-40 - and the only reason I know this is that I was working in Ottawa at the time and asked what -40 was in Fahrenheit ;-) I still can't believe I forgot to take gloves on that trip. Fortunately, I only had to walk a couple of blocks from the hotel to the Canadian Patent Office :-)
73, Dave W8FGU > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:elecraft- > [EMAIL PROTECTED] On Behalf Of ON4WIX > Sent: Wednesday, June 18, 2008 2:50 AM > To: [EMAIL PROTECTED]; 'Lyle Johnson'; [EMAIL PROTECTED] > Cc: [email protected]; [EMAIL PROTECTED] > Subject: Re: [Elecraft] K3 - REF CAL Question > > Let's see who first answers this one right (without looking at a > thermometer!): > > There is one point on the scale of a thermometer where the temp in °C > equals > the temp in F. > Which one is that? > Feel free to prove mathematically... > > Enjoy! > Glenn ON4WIX > > ----- Original Message ----- > From: "Joe Subich, W4TV" <[EMAIL PROTECTED]> > To: "'Lyle Johnson'" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> > Cc: <[email protected]>; <[EMAIL PROTECTED]> > Sent: Wednesday, June 18, 2008 12:58 AM > Subject: RE: [Elecraft] K3 - REF CAL Question > > > > > > F to C is much slower, > > Not really ... (F - 30)/2 is generally within 10% and > (F - 32) * 1.1 / 2 is within about 1%. Both are easy/quick. > > Unfortunately, mental math and estimation are skills that have > been lost with the "calculator generation." > > 73, > > ... Joe, W4TV > > > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of Lyle Johnson > > Sent: Tuesday, June 17, 2008 5:14 PM > > To: [EMAIL PROTECTED] > > Cc: [email protected]; [EMAIL PROTECTED] > > Subject: Re: [Elecraft] K3 - REF CAL Question > > > > > > > You have to do that with your calculator :-) > > > > C to F is fast and easy to do in your head. > > > > The "real" formula is: > > > > F = (1.8 * C) + 32 > > > > My mental algorithm is: > > > > double the value, > > subtract 10% (round it off, who cares if it is a degree or two off), > > add 30, > > then add 2 (if you feel the need for the extra precision). > > > > Most of us can double a number in our head pretty easily. > > Round it to > > the nearest 5 and then double it if you have trouble doubling > > 37 or 43 > > or 51. Hey! It's just the "two times" tables, which we all > > learned well > > before our 9th birthday. > > > > Doubling and then taking off 10% of the result is the same as > > multiplying by 1.8 (or 9/5 if you prefer) but a heckuva lot > > easier. I > > never did learn my "1.8 times" tables... > > > > Again, round it if you trip over something like 74 - 7.4. > > The answer is > > 66.6. But does it really matter if you decide to subtract 10 and get > > 64? Or subtract 7 and get 67? > > > > Subtract 30 then 2 rather than 32. Why? Because it is easier to not > > deal with the 1's digit until you have to. If you feel you have to. > > > > I find that I can usually work it out in my head in under a > > second and > > get within a few degrees of the "correct" result. Near > > enough for most > > needs. If I'm tired it might take 2 or even 3 seconds to make the > > conversion, especially if I refuse to round things off (being an > > engineer, I sometimes get anal about numbers, which is a good > > indicator > > I'm tired!). > > > > So, for example, let's take 52C. Is the PA too hot? > > > > The real method: > > > > 2 x 52 = 104. > > 104 - 10.4 = 94 (near enough) > > 94 + 30 = 124 > > 124 + 2 = 126(if you really care...) > > > > If you'd rounded it: > > > > 2 x 50 = 100 > > 100 - 10 = 90 > > 90 + 30 = 120 > > 120 + 2 = 122. > > > > Still close enough to decide if your finals are cooking! > > (They aren't). > > Would the 4 degree difference have made you change you mind > > about the > > safety of your PA transistors? I doubt it. > > > > F to C is much slower, but I rarely have to do that :-) > > > > Enjoy! > > > > Lyle KK7P > > > > _______________________________________________ > > Elecraft mailing list > > Post to: [email protected] > > You must be a subscriber to post to the list. > > Subscriber Info (Addr. Change, sub, unsub etc.): > > http://mailman.qth.net/mailman/listinfo/elecraft > > > > Help: http://mailman.qth.net/subscribers.htm > > Elecraft web page: http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > -------------------------------------------------------------------------- > ------ > > > > No virus found in this incoming message. > Checked by AVG. > Version: 8.0.100 / Virus Database: 270.3.0/1505 - Release Date: 16/06/2008 > 7:20 > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
