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Re: [TowerTalk] Topband: Filters for Detector

To: "'Wolfert, William R.'" <>
Subject: Re: [TowerTalk] Topband: Filters for Detector
From: "Tim Duffy K3LR" <>
Date: Sat, 20 Jun 2009 14:00:31 -0500
List-post: <">>
Hello Bill:

Take a look at some helpful papers by Greg, W8WWV:

Tim K3LR

-----Original Message-----
From: []
On Behalf Of Wolfert, William R.
Sent: Saturday, June 20, 2009 9:20 AM
Subject: Topband: Filters for Detector



I have 2 separate questions for you.


#1 I learned to use an OScope, well, decades ago and I've forgotten most
of what I learned. Using Low-Band Dxing and the Antenna Handbook (W7EL's
chapter on Phased Arrays) as a guide, to measure phase in a phased
array, a load resistor, equal to the line impedance, should be placed at
both ends of the line. The pickup end is easy, but how to put the
resistor across the scope end is eluding me. I'm sure there's a
down-and-dirty easy way to accomplish this. But how?


#2 I'm building the W1MK detector (LBDX Ch. 11, pg. 26) and am including
the antennascope (6 dB Hybrid) on the same board. I also thought to just
build a BCB reject filter and PB filter into the same box. Less to carry
to the site is good, right? Since there's 2 channels, filters for each
channel would be indicated. For simplicity, a rotary switch to select
the correct filter and small coax from the filter to the switch. Is this
idea acceptable? Keep in mind; this is a looooow power measuring setup.
Is shielding between the filters necessary or just shield the entire
filter board (I'd planned to build the filters on a separate, small


Your input will be greatly appreciated.


73, Bill WR8K

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