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Author Topic: Who or what is the best in RFI prevention?  (Read 3926 times)
N2RRA
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« on: January 07, 2008, 09:10:16 PM »

Who is the best in RFI prevention?

I see a lot of adds for filters from 1.8Mhz to 60 Mhz that connects between radio, and coax feed line.

You have snap on type, or sleeve over coax feed line Mix 31 Ferrites.

There is also Current Choke Baluns that are sold to prevent RF current from traveling back through the shield back into the QTH.

Last but not least you have the typical home brew wound Choke Balun 6-8 turns at 8-10 inch's in diameter up at the antenna feed point to help reduce RFI.

Which one of these actually works the best?

Who is the best distributer, or company that makes their products with the best ferrite, or other materials to prevent, and eliminate these problems?

Can placing a Filter between the rig, and coax feed line, installing Mix 31 Ferrites all through out any current carrying conductor on bench, and installing a Current Choke Balun (for example one made by D.X. Engineering) all together be a problem for the station such as loss of ERP out of antenna etc....?

Where would be the best place of installing each of these products, or in what order would be best.

Please! Only comments from experienced Hams, or field service technicians post their advice to eleviate any false, or missunderstood suggestions would be much appreciated.

73!




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KB9CRY
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« Reply #1 on: January 08, 2008, 04:55:21 AM »

You seem to believe that RFI can be prevented by applying devices to your rig or your cables.

That is not what you do.  You apply these things to the device that is experiencing the interference.  And, you do this to that device because 99% of the time that device is poorly designed and can not deal with your clean and legal RF signal.

Amidon and Fair-Rite are top ferrite/toroid/snap on manufacturers.  K-Com makes good telephone devices.  There's a lot of top notch manufacturers.  The type of device you apply depends on the problem; you have to deal with RFI on a case by case basis.  There is no one answer or one solution.
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N2RRA
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« Reply #2 on: January 08, 2008, 06:13:15 AM »

KB9CRY,

"You seem to believe that RFI can be prevented by applying devices to your rig or your cables.

That is not what you do."

Incorrect!

    This is what we do! We as Hams apply a choke balun at the feed point to reduce, or eliminate RFI. We also apply filters such as that big 12" can between rig, and coax feed line to antenna to reduce, or eliminate RFI. Current Choke Baluns the same etc......
We use these devices to actually reduce the current that is returning through the coax shield that is radiating R.F., but you would have to apply these device between coax and rigs.

The snap on type, or sleeve over barrel ferrites we install at our phone system, T.V. cable, P.C. speakers, microphone cables at the rig is to prevent RFI from getting into them. This would help reduce the R.F. in those cheap phones and T.V. sets that the antenna, or radiating feed line is emitting.

73!

P.S.

  Please! is there anyone with better knowledge on this subject.
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N2RRA
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« Reply #3 on: January 08, 2008, 06:15:47 AM »

Thanks for your suggestion on K-Com product.

73!
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WW5AA
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« Reply #4 on: January 08, 2008, 10:26:29 AM »

I prefer to design and construct an antenna with ground system that does not produce RFI. Thats how I do it.

73, de Lindy
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KB9CRY
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« Reply #5 on: January 08, 2008, 11:09:47 AM »

Where would be the best place of installing each of these products, or in what order would be best.


Eric not intending to get into a match but I personally use none of these products.  As another has stated, my system is such designed and operated that I don't radiate spurious signals.  Also my antennas and my house and my neighbors residences are far enough away and/or designed that they do not pick up any RF and/or they use electronic devices that are not susceptible to RFI.  A properly designed and installed amateur station DOES NOT radiate RFI.  RFI, by definition (you may want to study up more) is interference of a device that is not capable of filtering legal external RF signals.


As you stated:
We as Hams apply a choke balun at the feed point to reduce, or eliminate RFI.

Wrong, some of you need to install a choke balum at the feed point of certain types of antennas to prevent RF from flowing down the coax and disrupting the antennas radiating pattern or preventing RF getting into the shack.  But, if you don't need one, why install one.  It all has to be judged on a case by case basis.


We also apply filters such as that big 12" can between rig, and coax feed line to antenna to reduce, or eliminate RFI.


