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#1
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Interesting RF interference
Back in Austin at the dance studio I've started looking into a problem
with one of the Sennheiser EW100 G2 units. Sometimes the receiver puts out a lot of trash; other times is works as intended. I've just discovered that this is coming from the Gemini CDX-601 player immediately above it in the rack, and that the level of the interference is dependent on the amount of bass info in the CD being played! Not only that, but if the CD player is powered-up and there is no CD in the drive the RF is very strong. I've not yet run through all available channels to see if this happens accross the spectrum, but this seems very weird, and suggests the Gemini probably does not meet FCC standards for lack of spurious emissions. -- ha shut up and play your guitar |
#2
Posted to rec.audio.pro
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Interesting RF interference
hank alrich wrote:
I've not yet run through all available channels to see if this happens accross the spectrum, but this seems very weird, and suggests the Gemini probably does not meet FCC standards for lack of spurious emissions. This is about typical for consumer electronics these days. But it's possible that it may actually meet Part 15 requirements, which are pretty slack. It's expensive to build quiet switching supplies. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#3
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Interesting RF interference
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#4
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Interesting RF interference
"hank alrich" wrote...
Back in Austin at the dance studio I've started looking into a problem with one of the Sennheiser EW100 G2 units. Sometimes the receiver puts out a lot of trash; other times is works as intended. I've just discovered that this is coming from the Gemini CDX-601 player immediately above it in the rack, and that the level of the interference is dependent on the amount of bass info in the CD being played! Not only that, but if the CD player is powered-up and there is no CD in the drive the RF is very strong. I've not yet run through all available channels to see if this happens accross the spectrum, but this seems very weird, and suggests the Gemini probably does not meet FCC standards for lack of spurious emissions. Putting a sensitive receiver right next to any digital device may be beyond what the Part15 specs allow for. Are the antenna(s?) right on the back of the receiver, or are they mounted at least a few feet away? What happens if you swap the position of some of the rack equipment to put something between the CD player and the receiver? Metal rack? |
#5
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Interesting RF interference
hank alrich wrote:
Not only that, but if the CD player is powered-up and there is no CD in the drive the RF is very strong. Reminds me of a friend's stereo amplifier that broadcast its input signal five blocks down the street in the 49 m band. Ralf -- Ralf R. Radermacher - DL9KCG - Köln/Cologne, Germany private homepage: http://www.fotoralf.de manual cameras and photo galleries - updated Jan. 10, 2005 Contarex - Kiev 60 - Horizon 202 - P6 mount lenses |
#6
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Interesting RF interference
On Dec 4, 1:22 am, (Ralf R. Radermacher) wrote:
hank alrich wrote: Not only that, but if the CD player is powered-up and there is no CD in the drive the RF is very strong. Reminds me of a friend's stereo amplifier that broadcast its input signal five blocks down the street in the 49 m band. Ralf -- Ralf R. Radermacher - DL9KCG - Köln/Cologne, Germany private homepage:http://www.fotoralf.de manual cameras and photo galleries - updated Jan. 10, 2005 Contarex - Kiev 60 - Horizon 202 - P6 mount lenses In my experience Gemini occupies the lowest rung of Chinese electronics manufacturing--the worst design, lowest quality, most problem prone and least supported. But they are cheap! You could move the RX away from the player, maybe find some other device to put in the rack between the two, grab some lead sheeting (or mu metal, except that that's expensive) and see if any of that makes a diff. Remoting the antennas from the RX might help as well--it certainly does on my sound cart--get them up away from the local hash. Philip Perkins |
#7
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Interesting RF interference
Phillip Perkins wrote ...
... You could move the RX away from the player, maybe find some other device to put in the rack between the two, Excellent advice. grab some lead sheeting (or mu metal, except that that's expensive) and see if any of that makes a diff. Simple aluminum foil would do the job here (for RF). Lead is needed only if you need to block ionizing radiation (e.g. x-rays, etc.). Or for blocking acoustic transmission (such as lead sheets in walls, etc.) Mu-metal is useful in blocking magnetic radiation (as from a CRT, etc.), but we are talking about RF here. It is also frightfully expensive and difficult to use. Anything conductive will block RF (as in this case). While lead and Mu-metal would work, they are vast overkill and much more expensive than aluminum-foil. Of course, whatever the metal you use, it must be grounded to the chassis of the CD player at some point, or else it just becomes an antenna element itself. Remoting the antennas from the RX might help as well--it certainly does on my sound cart--get them up away from the local hash. Absolutely. And especially if the equipment is in a metal rack (which will *shield* the antennas from the desired signal (the microphone transmitter), while *enhancing* the ability to "receive" the hash from inside the rack. |
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