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On 7/18/16 9:05 PM, Richard L. Hess wrote:

> On 7/18/2016 1:43 PM, Paul T. Jackson wrote:
>> Anyone have an idea here? Contact Carla directly.
>>
>
> Ahhhh, the joys of two lists. I already posted this to the ARSCLIB list:
>
>> Hi, Carla,
>>
>> The reference I have used for years is:
>>
>> www.mrltapes.com/field-strength-for-partial-erasure.pdf

Or is she asking what field strength will result in objectionable hum 
pickup in a magnetic playback head?  My experience is that 1 milliGauss 
will cause a slight increase in hum level, and anything above 4 
milliGauss is a disaster.  (Or 0.1 microTesla and 0.4 microTesla, if you 
prefer that unit.)  YFSMV (Your Field Strength May Vary) depending on 
head construction and shielding.  In a professional transfer 
environment, I try to keep the field strength at the playback machine 
below 1 millGauss.

-- John Chester