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Clean Electrical Power, FM Radios and Reception, Static, and Antennae

12/31/2019 10:27 AM

I would like to describe a long-lasting problem, ask a few questions, and get some feedback:

I used to scrap-out buisness copiers/printers before scrapping-out computers. These copiers/printers almost universally had a noise filter directly on the power-cord before even going to the power-supply board (which most have there own on-board noise filters). These copiers were designed to be connected to a computer. I was using computers off-line for long time and noticed that some of them caused static on my FM radio (even tho there were noise filters in their power-supplies). There was no WiFi or other wireless devices in/on/around those computers (everything was cabled). The static would start immediately with "power-on" (even before boot-up). More static would appear depending what was running on the computer (using the mouse/keyboard/media playback/etc. Right now i have a big interference problem, and was wondering if it would be a good idea for those "surge-protectors" to also have their own noise filters in them. Seems right to me.

Any ideas how to get rid of this static, improve reception, and any other comments?

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#1

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

12/31/2019 10:59 AM

The radio must be moved.

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#21
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/05/2020 7:25 PM

I would prefer to move just the antenna.

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#2

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

12/31/2019 11:13 AM

I doubt your interference problem is traveling through your power lines.

In my experience, surge protection circuits are typically only useful for the infrequent surge produced by some large motors. In these cases they certainly can prevent premature device failures. A massive surge, lightning, will not be interrupted.

What I dislike of most surge protection products is that they do not indicate if the surge protection part still functions. They now include in their documentation the peak surge protection energy they can block but how does one know when that fails?

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#22
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/05/2020 7:26 PM

Adding another feature never really hurt anyone. But, the power lines can still be causing interference thru induced currents to surrounding metals (which I admit a noise filter won't cure).

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#3

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

12/31/2019 11:29 AM

"The static would start immediately with 'power-on' (even before boot-up)."

Most likely the interference is caused by the switching power supply in the computer. If that is the case, then anything you put on the power cord won't help.

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#23
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/05/2020 7:31 PM

Possibly. Worth considering.

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#4

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

12/31/2019 12:21 PM

Do these computers have the case or any shielding (mu-metal) removed? Devices that are commercially produced have to pass RF interference tests. Your static is likely being broadcast through the air.

I used to experiment with building computers and most of the time they consisted of circuit boards lying on a desk. I could turn on a radio not tuned to a station and hear all sorts of interesting static when I was running a program.

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#24
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/05/2020 7:34 PM

Well, actually I don't really know. I had the covers of several removed. I don't remember which was which, this is a possibility.

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#5

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

12/31/2019 4:32 PM

You do realize you can get FM radio on the computer...? Really no need for a radio anymore if you have a computer...

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#6

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

12/31/2019 7:24 PM

I appreciate all your comments. It's hard for me give up radios; they're so convenient. I have about ten scattered about. Not all of them are near computers. Not all of them are "cheapies", either. I also have about ten computers. Only three are up-to-date enough to go online with. It's a hassle to use a computer for online radio.

And also, My TV with a digital tuner for digital broadcast is also getting this interference. Every once in awhile, I have to restart it. Maybe my whole house is in a bad reception area. Maybe I need to go to automobile radios with multiple outdoor antennae, or something.

I know the tuner has a lot to do with reception, not just the antenna. But, all these devices can't all be junk.

I guess I'll just have to keep experimenting.

Thanks again.

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#7
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

12/31/2019 9:06 PM

Yes I get it, change is hard, and the older you get the more resistant to change you become...at some point you just say F it...but it can be fun to screw around with the new technologies, I use a bluetooth gizmo to link my phone with my Bose system, just use an aux channel...I have all my music on my phone, as well as internet radio and police fire emergency radio bands, podcasts etc...I almost never use them, but when something new comes out, I like to screw around with it...I just upgraded my DVD players to Blueray HD...

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#13
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/02/2020 6:21 PM

I somewhat agree. But, this is where "old-school meets new-school" (bridge between generation gaps; big potential). I wish computers/tech was more backward compatible.

Maybe all the metal around is causing the problem. This is what I'm dealing with:

Notice all the coat hangers hanging from the ceiling. There are two radios and a TV in this shot. The antennas are behind the coat hangers (against the outside wall). This is my home-made computer/workshop rack. This wire shelf used to be a wooden one (which I scrapped) and am now rebuilding. The step ladder is to my "bunk-bed".

