[time-nuts] Practical Survey-In Accuracy?
Bob Camp
kb8tq at n1k.org
Thu Aug 28 22:33:20 UTC 2014
Hi
Simple answer - yes.
My observation over the years is that your typical roof absorbs quite a bit of RF starting way below GPS frequencies. My *guess* is that shingles are a bit lossy. Shingles + moisture more so. Shingles + dirt + moisture even worse. I also believe that plywood suffers the same way. Also consider that you have things like flashing, ridge vents, and gutters involved. Somewhere below 2 MHz or so things begin to get less crazy.
I’ve spent a lot of time putting antennas up in a lot of attics and then moving them outdoors.
Bob
On Aug 28, 2014, at 9:30 AM, Bob Stewart <bob at evoria.net> wrote:
> Hi Attila,
>
>
> Is wood, nails, and asphalt shingle really that big of a problem at these frequencies? The antenna is within 2 ft of the highest point of the roof.
>
> Bob
>
>
>
> ________________________________
> From: Attila Kinali <attila at kinali.ch>
> To: Bob Stewart <bob at evoria.net>; Discussion of precise time and frequency measurement <time-nuts at febo.com>
> Sent: Thursday, August 28, 2014 8:15 AM
> Subject: Re: [time-nuts] Practical Survey-In Accuracy?
>
>
> On Sat, 23 Aug 2014 16:38:42 -0700
>
>
>
> Bob Stewart <bob at evoria.net> wrote:
>
>> Given that my antenna is just a puck at the peak of the attic (never got around to adding the DIY choke-ring)
>
> A choke ring will not help you much in the attic. You already have lots
> of reflecting and refracting surfaces/volumes above the antenna.
> Unless you get to the top of your roof, i wouldn't bother adding a choke ring.
>
>
> Attila Kinali
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