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K9ACT
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« Reply #25 on: December 29, 2009, 11:49:56 PM »



I wud do a spectrum sweep check there too, Jack.


Do you make house calls?  It would be cheaper that buying a spectrum analyzer maybe?

js


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K5UJ
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« Reply #26 on: December 30, 2009, 08:22:11 AM »


Your garage should be loaded with radio stuff and the car outside where it's safe.

Hey thats what I do  Grin  Garage became the antenna maint. shed a few years ago and is also home to some tools and spare parts.

Actually AM audio into consumer solid state stuff is common.  Speakers, diodes and cables all act in concert to become something like a boy's crystal set receiver.  I get into the neighbor's land line (glad they use cell phones) and used to come out of their solid state stereo even when it was turned off.  Wrapping up the speaker wires and putting torroids at the back of the audio amp fixed that.  This is partly why I run tube audio in the shack with plate to speaker transformers. 

Switching supplies seem to pass rf on the power cables and house wiring right into the appliance whereas before a linear supply's step down transformer would stop it.   This is fundamental diode rectification of your AM signal so the solution is to do the usual stuff with ferrite cores and shunt caps to ground but that last part may not work with these cheap plastic gadgets.
Given that at my place these things give me so much RFI misery on 75 and 160 receive, I do not loose much sleep over causing interference (this is a character flaw and not an example for others  Wink ).

Tom, I'm surprised you don't get into your computer speakers etc.  Your antennas must be far away from your house.

Rob
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K1JJ
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« Reply #27 on: December 30, 2009, 12:28:59 PM »

No problem with the computers or anything else in the house.

I've been testing the 4X1 rig into a Bird dummyload on the floor in the same room as the computer and no problems with audio into consumer stuff.  The 75M local antenna is right over the house at 60', though the other antennas are between 200'-400' away.

Jack, a general coverage receiver is all you need to do a spectrum sweep.   Use a 6" wire stub out the back for an antenna.   Maybe you have a RX to cover VHF too.   There may be something real obvious that jumps out. I've seen birdies on my own signal before, that did not show up on the scope or as swr on the power meter.

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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« Reply #28 on: December 30, 2009, 05:28:11 PM »

Hi Tom, you probably won't have a problem into a dummy load but try 200 or 300 watt modulated sig. into the local 75 m. ant. and I bet you'll hear something on ur computer speakers hi hi.

Those amplified PC speakers are usually the worst for pickup of AM.

73

rob
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W1RKW
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« Reply #29 on: December 30, 2009, 05:35:10 PM »

One leg of my 75m dipole hangs almost over the homestead.  No issue with the computer speakers or anything else for that matter with 500w. Got 4 computers here.  Every once in a while the wife states she faintly hears me on the landline but that is rare. Not sure why it varies. Maybe rig tuning.
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Bob
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K1JJ
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« Reply #30 on: December 30, 2009, 06:40:38 PM »

Hi Tom, you probably won't have a problem into a dummy load but try 200 or 300 watt modulated sig. into the local 75 m. ant. and I bet you'll hear something on ur computer speakers hi hi.

Those amplified PC speakers are usually the worst for pickup of AM.

73

rob


Like I said, the local 75M antenna is right over the house at 60' high on a tower.   200-300 watts modulated?   Sorry, the rig can't go that low...  Kiss

No pickup in the computer amplified speakers.

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
WA1GFZ
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« Reply #31 on: December 30, 2009, 11:22:21 PM »

Bob, don't you have underground service?
I get into the phones a bit here but nothing else.
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« Reply #32 on: December 31, 2009, 09:54:41 AM »

yes, we have underground here. 
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Bob
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