This is the bottom shelf where I'm going to put 3 computers. 2 of which will share a monitor with a KVM switch.

There are 4 household outlets with 4 Power-strips. 3 for each computer, and the other just in case I need it. When I'm done wiring it, a hardboard floor goes on top, then 3 computers.

These are the 2 monitors and 2 subwoofers. There's plenty of space for 3 systems and my tools/supplies. Access will be from the front and that one end:

This is a view of the monitors, another power-strip, the mounted lamp(which I'm using now, to take the picture), and the bottom shelf where the computers will go:

This is why I think I need noise filters everywhere. It still kind of makes sense to me.

If any of this changes your mind any, I'm still interested in your comments.

Thanks.

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#20
In reply to #13

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/05/2020 4:18 PM

The first place I would look is for proper system grounding, not only for the receptacles but for the house....I would also look for shorting in any 120v motors on the system, ceiling fans can short to ground and keep running but give a shock when touched....

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#27
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/05/2020 7:54 PM

I agree. After reading comment #17, I realized an oversight on my part.

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#28
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/05/2020 8:05 PM

I agree. The shelves on this unit are insulated from the poles by plastic support pieces. (after reading post #17) I have since bypassed that insulation with stainless steel lock wire at every joint. I have yet to determine if that helps with the static. This is an old house, and its entire wiring deserves a looking into. Maybe I should also put those coat hangers somewhere else, but I don't know where (yet).

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#43
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

06/22/2020 9:46 AM

I got you! you love your things.

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#44
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

06/27/2020 8:26 PM

This might be a little philosophical, but... Our consciousness(s) (subjective) must relate/interact with the physical world (objective). Anyone's "things" are part of that relationship/interaction. I admit that some are more important than others. But how they're prioritized is a subjective evaluation/judgement-call that we all make in our own lives. There's a fine line between love and need. Or is there? Where either stands in our priority list determines that. Sometimes it hard to tell the difference, but not impossible. And, it does all boil down to seeking/finding satisfaction (subjective). Sometimes we do, sometimes we don't. Sometimes we can, sometimes we can't. It's part of the "mystery" of life. And I don't mind talking (philosophizing) about it.

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#8

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/01/2020 3:33 AM

We used FM radios in Off Road Electric mining trucks with no problems even though the power being pumped to the motors by the SCRs was in the thousand amp renge. If you have access to a 200MHZ CRO then connect it to the antenna and see if the interference is being introduced into the antenna or if it is being injected into the radio front end by the computer power supply.

Better still if you have access to communication service monitor then you can sweep the FM radio band and pinpoint the frequency of the interference. Yes I understand not everyone has a com service monitor but I bought one a a great price to build repeaters for our HAM radio group.

IF you don't mind modifying your FM radio connect it to a FM radio whip antenna with coax cable, RG58/59 can be used. Put the whip antenna outside the workshop area and the increased signal gathered will likely smother the interference for you can use less volume.

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#9
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/01/2020 10:39 AM

That's not a bad idea. I already modified a few by replacing the stick/telescoping antenna with a connector for a di-pole. But most whip antennas are automotive, with a different connector than the RG58 or 59. Are there whip antennas with that connector? Or adapters to pair the two?

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#10
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/01/2020 10:44 PM

I used the antennas with the standard 1/4 thread which allowed them to screw to a standard mobile antenna base. In Aust we used the Mobile1 brand antennas on the trucks as the antennas were always getting shovel sickness, one swat and they're not.

I have found that these same antennas improve the coverage area for the old wireless handsets used on telephones.

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#11
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/01/2020 11:54 PM

Car AM/FM radios are 75 ohm (TV Cable RG59). So are most home stereo radios. Car AM/FM radios use a "Motorola" jack. There are F to Motorola adapters available. You must have some unusual stuff, many Ham operators have computer controlled radios. If the computer caused interference, it would make the "radio" useless. I have 2 and am building a 3rd. I have a Dell Opti something running 98. I also have a notebook and a custom built desktop running Win 7. All with no issues.

Start by finding a good computer and a radio. Add different hardware and see if it causes interference. Then move on to the next one \.

Please remember this gobbeldy gook:

"47 C.F.R. 15.5 contains a general provision that devices may not cause interference and must accept interference from other sources." A statement only a braindead bureaucrat could think of

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#12
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/02/2020 5:26 PM

"Car AM/FM radios are 75 ohm (TV Cable RG59)". I guess I can just cut off the existing connector from the car antenna, and put on a standard RG connector. I know the connectors are different, but it might not be a big problem.

