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 <att...@kinali.ch> Sender: time-nuts-boun...@febo.com Date: Mon, 1 Apr 2013 11:12:26 To: Discussion of precise time and frequency measurement<time-nuts@febo.com> Reply-To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: Re: [time-nuts] Photodiodes for high frequency OPLL On Sun, 31 Mar 2013 20:31:58 -0700 gary <li...@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 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.