Can RFI/EMI be temporary?

[RedPenguin]

I had some kind of interference about two days ago, that seemed to be driving my scanners nuts on the 453.xxx range. For some reason it hit 453.125 with constant static, and other channels had weird popping noises. You still heard audio but the static overcome sometimes and you couldn't make out what was being said.

Yet, all I did was going around and turn off various devices yet turn them back on after finding they didn't seem to be the source.

What seems like my culprit is either the charging base of my bubble-pack GMRS/FRS for family sometimes, or my older Realistic Pro-53.

What I don't get is, can a device only cause interference temporarily? I mean, I turned back on every single device that was on before, yet the interference is gone. It sounds clear as a bell now.

 

[gewecke]

Maybe the source of the RFI is temporary? Do you have any charging equipment which uses pulse technology,or anything which has a periodic cycle?
N9ZAS

 

[n4yek]

It's possible you had a switch on something arcing and when you cycled the switch off and then back on, it made the connection solid to where the arcing stopped. I have seen that actually happen, one of my light switches went bad and I had to replace it.

 

[jim202]

You can try tracking down noise problems for a long time. I have found out in farm areas that the
electric fence systems to keep their livestock in check to cause a pulsing noise.

Fish tank heaters can be a real problem. Most people don't think about them, but they can be a
real noise generator.

You might not think of it, but I have found that some of the older front door bell transformers have
been a source of noise. Problem they are either stashed up in the attic someplace or sealed in
a wall where you will never find them.

Don't forget that the power company might have a cracked insulator out on a pole. These can take
some effort in finding. Generally walking around with a portable AM radio will get you in the general
area. Next step should only be done after dark. Both the power company and your neighbors
will take a dim view of you going around and wacking the poles with a sledge hammer. The jolt
causes the insulator to change position enough to change the noise some. This indicates you
found the right pole. Next problem is getting the power company to come out and see if they can
find the same pole without you telling them you used a sledge hammer on the pole. Point to
bear in mind that the pole insulator noise will change with wet weather. it might get worse or
go away when wet. Neighbors tend to call the cops about some nut going around and hitting
the poles.

You might even have some branches from a tree rubbing the wires. Normally these take care of
themselves in a short time. The branch either gets set on fire or burns slowly through and will fall
to the ground over time.

Happy hunting.

Jim

 

[RedPenguin]

Well...

Well so far, it's been at least 2 days and I have gotten the interference back.

Though like I said when I had it, it was all day, unless I power cycled every device in the room I could think of.

I turned off various desktops, my laptop, older crystal scanner, monitors, everything.

Actually, my BCT15 was getting pops and noise, while apparently the interference was so bad, that my BR330T actually would sometimes completely miss transmissions programmed to the same channels.

I will keep hunting, but I've always read articles/posts where it seemed like if a device is going to cause noise, it will never stop making unless it's unplugged.

That's what I experienced with my old Linksys when Cambria County fire was 33.x. I had to either listen to fire with no Internet access or Internet access with no fire.

Luckily though, Cambria County eventually decided to move fire to 453.xxx, and I have never had a problem again with my Linksys.

 

[rvictor]

It's entirely possible that you haven't found the source of the interference. If you unplug something and the interference goes away and then plug it back in and the interference doesn't come back, it's possible that unplugging it just happened to be at the time that it went away for some other reason.

The real test is to be able to turn the interference off AND ON AGAIN by disconnecting and reconnecting something.

Dick

 

[RedPenguin]

Yes....

It's entirely possible that you haven't found the source of the interference. If you unplug something and the interference goes away and then plug it back in and the interference doesn't come back, it's possible that unplugging it just happened to be at the time that it went away for some other reason.

The real test is to be able to turn the interference off AND ON AGAIN by disconnecting and reconnecting something.

Dick

I completely agree, though I must admit it's weird how even still the interference has not come back.

I'm wondering it maybe with all of the construction going on in my area, one about 1 mile down the road, if something they are using, wasn't causing it.

Right now in my area, construction is going crazy, even crews working at night, when it seems like normally they only work during the day.

 

[RedPenguin]

Wtf

Alright, I'm back at this same problem again.

I don't know what happened, but the interference was gone for an entire week or more, so I figured it has to be gone.

But then today for some reason the interference is back.

After checking every electronic/electrical device I can think of in the room, I'm at a stand-still.

I mean, what can cause interference only once-in-a-while?

Don't devices cause interference constantly, not once every week or two?