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#15
In reply to #12

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/02/2020 11:25 PM

You can get BNC connectors for RG59 for the 75 ohm impedance. The only difference I have found between a 50 ohm BNC and a 75 ohm BNC is the extra length of the teflon sleeve used in them. Actually some of the radios used in cars had an impedance of 93 ohm RG62, if I remember correctly. Anyway the miss match caused by a BNC or a TNC connector will have negligible impact on the radio and I like to have a firm connection and not use RCA connectors.

Here is a link to cables that may interest you. https://www.digikey.com.au/en/product-highlight/a/amphenol-rf-division/cable-connectors?utm_adgroup=Amphenol&utm_source=google&utm_medium=cpc&utm_campaign=Dynamic%20Search_Suppliers&utm_term=&mkwid=s7FXZQGdm&pcrid=399539501434&pkw=&pmt=b&pdv=c&productid=&slid=&gclid=EAIaIQobChMIsoqHwsnm5gIVDCQrCh1-gwMOEAAYASAAEgKi5fD_BwE

I installed UHF antennas onto a 60m tower where we used 1 1/4" od Heliax but normally we used 3/4" heliax for VHF. FM radio falls into the VHF part of the spectrum.

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#19
In reply to #15

Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/03/2020 9:00 AM

There is more to the differences in 50 ohms and 75 ohms BNC connectors than the Teflon sleeve indicator. The diameter of the center conductor male pin is smaller for the 75 ohms. The center conductor female socket is also slightly smaller. So connecting a 75 ohms male connector to a 50 ohms female connector may make a poor connection but no damage. Connecting a 75 ohms female connector to a 50 ohms male connector can damage the female connector center conductor so that it can no longer properly connect with a 75 ohms male center conductor.

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#18
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Re: Clean Electrical Power, FM Radios & Reception, Static, and Antennae.

01/03/2020 6:21 AM

Some auto antenna cable is difficult to work with. Extension cables are also available.

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#14

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/02/2020 11:20 PM

First, turn off everything that you don't need right now to see if the interference gets better. Some TV sets are big interference generators. Some printers with switching power supplies are too. Ask for help from a local Amateur Radio club. Some have people that are experts in locating interference problems.

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#16

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/02/2020 11:28 PM

I live in a fringe area (in a valley with higher hills on all sides). All the walls are insulated with a layer of foam with aluminum foil (so signals can only come in through the windows or the attic), and am using a forty-something year old Technics™ receiver. I leave that receiver turned on and tuned to NPR essentially all my waking hours.

I used to have a special FM antenna up on the roof, but took it down several years ago to have a new roof installed, and haven't put it back up yet. Meanwhile, my "antenna" is a standard dual alligator clip test lead clipped to the bare center conductor of a 6-foot section of RG59 with a type-F connector, in the same room with the receiver.

I've been repairing computers for all of those 40-something years, so have literally had hundreds of computers of various kinds (mostly Macs, but others starting with Timex Sinclair and a number of 6502 computers up to fairly recent Windows machines), operating 10-20 feet from that receiver (and occasionally in the same small room), and I've NEVER experienced interference from ANY of those computers.

I suspect that your current FM tuner/receiver is a digital model, and is responding to the digital signals running around your computers. If so, go to your nearest Goodwill or similar store and buy an old analog tuner/receiver.

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#25
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/05/2020 7:43 PM

..."If so, go to your nearest Goodwill or similar store and buy an old analog tuner/receiver.". This is too simple. Even tho it might solve the problem, I like the features of a digital tuner. I'd rather fix this problem. Why take the easy way out when something better can come out of this? But, thanks.

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#17

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/03/2020 4:55 AM

I once managed a project fit to comms equipment in a special military vehicle. The vehicle had to pass the most stringent EMC tests and we received it after it had been fitted with suppressors on everything electrical. We then installed our gear with loads of EMC filters and maximum screening before submitting the vehicle for final testing - it failed!

After going over every bit of the vehicle with a 'sniffer' I discovered that the digital clock fitted in the dashboard instruments was the culprit. It was radiating at about 3Mhz and a simple filter solved the problem.

You might also check other equipment in your workshop which comes 'alive' at the same time as the computer such as printers, modems, fans, etc and definitely check any fluorescent lighting which is a really bad interference source.

