[time-nuts] Photodiodes for high frequency OPLL

lists at lazygranch.com lists at lazygranch.com
Mon Apr 1 12:31:04 EDT 2013


This thread has already drifted a bit, but as an aside, the "sky UV" filters sold for photography are a joke. (Easily verified with UV diodes and any material that reacts to UV.) The Andover 400nm long pass actually DOES filter UV. A 400nm is nearly cast free. A 420nm does have a bit of a cast, but can be useful at times. These UV filters reduce the effect of airborne water vapor in long distance photography/remote-sensing.



-----Original Message-----
From: Attila Kinali <attila at kinali.ch>
Sender: time-nuts-bounces at febo.com
Date: Mon, 1 Apr 2013 11:12:26 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] Photodiodes for high frequency OPLL

On Sun, 31 Mar 2013 20:31:58 -0700
gary <lists at lazygranch.com> wrote:


> On 3/31/2013 5:52 AM, Attila Kinali wrote:
> >
> > Probably. But as steep filters for optics are kind of hard to come by,
> > i think a super heterodyne design isn't realy going to work.

> I've bought optical filters from Andover. They are pretty cheap, at 
> least compared to the rest of the industry.
> > http://www.andovercorp.com/Web_store/index.php

Yes, but the usual optical filters are not steep enough for this application.
They are specified to a few nm, while we are talking here about GHz.
At those wavelengths this is IIRC a factor 100'000.

But thanks for the page anyways.. they might come handy as an ambient
light filter for the photodiodes.

				Attila Kinali

-- 
The people on 4chan are like brilliant psychologists
who also happen to be insane and gross.
		-- unknown
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