At 06:14 AM 8/16/2005, Wayne Greaves wrote:
>Several LP filters are reviewed in the August 2002 QST (but not Ameco).
>Response curves, insertion loss, and other specs were measured in the ARRL
>lab and compared to manufacturer published specs.
But were they measured into a mismatch?
Apparently not, based on a quick reading of the review. They measured the
input looking into the filter from the transmitter, but presumably they
were terminated into 50 ohms.
This is a real problem when you're trying to do harmonic suppression. More
than one designer has been bitten by a filter that attenuates well close to
the passband, but doesn't have very good attenuation farther out.
I'm not saying that the filters in the review don't work, nor that you
can't design a filter that works into any load impedance, but, as someone
pointed out, without any meaningful specs, it's all just advertising.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
TowerTalk mailing list