TopBand: MFJ Tunable Measurement Filter

Tom Rauch
Tue, 23 Feb 1999 09:16:17 -0500

Date sent:      	Fri, 19 Feb 1999 20:37:35 -0600
From:           	Rick and Angela <>
Subject:        	TopBand: MFJ Tunable Measurement Filter

> I just noticed the new MFJ Tunable Measurement Filter in QST 
>(MAR 99 page 139).  Has anyone purchased the unit and tested it 
>out on 160m in areas plagued with high levels of AM BCB fields.  

It adds about 20 dB or so of attenuation to AM BCB signals by 
virtue of an adjustable notch and an adjustable bandpass.

Whether it cures your problem depends on how severe it is.
>?Curious about how much the filter's transfer function affects 

It is transparent at the operating frequency, no phase shift and no 
impedance transformation. It is the equivalent of a 900 ohm resistor 
in parallel with the line at the operating frequency, so it simply 
modifies the impedance of the load about the same amount as a 
1k resistor in parallel would for 160 meters.

73, Tom W8JI

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