[R-390] Filters

[KA9EGW]

So if I understand this right, if the coupling wire needs to go to the 
center of the end disk, would not the technology used for attaching 
.002" nickel "drive rod" wires to the center of the diaphragm in a 
hearing-aid speaker have some applicability?  Sounds a lot like a 
hearing aid--one end of the wire goes to the center of the diaphragm and 
the other end just floats in the middle of a coil.

It's "plunge welding"--put the wire at one potential, the end disk at 
the opposite potential, time/current-limit so it makes like a newbie 
stick welder on his first practice piece [i.e. me 2 weeks ago :-) ].  
Rather than a welding machine or even a small power supply, I would 
maybe use a low-series-resistance capacitor of the right size, charge it 
up to not-much voltage, and approach the disk with the wire.  Which 
polarity on which side of the weld, I leave to those who can strike an 
arc without welding the stick to the workpiece HI [i.e. those who know 
anything about welding].

The technology exists; I troubleshot and kept running a bunch of drive 
rod welders when I worked for a hearing-aid manufacturer some years 
ago...but the time/current/etc parameters we never touched.

KA9EGW

On 2/16/2013 5:19 PM, MICHAEL TALLENT wrote:
> There is a small magnetic wire probably spot welded to the center on 
> each end disk and goes through the center of the coil to convert the 
> magnetic field produced by the coil into mechanical movement to form 
> an acoustical wave that travels through the disks and causes the small 
> wire at the other end to vibrate and then generate a small signal into 
> the coil at the "output" end of the filter.
> http://en.wikipedia.org/wiki/File:Mechanical_filter_with_disk_flexual_resonators.svg 
>
>
> Mike T  W6MXV
>
> ----- Original Message ----- From: "k2cby" <k2cby at optonline.net>
> To: "R-390 Mailman" <R-390 at Mailman.qth.net>
> Sent: Saturday, February 16, 2013 5:48 PM
> Subject: [R-390] Filters
>
>
>> I took a hard look at the photos, and it seems to me that all of the
>> magnetic coupling wires are in place.
>>
>>
>>
>> While there are fine wires in the coils, the coupling wires that 
>> everyone
>> seems to be referring to are on the perimeter of the filter discs and 
>> appear
>> to be at lease 0.5 mm (the lead in a mechanical pencil)  or about #20 
>> awg.
>>
>>
>>
>> Whatever is described as a "hair thin wire" has to have come from the 
>> coils,
>> not the resonators, unless is just an artifact that crept in from the 
>> bench
>> during manufacture.
>>
>>
>>
>> Miles B. Anderson, K2CBY
>> 16 Round Pond Lane
>> Sag Harbor, NY 11963
>> Tel.: (631) 725-4400
>>
>> Fax.: (631) 725-2223
>> e-mail: k2cby at optonline.net
>>
>>
>
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