Whatever the interference is, it seems to hit almost the entire 453.xxx band. It hits 453.000 (no frequency in my area) all the way until about 453.885.

 

[rvictor]

Don't devices cause interference constantly, not once every week or two?

I think that you really already know the answer to this question as is the case with most of the questions that you post. Why don't you just give it a bit of thought.

Hint: Do all your appliances and those of your neighbors run 24/7 every day of the year?

Hint: Does it ever rain in PA?

Etc.

Dick

 

[kruser]

I had an interference problem similar to yours.
Mine would come and go at random times and often not heard for days.
So I did like you and killed everything I could think of including unhooking 12 volt batteries that keep equipment running during power outages. Finally one afternoon I grabbed a 25' hunk of coax with bnc connectors and attached one end to a receiver (powered from battery) and placed a small wire into a female bnc coupler attached to the other end.
I then killed all power and started waking around the room. At first I used an actual rubber duck antenna and it led me close to the strongest noise level.
Then I used the small wire figuring I'd have to get very near the noise source. It worked and I found my RFI source. It was the darn RCA visys (something like that) 2 line corded speakerphone! All the times I tried killing power I completely forgot the phone has AA batts inside for backup plus to allow it to work without AC power. As soon as I yanked the batteries, the noise disappeared and would never return as I gutted the thing. I did take it apart and found a small daughterboard attached to the main board. It was this small board that was emitting the noise. The noise frequency would drift so that explained why it was often unheard. I think it had a 2.?? or 4.?? MHz crystal oscillator on the board. I did an spectrum analysis and discovered the thing was radiating harmonics from its set frequency all the way up above 900 MHz! I actually removed the small board and built a full metal shield around it but the signal was so strong that the shield did not help much. The phone was scrapped and replaced by a similar at&t branded set made by V-Tech. It is noise free.
So, make sure you also look at battery backed up devices while snooping around for the source

 

[RedPenguin]

Well...

I think that you really already know the answer to this question as is the case with most of the questions that you post. Why don't you just give it a bit of thought.

Hint: Do all your appliances and those of your neighbors run 24/7 every day of the year?

Hint: Does it ever rain in PA?

Etc.

Dick

Well, I have been trying to give it thought. I went trough the entire house and never found anything that seemed to mess with the 453.xxx band.

It must be some sort of device that runs 24/7 because 2 weeks ago or so for 3 days straight NO BREAK I got the interference.

It rains yes, but I've heard the radios of some of agencies I listen to, and they never sound staticy in the rain, so I ruled that out.

I mean it's a static to the point you can hardly make out what's being said.

Well I'm going to try turning up the BCT15's Squelch up to 4 from 2, it seems to ignore the interference somewhat. Maybe when it picks up traffic it will not have static in it.

 

[RedPenguin]

Darn Laptop

I did a sweep again using my scanner just to make sure during my last sweep I did not miss anything.

At first I thought it was hitting on a set of VCRs, but unplugging them, their cable connectors, composite, nothing ever worked.

Then suddenly near the laptop it started reacting.

So it looks like the darn culprit is my laptop, which is rather a problem for me, since I use my laptop all the time to record TV shows and sometimes record scanners.

Though I guess the laptop is a NO-NO in my scanner room.

Though why the laptop didn't mess with me for about 2 weeks, is unknown to me.

EDIT: NEVERMIND, this looks like it only stops interference on 453.125 on the BR330T. The BCT15 still picks up interference on random channels in the 453.xxx range. So I only found one problem, apparently.

EDIT #2: I did find out the problem finally. I know people are going to tell me, not again, but it seriously is again. I took a look at changes near 453.350 on my BCT15. It seems that even in NFM, 453.3375 is picked up on 453.33, 453.335, 453.34, 453.345, yet not on 453.350. I'm suprised before it was only my BR330T that was acting like this but now my BCT15 is acting like this. Oh well, it should go away in a day or two.

So I guess my final conclusion is, to never listen to 453.350, because it's almost like fate is trying to tell me not to listen, because even the scanner that had no issues before is having issues. I enjoy listening to it, but oh well. LoL.

 

[TBennettcc]

...so what was the source of the interference?

 

[RedPenguin]

Well

...so what was the source of the interference?

Well all I can figure so far is, that 453.3375 might accidentally be set to NBFM instead of SNFM like one person one said they believe is the problem.

I've put a PL tone on and hopefully that will rid the interference, but I have to wait until tomorrow to see, since no chatter will be on tonight.

