ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3 4   Go Down

Author Topic: AM Radio bleed out of the amp...  (Read 1508 times)

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 21627
  • Wichita, Kansas USA
Re: AM Radio bleed out of the amp...
« Reply #10 on: October 19, 2020, 05:07:51 pm »

I know residents of Hooke in Dorset (UK) were complaining that they were getting Russian radio coming out of their toasters ans their remote car keys weren't working, I believe this was to blame,
http://tx.mb21.co.uk/gallery/gallerypage.php?txid=1662&pageid=2500

Another solution that can work for RFI are neutrik EMC XLR connectors http://www.neutrik.co.uk/neutrik/products/xlr-connectors/xlr-cable-connectors/emc-series

Have you posted here about Rampisham or other high power transmitter sites in the UK?  I'm certain I followed a rabbit down a hole and looked at maybe a half dozen such historic site pages.  I think I got RF burns just looking at the pictures. ;)
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

frank kayser

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1549
  • Maryland suburbs of Washington DC
Re: AM Radio bleed out of the amp...
« Reply #11 on: October 19, 2020, 11:12:16 pm »

I know residents of Hooke in Dorset (UK) were complaining that they were getting Russian radio coming out of their toasters ans their remote car keys weren't working, I believe this was to blame,
http://tx.mb21.co.uk/gallery/gallerypage.php?txid=1662&pageid=2500

Another solution that can work for RFI are neutrik EMC XLR connectors http://www.neutrik.co.uk/neutrik/products/xlr-connectors/xlr-cable-connectors/emc-series

Good news, my XLR cables did not appear to be leaking.  Nice to know of the EMC XLR connectors.  Some of those antennas look much like the ULF antenna array at the Naval Academy in Annapolis.  Any subs (as in the under-water kind) close by?[


Ditch the keyboard amp for a DI (I've never understood the need for keyboard amps; isn't that what monitors are for?) or, better yet, ditch the amp and get a keyboard with balanced outs; common mode rejection is your friend.

Option 1, with option 3 as a backup (I don't see any advantages to option 2).

-Russ


Thanks Russ.  I appreciate your expertise in the wireless world for for previous posts, and weighing in here.  I was hesitant using UHF gear as close to the transmitter as I will be, though the Senn wireless gear will be operating way above the AM broadcast band.  I was fearful of just pure overload due to the proximity of the antenna, or some high-power harmonics.  With the amp issue, I'm a bit gun shy. 


I agree that a monitor would be a much better solution than the keyboard amp.  Some habits die hard in some folks.

As for the 2.4ghz option: I know most people here want nothing to do with the 2.4ghz wireless. Logical and understandable. FWIW, I've been using four channels of AT System 10 wireless in one RU for over four years with nary a problem.  I believe AT figured out how to use the 2.4ghz band and co-exist even in locations with lots of 2.4ghz WiFi, including my WiFi for mixing very close by.  Even a dyed-in-the-wool Sennheiser wireless mic fan, natural skeptic, and owner of nine channels of Senn mic gear, and two Senn IEM sets was impressed with the sound quality of the rig - also no interference or drop out in many venues where we worked together.  I'm 100% confident using it on any gig I do - granted, this is The Lounge, and I barely qualify for question privileges here, let alone endorsements with any weight.

All that said, I've found the AT System 10 gear to be rock solid, and mindlessly easy to run.  I'm not trying to change any minds.  I humbly offer a defense of the AT System 10 gear, but I am quite sure my  endorsement will change few, if any, minds.  YMMV.


frank
Logged

Daniel Levi

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 407
Re: AM Radio bleed out of the amp...
« Reply #12 on: October 20, 2020, 02:19:22 am »

Yes I have posed about Rampisham before I think, the transmission gallery is a gem of UK radio/tv transmitter pictures, even including vintage shots of some transmitters, I would assume they have at least 95% of all UK TV/radio transmitters on there. I just find transmission masts/towers fascinating, esp. the tubular masts (of which there are 5 in the UK (there were 6, but Emley Moor came crashing down and was replaced with a concrete tower). Plus when I have come back for either relatives or shopping via the A30 near Chard/Honiton/Axminster when it's dark you can see the lights of the Stockland hill mast in the distance, it's also visible from the train and the quickest rout form our house to my Aunties took you right next to the Stockland Hill mast (I would say less than 100M from the base).

As for what Rampisham transmitted, it was primarily a SW site broadcasting services like BBC World Service and the like to Africa (I believe), A few MW of installed transmitter power (and we are not talking ERP here!). Most of the towers are now gone though due to cut backs in various broadcasters foreign services with just two remaining for various other services such as wireless internet (I believe) and a low power TV relay (and how that ever worked is beyond me, I know (from reading articles on the transmission gallery) that there was a few problems when the Sutton Coldfield TV mast had a MW transmitter added causing the MW signal to get into equipment at the site.
Logged

Russell Ault

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 825
  • Edmonton, AB
Re: AM Radio bleed out of the amp...
« Reply #13 on: October 20, 2020, 02:40:02 am »

[...]
Thanks Russ.  I appreciate your expertise in the wireless world for for previous posts, and weighing in here.  I was hesitant using UHF gear as close to the transmitter as I will be, though the Senn wireless gear will be operating way above the AM broadcast band.  I was fearful of just pure overload due to the proximity of the antenna, or some high-power harmonics.  With the amp issue, I'm a bit gun shy. 
[...]