You mean a high pass filter or a low pass filter?  I never use those and most modern rigs, properly operated, don't need those.


The snap on type, or sleeve over barrel ferrites we install at our phone system, T.V. cable, P.C. speakers, microphone cables at the rig is to prevent RFI from getting into them.

There you go again.  You're using these devices to not "prevent RFI" from getting into them but you're using these devices to prevent legal RF from getting into them because if you didn't, then by the crappy design of these devices, the RF causes them to not function properly.  We as amateurs don't go around radiating RFI, we go around radiating RF signals as our FCC license allows us.  It's not our problem that there are poorly designed electronics nearby that can be disrupted.  That's their problem, not ours.


This would help reduce the R.F. in those cheap phones and T.V. sets that the antenna, or radiating feed line is emitting.

Yes you are correct.


But what are you really asking?  I consider myself an expert as in my old QTH, with very close houses, I had to employ virtually every trick you've mentioned for one reason or another. Present QTH requires nada.



To answer your question:
Where would be the best place of installing each of these products, or in what order would be best.

It depends.  There is no one answer.  It's all on a case by case basis and some experimentation is required.  Yes placing a ton of "stuff" into your feedline can create some amount of attentuation.


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N2RRA
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« Reply #6 on: January 08, 2008, 03:30:46 PM »

KB9CRY,

   Thank you Philip, and yes! nor am I intending on getting into a match, but too just find out the facts from someone who knows something on the subject. Here are a few questions.

"my system is such designed and operated that I don't radiate spurious signals."

Question #1:

How is your system specially designed that you don't radiate any type of R.F. that would not interfere with anything if it were in closer proximity to it?

 
"I consider myself an expert as in my old QTH, with very close houses, I had to employ virtually every trick you've mentioned for one reason or another. Present QTH requires nada.

Let me take a good guess here! Maybe you arent getting any R.F. towards any of your house hold electronics, or your neighbors because.....

"My antennas and my house and my neighbors residences are far enough away and/or designed that they do not pick up any RF and/or they use electronic devices that are not susceptible to RFI."

"A properly designed and installed amateur station DOES NOT radiate RFI. RFI, by definition is interference of a device that is not capable of filtering legal external RF signals."

My antennas are made by a company called Cubex Quads. Same people who manufacture Tennadyne Log Periodics. They require coax feed line to be wraped around the boom on both their 2 meter, and 432 quad beams, and are feed with 1/2" Andrews Hardline. I also have a 6 meter Moxon below that is feed with LMR 400 coax which design requires it to have choke balun, or stream of ferrite beads of experimental amount to be placed along coax.

Antenna's are mounted on a chimmeny on 1 length of     1 1/2" pipe. The ground system consists of a ground clamp at the bottom of the pipe, and a #1/0 gauge electrical cable of 16 ft. in length to a 3/4" in.dia. ground rod 10 ft. in length buried about 2" in. below dirt. The antennas are 35 ft., and 40 ft. from ground. The neighbors at ground level are getting the R.F. mostly on 6 meters.

Rigs are an Icom 756pro III, and a IC-7000 for 2 meters, and 432. Mike is a IC-SM8, or a Heil PR-40 feed directly into rigs. All equipment is grounded to each other with a 1" ground strap (not electrical wire), and Power Supplys are Astron.

Question #2:

Where is the flaw in this design of equipment?


Last but not least!


"The snap on type, or sleeve over barrel ferrites we install at our phone system, T.V. cable, P.C. speakers, microphone cables at the rig is to prevent RFI from getting into them.

There you go again. You're using these devices to not "prevent RFI" from getting into them but you're using these devices to prevent legal RF from getting into them because if you didn't, then by the crappy design of these devices, the RF causes them to not function properly."

I had to re-read your comment here twice, but I understand where your coming from. Your trying to make me realize that I should be saying we use ferrites to prevent our legal RF from getting into people's cheap electronic equipment. I hope I'm getting the message. Very Good!

Still! Do these damn ferrites work, and how many would it take to prevent RF from being a problem other than buying these cheap Bas^$&* good equipment. They live right down stairs so I need some sort of solution.

73!


