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[TowerTalk] 160m shunt feed followup

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Subject: [TowerTalk] 160m shunt feed followup
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Date: Sun, 30 Sep 2001 14:47:39 EDT
In regard to possible BC station interference as outlined below, the BC 
signal can generate a 2nd harmonic in the receiver.  Hi-pass filters that 
allow passage of frequencies above say 1.7 MHz block the fundamental and 
solve the problem. I'm told this would clean up the measurement for the test 
equipment. Also try a single series resonant circuit with a BC variable and 
inductor for the BC band signal and observe the affect at 1.8 MHz. Jokey the 
L/C ratios.  k7gco

In a message dated 9/30/01 9:06:44 AM Pacific Daylight Time, 
 The trick I use is to make my 75 ohm feedlines a 
 multiple of 1/2 WL.  Of course on 160M that can
 result in inconvenient lengths.  
 Another trick is to match the antenna to 75 ohms.
 Then you have NO SWR on the CATV feedline and 75 ohms
 at the transmitter regardless of the feedline length.
 75 ohms results in a 1.5:1 SWR for a 50 ohm system and
 is pretty easy to match for most radios / amplifiers.
 Tom  N4KG
In a message dated 9/30/01 8:27:48 AM Pacific Daylight Time, 
     If you think you have a BC station problem, you might try the same 
 measurement late at night if your suspect station is far enough away to 
 change field strength with skip.
 Bruce  AA4Z 

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