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Author Topic: 10Khz 'flutter' every 100Khz on 20m  (Read 2694 times)
KC5GB
Member

Posts: 13




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« on: August 06, 2010, 10:54:35 AM »

This isn't the usual electrical pulse, but a strong flutter (S7-8) that is a constant at every 100Khz. 
A new one for me.  Any ideas?

GB
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W2MV
Member

Posts: 207




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« Reply #1 on: August 09, 2010, 06:01:12 AM »

My best guess would be a switching p/s, given that it's periodic every 100 KHz.
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W2RKJ
Member

Posts: 55




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« Reply #2 on: October 13, 2010, 01:05:13 PM »

What type of receiver are you getting that on? My Ten Tec Jupiter did the same thing until I sent it back to them for an upgrade and it hasn't done it since.
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AA4HA
Member

Posts: 1640




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« Reply #3 on: November 03, 2010, 09:58:13 AM »

Most switching supplies are not very stable on their oscillation frequency (free running oscillators) and can wander around in frequency depending upon load, temperature, etc... I would be really surprised if a manufacturer made one run right at 100 kHz. It sounds like a crystal derived oscillator noise (computer, radio, clock, etc...).

I have used a portable AM radio as a bug hunter around the house. If you can pick up the 100 kHz source by tuning around in the AM band it may help you find the offending device.

A neat trick I picked up a few decades ago was to take an old cassette tape deck head and wire it to an op-amp (LM324) with a fairly high amp gain set by a feedback resistor and a 9 volt battery. Using an earpiece I could find all sorts of lower frequency offenders and even trace them down to the component level or wire by moving around the tape deck head. You could do this with parts in "ye junque box" in 10 minutes and have a nifty little toy.

Tisha Hayes, AA4HA
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KC5GB
Member

Posts: 13




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« Reply #4 on: November 03, 2010, 10:44:41 AM »

Thanks for your replies.  I tracked it down to a HD cable box in the same room as radio.  It was a very consistent in its output frequencies.
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