EDIT: Actually maybe it wasn't a problem with me after all, because when going through transmissions, I heard guys saying, they should be on Ch. 2 (M2M, Direct), which is never true, they are on Ch. 1 which is their main Repeater. I guess they must have had repeater issues then, which makes sense because in later transmissions, some people heard some people that others did not, which sounds like a no-repeater type thing.

EDIT #2: Well I guess this must have been the issue because while most people are staticy some are worse than others, yet some few people ended up being crystal clear, so I'm assuming it was all based on who was how far away from me/line-of-sight which is obviously what happens in a no-repeater situation. This has been confirmed as later during the day, I heard, "Radio Maintenance Testing 1, 2, 3, 4, 5" and other testing stuff, so I guess after all it was not me.

 

[kruser]

EDIT: NEVERMIND, this looks like it only stops interference on 453.125 on the BR330T. The BCT15 still picks up interference on random channels in the 453.xxx range. So I only found one problem, apparently.

EDIT #2: I did find out the problem finally. I know people are going to tell me, not again, but it seriously is again. I took a look at changes near 453.350 on my BCT15. It seems that even in NFM, 453.3375 is picked up on 453.33, 453.335, 453.34, 453.345, yet not on 453.350. I'm suprised before it was only my BR330T that was acting like this but now my BCT15 is acting like this. Oh well, it should go away in a day or two.

So I guess my final conclusion is, to never listen to 453.350, because it's almost like fate is trying to tell me not to listen, because even the scanner that had no issues before is having issues. I enjoy listening to it, but oh well. LoL.

Is the signal from 453.3375 very strong? If so then you may be suffering from an overload condition. Or I think maybe they were re-tuning the transmitter due to you hearing the radio techs. Maybe they had it set off freq. Do either of your radios have an attenuator that you can turn on for the 453.350 channel that you like too listen to? I'm not familiar with neither of your radios.
Of course if 453.350 is a weak signal then attenuating it may wipe it out all together.
Will either radio allow you to program 453.355? That may get you far enough away from the .3375 transmitter but still sound clear and not off frequency. Maybe even 453.360 set back to normal fm.
Setting a PL tone for the 453.350 was a good idea and will at least keep your squelch from opening when the .350 is off the air and .3375 comes on.
The only other thing you may try would be to install a directional yagi antenna as long as both stations are different directions from your qth. This may reduce the .3375 signal enough and of course increase the .350 signal strength.
If the .3375 transmitter is like right next door then that would probably not help.
Good luck!

EDIT: I forgot to mention the laptop. If you do see interference from it then try and unplug the power transformer from the wall socket and let it run on batteries alone. If the interference dies then you may wish to try maybe a universal type. I've seen some very dirty switching type power supplies but they generally don't mess with anything much above the shortwave bands and VHF Low band. Also desktop power supplies can be very bad noise makers. They will wipe out a dsl signal. I've had many of these and they were all cheap chinese made no name supplies. I've replaced them all with brands like Antec or better name brand supplies and problem solved. Again though, most of the noise from dirty supplies seems to keep itself down in the lower parts of the radio spectrum.

 

[RedPenguin]

Well....

Well 453.3375 comes in with a 5 signal basically anywhere you are in my area. Yet, .350 comes in with usually 4 at the most, one in a while 5. On my BR330T though sometimes it's only 3.

I always thought maybe it was intermod/interference near my actual home, yet my BR330T does this no matter where I move in the city or suburbs. Also my friend's 346XT does the same. Also, both my mother and dad's scanners do the same thing.

I don't know what happened to them today, but their entire repeater must have gone bonkers, because they never in 8 months to almost a year or more that I've listened to them, and somewhat before, NEVER had to use Ch. 2, except for a few random maintenance workers that didn't want to tie up the frequency for everyone. I mean they commanded the entire agency to go to the talkaround, so I wonder if .3375 ended up screwing their repeater somehow. Unless the rain today did something, but it's rained before, no problems.

Though before I only had interference on .350, but now my laptop seems to cut off 453.15 even though it's mainly on 453.125. I think that's why no matter what, no UPJ Police was picked up even though they use 453.15. I'm amazed, for 2 years I never really had any interference issues except Linksys on 33.xx, now I'm getting it high up in Police, Fire, and EMS bands. I'm amazed how no interference one day then another day a huge amount.

