[Amps] Black heat shields

[Fuqua, Bill L]

    I am not sure if the paint would have much effect on the NF at GHz frequencies since it is most likely completely transparent , very low emissivity, at those frequencies. Ir it had a high emissivity it would absorb the GHz radiaion and drop the gain of the dish. 
It may raise the temperature of the dish a little. 
73
bill wa4lav
________________________________________
From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of Carl [km1h at jeremy.mv.com]
Sent: Sunday, December 19, 2010 6:53 PM
To: Roger (K8RI); amps at contesting.com
Subject: Re: [Amps] Black heat shields

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?

Carl


----- Original Message -----
From: "Roger (K8RI)" <sub1 at rogerhalstead.com>
To: <amps at contesting.com>
Sent: Sunday, December 19, 2010 3:15 PM
Subject: Re: [Amps] Black heat shields


>
>
> On 12/19/2010 11:04 AM, donroden at 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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