I am thinking of getting some split core ferrite beads to put over some of my RG-6 cables. Anyone tried this and see any significant improvement such as less EMI and RFI noises or even a stronger signal because of less noise ?

I found an interesting article on ferrite beads (http://www.antennex.com/shack/Dec99/beads.htm). Regarding coax, it says:

The signal going through the coax is confined to the inside of the coax shield. But the outside of the shield acts just like any wire; it can pick up RF and that RF can be carried to the TV or monitor. Shield beads placed over the cable will suppress this interference.

IMHO, unless you are particularly close to (or your cable runs near) a large source of RF noise, a ferrite bead isn't going to do much for you. In those cases quad shield cable might be a better option, otherwise I would use traps to filter out the problem frequencies.

If EMI and/or RFI problems are that serious (such as being under a flamethrower VHF-LO station) you could try to encase as much of your coax run in grounded EMT or aluminum cable armour that has been grounded so that you have the Faraday Cage effect protecting it.

If EMI and/or RFI problems are that serious (such as being under a flamethrower VHF-LO station) you could try to encase as much of your coax run in grounded EMT or aluminum cable armour that has been grounded so that you have the Faraday Cage effect protecting it.
That would certainly be another alternative. I think the article I posted a link to was for Ham radio opperters to deal with RF interference from their radio on other devices in the home (such as TV). Most of what they are talking about isn't applicable to the average person.

@roger1818: I can definitely hear a high pitch sound emitting from my set-top Apex digital tuner. I placed a ferrite at the antenna coax going into the tuner and another one at the coax out of the tuner going into the set.

I picked up 10 of these ferrites for $7.99 so heck if they do anything or not and they specifically written on the box that they were for RG-6 and RG-59 coax cable applications.

edt, at the time we suspected local electrical, RFI, due to wildly fluctuating signals at my 55 yrs old cottage near the lake.

so I tried everything to locate the source, and eliminate it, including the ferrites. but they & other measures did nothing, soooo, I guess that wasnt the problem to begin with, who knows :rolleyes:


i think another option are those power cleaners if its coming in thru the power supply, circuits, or other faulty devices. they sell so-called power cleaners, a type of surge protector...

@balm: Oh I see, if the interference is "within" the cable such as electrical fluctuations from the source then a ferrite isn't going to do anything and a power regulator or filter is the thing to use. I am just concern about the cable acting as a large antenna picking up EFI and RFI along the way on the coax and then entering the set since most TV sets are surrounded with set-top devices such as tuners, cable boxes, DVD players, VCRs etc...

Not an OTA problem but definitely a signal distribution one - if anyone wants to take a crack at his request please do so in that thread:

http://www.digitalhome.ca/forum/showthread.php?t=119692

No replies here about it. :)

@roger1818: I can definitely hear a high pitch sound emitting from my set-top Apex digital tuner. I placed a ferrite at the antenna coax going into the tuner and another one at the coax out of the tuner going into the set.

Did the ferrite beads solve the problem? It sounds to me like a problem with your Apex box and not the type of problem ferrite beads would solve, but I could stand corrected.

@roger1818: Wasn't really a problem to start with, I just added the ferrite chokes to each of my HDTV/Tuner ANT intakes as a precaution.

On the other hand I put one on my phone line leading into my ADSL modem and another on the ethernet cable leading into the NIC and all the Sent/Receive errors disappeared to "0" and it definitely seems faster ! So it does do something objectively in reducing EMI/RFI noise. My ADSL SpeedStream modem also emits a high pitch sound so I guess it interferes with the cable along with the electrical cords that are close to it since CAT5e cables are not shielded and their twist is only cancels out differential mode and nothing stops common mode signals from interfering.

im about to order some attenuaters,

1) they specify " DC block ", i assume this means they can ONLY be placed between an amps power supply and the TV?


2) also what would be a reasonable range figure of attenuation to buy in, eg. 3, 6, 8, 10 dBs?

thanks

are you sure you want ones without DC POWER PASS? That really limits their possible uses.
if you can afford lots of 3dB attenuators I'd suggest keeping the value low so that you have finer grained control of the total Ω when combining them

Stampeder,

thanks for the PROMPT response :eek:

its just that the retailer site im ordering other stuff from only seemed to have this type (oddly), so I guess ill look around some more....

for example it says:

6 dB Attenuator In-line F-Coaxial Cable Reduce Signal Levels Adapter DC Block F to Male Nickle Plated Coupler 5 - 1750 MHz Connector Female to Male 1 Pack Coaxial Coupler Audio Video Adapter Connector

OR am i misreading the meaning here...

Given the amount of testing and experimenting you do I would say a couple of variable attenuators would be a good investment too. Antennas Direct used to sell a variable attenuator to U.S. customers via their website but I don't think they ship them to Canada. Radio Shack U.S. might still have them. Maybe mlord's favourite bargain bin store in Toronto might have them too.

theres always the Winegard TA8700, variable 0-18 dbi....correct?

2) also what would be a reasonable range figure of attenuation to buy in, eg. 3, 6, 8, 10 dBs?

Given those choices, if you get one of each plus a second 6 dB one you can mix and match to produce a wide variety of attenuations. For example.

3dB = 1x3dB
6dB = 1x6dB
8dB = 1x8dB
9dB = 1x6dB + 1x3dB
10dB = 1x10dB
11dB = 1x6dB + 1x3dB
12dB = 2x6dB
13dB = 1x10dB + 1x3dB
14dB = 1x8dB + 1x6dB
15dB = 2x6dB + 1x3dB
16dB = 1x10dB + 1x6dB
17dB = 1x8dB + 1x6dB + 1x3dB
18dB = 1x10dB + 1x8dB
19dB = 1x10dB + 1x6dB + 1x3dB
20dB = 1x8dB + 2x6dB
etc.

If you can get your hands on a couple 1dB attenuators, it would fill in the holes and remove the need for the second 6dB attenuator.

Unfortunately, the inexpensive Variable RF Attenuators from W-G, A-D and R-S don't have dB markings.
I "calibrated" my R-S attenuator, using dBmV signal levels displayed on diagnostic page in my Cable box.
Cable system is convenient because there are a bunch of VHF & UHF "test" freqs.

Unfortunately, the inexpensive Variable RF Attenuators from W-G, A-D and R-S don't have dB markings.


Very true. You can use one to a) Quickly try a bunch of different levels of attenuation to determine if it is going to help and b) Get a very rough estimate (likely +/- 3dB) of how much attenuation you need and then try mixing and matching fixed attenuators (as I described above) to fine tune your results.

BTW, if anyone in the Ottawa area wants to borrow a R-S variable attenuator, send me a PM and I can arrange that. I will want it back though.

roger1818 & holl_ands,

thank you for those helpful comments

so far i cant find any current RS unit, at least not online.

Maybe mlord's favourite bargain bin store in Toronto might have them too.
Active Surplus has 6dB and 10dB inline attenuators, but I haven't seen variable ones there. I got my own Radio Shack variable attenuator from fleabay. In Ottawa, Reset Electronics has fixed attenuators.

-ml

thanks, ill try the individual different units for now, as Roger said, they will give me several increaments, i just wasnt sure whats meant by "DC block"