[Elecraft] Remoting KAT500 to base of antenna

David Anderson gm4jjj at yahoo.co.uk
Thu Jan 21 13:38:04 EST 2016 

Dear Walter,

It isn't -all- it does really - because without the vent the problem is that the water vapour that gets in due to diurnal temperature pressure differentials cannot get back out and then continues to build up inside and forms liquid water inside your lovely expensive box. Other solutions like drain holes have problems with blockage and insect ingress.

Further, it is normal to conformal coat the delicate the electronic PEC's to protect it from condensation you will still get, but equalising pressure with a breathable vent will stop that from becoming a pool of water. If you need more protection than this then you need to have a heater as well, possibly with a fan to assist with ventilation. It all depends on how much you have to protect from the damaging effects of water. The cost of these vents is tiny in comparison. 

I only mentioned Gore because that is one of the best know manufacturers of such membrane vents, but there are many others of a similar type and appearance. We all know of Gore-Tex breathable fabrics used in outdoor wear and how well they work. They all work on the same principle. 


73 from David GM4JJJ

> On 21 Jan 2016, at 17:07, Walter Underwood <wunder at wunderwood.org> wrote:
> 
> I have no doubt that the Gore solutions work well. But Gore does have an amazing hype machine, and has encouraged people to believe that putting a plastic membrane in clothing does something magic. The Gore vents will make sure that the inside of the box is about as humid as the air outside the box. That’s all.
> 
> wunder
> K6WRU
> Walter Underwood
> CM87wj
> http://observer.wunderwood.org/ (my blog)
> 
>> On Jan 21, 2016, at 8:04 AM, David Anderson <gm4jjj at yahoo.co.uk> wrote:
>> 
>> Dear Walter,
>> 
>> Please see Gore's website where this is all explained.
>> 
>> http://www.gore.com/en_xx/products/venting/protective/index.html
>> 
>> It is the way professionals do this, they don't use bits of gauze, wicks made from shoe laces or any of the other amateur solutions seen ;-)
>> 
>> 
>> 73 from David GM4JJJ
>> 
>>> On 21 Jan 2016, at 15:48, Walter Underwood <wunder at wunderwood.org> wrote:
>>> 
>>> Gore-Tex might let moisture out, but it might let it in. Moisture migrates from the more humid side of the membrane to the less humid side. It is a pretty slow process.
>>> 
>>> wunder
>>> K6WRU
>>> Walter Underwood
>>> CM87wj
>>> http://observer.wunderwood.org/ (my blog)
>>> 
>>>> On Jan 20, 2016, at 11:39 PM, Ian White <gm3sek at ifwtech.co.uk> wrote:
>>>> 
>>>> The key point about a semi-permeable vent is that it blocks liquid water
>>>> (and insects) from getting into the enclosure, but *always* allows water
>>>> vapor to escape.  As David points out, plain mesh won't do that under
>>>> all conditions.
>>>> 
>>>> In the UK, an equivalent to the Gore-Tex engineered vents is available
>>>> from Farnell for about £5 ($7.50). Part numbers 2308394 (black) or
>>>> 2308395 (grey).
>>>> 
>>>> CPC normally has them a little cheaper (part numbers EN83188 or EN83189)
>>>> but they are currently out of stock.
>>>> 
>>>> Compared with the value of the KAT500 inside the enclosure, a properly
>>>> engineered semi-permeable vent is a very good investment.
>>>> 
>>>> 
>>>> 73 from Ian GM3SEK
>>>> 
>>>> 
>>>>> -----Original Message-----
>>>>> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of
>>>>> David Cutter
>>>>> Sent: 21 January 2016 07:08
>>>>> To: Lewis Phelps; Elecraft at mailman.qth.net
>>>>> Subject: Re: [Elecraft] Remoting KAT500 to base of antenna
>>>>> 
>>>>> Yes, but the weight of water eventually pushes it through - it's cheap
>>>> but
>>>>> not perfect. If you use a 20mm fitting as I did back then, water
>>>> accumulates
>>>>> inside until a large droplet forms then exits. The Gortex is better but
>>>> more
>>>>> $ £.
>>>>> 
>>>>> David, G3UNA
>>>>> 
>>>>> 
>>>>> ----- Original Message -----
>>>>> From: "Lewis Phelps" <lew at n6lew.us>
>>>>> To: <Elecraft at mailman.qth.net>
>>>>> Sent: Wednesday, January 20, 2016 8:03 PM
>>>>> Subject: Re: [Elecraft] Remoting KAT500 to base of antenna
>>>>> 
>>>>> 
>>>>>> But might not this re-introduce the surface tension problem?
>>>>>> 
>>>>>> Lew N6LEW
>>>>>> 
>>>>>> 
>>>>>>> On Jan 20, 2016, at 10:18 AM, David Cutter <d.cutter at ntlworld.com>
