🚀 go-pugleaf

In article <1992Apr6.212912.18723@phx.mcd.mot.com> hbg6@phx.mcd.mot.com 
(John Schuch) writes:
>I have a close friend who is an engineer at the local PBS TV affiliate.
>He has mentioned a few times that they can cook hot dogs by skewering
>them with a stick and holding them, one at a time, in front of the
>microwave transmitter dish on their remote van. He said it takes about
>5 minutes ( as opposed to one in an oven ) but works quite well. He is
>not known to exagerate ( or fib ) so I believe him.

Let's do a simple back-of-the-envelope calculation to see if this is possible.

Assume you have a small, run-of-the-mill hotdog and not a big, fat knockwurst.
I would guess this would be about eight per pound or two ounces each.  Assume
it has to be heated from 72 F to the boiling point of 212 F, a difference of
140 F.  I do not have any specific heat data for hotdogs but a reasonable
guess would be about half that of water.  Running this out, I calculate that
the heat needed is about 8.25 BTU.  To do this in five minutes, it takes about
105 BTU/hr of heat transfer.  Assuming all of the energy from the microwave is
available to heat the hotdog (which is NOT a reasonable assumption), this
corresponds to a power level of approximately 31 watts.

Most STL (studio to transmitter links) and similar remote microwave links
use a power level of less than 10 watts.  Considering the hotdog cannot absorb
all of the power coming from the dish (consider the area of the dish and the
area of the hotdog as a first approximation), it is VERY unlikely that this
story can be true.  If you stuffed the hotdog down the waveguide so the
energy transfer would be optimum and all of the microwave energy went into the
hotdog, the energy level is probably still too low.  Microwave ovens are
operated as multi-mode resonant cavities, of course, so all of the microwave
energy gets bounced around enough to be absorbed (a small amount gets back to
the magnetron as reflected power creating standing waves in the tube to oven
waveguide).

My conclusion is that this story is quite improbable!

				Barry L. Ornitz   ornitz@kodak.com