Talk:Waffle-iron filter

Circular teeth
The current version (for me, http://en.wikipedia.org/w/index.php?title=Waffle-iron_filter&oldid=461587287) says "Circular teeth will handle about 1.4 times the power capability of square teeth without arcing". I suspect that a factor of "about 1.4" is actually "square root of 2" (1.4142…) as this ratio happens to occur quite often, but without a reference I cannot be sure. -- Whitepaw (talk) 12:47, 20 November 2011 (UTC)
 * I believe the figure was arrived at experimentally and is not connected with a root-2 relationship.  Spinning Spark  20:12, 20 November 2011 (UTC)

Propagation of modes localized in the longitudinal slots
This bit:
 * Incident signals containing TM modes above a certain frequency can generate modes which propagate along the longitudinal slots with the slots themselves acting as waveguides. The point at which this can start to happen is the frequency at which the height of the slot is greater than half the free-space wavelength of the signal. If this frequency is above the required stopband of the filter the effect is of no consequence. Otherwise, steps outside the filter are needed to suppress these modes and can be incorporated into the end-matching sections.

isn't entirely clear to me. In this mode, is the E field going from one side of the slot to other? If so, then given that the bottom of the slot is a short, and the top is open, then shouldn't this mode start to propagate when the depth of the slot is greater than a quarter of the the free-space wavelength. Also, why does this couple to TM modes in the main guide more than TE modes? - or is it assumed that TE0n modes have been suppressed? You have my applause for your work on this article by the way. --catslash (talk) 00:36, 29 December 2011 (UTC)
 * I got it from Matthaei et al. who do not give any calculations but I am prepared to take their word for it. If you ping me an e-mail I will send you a copy of the page if you like.  Spinning  Spark  09:04, 29 December 2011 (UTC)
 * ...but the answer appears to be that Matthaei takes the slot depth as the distance from the "ceiling" of the filter to the "floor". That is, he is considering the slot cut in the top set of corrugations and the bottom set as a single slot whereas you are considering just one of these sets.  In Matthaei's version, of course, both the top and the bottom of the slot are a short, hence half-wavelength modes.  Spinning  Spark  10:51, 29 December 2011 (UTC)