Is the signal from 453.3375 very strong? If so then you may be suffering from an overload condition. Or I think maybe they were re-tuning the transmitter due to you hearing the radio techs. Maybe they had it set off freq. Do either of your radios have an attenuator that you can turn on for the 453.350 channel that you like too listen to? I'm not familiar with neither of your radios.
Of course if 453.350 is a weak signal then attenuating it may wipe it out all together.
Will either radio allow you to program 453.355? That may get you far enough away from the .3375 transmitter but still sound clear and not off frequency. Maybe even 453.360 set back to normal fm.
Setting a PL tone for the 453.350 was a good idea and will at least keep your squelch from opening when the .350 is off the air and .3375 comes on.
The only other thing you may try would be to install a directional yagi antenna as long as both stations are different directions from your qth. This may reduce the .3375 signal enough and of course increase the .350 signal strength.
If the .3375 transmitter is like right next door then that would probably not help.
Good luck!

 

[kruser]

It does kind of sound like maybe the 3375 transmitter was or is ahving problems and interfering with the 350 syste hence the need for the users of 350 to switch to talkaround.

I'm in an apartment complex and finding and eliminating noise is a chore. Whenever a new person moves in, it leads to possible new sources of noise. So for me I do see new sources of interference often unfortunately.

In my newer desktop computers there is often a bios setting called "Spread Spectrum" and it can be enabled/disabled. I never did figure out for sure what it really did but several things I read suggested to turn it off as it can alter the frequency of something at random which. The something may be the PCI bus or maybe the CPU speed but I never reallly found out other then it can sklightluy change some type of clock speed.
The theory behind it was that it would prevent constant external RFI as the frequency would always be changing. Those that suggested disabling it did so to always know what frequency too avoid when monitoring. That way the noise frequency would never change.
Maybe someone here will see this and comment on the spread spectrum setting and if what I've read is in fact true.
Several years ago my main scanning interest was our state highway patrol on 42 MHz.
The main dispatch channel was 42.060 and almost every one of my computers in those days emmited a very strong signal dead center on that frequency! So I could not have a computer running. That was before the internet so the need for a computer was light.
Today my new computers still emit a signal in the same 42 MHz area but I've grounded and shielded them plus rewired everything with shielded cat5 cable. I've also put ferrite chokes on anuything that was radiating noise out of cables. I'd bet it took me at least two years to complete this but it actually worked. My apartment manager let me put some antennas on the roof which placed them far away from the computers and that really helped as well. I now have a discone and an 800 MHz yagi on a rotator all coupled together and then feeding two 8 port stridsberg multicouplers so I can have up to 16 receivers.

Oh well, enough rambling and I hope your issue resolves itself.

 

[RedPenguin]

Well

It does kind of sound like maybe the 3375 transmitter was or is ahving problems and interfering with the 350 syste hence the need for the users of 350 to switch to talkaround.


Oh well, enough rambling and I hope your issue resolves itself.

Well I guess they actually did.

When I tried contacting their radio company they were like, "It's always frequency checked and no issues EVER."

Yet, for some strange reason, after yesterday's radio blowout, suddenly 453.3375 is only a signal 3-4 instead of 5 now on my scanners.

And 453.350 sounds clear as a bell. It used to have strange and bizarre noises, but now it sounds so clear like the guys/gals chatting are right outside my house, it comes in so clear now.

I find it hard to believe that the transmitters were frequency checked constantly, especially since now .350 sounds way better and yet .3375 seems to be a lower signal now.

Also, my BR330T can listen to .350 without constantly getting static/interference.

So I fail to see how it was ever any issue of mine, like they made it sound, if just after one day of radio maintenance from them, every single interference issue I had is gone.

 

[RedPenguin]

Well

Well thanks again it looks like the problem is still somewhat there, hitting me 4 times in a 2 hour period, but way less than it used to.

Looks like it's almost fixed but slightly not, though I think maybe they are not done repairing it completely.

Though at least I know it's not my problem at all, but theirs.

 

[RedPenguin]

I just wanted to say

I just wanted to tell everyone this issue as far as I am concerned is over with.

The interference is basically not there any more except some random times, which I think can happen with really any system.

I did not mean for this thread to go to .350 and .3375, it just happened because truly I was getting interference on 453.125, 453.150, 453.885, etc.

Though, everyone will be relieved that this issue is basically resolved. I'm hoping that the radio techs will have a follow-up call or two to their transmitters to make sure everything is working, so that they can make sure the interference will never be back.

Though at least it's at least 95% better than it was before.

Also: Anyone know why after only an hour or two, it seems you can't edit your old post? I wanted to add this to my former post, but it would not let me.