>>>>> wrote:
>>>>>>> 
>>>>>>> From my work in the food industry (if memory serves), critter
>>>> invasion is
>>>>>>> prevented with 0.64mm square nylon netting.  This is common in the
>>>>>>> dress-making industry.  (I think it can also be found as a stainless
>>>>>>> steel gauze). This can be glued over a breather (drip) hole in the
>>>> base.
>>>>>>> 
>>>>>>> David
>>>>>>> G3UNA
>>>>>>> 
>>>>>>> 
>>>>>>> ----- Original Message ----- From: "Edward R Cole"
>>>> <kl7uw at acsalaska.net
>>>>>>> <mailto:kl7uw at acsalaska.net>>
>>>>>>> To: <Elecraft at mailman.qth.net <mailto:Elecraft at mailman.qth.net>>
>>>>>>> Sent: Wednesday, January 20, 2016 8:29 AM
>>>>>>> Subject: Re: [Elecraft] Remoting KAT500 to base of antenna
>>>>>>> 
>>>>>>> 
>>>>>>>> Fred,
>>>>>>>> 
>>>>>>>> Your high desert climate will probably produce less condensation
>>>> than
>>>>> my
>>>>>>>> sub-arctic/maritime environ.  What I do for enclosures is to not
>>>> seal
>>>>>>>> them airtight but provide good drain openings which air can
>>>> exchange.
>>>>>>>> Of course the shelter is made to repel direct rain/snow.
>>>>>>>> 
>>>>>>>> I suspected that my TR relays were "freezing up" at lower temps
>>>> making
>>>>>>>> the action delayed so I used some big aluminum  Dale resistor
>>>> strapped
>>>>>>>> onto the relays to add direct heat by conduction.  I happen to have
>>>> 28v
>>>>>>>> equipment so used 28v thru the resistors to produce heat within
>>>> their
>>>>>>>> wattage rating (used 40w resistors at both relays).  Of course this
>>>> also
>>>>>>>> provided some heating of the ambient air of the enclosure which
>>>> helped
>>>>>>>> keep moisture from forming even in 90% humidity of the fall.  It
>>>> rains
>>>>>>>> 8-days with one day off from August to October when temps finally
>>>>> drop
>>>>>>>> below freezing and rain becomes snow.  You don't have anything near
>>>>>>>> that.
>>>>>>>> 
>>>>>>>> One thing I have noticed about drain holes in some equipment is
>>>> they
>>>>> are
>>>>>>>> too small to allow water to drop free due to surface tension and in
>>>> my
>>>>>>>> environ that results in the weep holes freezing tight.  I drill
>>>> them out
>>>>>>>> to 1/4 inch.  Of course if you are prone to insect/archnid invasion
>>>> that
>>>>>>>> is problematic.
>>>>>>>> 
>>>>>>>> PS: I lived five years in the high Mojave Desert so know all about
>>>>>>>> "critters of the desert" (never stick your hand into a confined
>>>> space
>>>>>>>> before kicking it to see what crawls out or "rattles"!
>>>>>>>> 
>>>>>>>> 73, Ed - KL7UW
>>>>>>>> ------------------------------------------
>>>>>>>> 
>>>>>>>> 3.  Reno/Sparks is a high desert [4,500'] directly adjacent to the
>>>>>>>> Carson Range and Sierra Nevada [really big mountains].  Winter
>>>> temps
>>>>> go
>>>>>>>> down into single digits, it does snow/rain.  Should I do anything
>>>> to
>>>>>>>> prevent condensation in the weatherproof box [light bulb, drain
>>>> hole,
>>>>>>>> ???].
>>>>>>>> 
>>>>>>>> 73,
>>>>>>>> 
>>>>>>>> Fred K6DGW
>>>>>>>> - Northern California Contest Club
>>>>>>>> - CU in the Cal QSO Party 1-2 Oct 2016
>>>>>>>> - www.cqp.org
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 73, Ed - KL7UW
>>>>>>>> http://www.kl7uw.com
>>>>>>>> "Kits made by KL7UW"
>>>>>>>> Dubus Mag business:
>>>>>>>> dubususa at gmail.com
>>>>> ______________________________________________________________
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>>>>> ______________________________________________________________
>>>>>>> Elecraft mailing list
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>>>>>>> Message delivered to lew at n6lew.us <mailto:lew at n6lew.us>
>>>>>> Lew Phelps N6LEW
>>>>>> Pasadena, CA DM04wd
>>>>>> Elecraft K3-10 / KXV144 / XV432
>>>>>> Yaesu FT-7800
>>>>>> Lew at N6LEW.US
>>>>>> www.n6lew.us
>>>>>> 
>>>>>> Generalized Law of Entropy: Sooner or later, everything that has been
>>>> put
>>>>>> together will fall apart.
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> ______________________________________________________________
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>>>>> 
>>>>> ______________________________________________________________
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>>>> 
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>>> 
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> 
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