One other thing which could cause interference is 'static' from all that metalwork. You must have the best possible electrical bonding between ALL metal parts to cut down the static and also to provide a SAFE working environment for yourself and any visitors you might have!

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#26
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/05/2020 7:50 PM

"You must have the best possible electrical bonding between ALL metal parts to cut down the static and also to provide a SAFE working environment for yourself and any visitors you might have!". Good idea. This is one thing I neglected.

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#29

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/05/2020 10:01 PM

I forgot to mention a serious problem I had in a short-wave radio (AM) a few years ago. There were spurious signals everywhere on all bands causing serious degradation of signal strength. I thought it was an oscillation internally. After tearing my hair out trying to fix it, I decided it was external interference. I unplugged everything in the room and the problem went away. It was a Lexmark printer that was no longer used about 5 feet from the radio. It was turned off but still plugged in. The switching power supply still runs when the line switch is off. The supply had no metal shield around it, just plastic.

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#30

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/07/2020 8:53 AM

You are experiencing "Dirty Power" and it's a lot more of a problem in many more ways than is currently suspected.

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#31
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/07/2020 10:47 AM

I miss the days of Radio Shack, Edmund's, and Heath kits (anyone remember those?). It was an experimenter's paradise.

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#32
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/07/2020 11:14 AM

There is radio amateur in northern Colorado that has a Heathkit museum in his shop. I picked up a couple of Heathkit instruments at hamfests (one was free). My stereo amplifier and am-fm tuner are Knight kits that I put together in the '60s. Higher quality cases and chassis than Heathkit.

The radio in my last post had a commercial line filter added, so the interference was transmitted through the air by the printer.

Have you made any progress?

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#33
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/07/2020 4:09 PM

I'm not sure yet about progress. I'm still building/rebuilding the computers I'm going to put there. But, the reception still changes as I move (things) around the house (not a good sign). I might have to resign to an outdoor antenna for everything (except for the WiFi antennas on the computer-cart. I do hope that won't be a problem.). But, not everything supports a remote antenna. Looks like adding an antenna connector to some of them will be required. It will take a while to finish this (if that's possible).

In the mean time, I'll just have to put up with the bad reception. But, I'm not ready to give up hope yet, either.

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#34

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae. Isolation Transformer

01/10/2020 2:53 AM

Noise Sleuthing with an Isolation Transformer

You could buy or make yourself a beefy isolation transformer with
one of your copier filters between the input cord and the transformer.
Provide an outlet on a short wire from the output of the transformer.
Build it all in a metal box with the wire from the input round pin on
the plug(earth ground) attached to the box. You can move this around,
inserting it in your existing setup between each potential source
of noise and the receptical you have it getting power from now.
If your noise level drops when you insert your isolation transformer
then you have identified a source of noise into your power network.

You should consider all potential sources including wall warts,
lighting(including builtins such as fluorescent ceiling lights),
fans, etc. You can also use it to see if noisy power is feeding
any of your radios. Another potential source of noise is faults
including weird chassis grounds which may be touching your metro
(metal) shelving and providing a big antenna for the fault. Since
inserting the isolation transformer into prewired circuits with
no plug/jack pairs installed you could turn those on and off with
their normal controls to see if they are generating noise.

Usually, AM is far more noise sensitive than FM so for sleuthing
you may want to have both bands operating and pay attention to
whether there is any difference between the amount of noise from
each. You could use a battery operated pocket radio to determine
if the noise seems to be mostly radiated RF or powerline coupled.
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#35

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

01/30/2020 7:46 AM

I like the helpful info you supply in this thread. thanks!

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#36

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

03/03/2020 6:26 PM

An SDR dongle. A poor man's test instrument. 20 bucks on ebay.

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#37

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

03/07/2020 5:59 AM

And speaking of cheap instruments.......one can now purchase a nano VNA for about 50 bucks. vector network analyzer. It's a great time for electronic experimenters.

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#38
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

03/07/2020 9:04 AM

This sounds interesting. But, I'm not sure of the best way to use it. I'm thinking that maybe this would be good in conjunction with a highly-directional antenna and pointing it at potential noise sources (to identify a specific Hz output source). If this could select specific bands (ranges) and frequencies (single stations) to detect, this could be the answer. I'll have to search for a good antenna to use with this. I'd even be able to determine the direction of the station that I'm trying to play on the radio. A lot better than guessing.

