RF preventing me from using my home studio

Gus Machado

Member
Joined
Aug 26, 2016
Location
Buenos Aires
Just moved to a new apartament, set up my old gear in a new room and turns out that now I'm receiving an unbearable amount of Radio sign. I can even listen to what the Radio show is broadcasting.

To explain the situation better, I'm going to list some info

If I plug my microphone (condenser) ----> Focuriste, then I get lower/almost nothing radio noise

If I plung my microphone (condenser)/or my p10 guitar cable (even without the guitar) ----> Presonus Bluetupe V2 Pre Amp ----> Focusrite, the I get a larger amount of radio noise.

I am the 9th Floor of a 10 story building. There is a lot of different and big antennas above the building.

So, I decided to conduct an experiment a first experiment , i Turned my drawer into a Faraday's cage and put my gear on it.

Noise solved, when the cables are on the drawer. But everytime I need to plug a cable in a instrument or anything outside this drawer, then I start getting Radio noise again.

Based on the learnings, I tried another thing. I've tried to use aluminum foil to "shield" my p10 cable, just to see what happens:

Well, this was the moment when I got the lesser amount of Radio sign. Still the solution I came up with is too sketchy.

You guys have advices or hints on how to solve that? If so, can u teach me how to do it?
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
It can be difficult to keep out strong radio broadcast signals, especially when the mains earth to your apartment block will have to travel nearly all the way up to the top of the building.

Top marks for doing the foil-lined drawer experiment! It demonstrates that the problem is primarily electromagnetic in nature rather than mains-borne (conducted).

Can you tell us which model of Focusrite you have, and whether it is USB-powered or has an external mains power supply? The Presonus Bluetube pre-amp is separately mains powered, but does its power supply have a 3-pin mains plug so that it gets an earth connection? When you connect the Bluetube to the Focusrite, Do you use a balanced cable (two signal cores with outer screen)? Which Bluetube output socket and Focusrite input socket do you use for this connection?

PS none of your attached pictures is accessible (at least for me). The icons are all crossed out in red.
 

Gus Machado

Member
Joined
Aug 26, 2016
Location
Buenos Aires
Hey Boswell. First of all thanks for answering so romptly.
Those are the images.

Drawer experiment
Cable shielding experiment

My Focusrite is a Thunderbolt powered Saffire Pro 26

And my signal chain is Guitar UNBALANCED p10 ----- BlueTubev2 ---- UNBALNCED p10----Focusrite

My Bluetube is using a Powerchord to a. external power supply that only has two pins.

I use Channel 4 for Focusrite input, which I believe is combined XLR + P10 input.
And I use channel 1 unbalanced output in Focusrite.

Please lemme know if you need any more info, I would be glad to provide it to. you :D
 

paulears

Well-Known Member
Joined
Feb 7, 2014
Location
Lowestoft - UK
RFI interference is interesting. The fact you can hear the music and identify the station is a clue, but a very strange one. FM - the most common modern mode is very difficult to detect - but if you have the broadcast station on your roof running lots of power, it can easily get into your audio system. For many years, a guy called Jim Brown has been a US authority on these things - here's a link too a heavyweight document that does have some solutions you can try. http://audiosystemsgroup.com/RFI-Ham.pdf

Essential the interference gets in, and your system is detecting it - as in converting it back to audio. The usual solution involves finding out where it is getting in, and then putting a barrier to block the interference, before it gets to the part of your system that is detecting it! Your drawer experiment shows you can stop it, so the next step probably would be a bug ferrite ring on the cables leading into the system.
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
Your last post and your photos give a clue to the problem: unbalanced cables. Your experiment of wrapping the connecting cable in foil turns it into a form of twin-conductor-in-a-shield cable, giving an improved result. Before you go any further, please try a proper balanced cable that uses TRS plugs rather than TS. (T=tip, R=ring, S=screen/shield)

Running the Bluetube in the form it was supplied (2-prong mains PSU) is not going to help matters. About the only thing you can do about that is to run a separate ground wire from the Bluetube chassis to mains earth. The combination of Thunderbolt cable and a TRS connecting lead should do this for you, assuming the Thunderbolt plug carries a good earth from the computer, and that the computer is properly earthed.
 

