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Re: [RFI] Magnetic Field Interference

To: Jim Brown <jim@audiosystemsgroup.com>
Subject: Re: [RFI] Magnetic Field Interference
From: dalej <dj2001x@comcast.net>
Date: Sat, 13 Mar 2010 19:04:21 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
CM500, a good headset/boom mike, I bought mine at Full Compass for  
under $40.  It sounds beautiful on the K3 and is plug-n-play with bias  
provided in the K3 menu.

Those EC folks thought of everything.

Dale, K9VUJ

On 13, Mar 2010, at 18:41, Jim Brown wrote:

> On Sat, 13 Mar 2010 14:56:47 +0000, Brendan Minish wrote:
>> Is there anything I can do to increase the magnetic shielding of the
>> amplifier? Will using 'Mu metal ' type material on the outer case  
>> of the
>> amplifier in the vicinity of the PSU help?
> It is VERY unlikely that you can fix this with shielding. There are  
> two
> good and simple fixes that you MAY make work. 1) Increase the distance
> between the field source and the mic. 2) Rotate the field so that it  
> is
> perpendicular to the pickup field of the mic.
>> 2/ Is there anything I can do to improve the immunity of the the  
>> dynamic
>> microphone element to the magnetic field ( I suspect there isn't.)?
> This is solved with pro mics by adding a "hum-bucking" coil that is in
> series with the mic element and out of polarity with it. I don't  
> think it's
> practical with the DT-109. I don't know of any other good solutions.
>> I would really like to be able to continue ot use this headset, the
>> DT-109 headset
> I know those headsets well -- for many years, I've specified them for
> production intercom systems in the theaters for which I design sound
> systems.
> Something else you can (and should) do with the K3 is roll off the low
> octave bands in TXEQ. For most mics and most voices, the two lowest  
> bands
> should be full cut on the K3. That's 16dB for each band, and if  
> they're
> minimum phase filters, they'll combine to add a bit more. There's no  
> useful
> speech content in those two bands, but that's the spectrum where  
> breath
> pops and handling noise are prevalent. Indeed, many mics should also  
> have
> the next higher band cut as well.
> Another headset that works VERY well with the K3 (and most other ham  
> rigs)
> is the Yamaha CM500, which sells in the US for under $60 (I've seen it
> discounted at $40). If that is available to you, it's worth  
> considering.
> Although some catalogs (including Yamaha's) list it as a dynamic, it's
> actually an electret.
> 73,
> Jim Brown K9YC
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