VK9MT transmit audio distortion.

[peterc281]

It was disappointing to hear some of the SSB signals from VK9MT, especially on 20 metres late Wednesday 2/4 , the transmit audio especially on that occasion was weak and distorted.

I had similar bad Tx audio reports when I took my K3 to Norfolk Island VK9NT which was never completely resolved, maybe it’s an earthing problem at remote locations as I don’t have the problem at my home QTH.

It is fantastic to see Elecraft supporting DX-peditions with equipment loans or donations but their reputation is easily tarnished if the equipment does not perform correctly when the whole amateur population is tuned in. I hope the engineering people at Elecraft are onto this and able to solve the problem.

Finally, thanks to the VK9MT team who did a great job under very difficult conditions and I hope they arrive home safe and sound.

73, Peter
VK3IJ

[Jim Brown-10]

On 4/5/2014 5:21 PM, peterc281 wrote:
> I had similar bad Tx audio reports when I took my K3 to Norfolk Island VK3NT
> which was never completely resolved, maybe it’s an earthing problem at
> remote locations as I don’t have the problem at my home QTH.

I seriously doubt that a connection to earth has anything at all to do
with the observed problem. Rather, I suspect some fundamental problem
with a bad interconnecting audio cable from the computer or microphone,
an antenna problem, or simple mis-adjustment of the microphone gains (or
gain the the line input, if computer playback was being used).

Remember that there should be a bond (short, fat copper) from chassis to
chassis of every piece of equipment in the station, and this collection
of equipment must be bonded to earth for safety.

73, Jim K9YC


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[Jim Brown-10]

On 4/7/2014 6:26 AM, K4ia wrote:
> Jim
>
> Didn't you mean from chassis of every piece of equipment to ground?  
> No daisy-chaining.

No, I meant exactly what I said. The long-standing advice against
daisy-chaining chassis connections is WRONG. The logic for that advice
is that a connection forms a loop with the connection to whatever common
point is chosen, but those who give the bad advice forget that there are
point-to-point connections between the equipment in the form of coax
cables, audio cables, serial cables, and control cables. These cables
form a much larger loop, that results in far greater induced voltages,
and often the shields of these cables are not even connected to the
chassis, but to the circuit board inside the gear. That combination
makes it FAR more likely that a strike will cause lightning damage, both
because the loop area is greater and the connection is not to the
chassis. So short chassis-to-chassis bonding combined with a bond from
one of those chassis to the common point is the safest from a lightning
safety point of view, because it
minimizes the loop area.

The short chassis-to-chassis connection also minimizes the power
line-related leakage voltage between equipment that causes hum and buzz
when we connect that equipment using unbalanced connections.

73, Jim K9YC.
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[NK7Z]

I run a ground buss across the back of the radio desk, connect all rigs
to that, then connect that buss to a star ground which also goes to a
second bus running across the second level of equipment.  The star then
goes to ground.

--
Support better RFI practices, please sign this petition:
at Whitehouse.gov

http://wh.gov/lpz5Y




On Mon, 2014-04-07 at 09:35 -0700, Jim Brown wrote:

> On 4/7/2014 6:26 AM, K4ia wrote:
> > Jim
> >
> > Didn't you mean from chassis of every piece of equipment to ground?  
> > No daisy-chaining.
>
> No, I meant exactly what I said. The long-standing advice against
> daisy-chaining chassis connections is WRONG. The logic for that advice
> is that a connection forms a loop with the connection to whatever common
> point is chosen, but those who give the bad advice forget that there are
> point-to-point connections between the equipment in the form of coax
> cables, audio cables, serial cables, and control cables. These cables
> form a much larger loop, that results in far greater induced voltages,
> and often the shields of these cables are not even connected to the
> chassis, but to the circuit board inside the gear. That combination
> makes it FAR more likely that a strike will cause lightning damage, both
> because the loop area is greater and the connection is not to the
> chassis. So short chassis-to-chassis bonding combined with a bond from
> one of those chassis to the common point is the safest from a lightning
> safety point of view, because it
> minimizes the loop area.
>
> The short chassis-to-chassis connection also minimizes the power
> line-related leakage voltage between equipment that causes hum and buzz
> when we connect that equipment using unbalanced connections.
>
> 73, Jim K9YC.
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>
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[mcduffie]

> So short chassis-to-chassis bonding combined with a bond from
> one of those chassis to the common point is the safest from a lightning
> safety point of view, because it
> minimizes the loop area.

You've got a good point, Jim.  However, I would prefer a combination of
both methods.  I'd run a (good low reactance) buss, AND another to the
grounding point from each buss attachment point on each unit.  Your
point about all of the ins and outs on this stuff leaves plenty of room
for loops.  Also, any time storms approach, I pull the USB ports.  They
seem to be sensitive to such damage.

Gary
--
http://ag0n.net
3055: http://ag0n.net/irlp/3055
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[Joe Subich, W4TV-4]

 > Also, any time storms approach, I pull the USB ports.  They
 > seem to be sensitive to such damage.

They would not be if you include the computer in the "short, fat"
ground bus.  The problem is that many computers do not provide
a reasonable ground connection ... the only "ground" is via the
power supply return to the third wire of the power cord (if it
even exists).  Many amateurs do not properly bond their tower and
RF ground to the power line entry ground (as required by NEC)
which allows the computer and rig to float separately in event
of a storm.

All it takes is for the rig/interface to go more that 7 or 8 volts
more positive than the computer or more than about 0.5V more negative
than the computer and the USB interface is over or reverse voltage
and "poof" goes the USB port.  Better devices now contain external
"protectors" - diodes that clamp the power supply and data lines
relative to circuit common but they still have limited capacity in
event of a strong, nearby lightning strike.

While the USB or serial port (particularly "low power" serial ports
designed with 3.3 or 5V logic) may be especially sensitive to the
"separate ground" issue, failing to bond the tower/RF ground to the
power line entrance is a significant issue of safety for your house
and *all* devices connected to the power distribution system.  With
separate grounds, a direct strike can force several *thousand* amps
between the two grounds via the "safety" ground (third wire)
connection.  The result can be massive damage to appliances and even
serious house fire.

73,

    ... Joe, W4TV


On 4/7/2014 2:58 PM, AG0N-3055 wrote:

>
>> So short chassis-to-chassis bonding combined with a bond from
>> one of those chassis to the common point is the safest from a lightning
>> safety point of view, because it
>> minimizes the loop area.
>
> You've got a good point, Jim.  However, I would prefer a combination of
> both methods.  I'd run a (good low reactance) buss, AND another to the
> grounding point from each buss attachment point on each unit.  Your
> point about all of the ins and outs on this stuff leaves plenty of room
> for loops.  Also, any time storms approach, I pull the USB ports.  They
> seem to be sensitive to such damage.
>
> Gary
>

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[Jim Brown-10]

On 4/7/2014 12:19 PM, Joe Subich, W4TV wrote:
> They would not be if you include the computer in the "short, fat"
> ground bus.

Exactly. When we say "everything," we mean EVERYTHING that is connected
in any way with the gear.

73, Jim K9YC
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