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Old March 10th 04, 05:15 AM
Dale H. Cook
 
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On Tue, 9 Mar 2004 14:01:40 -0600, "Steve Nosko"
wrote:

Be careful with this. I haev an ICOM 706 which I have been listening to
350kHz beacons and I suspect sensitivity is not an issue. The receive is
not selective enough to keep out much noise.


Steve -

You suspect correctly. That is why the antenna preamp for the HP 117A
VLF Comparator incorporated a magnetorestrictive 60 kHz filter with a
half-power bandwidth of 30 Hz.

Dale H. Cook, Chief Engineer, WWWR Roanoke VA, WCQV Moneta VA, WKBA
WZZI Vinton VA, WKPA WLNI WZZU Lynchburg VA, WMNA/WMNA-FM Gretna VA
http://members.cox.net/dalehcook/starcity.shtml
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Old March 10th 04, 05:44 AM
Mike Knudsen
 
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In article , "Steve Nosko"
writes:

Be careful with this. I haev an ICOM 706 which I have been listening to
350kHz beacons and I suspect sensitivity is not an issue. The receive is
not selective enough to keep out much noise. Below about 200KHz I heae
locam AM broadcase stations. Some kind of IM or something. I want to build
some kind of a low / band pass filter to see if it makes a diff. The
specific antenna can also make a diff. I'm using a 40M dipole.


Pretty sure that the best antenna is a loop -- a big one with lots of turns,
and a fat cap to resonate it to 60 KC. Maybe not practical. Or use a big
ferrod loopstick and wind LOTS of turns on it.

And like you say, many RX suffer from intermod and images from the BC stations.
A low-pass filter would probably help a lot. A resonant loop would of course
eliminate all that stuff.

I haven't cracked my Rat Shack clock open, but I suspect there's some kind of
loop antenna inside. --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.
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