Re: [Elecraft] [PX3] Carrier Null

[Joe Subich, W4TV]

On 6/3/2016 10:03 AM, Don Wilhelm wrote:
> The bonding wire eliminates much of that "pin 1 problem".

That is only true of two conditions are met:
1) the case is metal (conductive)
2) the case is tied to the power supply return (negative) at
   the power input.

Otherwise, *bonding* tends to circuit board "ground plane" to
circuit board "ground plane" and spread the noise through all
of the connected devices - particularly if the device does
not have a single "ground post" and the bonding is connected
haphazardly to whatever case/chassis/connector screw is handy.

73,

   ... Joe, W4TV


On 6/3/2016 10:03 AM, Don Wilhelm wrote:

Joel and all,

Use BONDING rather than "Grounding"

You may create more noise problems by attempting to "ground" everything.
"Ground" is not a sink for noise and RFI problems, it is only protection
for AC mains safety and lightning surges.  Grounding will not carry away
noise that is picked up on the shields of connecting cables, and in some
cases may even make it worse.  Yes, you should have a good Mother Earth
ground in the hamshack, but it will likely not help with noise, hum and
buzz problems.

Take the advice of Jim Brown K9YC and BOND the equipment enclosures
together.
In other words, connect the KX3 and PX3 enclosures together with a heavy
wire or braid.

What you accomplish by bonding is to take a major portion of the noise
that would appear on the cable shield(s) and conduct it to the outside
of the enclosure so that it does not get onto the ground plane of the PC
board.

We did not have that problem years ago when all connectors were mounted
to a metal enclosure.  The outside of the cable shield braid was
connected to the outside of the enclosure.
But modern construction techniques connect the shields of cables to the
ground plane of the PC board and not to the enclosure.  So any noise
present on the outside of the cable shield is conducted into the
electronics.  The bonding wire eliminates much of that "pin 1 problem".

73,
Don W3FPR


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Re: [Elecraft] [PX3] Carrier Null

[Don Wilhelm]

Joel and all,

Use BONDING rather than "Grounding"

You may create more noise problems by attempting to "ground" everything.
"Ground" is not a sink for noise and RFI problems, it is only protection 
for AC mains safety and lightning surges.  Grounding will not carry away 
noise that is picked up on the shields of connecting cables, and in some 
cases may even make it worse.  Yes, you should have a good Mother Earth 
ground in the hamshack, but it will likely not help with noise, hum and 
buzz problems.


Take the advice of Jim Brown K9YC and BOND the equipment enclosures 
together.
In other words, connect the KX3 and PX3 enclosures together with a heavy 
wire or braid.


What you accomplish by bonding is to take a major portion of the noise 
that would appear on the cable shield(s) and conduct it to the outside 
of the enclosure so that it does not get onto the ground plane of the PC 
board.


We did not have that problem years ago when all connectors were mounted 
to a metal enclosure.  The outside of the cable shield braid was 
connected to the outside of the enclosure.
But modern construction techniques connect the shields of cables to the 
ground plane of the PC board and not to the enclosure.  So any noise 
present on the outside of the cable shield is conducted into the 
electronics.  The bonding wire eliminates much of that "pin 1 problem".


73,
Don W3FPR



On 6/3/2016 6:18 AM, Joel Black wrote:

Someone on this list or the Yahoo reflector posted a picture of a BNC star 
washer with a ground lug on it. I’m going to order one of those and also put 
some kind of ground lug on the PX3 and make sure I have a good ground in the 
shack and *try* to eliminate any ground loop issues between the KX3 and PX3.




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Re: [Elecraft] [PX3] Carrier Null

[Joel Black]

I’m not sure, but I think the problem has solved itself. I’m listening to a 75 
m group this morning and listened to a little 20 m PSK last night and the 
artifacts, for the most part, appear to be gone.

Not sure what happened or what I did to fix it - I did not go through the 
Opposite Sideband Nulling procedure.

Here *is* what I did:

1. After I received the PX3, I updated the F/W. After I updated, I saved a 
config (yep, should have saved before but forgot). I reloaded that saved config 
last night.
2. Recently, I tried a new power-up procedure - KX3 *then* PX3. I had the power 
jumper set on the PX3 to turn on when DC is applied and didn’t like the lack of 
control that offered so I put the jumper back.
3. I have arranged my cables a tad differently and will take a picture of that 
arrangement trying to duplicate it each time.