Given that we're talking about ~9 octaves of separation, if your G3s are being desensed (let alone overloaded) then I feel like the FCC would want to have a word with that broadcaster (I mean, I've heard of spurious emissions before, but that's a little ridiculous); 5kW is only ~62dB more than the output of your beltpacks, and even modest bandpass filters should totally decimate that 9 octaves from centre. As for the 2.4 GHz, although I am generally not a fan, in this instance I was more referring to my assumption that if 9 octaves of separation aren't enough to save you then 11 aren't going to do much better...

-Russ
Logged

Kevin Graf

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 333
Re: AM Radio bleed out of the amp...
« Reply #14 on: October 20, 2020, 07:39:03 am »

AES Fellow Jim Brown is an interference expert and a Ham radio operator. Several of his 50 papers & Power Points have sections on this type of problem.

"RF Interference in Audio Systems"
http://www.audiosystemsgroup.com/AES-RFI-SF08.pdf

"RFI, Ferrites, and Common Mode Chokes For Hams"  (and audio)
http://www.audiosystemsgroup.com/RFI-Ham.pdf

"Understanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems" 2005
http://www.audiosystemsgroup.com/SAC0305Ferrites.pdf

more of his papers:
http://www.audiosystemsgroup.com/publish.htm
Logged
Speedskater

Kevin Maxwell

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1362
Re: AM Radio bleed out of the amp...
« Reply #15 on: October 20, 2020, 09:33:34 am »

I posted this recently and have just added a little bit more info.

To add another thing to check out to what the other have said. One time in a church youth room (that years ago was their main sanctuary) they told me they occasionally had a radio station broadcast coming over their sound system. This had been going on for years, even when it was their main sanctuary. I tracked it down to a badly wired Electrical outlet, it was miss-wired and there was a small hole in one of the wires and the screws were loose. I fixed it and they havenít had the radio station interference since.

Maybe try a different outlet. The outlet was used for the keyboard and I donít think they even had a keyboard amp. It was just coming from the keyboard.
Logged

frank kayser

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1549
  • Maryland suburbs of Washington DC
Re: AM Radio bleed out of the amp...
« Reply #16 on: October 20, 2020, 10:36:11 am »

Given that we're talking about ~9 octaves of separation, if your G3s are being desensed (let alone overloaded) then I feel like the FCC would want to have a word with that broadcaster (I mean, I've heard of spurious emissions before, but that's a little ridiculous); 5kW is only ~62dB more than the output of your beltpacks, and even modest bandpass filters should totally decimate that 9 octaves from centre. As for the 2.4 GHz, although I am generally not a fan, in this instance I was more referring to my assumption that if 9 octaves of separation aren't enough to save you then 11 aren't going to do much better...

-Russ


Russ, thanks again for your educated and practical expertise.  Your explanation quelled all my fears about using UHF in that situation.  UHF 9 octaves vs 2.4ghz 11 octaves,  you're right: two additional octaves already that far away is of little to no help.  I love data.
Thanks Kevin for your interesting and pertinent information and articles.

Those above named thanks do not reduce the thanks to all the others helping out with my problem.  I have hard, logical suggestions to try and implement thanks to your sharing of experience and info.


There is a good reason I refer to the folks on this site as my "BrainTrust©".


frank
Logged

Geoff Doane

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 857
  • Halifax, NS
Re: AM Radio bleed out of the amp...
« Reply #17 on: October 20, 2020, 10:57:14 am »

You've still got AM radio where you live?  It's been gone for 15 years where I am.  I don't miss it a bit.



A note: The keyboard has 120v power supply on board,  The IEC input socket is pulled out from the chassis, and the wires are still insulated, but not within the shielded enclosure.  I don't know if that matters...


This tid bit concerns me.  Are you saying that the IEC socket is mechanically loose in the keyboard, hanging out of the chassis by the wires?  Is it even a grounded IEC (many keyboards use a 2-pin version of the C-13 connector)?  If the hot wire happens to fray and touch the chassis, nasty things will happen.  At best you'll blow up some gear.  At worst, somebody will be electrocuted.  I've seen it happen (luckily just the blowing up gear part).

Also, if the keyboard is meant to be grounded and isn't, it's just asking to pick up stray RF.  You didn't mention what your power situation is, but if you're outside, the thought occurs to me that you might be on a generator, and if it's a small one, there may not be a proper earth ground.  If you are on shore power, are the power cables feeding the gear yours, or somebody else's and maybe in questionable condition?

