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K0CQ > TECH 05.07.07 06:41l 24 Lines 1019 Bytes #999 (0) @ WW
BID : 37109_W0AK
Read: GUEST OE7FMI
Subj: > Hi Jerry,
Path: DB0FHN<DB0FOR<DB0SIF<DB0GV<DB0ZDF<DB0LJ<DB0OVN<DB0GOS<ON0AR<DB0RES<
F5GOV<F5KBJ<F4DUR<CX2SA<N9PMO<K9BBS<W9OTR<N9LYA<N9NDS<KQ0I<W0AK
Sent: 070705/0048Z @:W0AK.#CIA.IA.USA.NOAM #:37109 [Des Moines] $:37109_W0AK
From: K0CQ@W0AK.#CIA.IA.USA.NOAM
To : TECH@WW
> Thanks for the feedback on my bul, you have described the problem well.
> As to why a commercial filter maker, would have made both coils so identical to
> cause this flaw I don't know.
> 73 de John G8MNY 2007-JUL-02 @ 10:17, using PaKet6.2/Win98/Pent2
The concept of a wire length being resonant in a coil at very
nearly the wire length as if it was an antenna, e.g. showing a
velocity of propagation near to that of light is not well known.
But it sure shows up to bite one occasionally. Probably the
commercial filter maker didn't think to check at a higher
frequency, like the pass band you found.
Another cure would have been to have used a different length of
wire in the coil and a different tuning, but that would be a
whole lot harder to design the coupling to make it work because
filter synthesis techniques are dependent on symmetry which that
would destroy. The tab also works.
73, Jerry, K0CQ @ W0AK.#CIA.IA.USA
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