[R-390] Filters

[Bob Camp]

Hi

Another thing the filters share a background with are the Vibrasponder / Vibrasender PL tone reeds used in FM two way gear. The most direct link is with crystal filters. A crystal is an electrostaticaly excited mechanical resonator (as is a ceramic). You rarely see crystals acoustically coupled. You do see old GTE gear with crystal filter banks made with the same weld and stack arrangement as the Collins mechanicals. 

Bob

On Feb 17, 2013, at 9:22 AM, Bruce Ussery <twc9198764412 at earthlink.net> wrote:

> I appreciate the excellent discussions of theory of operation, as well as the photos. My understanding of the filters was minimal; now it's better. One description reminded me of the spring reverb units in guitar amps.
> 
> Thanks all,
> Bruce WA4ZLK
> 
> -----Original Message----- From: Raymond Cote
> Sent: Sunday, February 17, 2013 6:26 AM
> To: quartz55
> Cc: R-390 at mailman.qth.net
> Subject: Re: [R-390] Filters
> 
> You most likely have more than 50 Collins owners reading your posts and like me saving them as gold for later use.
> Many do. Of have the experience to comment so don't think your sharing is falling on deaf ears.   That goes foe all y'all
> Who share your experiences. Most likely ss of the data is not accessed until much later and source is not listed to thank. So I thank you and all that take the time to post even short experiences. Someone will benefit.
> 
> Ray, longtime Collins 51J4, 388, 389, 390, 391 owner
> 
> 
> 
> On Feb 16, 2013, at 13:55, hat "quartz55" <quartz55 at hughes.net> wrote:
> 
>> I get the feeling like no one is really reading my posts so I may quit dealing with it, too bad for someone that wants to rebuild filters.  But I will post pictues on my photobucket account for anyone that is interested.
>> 
>> Here's a picture of what I think is the center wire attached to the second resonator disk on the top (output) end of the filter.  On the bottom end (input), I don't see the wire like that, but I have not yet pulled out the coils on that end, the center wire may be coming off the end disk there and that's why I don't see it in the resonator disks.
>> 
>> http://s251.beta.photobucket.com/user/DogTi/media/R390A/filtertopcenterwire_zps1e973e91.jpg.html?sort=3&o=0
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