiers or pre-amplifiers. I receive no RF EMI from four, million-watt TV transmitters nor any of the dozens of ancillary transmitters on the same towers which are about a mile away from me. I hope this helps.

There's no splitter,what I meant is I peeled/pulled/separated the double cable apart and used only one strand/side/single cable,LOL. Gotta watch those technical terms don't I!

Jim
One other thing,the "amp" I mentioned is actually a pre-amp,which I understood would be better to amplify signal but not the noise too. At any rate,when I removed it from the system,signal fell right through the floor.
 

Kill EMI

DTVUSA Jr. Member
#14
The am radio trick - for sure! Walking around the house with a radio may help pinpoint sources.

I recall building an AM "transmitter" for morse code using a noisy DC motor as a kid. It had a range of about 50 feet.
I haven't owned a small AM radio since Shep's great great great grampa was a pup. Maybe I'll put the Kenwood and the old Bose 901s on my hand cart,string out 200' of power cord and walk around the area stopping traffic and making all the neighbors laugh LOL. Seriously,I don't have one,after my nice new job radio was stolen from a site almost 10 years ago I was so pissed off I still haven't bought another good one,and,the cheapos just don't last.
 

MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#15
One other thing,the "amp" I mentioned is actually a pre-amp,which I understood would be better to amplify signal but not the noise too. At any rate,when I removed it from the system,signal fell right through the floor.
What make / model is the pre-amp? It could be defective.

According to your TVfool, you have a pretty strong signal, you should still have signal without the amp.

After you check everything, try this experiment:

Run a single coax cable from your antenna to one TV, and turn off all electric / electronic appliances you can, and see if the EMF goes away. Then start turning things on until you find the culprit. If you find the signal still good after all your stuff is turned back on, then start to work through your wiring to locate the problem.
 
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MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#16
I haven't owned a small AM radio since Shep's great great great grampa was a pup. Maybe I'll put the Kenwood and the old Bose 901s on my hand cart,string out 200' of power cord and walk around the area stopping traffic and making all the neighbors laugh LOL. Seriously,I don't have one,after my nice new job radio was stolen from a site almost 10 years ago I was so pissed off I still haven't bought another good one,and,the cheapos just don't last.
It may be worth $10 to buy an am/fm radio to search this problem down, and then unhook the battery and stash the radio in your emergency kit (You DO have an emergency kit, don't you? )

;)
 

Kill EMI

DTVUSA Jr. Member
#17
"Yes, in theory putting your coax inside grounded rigid or non-rigid conduit would have a shielding effect."

THAT'S what I was lookin for Jim! A "yes" or "no" answer! And I do take note that you said "in theory" so there's no guarantee. I found some online here-

1/2" 1/2FLEX ALUM - Aluminum Flex Conduit :: Flexible Greenfield - Aluminum :: Conduit & Fittings :: Electrical and Industrial Supplies - Galesburg Electric Supply

-it is 1/2" aluminum,40cents per foot + shipping and handling. I have a brother that inspects electrical/electronics parts,maybe they use aluminum conduit and I can get it for less through him. Amazon and several other places have it too. I am curious/eager to try it,if it is a fail then so be it,maybe I will get enough conduit to put on the canoe trailer too.

If I remember right quad shield has two 100% aluminum shields and two 60%-40% shields and would be another option,also,I seem to remember seeing reference to an even better shielded coax somewhere,I don't remember where,but it was very expensive,I don't remember how much either! LOL.

All 3 things,ground block,filtered power strip,and,conduit/shield will have to wait until I get done with work here then get done on the road,estimated 3 weeks. In the meantime any and all ideas are welcome. Thanks much folks!
 

Kill EMI

DTVUSA Jr. Member
#18
It may be worth $10 to buy an am/fm radio to search this problem down, and then unhook the battery and stash the radio in your emergency kit (You DO have an emergency kit, don't you? )

;)
I see your points MrPogi,logged and dated in my old brain pan,I might add a small AM radio to the list. At present my only emergency equip is a 12V lighting setup that will also charge a cellphone and power my hand held scanner during power outages. There's a concrete well house pretty much in my yard in case the scanner warns of tornado,I could grab a big box of beer from the fridge and be sitting on the bench surrounded by concrete in very short order! :) Emergency food is well stocked just above my waist,I can thank the men/genetics on both mom and dad's side for that! Well,ok,I'm to blame/thank too :(
 

Kill EMI

DTVUSA Jr. Member
#19
What make / model is the pre-amp? It could be defective.

According to your TVfool, you have a pretty strong signal, you should still have signal without the amp.

After you check everything, try this experiment:

Run a single coax cable from your antenna to one TV, and turn off all electric / electronic appliances you can, and see if the EMF goes away. Then start turning things on until you find the culprit. If you find the signal still good after all your stuff is turned back on, then start to work through your wiring to locate the problem.
Just now saw this post.

I tuned to 31.3 and 24.3 which are experiencing fairly steady breakups right now. Turned off everything but the laptop and Zhone router. It still happens,almost every motor sound or vehicle passing causes a breakup. This is with the CM 0747 pre-amp still in place. Ok,just bypassed the pre-amp and hooked directly to the converter box again,the ONLY station I receive is KTTC ch 10 which is steady but shows very low on the signal meter. Nothing is bothering KTTC signal,a car just passed close and no prob. I'm going to put the pre-amp back in and try shutting the laptop off and unplugging the cord to it,then everything in the house will be off except the tv and components of it's system. Will post when I power up again.
 

Kill EMI

DTVUSA Jr. Member
#20
"I'm going to put the pre-amp back in and try shutting the laptop off and unplugging the cord to it,then everything in the house will be off except the tv and components of it's system. Will post when I power up again."

Just did that and it's the same as when everything is on,time to plug the fridge and such back in.

The neighbor was just running her push mower and the breakup on channel 24 KYIN was constant,almost no reception,she shut the mower off and it's back to breaking up when a car goes by. She's having problems and her mower quits every few minutes,my signal improves til she starts it again,unless of course there's another nearby engine!. I'm convinced that the UHF signals are low enough that engine's EMI can affect them,or something like that anyway,coincidence only goes so far.

I'm going to try again to add the pic of my antenna,if I can't I might put it somewhere and post a link.
 

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