 
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KB9CRY
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« Reply #7 on: January 08, 2008, 04:41:01 PM »

Thank you Eric for the opportunity.  There is no one person who is an "expert" in RFI prevention but there are many of us who have battled it and know what has worked for them.  Again, everything RFI-wise MUST be on a case by case basis.  There is no ONE answer; if there was then there wouldn't be a problem.  Do you understand that?


How is your system specially designed that you don't radiate any type of R.F. that would not interfere with anything if it were in closer proximity to it?

Here's a link to some piks and descriptions of my stuff:

http://www.nidxa.org/memberWWW/kb9cry_home.htm

On the upper left menu bar click on antennas and shack for more info.  I am not bragging.  I do also have a properly designed and installed grounding system as use top notch cables and connectors.

Maybe you arent getting any R.F. towards any of your house hold electronics, or your neighbors because.....

Yes, because the towers are high, the houses are far away, and I monitor everyone and no one, even in my house has an issue.

The antennas are 35 ft., and 40 ft. from ground. The neighbors at ground level are getting the R.F. mostly on 6 meters.

Your problem is not with your system but with your neighbors being so close and they are most likely getting Fundamental Overload from your RF signals.  There is nothing at your end that you can do, short of not transmitting, to solve "their problem".  It has to be solved at their end.

Where is the flaw in this design of equipment?

Too low to the ground and too close to the neighbors. (And poorly designed electronic equipment used by the neighbors.)

Do these damn ferrites work, and how many would it take to prevent RF from being a problem other than buying these cheap Bas^$&* good equipment. They live right down stairs so I need some sort of solution.

Yes they do work, but it's again on a case by case basis.  How many and exactly where to place them has to be done by experimentation.  If you wish, give us more specifics and we ought to be able to steer you in the directions you need to investigate.  If you can't experiment on the neighbor's equipment then you have another problem which others will be able to comment on how to handle.  

EVERY RFI PROBLEM HAS AN ENGINEERING SOLUTION IF ALLOWED TO PURSUE THE PROBLEM LONG ENOUGH.
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KB9CRY
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« Reply #8 on: January 08, 2008, 05:18:16 PM »

OK folks, let's help Eric out with his neighbors' problems.  The ground level neighbors are experiencing RFI (not sure to what) when he operates on 6 meters.  Any advice?




My antennas are made by a company called Cubex Quads. They require coax feed line to be wraped around the boom on both their 2 meter, and 432 quad beams, and are feed with 1/2" Andrews Hardline. I also have a 6 meter Moxon below that is feed with LMR 400 coax which design requires it to have choke balun, or stream of ferrite beads of experimental amount to be placed along coax.

Antenna's are mounted on a chimmeny on 1 length of 1 1/2" pipe. The ground system consists of a ground clamp at the bottom of the pipe, and a #1/0 gauge electrical cable of 16 ft. in length to a 3/4" in.dia. ground rod 10 ft. in length buried about 2" in. below dirt. The antennas are 35 ft., and 40 ft. from ground. The neighbors at ground level are getting the R.F. mostly on 6 meters.

Rigs are an Icom 756pro III, and a IC-7000 for 2 meters, and 432. Mike is a IC-SM8, or a Heil PR-40 feed directly into rigs. All equipment is grounded to each other with a 1" ground strap (not electrical wire), and Power Supplys are Astron.
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N2RRA
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« Reply #9 on: January 08, 2008, 05:45:30 PM »

Philip,

I'm going to order a ton of Mix 31 ferrites different sizes to place either on phone lines, T.V. coxial cable, or P.C. equipment to experiment with then I will get back with more info. Keeping in mind that I know Mix 31 ferrites only have an affective operating range from a frequency response between 1.8 Mhz to about 35 Mhz range.

The 6 meter antenna is another problem. Apparently a Current Choke Balun like the one made by D.X. Engineering has an operating range from 1.8 Mhz to 60 Mhz. Obviously the only thing that I can find that will help with the 6 meter antenna being in the 50 Mhz range. What else is there for the 6 meter band?

Doesn't sound like I can do much in the shack, but what can I do here first?