Gus Machado

Member
Joined
Aug 26, 2016
Location
Buenos Aires
Your last post and your photos give a clue to the problem: unbalanced cables. Your experiment of wrapping the connecting cable in foil turns it into a form of twin-conductor-in-a-shield cable, giving an improved result. Before you go any further, please try a proper balanced cable that uses TRS plugs rather than TS. (T=tip, R=ring, S=screen/shield)

Running the Bluetube in the form it was supplied (2-prong mains PSU) is not going to help matters. About the only thing you can do about that is to run a separate ground wire from the Bluetube chassis to mains earth. The combination of Thunderbolt cable and a TRS connecting lead should do this for you, assuming the Thunderbolt plug carries a good earth from the computer, and that the computer is properly earthed.

Thanks again. I'm going to buy cables today. So, just to be sure. I can try connecting a wire from Bluetube chassis to Focusrite chasis?
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
Try it first with just the TRS cable. This is an example where RF screening can be really important.

You didn't say what type of computer you had, and whether it was earthed.
 

paulears

Well-Known Member
Joined
Feb 7, 2014
Location
Lowestoft - UK
Linking grounds like this usually either makes it better or worse - and won't hurt, but do remember that the purpose of grounding is NOT to stop hums, it's to save your life. In most cases, making it safe, makes it quieter - but there have been cases of where casual extra grounding can be problematic. However - devices fed from wall-wart style power supplies often don't actually have a real ground anyway.

Interference reduction/removal usually benefits from good grounding - but most audio kit gets grounded by the audio cabling. Just remember multiple ground paths in audio are generally bad - but in a small studio, there's often only one real ground anyway.

My warning is really for people who like to ground their systems to radiators, water pipes etc. Just remember that the water main ground in a tall building can be very different potential wise to the grounding of electrical outlets. If there is a 4 Volt difference - and you do extra grounding, you are sticking 4 Volts at 50/60Hz INTO your nice quiet audio system. When a fault occurs anywhere in the building that could also be an awful lot of Amps trying to get from the electricity outlet ground to the water main ground THROUGH your audio system. This is why people often advise against it, but loads of people do it. General best practice is to be careful and if you are unsure on electricity, ask somebody local you trust. I hate being the doom and gloom merchant, but I still have a scar on my hand from this going wrong when I was in my 30's!
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
I am using a macbook. But the power out let is just two pin. My building wall outlet is grounded though.
The Focusrite Saffire Pro26 also runs off an external 12V PSU, so there's a good chance that nothing in your audio chain is connected to mains earth. In addition to using TRS cables, I would try an earth link from (say) the Focusrite chassis to a ground pin of your wall outlet.

Some of these experiments may not have much effect on your radio breakthrough, others (or combinations) could bring it down to an acceptable level. Remember that the interference is not originally at audio frequency; whatever's interfering is a radio frequency, and this is being rectified by active devices (valves, diodes, transistors etc) in your audio setup down to audio. That makes it unlikely to be an FM band transmitter, as FM usually interferes as whistling noises, but there could be other transmissions going on from all those aerials on your rooftop. Have you ever identified the interfering audio that you get with what is playing at the time on a local radio station?
 

Gus Machado

Member
Joined
Aug 26, 2016
Location
Buenos Aires
The Focusrite Saffire Pro26 also runs off an external 12V PSU, so there's a good chance that nothing in your audio chain is connected to mains earth. In addition to using TRS cables, I would try an earth link from (say) the Focusrite chassis to a ground pin of your wall outlet.

Some of these experiments may not have much effect on your radio breakthrough, others (or combinations) could bring it down to an acceptable level. Remember that the interference is not originally at audio frequency; whatever's interfering is a radio frequency, and this is being rectified by active devices (valves, diodes, transistors etc) in your audio setup down to audio. That makes it unlikely to be an FM band transmitter, as FM usually interferes as whistling noises, but there could be other transmissions going on from all those aerials on your rooftop. Have you ever identified the interfering audio that you get with what is playing at the time on a local radio station?