I understand what it's like to be under pressure to make things happen, and I've made some questionable decisions myself in the past, but using dodgy electrical equipment is just asking for trouble.

GTD
Logged

Russell Ault

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 825
  • Edmonton, AB
Re: AM Radio bleed out of the amp...
« Reply #18 on: October 20, 2020, 03:20:35 pm »

[...] UHF 9 octaves vs 2.4ghz 11 octaves,  you're right: two additional octaves already that far away is of little to no help.  I love data. [...]

Although it has little practical application, if you like data, try this on for size: thinking in terms of octaves, your AM radio station is almost as close to a 1 kHz sine wave as it is to a UHF wireless microphone. :D

One thing I should clarify, though, is that just because you RF is working doesn't mean your lavs will. Lavs (even wired ones) tend to unbalanced devices, and it's not impossible that you might run into some RF-induced noise in the lav itself. At that point the articles Kevin linked to will be your friend (although maybe a bit daunting in the midst of combat audio); Ike Zimbel (one of the real RF experts around here) found success to a similar issue by adding ferrite clamps.

[...] This tid bit concerns me. [...] If the hot wire happens to fray and touch the chassis, nasty things will happen.  At best you'll blow up some gear.  At worst, somebody will be electrocuted.  I've seen it happen (luckily just the blowing up gear part). [...]

I'm glad Geoff caught this, and I totally agree. RF issues aside, this needs to be fixed or retired.

-Russ
Logged

frank kayser

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1549
  • Maryland suburbs of Washington DC
Re: AM Radio bleed out of the amp...
« Reply #19 on: October 20, 2020, 06:01:01 pm »

You've still got AM radio where you live?  It's been gone for 15 years where I am.  I don't miss it a bit.

This tid bit concerns me.  Are you saying that the IEC socket is mechanically loose in the keyboard, hanging out of the chassis by the wires?  Is it even a grounded IEC (many keyboards use a 2-pin version of the C-13 connector)?  If the hot wire happens to fray and touch the chassis, nasty things will happen.  At best you'll blow up some gear.  At worst, somebody will be electrocuted.  I've seen it happen (luckily just the blowing up gear part).

Also, if the keyboard is meant to be grounded and isn't, it's just asking to pick up stray RF.  You didn't mention what your power situation is, but if you're outside, the thought occurs to me that you might be on a generator, and if it's a small one, there may not be a proper earth ground.  If you are on shore power, are the power cables feeding the gear yours, or somebody else's and maybe in questionable condition?

I understand what it's like to be under pressure to make things happen, and I've made some questionable decisions myself in the past, but using dodgy electrical equipment is just asking for trouble.

GTD


Hi Jeff   Geoff (Mea Culpa for using the wrong form of your name...)
I'm on shore power.  The outlet on the side of the building is in bad shape - the note I sent to the church, requesting an electrician to address it by the next service:

 - "As you know, that outlet we're working with at the church is just about shot: bleached by the sun, and exposed to the rain and other elements, no cover, and won't hold a cord (remember the tape?).  That, and outside outlets should be GFCI (Ground Fault Circuit Interrupter) for safety from electrocution. "


I did see an interesting email as it went up the food chain:
Hi,
"I got this email from Frank. He has a good point. We had to use duct [sic] tape to hold the plug in, and it really should be a GFCI outlet. Could Jesus do this before the next service?"
Look.  I'm all for prayer, but for this I was looking for something a little more earthly, and less divine...  :o


I should have asked for the piano to be repaired as well.  D"Oh! A new email is in order.!!
Good thing is all of my point-to-point cords (extensions, stringers) are all GFCI equipped.  (I know the GFCI is a SECONDARY safety system)


 
Although it has little practical application, if you like data, try this on for size: thinking in terms of octaves, your AM radio station is almost as close to a 1 kHz sine wave as it is to a UHF wireless microphone. :D

One thing I should clarify, though, is that just because you RF is working doesn't mean your lavs will. Lavs (even wired ones) tend to unbalanced devices, and it's not impossible that you might run into some RF-induced noise in the lav itself. At that point the articles Kevin linked to will be your friend (although maybe a bit daunting in the midst of combat audio); Ike Zimbel (one of the real RF experts around here) found success to a similar issue by adding ferrite clamps.

I'm glad Geoff caught this, and I totally agree. RF issues aside, this needs to be fixed or retired.

-Russ


Me too. Thanks, Geoff.


I think Steve Goodman said it best "I got the I don't know where I'm going, but i"m going nowhere in a hurry blues"




« Last Edit: October 22, 2020, 11:07:13 pm by frank kayser »
Logged

ProSoundWeb Community

Re: AM Radio bleed out of the amp...
¬ę Reply #19 on: October 20, 2020, 06:01:01 pm ¬Ľ


Pages: 1 [2] 3 4   Go Up
 



Page created in 0.058 seconds with 22 queries.