Someone on this list or the Yahoo reflector posted a picture of a BNC star 
washer with a ground lug on it. I’m going to order one of those and also put 
some kind of ground lug on the PX3 and make sure I have a good ground in the 
shack and *try* to eliminate any ground loop issues between the KX3 and PX3.

Late yesterday afternoon, I was kicking myself; today, I’m quite pleased with 
the PX3 - fickle lot, aren’t we?

73,
Joel - W4JBB
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Re: [Elecraft] [PX3] Carrier Null

[Paul Saffren N6HZ]

Hi Joel, 

It sounds like  you might be confusing the Rx null for the KX3 with the
opposite side band nulling for the PX3.  (easy since they both are
'nulling') .  If you are interested in removing opposite side bands from the
display of the PX3, follow the PX3 OSB nulling procedures as noted in the
PX3 manual.  As others have mentioned, be sure to plug that little I/Q
connector firmly into the KX3.  It is common to have it only partially
seated which only feeds one of the I/Q signals into the PX3.  

-Paul




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Re: [Elecraft] [PX3] Carrier Null

[Don Wilhelm]

Joel,

Mirror images normally mean that only one channel of the I/Q outputs are 
being received by the PX3.  Make certain the RX I/Q cables are fully 
plugged in (both ends).
So rather than "holding your mouth right", try "holding your fingers 
right" to fully insert the plugs.


Start over with the default settings after checking the cable and go 
from there.
I doubt the service monitor will do much unless it tunes down to the low 
audio range.


You can try plugging a set of amplified speakers into the KX3 RX I/Q to 
see if you get something in each channel, or if you want to get more 
exotic, use an audio spectrum analyzer that will display stereo channels 
and feed the RX I/Q to a computer soundcard.

The 2 audio channels from the KX3 should be shown, but out of phase.

73,
Don W3FPR

On 6/1/2016 8:31 PM, Joel Black wrote:

I recently acquired a used PX3 and am quite pleased with it. I am, however, 
having a difficult time with the carrier null procedure. If memory serves, I 
had a problem trying to do the carrier null on an SDR I built five or six years 
ago too.

I never could quite get the signal generator in the PX3 to get to -40. It 
stayed around -45. I did write everything down and did try to adjust the nulls 
but I’ve either got too much noise in the shack or I just don’t know what in 
the world I’m doing.

Right now, I’m listening on 75 m and I can see the center carrier plus mirror 
images of each side of the carrier. The span is set to 50 kHz.

Any certain way I’m supposed to “hold my mouth” or “stick out my tongue” while 
I do this? :)



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Re: [Elecraft] [PX3] Carrier Null

[Nr4c]

Please check that ALL connectors are plugged in ALL the way. 

Sent from my iPhone
...nr4c. bill


> On Jun 1, 2016, at 8:31 PM, Joel Black  wrote:
> 
> I recently acquired a used PX3 and am quite pleased with it. I am, however, 
> having a difficult time with the carrier null procedure. If memory serves, I 
> had a problem trying to do the carrier null on an SDR I built five or six 
> years ago too.
> 
> I never could quite get the signal generator in the PX3 to get to -40. It 
> stayed around -45. I did write everything down and did try to adjust the 
> nulls but I’ve either got too much noise in the shack or I just don’t know 
> what in the world I’m doing.
> 
> Right now, I’m listening on 75 m and I can see the center carrier plus mirror 
> images of each side of the carrier. The span is set to 50 kHz.
> 
> Any certain way I’m supposed to “hold my mouth” or “stick out my tongue” 
> while I do this? :)
> 
> I’ll bring home a service monitor from work tomorrow and hope it tunes down 
> as low as I need it to go.
> 
> 73,
> Joel - W4JBB
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[Elecraft] [PX3] Carrier Null

[Joel Black]

I recently acquired a used PX3 and am quite pleased with it. I am, however, 
having a difficult time with the carrier null procedure. If memory serves, I 
had a problem trying to do the carrier null on an SDR I built five or six years 
ago too.

I never could quite get the signal generator in the PX3 to get to -40. It 
stayed around -45. I did write everything down and did try to adjust the nulls 
but I’ve either got too much noise in the shack or I just don’t know what in 
the world I’m doing.

Right now, I’m listening on 75 m and I can see the center carrier plus mirror 
images of each side of the carrier. The span is set to 50 kHz.

Any certain way I’m supposed to “hold my mouth” or “stick out my tongue” while 
I do this? :)

I’ll bring home a service monitor from work tomorrow and hope it tunes down as 
low as I need it to go.

73,
Joel - W4JBB
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