[time-nuts] wwvb weak on east coast especially when the pre-amps under wa...

[Azelio Boriani]

We use the Plastik70 from Kontakt chemie

On Tue, May 15, 2012 at 1:23 AM, Michael Blazer <mblazer at satx.rr.com> wrote:

> Here's comparison for various type of conformal coating:
> http://mgchemicals.com/downloads/appguide/appguide0404.pdf.<
> https://assist.daps.dla.mil/quicksearch/>
>
> I think there is a type that is 'serviceable' and removable with alcohol.
>
> Mike
>
>
> On 5/14/2012 6:01 PM, GandalfG8 at aol.com wrote:
>
>> The other option of course is to pressurise the box with dry air to ensure
>> a positive pressure differential, such that the net flow is always
>> outwards
>> at  all points, but it's probably easier just to provide a drain hole:-)
>>
>> However, whilst a drain hole will prevent the build up of a lake inside
>> the
>>  enclosure it still doesn't prevent condensation forming on circuit
>> boards,
>> and  powered circuit boards and condensation don't really go well
>>  together.
>>
>> As per earlier comments, it's quite difficult to keep any externally
>> mounted enclosure totally moisture free, so it's much easier to accept the
>> inevitable and allow for it.
>>
>> In a past life I designed quite a few circuit boards that  were required
>> to
>> be fitted in externally mounted vented enclosures, so not  a great deal of
>> pressurisation there then:-), and I usually specified that  both sides
>> should be sprayed with a plastic coating following final test.
>>
>> I can't remember now exactly what this stuff was called, but it  was
>> readily available in the UK from both RS and Farnell as an aerosol
>> plastic  spray
>> that provided a good barrier but was a bit more flexible than the  usual
>> MOD
>> spec conformal coatings.
>> It melted easily under a soldering iron, albeit with a foul  pong:-), so
>> reworking was no problem, and resisted moisture remarkably  well.....
>>
>> problem solved:-)
>>
>> Nigel
>> GM8PZR
>>
>>
>>
>>
>>
>> In a message dated 14/05/2012 23:10:30 GMT Daylight Time,
>> arnold.tibus at gmx.de writes:
>>
>> The only  solutions I think:
>> Apply air pressure tight boxes having a breathing hole  an the bottom,
>> mount the
>> box that no rain and water can penetrate from  the top or sides. If the
>> hole is big enough,
>> eg. 2mm, no pressure  difference is possible and no pumping effect will
>> occur.
>> (If the hole is  too wide, small animals may penetrate).
>> Or,
>> when using a pressure tight  box, it must be stiff and sealed to
>> withstand under all
>> temperature  conditions more then 1 bar/ 100 kPa. Do not forget that  all
>> feed
>> throughs must be of real hermetic type, normal coaxial  connectors are
>> not tight!
>> Don't route cables directly in, because no  cable braid or mesh is  vapor
>> tight.
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