On 12/19/2010 6:53 PM, Carl wrote:
> It must have done wonders for the NF after you went black. Maybe thats
> why dishes are normally painted a light flat color dont you think?
>
The LNB was well out in the open so it stayed pretty well at ambient and
the signals were strong enough NF was no problem ... With the exception
of one satellite that was way down on the Western horizon (through the
trees) OTOH we never did get that one well before or after the paint
job. It was actually warmer *behind* the dish than in front of it. OTOH
I assume the NF for the LNB that was there when it had the fancy paint
job was probably pretty poor<:-))
73
Roger (K8RI)
> Carl
>
>
> ----- Original Message ----- From: "Roger (K8RI)"
> <sub1@rogerhalstead.com>
> To: <amps@contesting.com>
> Sent: Sunday, December 19, 2010 3:15 PM
> Subject: Re: [Amps] Black heat shields
>
>
>>
>>
>> On 12/19/2010 11:04 AM, donroden@hiwaay.net wrote:
>>>>> Bare Aluminum if real can make a real good IR reflector.
>>>
>>> http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html
>>>
>>>
>>> Anybody ever see a polished solar hot water collector ?
>> I once had a number of C-band satellite dishes. One, an 8 footer was
>> solid Aluminum. It was getting pretty scruffy looking out in the
>> elements so I decided to paint it. The only suitable paint I had, or so
>> I thought, was some left over aircraft paint. Now this is some HIGH
>> gloss stuff that looks like it's had "clear coat" sprayed over it. It
>> would have been far more expensive to purchase than painting the dish
>> was worth, but "it was left over".
>>
>> The finished dish looked great and worked very well. However twice a
>> year for a couple of days the sun is directly in line with the
>> geostationary satellites. It's only for a couple of minutes at most.
>> This normally results in signal loss from that satellite during that
>> period. It also means the dish, which is really one giant mirror, it
>> also pointing at the sun with the focus on the LNB. This was one little
>> detail I had forgotten.
>>
>> I remember pulling in the driveway and something just didn't look right,
>> but I couldn't put my finger on it. Then my focus shifted to the
>> satellite dish. Even from a 100 feet I could see what looked like "some
>> things" hanging from the LNB. Inspection showed that the heat had
>> melted the fittings right of the LNB and of course had melted the solder
>> and completely cooked the LNB
>>
>> I repainted the dish, but this time it was flat black. Man, did that
>> dish get hot, but it never melted another LNB. You could feel the heat
>> from that dish a good 10 feet behind it. BTW that particular dish is
>> visible in the "Google Earth" image so I know that image hasn't been
>> updated in quite a while.
>>
>> 73
>>
>> Roger (K8RI)
>>
>>
>>> Ever wondered why not ?
>>>
>>> Don W4DNR
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>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
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>
>
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