Curiosity

[Martin Gillen-2]

Hi, Folks.

I had an interesting experience yesterday.

I was "practicing" using a desoldering tool as I have never used one
before and wanted to get my choreography figured out before I start
desoldering components to install the 80m module, so picture this:

The KX1 board is sitting in a plastic (yuch - I know...) PCB vise
which is attached to a wooden bench.  My weller soldering is not
plugged in.  My FT-51 is monitoring the local repeater.  The cable
between the soldering station and the soldering iron runs very close
to the FT-51 rubber duck antenna.

OK - so I touch the tip of the soldering iron to one of the solder
pads on the PCB, and I get a humming from the FT-51.  Remove the tip,
the humming goes away.  Touch the tip to the pad and the humming
starts again...

What on earth could be causing this?  Neither the KX1 board or the
soldering station are powered, and the hum is only present when the
soldering iron tip touched the board.

Now - in retrospect I suppose it was pretty dumb to touch the iron tip
to the board when the board is "floating" in a plastic vice and the
soldering station is "floating" as it is not plugged in...  I am
wearing a grounding strap but I'm only touching the vacuum pump and
soldering iron...

Hope I didn't fry anything :)

But I am curious what the humm is.   I'm assuming it's 60Hz being
picked up by the soldering station perhaps through the cable, but I
don't now why the hum is only present when I touch the soldering iron
tip to the KX1 board.

73 for now,
Martin.
VA3SIE.
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[Don Wilhelm-3]

Martin,

Quite simply, you were creating a 'ground loop' and the FT-51 was inside the
electric field created by that ground loop.  If you had a 'rubber ducky' on
the FT-51 that should be explaination enough, but if you were using an
outside antenna, then you may want to look at the field of the antenna
carefully.  This RF does 'funny stuff' at times.

73,
Don W3FPR

> -----Original Message-----
>
> I had an interesting experience yesterday.
>
> I was "practicing" using a desoldering tool as I have never used one
> before and wanted to get my choreography figured out before I start
> desoldering components to install the 80m module, so picture this:
>
> The KX1 board is sitting in a plastic (yuch - I know...) PCB vise
> which is attached to a wooden bench.  My weller soldering is not
> plugged in.  My FT-51 is monitoring the local repeater.  The cable
> between the soldering station and the soldering iron runs very close
> to the FT-51 rubber duck antenna.
>
> OK - so I touch the tip of the soldering iron to one of the solder
> pads on the PCB, and I get a humming from the FT-51.  Remove the tip,
> the humming goes away.  Touch the tip to the pad and the humming
> starts again...
>
> What on earth could be causing this?  Neither the KX1 board or the
> soldering station are powered, and the hum is only present when the
> soldering iron tip touched the board.
>
> Now - in retrospect I suppose it was pretty dumb to touch the iron tip
> to the board when the board is "floating" in a plastic vice and the
> soldering station is "floating" as it is not plugged in...  I am
> wearing a grounding strap but I'm only touching the vacuum pump and
> soldering iron...
>
> Hope I didn't fry anything :)
>
> But I am curious what the humm is.   I'm assuming it's 60Hz being
> picked up by the soldering station perhaps through the cable, but I
> don't now why the hum is only present when I touch the soldering iron
> tip to the KX1 board.
>
> 73 for now,
> Martin.
> VA3SIE.
>

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