> "But traps are kind of difficult to model (at least in NEC) at a very
detailed level. So maybe if the L or the C of the trap changes
significantly, then the trap resonance changes, which then changes the
apparent series L or C in the element.
Trap Q is more difficult to accurately model than it is to measure. A few
measurements are worth a thousand words that talk about trap loss.
> "As Markku pointed out, the Q of the trap has to be fairly high, or they'd
melt from the losses."
And they do melt from loss. During the 8th grade, I owned a TA-33 Jr. When
I upgraded to the U.S. General Class license, I received a Heath SB-230 as a
birthday gift. The moment I used the SB-230 on 20m with 500W, the driven
element traps melted. I still remember calling Mosely about the issue and
their advice was to upgrade the DE to the MP-33 model. The MP-33's DE
traps can better withstand loss. I don't know whether or not the larger
traps withstand more power due to higher Q, or just that the larger diameter
coil and insulating material are just better at absorbing power before the
melting point occurs. Back then, I was only interested in making contacts
and not understanding antenna theory. The MP-33 worked fine, but then so
did a 15m Gotham 3L that was replaced by the TA-33 Jr. The Gotham could
very well have been a better performer on 15m than the Mosely.
Paul;, W9AC
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|