[NLRS] 6 Meter interference question

[kr7o at vhfdx.com]

Get an ICE bandpass filter.  They have models that cover 50-50.500 or the 
entire band with 60-80db out of band rejection (if I remember 
correctly).  They have several power levels .1, 2, 6kw I think.  I am 
running two on my station with an 8877, the low power one after the radio 
and the 6kw one after the amp.  If you are interested in listening out of 
band just run the filter through a transfer relay and you are done.   Cost 
is about $50, probably not much more than the Drake.



At 07:47 AM 12/14/2004 -0600, jcplatt1 at mmm.com wrote:






>Hi Patrick.
>
>When trouble shooting this type of problem the key is trying to determine
>if the interfering signal is real or not.     Whether its real or not
>determines how to fix it.
>
>Your note contains two significant clues.   The first clue is that when you
>face your beam north or south the signal is very strong, but when you face
>east or west, you do not "experience the problem" (does this mean you don't
>hear the signal ?).    No beam in the world has this kind of front-to-back
>ratio (that could make such a strong signal disappear).    The second clue
>is that when you turn on the attenuator the signal "completely disappears"
>.... this is a classic clue.
>
>Both of these are strong clues that something inside your radio is being
>overloaded and that this internal overload is generating the interfering
>signal that you are hearing, the signal is not real.    The overload may be
>due to one, or several, very strong out of band (not 6m) signals that are
>doing evil things inside your radio.    Anytime you can flip in 10 dB of
>attenuation and the signal changes by more than 10 dB, the signal isnt
>"real", its sometime else.
>
>As has been suggested, the fix is to get some front selectivity and/or
>notch out the problem signal (Ch 3 ?).    I think there were a couple of
>suggestions to try out a low pass filter that has a cut off freq above 50
>MHz (passes 50 MHz) but below the Ch 3 freq (attenuates Ch3).    There are
>some commercial filters that can do this and you can also home brew
>filters.   Most of these are designed for 100 watts.   Pay attention to
>what the cut off frequency is and how much attenuation is offers at Ch3
>.... that may allow you to do some filter spec comparison.     Such a
>filter should have almost no affect to your 6m signal.
>
>73, Jon
>W0ZQ
>
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73, Robert KR7O/YB2ARO, DM07ba/OI52ee  (ex.  N7STU)
kr7o at vhfdx.com

www.vhfdx.com (KR7O/YB2ARO Weak signal, EME, microwave Site)