Yes, but the Focusrite ins being powered only by the thunderbird connected to the mac.
It is playing radio, because sometimes I listen to music and and voiceovers. It is a Radio that stays 7 minutes from my house, FM 107,9 is that your question?
 

paulears

Well-Known Member
Joined
Feb 7, 2014
Location
Lowestoft - UK
Hang on - is the radio station transmitter on your building? What we are talking about here is direct radio frequency induction into the system you have, and this means close - very c lose actually, even with moderate local radio powers. 7 minutes away? As in 7 minutes walking, driving or running TO THE TRANSMITTER, not the local studio? I was under the impression you were one floor below loads of radio equipment? Remember that RF energy dies away with the inverse square law. Double the distance and the power drops to a quarter, double it again and it's a 16th of the original strength - a few floors make a difference. Hopefully the tips here will cure it for you. What is a bit unusual is that FM broadcast radio rarely allows music and voices to be heard - it's usually noise and buzzes. AM radio would often allow voice to be heard with music, but much, much rarer to get music detected from high signal strengths. There could be something more interesting going on?
 

Gus Machado

Member
Joined
Aug 26, 2016
Location
Buenos Aires
Hang on - is the radio station transmitter on your building? What we are talking about here is direct radio frequency induction into the system you have, and this means close - very c lose actually, even with moderate local radio powers. 7 minutes away? As in 7 minutes walking, driving or running TO THE TRANSMITTER, not the local studio? I was under the impression you were one floor below loads of radio equipment? Remember that RF energy dies away with the inverse square law. Double the distance and the power drops to a quarter, double it again and it's a 16th of the original strength - a few floors make a difference. Hopefully the tips here will cure it for you. What is a bit unusual is that FM broadcast radio rarely allows music and voices to be heard - it's usually noise and buzzes. AM radio would often allow voice to be heard with music, but much, much rarer to get music detected from high signal strengths. There could be something more interesting going on?

Só muh deep info I promise I will take time to assimilate. Thanks me.
I guess I expressed myself poorly. So here it goes again:

I live in the 9th floor. On the top of my building there is a lot of antennas that I don't know why are they for.

2,9 km of my house. (I live in the highest part of Sao Paulo ), there is a Radio station.

I'm going to try changing all my cables to balanced ones first and see what happens.
 

paulears

Well-Known Member
Joined
Feb 7, 2014
Location
Lowestoft - UK
The location of the transmitter is the vital part - the radio station is simply on the end of a piece of wire or fibre. Local radio often use roof space on modesty tall buildings. Do you know the frequency the station operates on, as you recognise it?
 

Gus Machado

Member
Joined
Aug 26, 2016
Location
Buenos Aires
The location of the transmitter is the vital part - the radio station is simply on the end of a piece of wire or fibre. Local radio often use roof space on modesty tall buildings. Do you know the frequency the station operates on, as you recognise it?

There's is a huge antenna o the radio building. I CHECKED on google street view. It is 107,9 FM
 

paulears

Well-Known Member
Joined
Feb 7, 2014
Location
Lowestoft - UK
If it is local radio, then the service area will be moderate - maybe only ten miles or so around your location. Area stations tend to be located on hilltops to get more coverage. Local radio is unlikely to have more than 250W or so of power, but this is enough at 10m or so, to get in where it shouldn't. Please let us know when your new cabling is in.
 

Gus Machado

Member
Joined
Aug 26, 2016
Location
Buenos Aires
If it is local radio, then the service area will be moderate - maybe only ten miles or so around your location. Area stations tend to be located on hilltops to get more coverage. Local radio is unlikely to have more than 250W or so of power, but this is enough at 10m or so, to get in where it shouldn't. Please let us know when your new cabling is in.


I'll be back home in a while with the new cables I just built. A d keep you guys posted.

I dunno what do you mean by local radio. I mean Being Sao Paulo a 22 million inhabitants city, and being this a city radio...
 

paulears

Well-Known Member
Joined
Feb 7, 2014
Location
Lowestoft - UK
Radio stations can cover wide areas or local radios - I checked and your country has both kinds. If you are in the centre of the city, then 10 storeys is not a hugely tall building unless you are own a hill, with the surrounding areas lower. If you have a city wide transmitter above your head, then distance is quite critical as it's going to be considerably higher in power. Fingers crossed on the cables.
 

Gus Machado

Member
Joined
Aug 26, 2016
Location
Buenos Aires
Ok guys, here is the veredict: it improved, I have a better ratio volume/interference. But it is still there, and it is unbearable yet.
I think I should tried the ferrite stuff now, right?!
 
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