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Author Topic: A/C Hum  (Read 2922 times)
W8RID
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Posts: 45




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« on: January 02, 2013, 06:20:12 PM »

Was just told that I have A/C Hum on my signal.
(at the time I had power supplies running, Amplifier running, Florescent lights on)

I know that this can be caused by several things. Florescent lights, power supplies, bad grounds, etc.

Is there a way to help find out where it is coming from??

I know it is going to be a case of turning things on and off till I isolate it.

Just need some guidance at this point in time.

Bob
W8RID
 Huh
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K8AXW
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Posts: 3636




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« Reply #1 on: January 02, 2013, 08:30:57 PM »

Bob:  The reasons for AC hum on a signal are many as you point out.  Please explain what kind of gear you're running.  External power supply?  Have you monitored the voltage on the transmitter as you key it? 

More detail please.
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W8RID
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Posts: 45




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« Reply #2 on: January 03, 2013, 02:34:48 AM »

OK, Thanks for the Quick reply.

Here is what I can give you at this moment. (I'm a Firefighter/Paramedic, getting ready to leave for work. Will not be home until Friday AM)

I'm running an IC-735 with a PS-55 and a AT-150. Also what was running at the time was my Drake L4-B.
My Pyramid Phase III power supply was running for my APRS setup and rig (FT-1500)
My Computers and 2 Florescent lights. (One that I have already replaced the bulb with a incandescent bulb)

Is there a way for me to track this down without contacting someone on my rig??

Some kind of "A/C Hum Radar"??

Bob
W8RID
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WB2EOD
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Posts: 214




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« Reply #3 on: January 03, 2013, 03:27:26 AM »

It has been my experience that hum on the signal is either power supply problem or a bum mic/mic cable.
Florescent lights in the shack should not be an issue, at least I haven't seen it.
You need to determine if the AC hum is coming from the power supply or is being picked up on the mic cable.
Establish contact with another station, then put the radio in CW and send a  few seconds  of "dead carrier". 
If the other station reports the hum on your carrier, suspect a power supply issue. 
If the other station reports a clean carrier, suspect that your microphone cable may have an open shield connection at one end or the other.  Try another mic, if you have more than one

Hope this helps
73
WB2EOD
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K1CJS
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Posts: 5855




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« Reply #4 on: January 03, 2013, 04:15:15 AM »

Another thing to check is if you've got your antenna cables running alongside AC cables.  Not running those cables together isn't just because it may play havoc with SWR--the antenna cables just may pick up that 60Hz signal if the run is long enough and the AC cable(s) are feeding something that runs constantly.  It isn't a sure thing that that would be the cause, but it is something to check.
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G3RZP
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Posts: 4358




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« Reply #5 on: January 03, 2013, 04:44:22 AM »

The frequency of the hum will be a good pointer. Is it 60 or 120Hz?
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WB2WIK
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Posts: 20542




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« Reply #6 on: January 03, 2013, 09:31:35 AM »

Re: AC hum.

Is there such a thing as DC hum? Wink
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K8AXW
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Posts: 3636




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« Reply #7 on: January 03, 2013, 09:53:39 AM »

WIK:  Yes.  As one who worked in an old power house for 22 years, I can assure you that a knife switch carrying DC will "hum" as it approaches the point where it's going to blow!  Not a good place to be standing.  Shocked

However, your point is well taken and correct.  AC hum is somewhat redundant, eh?
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KE3WD
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Posts: 5694




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« Reply #8 on: January 03, 2013, 02:35:01 PM »

But that slash. 

A/C  --  Air Conditioning


AC  --  Alternating Current

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G3RZP
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Posts: 4358




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« Reply #9 on: January 04, 2013, 12:45:17 AM »

There's always AC Volts which should be AV

Similarly DC Volts instead of DV

What is an IF (or HF or VHF etc) Frequency ? Intermediate frequency squared?

Another one is 'pcb board'

But we generally understand what is meant....
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K8AXW
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Posts: 3636




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« Reply #10 on: January 04, 2013, 10:00:24 AM »

Peter:  Trying to correct an American's "English" or method of speaking is a waste of time!  If the English language was compared to a two-car funeral, we would still screw it up!   Grin
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G3RZP
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Posts: 4358




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« Reply #11 on: January 05, 2013, 01:47:12 AM »

AXW,

They are just as common over here, so it isn't all Americans........the education system here is so screwed up that there are kids leaving school who can't adequately read or write!
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KE3WD
Member

Posts: 5694




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« Reply #12 on: January 05, 2013, 07:33:37 AM »

Oh. 

Then that's neither A/C hum nor AC hum.

It is Sir Winston Churchill spinning in his grave.


73
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N6AJR
Member

Posts: 9887




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« Reply #13 on: January 16, 2013, 12:05:33 PM »

and if you teach it the words, it will no longer hum..... Smiley
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K7KBN
Member

Posts: 2756




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« Reply #14 on: January 16, 2013, 06:11:20 PM »

Every Christmas I notice a humming sound from my key collection.  I seem to have acquired a "hum-bug" somewhere along the way...  Grin .
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73
Pat K7KBN
CWO4 USNR Ret.
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