Based on my testing (with a Times technologies T-100), field trial and my (book) reading, the four pole filter will work as a bandpass filter. It does not have the steep skirts that a resonant cavity possesses. It will, however do some things one cavity will not. Playing with it showed a mode where there were two pass notches with a reject between (like the letter "W"). Looked like what would be ideal for a repeater.

I did use the DCI in a noisy RF environment. Did work. Next trip the resonant VHF cavity is going, the DCI is staying home. Shaking on the plane makes the tuning slugs come loose. No fun.

The DCI slugs shook themselves loose on the return trip.

The first and last poles are supposedly to help match (couple?), in and out.

Picked up an elderly (but in cal) Sitemaster a few months ago. If you're interested in sweeps of the DCI and for comparison, a resonant cavity, let me know. Much nicer tool than the T-100. (Have a Narda OSL for field cal.)

Anritsu has lots of quality application notes regarding using it's gear. Great entertainment.

Norm n3ykf

On Mon, Jul 17, 2017 at 11:43 AM, Robert Bruninga [email protected] wrote:

The DCI brand of interdigital bandpass filters are neat for cleaning up reception by blocking out of band Intermod sources etc. But they are too board for any effect on in band signals.

Has anyone re-tuned the cavities to all the same frequency to see how well the filter performs as a narrowband filter?

Bob, WB4APR _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb