[Antennas] Trap design, how far from operating freq, should I hit?

Sun Apr 3 19:18:46 EDT 2005

I haven't seen that particular trap, but on the Taylor Radio and Hustler
trap verticals as well as on many beam designs, the trap consists of a coil
and a capacitor, the capacitor being the aluminum can shorted to one side
and overlapping the coil. You may be able to trim the trap enough by
shortening the coil alone. However, if that doesn't work, consider
adjusting the coil up or down a bit if it doesn't work.
Buck
N4PGW
> -----Original Message-----
> From: antennas-bounces at mailman.qth.net [mailto:antennas-
> bounces at mailman.qth.net] On Behalf Of john
> Sent: Sunday, April 03, 2005 6:14 PM
> To: antennas at mailman.qth.net
> Subject: [Antennas] Trap design, how far from operating freq, should I
> hit?
>> I'm modifying a 15m Cushcraft trap into a 12m trap by removing
> turns on the coil. I have read that it's better to design the trap to
> be resonant at a different frequency than the target (operating
> frequency) to minimize losses. I'd like to understand why this is so.
>> I'm planning on making the trap resonant above the operating
> target, and adding a bit more length to the element "inside" the
> traps,to resonate the system at my operating freq.
>> My question is, how far off the operating freq should I build
> the traps for?
>> My goal is a 12 and 17m shortened dipole (or 2 el yagi, should
> this work). An understanding of why a trap resonant at the
> operating frequency is more lossy than otherwise, would be a plus.
>> Thanks!
> John
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