Speaking of test equipment... I've been looking for a USB port tester to identify USB ports (1.0, 1.1, 2.0, 3.0 etc.), but all I've found are ones that test the power output, without testing the other properties of the port (type, rate-transfer, wire/connector integrity, etc). Any ideas/recommendations?

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#39
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

03/29/2020 2:59 PM

This thread seems a little dead...but

I first noticed what a PITA that copiers could be when doing panel surveys In a communications space. The heater circuits would create spikes on neutral every minute for some models.

The SMPS’ make a crapload of noise.

I started checking into their (copiers) entire RF emission spectrum soon after fixing that neutral issue...it was creating a lot of harmonic noise and interfering with gig ether networks. Moving the copier to a new receptacle on a different branch solved the issue...simple.

One of the best (in my experience) and extremely simple tools to use for RFI, is a cable hound for facility surveys. The wand has a pretty good frequency range and was able to pick up a lot of interesting emissions. This test equipment is easy to make, and/or cheap to buy...and the learning curve is really flat.

It’s also a great demonstration for those new to or lacking interest (non-technical supervisors) in what an EMI/RFI hunt looks like for techs and engineers. When they can hear for themselves, and they don’t understand what they see on regular test equipment, it can make a big difference.

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#40
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

03/29/2020 3:43 PM

Laser printers have similar heaters, so could be a problem as well.

I'm not familiar with the "cable hound". Could you please elaborate.

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#41
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

06/16/2020 1:14 PM

Sorry for the absence...didn't see your response.

The new Cable Hound has a digital filtering circuit that the old one did not. The old one was great at picking up exactly what the new one states that it does not: "The DSP that is now built into the Cable Hound DSP receiver rejects all signals except the Cable Hound transmitter tone. That means no more annoying A/C hum, no more static, only a crisp clear signal."

Effectively, the older Cable Hound was great and cheap for basic EMI/RFI surveying. This is only one tool, though, and there are others that can be used as well.

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#42
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

06/16/2020 8:45 PM

This does sound interesting. How can I learn more about it? A general Google search? Wikipedia? Any better way?

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#45

Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

07/14/2020 11:47 AM
  1. Surge Limiters do not conduct till there is a surge - not the first suspect.
  2. Do you get the noise on a battery powered FM radio, at the location of the victim?
  3. Use the portable FM radio to sniff-out the culprit. AM radios [when tuned off any broadcast] sing or snarl close to computers or other noise generators or noisy cables, even localise noise within culprit to PSU or part of screen.
  4. If you disconnect the antenna from victim, do you get problem still? If you do it is induction or direct radio pick-up within the victim or conducted along one of its cables.
  5. Turn off all electrical gear except victim. Turn each back on alone, until you get interference.

If you can identify the culprit, you can suppress it (even its PSU internally, noise will come out on any wire of a sub-unit). At FM wavelength, all cable RFI conduction will be same on each wire of a cable or loom [common mode]. Frequently, every cable has to be treated close up to culprits's or victim's case before noise goes. It could be the monitor, keyboard, mouse of a computer or a router. The antenna coax of a TV/radio can act as aerial to radiate or pick up EMI.

Ferrite toroid rings are used around each cable and ground bond (if you connect an exterior ground lug). Rings must go around the whole bundle of wires or cable not individual wires of a loom/cable - you can put several turns of the cable through bigger toroids. At FM frequencies the toroids work by dissipation, more than inductance. RFI test houses may have a whole "pipe" of toroids over power feeds or test leads to stop extraneous RF entry to equipment under test.

There is a lot of info on web from radio amateurs who have a lot of trouble with RFI from internet over telephone wires, switch mode power supplies, lamps [no longer just a tungsten bulb] etc wiping out reception.

Following URL looks weird [tu.be??, I have tried several times - still comes up same]- searching for "KF7P ferrite, chokes and RFI" found it on Youtube. It's a start.

https://youtu.be/LuMlM8zWQFk

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#46
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

07/14/2020 7:57 PM

1. "Surge Limiters do not conduct till there is a surge - not the first suspect." I agree, but that wasn't the point. The point was that since surge protectors are so widely used, they might as well have a secondary function of filtering noise.