One other thing! One trip that I made into there home was to figure out the problem. The little T.V. he had a problem with was connect to an old cable scrambler. Thing was the cable coax was'nt connected to the scrambler box which was'nt connected to the T.V. The cable coax was running into the T.V. directly. What he had was the T.V. being powered by the scrambler box accessory power outlet located on the back. When I disconnected it from the scrambler to plug the T.V. right into the wall outlet after testing for interference (which there was) it was not present there after.

Just by plugging the T.V. right into the wall outlet solved the problem. He then a couple of days later complained that he was getting it again through the same T.V., but of course that could've been when I was working H.F. Maybe placing some ferrites might fix it, and bring that problem to a resolution. What do you make of this?

73!
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KB9CRY
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« Reply #10 on: January 09, 2008, 05:01:40 AM »

What else is there for the 6 meter band?

Your chasing after a problem that isn't there.  You most likely have problems will fundamental overload from the 6M RF that is coming out of the antenna (which is what you want in an antenna).  I doubt you have any feedline problems.

With the TV fix, sounds like what you discovered was that RF was getting into the power lines (most likely via the power lines running along the alley behind the house?.....we need more physical information) and/or picked up by the power wiring in the house (are the lines in conduit?....if so then most likely not via that route).

Wrapping the TV's power cord through a few ferrites may solve the problem.

Where are you going to buy your mess of mix 31s from?

I'd only go to the reputable manufacturers since they have the quality control process in place to ensure you really get mix 31s.  And there may be other mixes that may be better.  The Amidon website has tons of info on what to use and what is best.

Gd luck.
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N2RRA
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« Reply #11 on: January 09, 2008, 08:28:53 PM »

Thanks Philip,

    I hope all this is being read by those with the same problem. I think some very good information that couldn't really be found any where was achieved here. Well I have some more info.

I called Amidon Corp. which deals souly with ferrites. I spoke with the engineer which I wasn't that impressed with their responses, but confirmed that using Terroids are really the best way to go when combating R.F. and is far more affective than the snap on type ferrites. Just by placing at least one Terroid, and needing to cover up a little bit more R.F. can be done by placing a couple snap on types which would result in less snap on ferrites that you would have normally used without the one Terroid.

My plan of attack is too start with 1 Terroid which would have to take each Tele. line, T.V. coax, or other leads to devices, and wraping them around the terroid as much as possible. Then clipping some snap on ferrites as needed. Hopefully needing less ferrite beads on each line.

One problem! I will need a third, or forth opinion on the frequency range of type of ferrites.

D.X. Engineering told me that Mix 31 Ferrites are only effective from 1.8 Mhz to about 35 Mhz.

Amidon is saying, and posts on their web sight that Mix 31 has a range of 1.8 Mhz to 300 Mhz and has a nice roll off.

Hmm!!!!!!!!! what to make of it I don't know, but neither would advice which manufacturer has the best effective rating. I didn't expect to get a trust worthy answer. They do have to make money. Smiley

Any way I will post further information has I make progress within the next few days before the VHF/UHF contest, but I did work some great VHF D.X. today. Big E-Scatter opening on 6 meters today later afternoon, and worked alot of mid-west states running the proIII on 3 watts, and I rocked using my home brew 6 meter Moxon with no less than 5/5 reports. In fact I only got one 5/5 report, and the rest were higher up too 59+15 over with 20 new grids, and 8 states.

Tongue QRP rocks!

73!
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KF7CG
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« Reply #12 on: March 10, 2008, 06:36:19 PM »

RFI can be a very interesting problem, even for those of us that live out in the country. I have experienced RFI to the neighbors telephone that was best cured by strategic watering of the lawn at a spot between the two houses.

Sometimes ground is not ground and not a good sheild.

KF7CG
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N0NDV
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« Reply #13 on: August 11, 2008, 06:17:51 PM »

kc6pga has the idea. i think prolly the best tool i use for rfi is an old cb FS meter i picked up at a yard sale years ago. i tune the antenna so it works good and has no rf in my house and none of my junk is bothered (lots in here).

i have learned keep the antennas up as high as i can and as far from any house as i can. and i too am a believer in resonate or very close to it antennas. i use coax chokes at feedpoints and i ground coax and bury it. and above all i watch my field strength meter. if i dont bother my junk then lot less chance ill bother the others.

my old FS meter sets on top of my tuner which is on top of my amp it dont wiggle im happy guy.
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