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Author Topic: Thumping in headphones  (Read 3607 times)
K1CJS
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« Reply #15 on: May 31, 2013, 06:01:37 AM »

On the lighter side, you sure it isn't someone thumping your head trying to get your attention?   Cheesy  Some of us get so absorbed that the house could fall down and we wouldn't notice!  73!
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N4DSP
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Posts: 124




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« Reply #16 on: May 31, 2013, 11:37:59 AM »


[/quote]

One other possibility:

Set the rig to semi-break-in, with a long "hold time", so that it stays in TX mode between words.

If you _still_ hear the "thumping", and it "thumps" each time you go key-up (or key-down):

. . . You have "RF in the shack".

The easiest cure is to get a ferrite clamp-on choke, and run a few turns of the CM500 cable through it, as a toroid.

I find "hi-fi" headphones perfectly OK for ham use.  The receiver's IF is supposed to remove "out-of-band" signals;  it's not the headphone's job.

What rig are you using?  How far is the antenna from the rig?  What kind of antenna?

.             Charles
[/quote]

According to your instructions Charles then I must have rf in the shack. Rigs are TenTec's Corsair II and Omni C. Antenna cables are 3 feet away from the rigs. Going to install the ferrites and hopefully that will resolve it. The headphone cables are about 6 feet long so perhaps it is picking up some stray rf. Sorry for the delay on answering your question. Been away for a couple of days.
73
john
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N4DSP
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« Reply #17 on: May 31, 2013, 11:43:16 AM »

The OP should do something in the way of ISOLATION of the reported problem or all answers are mere conjecture. 

**Substitute another set of headphones of any kind, even cheap earbuds, just to see if the problem persists.**

**Try the several CW modes available to you, such as Full Breakin, Semi QSK, and manual to see if the problem persists in all.**

**Try it with the rig connected only to a Dummy Load with short jumper.  Vary the power level from low to high to see if that affects the reported problem as well.**

**Try it into the antenna again at varying RF power levels, see if it only happens when sending full power but perhaps does not happen at say the 5 or 10 W level, indicating an "RF in the shack" situation.


73

Excellent suggestions. Thanks. I purchased another set of headphones so in addition to the CM-500's I now have Kenwood HS-5's. Regardless I needed an another set. But in regard to all of your suggestions I still have the thumping in both headphones. Now I have not added torroids and will do that next. Thanks again.
73 Clark

john
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N4DSP
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Posts: 124




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« Reply #18 on: May 31, 2013, 12:08:58 PM »

Before diddling with the headset, try backing off the RF gain on the receiver. I suspect the "thump" is due to AGC action.
Or turn off the AGC if your rig allows it and use the RF gain for comfortablelistening.
Regards
Dick

Put a couple of torroids on the headphone cables and the clamp ons. Turned the rf gain and af gain to zero and turned the drive so there was no power output and I still have that thumping. Rig is a TenTec Omni.

73
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KE3WD
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« Reply #19 on: May 31, 2013, 12:19:43 PM »

If John tried my step three, with dummy load at low power, it is rather doubtful that ferrites are going to help here. 
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N4DSP
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« Reply #20 on: May 31, 2013, 01:14:38 PM »

If John tried my step three, with dummy load at low power, it is rather doubtful that ferrites are going to help here. 

Sure did so this looks to be a lost cause. Maybe just the rigs.

john
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