2. "Do you get the noise on a battery powered FM radio, at the location of the victim?" Good question. I wish I can find a good battery powered portable radio. They either have bad antennas, operate on the wrong voltage/power supply, have bad tuners, or otherwise are not worth getting. I think the best bet is a car radio, but they don't the features I want. It seems like nobody knows how to make a good radio that doesn't cost your soul.

3. There are many culprits. Including just me moving around, affecting the reception. I just don't know how the interference is produced or how to stop it.

4. Without an antenna, I get background static without any "culprits".

5. Identifying the culprits is not as big of a problem as stopping it. Not using the culprits is not an option. And, I don't want to be without the radio(s) either.

I'm not sure what you mean when talking about suppressing it (what's a PSU? Power Supply Unit?). "The antenna coax of a TV/radio can act as aerial to radiate or pick up EMI."? I thought coax had the 2nd "ax" as shielding to prevent picking up unwanted signals. Why does this shielding not work? This is why I think all radios should have a remote antenna, not built-in ones. it's important to be able to place the antenna away from the radio itself. Car radios are the only ones (battery powered) of good quality that do. But, they don't have the features of a good quality portable "home stereo". I'm tired of looking for the right radio, so I think it's better to shield/fix my existing ones. But then again, there were a few stations that lowered their broadcast power or stopped broadcasting, and I might just have to do without a radio anyway. Oh... such is life. I appreciate your input. Maybe all I can do is cross my fingers and hope.

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#47
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

07/14/2020 8:29 PM

Have you tried looking in Goodwill or similar stores fro a battery-powered FM radio?

I've been using just an inside whip antenna for my FM Stereo receiver for several years, but this spring the signal got so weak on my favorite station that there was more noise than music. The house has insulation including aluminum foil, so signals can only get in through the windows. I finally realized that the trees and bushes grew so much that they are attenuating the signal significantly.

I had been using that whip, because I had removed my rooftop FM antenna while they installed a new roof. The noise finally motivated me to get that antenna refurbished and put back up. The antenna is connected to the receiver with new coaxial cable, and the noise is totally gone.

My FM antenna is a homemade Dual Cubical Quad, which I designed many years ago to suppress an unwanted station that was closer and stronger than the desired station. Fortunately, there was enough angle between the directions to the two transmitters that I could make the two antennas have constructive interference for the desired station and destructive interference for the undesired one. If anyone is Interested, I can provide more details.

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#48
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

07/15/2020 7:30 AM

"If anyone is Interested, I can provide more details."... This does sound interesting and I would like to try it. But, I'm already backlogged on unfinished projects; I don't know if I'll ever get around to it. It would be good to have the info for later, but I wouldn't want you to go thru the time & effort if I'll never get around to it. How big/time-consuming of a project would it be? A directional antenna would have to be rotated all the time for different stations. I don't know if I really want to get into using a rotator. I was hoping for set it up and forget it, something simple. Maybe even something I can just hang up in a tree. But, maybe that's asking too much.

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#49
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Re: Clean Electrical Power, FM Radios and Reception, Static, and Antennae

07/15/2020 10:48 AM

I have only two FM stations of major interest, and both transmitters happen to be within a few degrees of the same direction from my location, so a directional antenna works well with no rotator. It may or may not be obvious that a directional antenna will receive a stronger signal than a non-directional one, when aimed correctly. As I indicated, I added a second antenna to greatly reduce the signal from a relatively close station that interfered with the desired ones.

Here's a poor photo of one of the two antennas, taken just before I started to refurbish it:

This antenna has been on a mast above my roof for around 30 years or more, and has held up well. The main support is 3/4" PVC with end caps on both ends. 1/4" fiberglass rods fit holes in those end caps, and support the active element and the reflector, which are made of bare #12 copper wire. The horizontal piece separating the two antennas is actually a section of a broken fiberglass pole-vaulting pole. A 2.5" length of Teflon rod has holes drilled through both ends to hold the ends of the wire loops. The coax is soldered directly to the ends of the driven element loop with no impedance-matching device. If you look closely at the top of the photo, you can see that the reflector loop has a few inches of wire sticking up to a shorting bar soldered a couple of inches from the insulator. The position of the shorting bar is a tuning device, but not critical.

The exact dimensions depend on the frequency of the desired station. This one was designed for 100MHz, roughly the middle of the FM band, but also a number that makes easy calculations. It still works well at 90MHz, near the bottom of the FM band. I'm sure you could find those dimensions in an internet search for cubical quad antennas.

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