Elecraft

RS232 Noise

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Mike Harris-9

RS232 Noise

G'day,

Just in case anyone is interested.

Today I was investigating the effectiveness on a local 6m low level signal
of the various combinations of NO PREAMP, K3 PREAMP ONLY, PR6 ONLY, K3
PREAMP + PR6 in preparation for a 6m EME test.

All was as expected then I turned on the PC. With the two preamps in line
there was a 1-2 S-point increase in background noise (SSB bandwidth).
This extra noise vanished when I removed the "RS232" cable from the K3.
The cable is actually the one I made up for the K2.

Touching the shell of the connector to the K3 shell didn't restore the
noise, only when actually inserting the pins did it come back.

No noise being carried on the two audio leads to/from the PC so no big
deal the disconnect the RS232 during the moon run.

No further investigations to date.

Regards,

Mike VP8NO

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N5GE

Re: RS232 Noise

On Wed, 22 Apr 2009 19:11:51 -0400, "Mike Harris"
<[hidden email]> wrote:

Being concerned by your report, I checked my K3 #806 and did not
experience the symptom you describe.

Tom, N5GE
K3 #806, K3 #1055
XV144, XV432
W1 and other small kits.
http://www.n5ge.com

>G'day,
>
>Just in case anyone is interested.
>
>Today I was investigating the effectiveness on a local 6m low level signal
>of the various combinations of NO PREAMP, K3 PREAMP ONLY, PR6 ONLY, K3
>PREAMP + PR6 in preparation for a 6m EME test.
>
>All was as expected then I turned on the PC. With the two preamps in line
>there was a 1-2 S-point increase in background noise (SSB bandwidth).
>This extra noise vanished when I removed the "RS232" cable from the K3.
>The cable is actually the one I made up for the K2.
>
>Touching the shell of the connector to the K3 shell didn't restore the
>noise, only when actually inserting the pins did it come back.
>
>No noise being carried on the two audio leads to/from the PC so no big
>deal the disconnect the RS232 during the moon run.
>
>No further investigations to date.
>
>Regards,
>
>Mike VP8NO
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
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Amateur Radio Operator N5GE

Jim Brown-10

Re: RS232 Noise

In reply to this post by Mike Harris-9

On Wed, 22 Apr 2009 19:11:51 -0400, Mike Harris wrote:

>This extra noise vanished when I removed the "RS232" cable from the
K3.
>The cable is actually the one I made up for the K2.

There are several problems in the setup. First, the K3 connector shells
are not properly bonded to the chassis, so the cable shield is useless.
Second, the cable Elecraft sold with the K2-series products used
parallel conductors, not twisted pairs. That's a recipe for noise and
RFI.

I live in a fairly quiet area in the Santa Cruz Mountains, and lots of
small electronics produce noise that I can hear, both HF and VHF. Much
of that noise is radiated as a common mode signal on the various cables
connected to the noise source. I have several suggestions for you.

1) Build the serial cable shown in my RFI application note.
http://audiosystemsgroup.com/RFI-Ham.pdf It uses CAT5 cable. When VHF
noise is a concern, shielded CAT5 may offer further improvements.

2) Use ferrite chokes on every cable to kill common mode current. A
single turn through a #43 core peaks the choking action around 150 MHz.
Two-three turns moves the peak down to 6M and provides about three
times the choking impedance. If you're concerned about both bands, use
multiple cores in series. The equipment at both ends of any cable can
be the noise source, so if the cable is longer than about 1/4 wave, use
chokes at both ends. I did all of this in my station (and around my
XYL's computers) and killed a lot of noise.

3) Fix the pin 1 problem in the K3 by bonding the DB-connectors to the
chassis. Pin 1 problems couple RFI in both directions -- that is, they
let RF into equipment and they put RF onto cables that radiate it.

73,

Jim Brown K9YC

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Mike Harris-9

Re: RS232 Noise

In reply to this post by N5GE

Hi Tom,

I'm beginning to wonder if it might not be due to shorting out the chokes
for PC out and PC in of the RS232 connector whilst doing the rear panel RF
immunity mods.

The problem is I don't have a "before" benchmark. I can now hear PC
activity, screen update (the seconds ticking by in WSJT).
----- Original Message -----
From: "Radio Amateur N5GE" <[hidden email]>
To: "Mike Harris" <[hidden email]>
Cc: "Reflector Elecraft" <[hidden email]>
Sent: Wednesday, April 22, 2009 8:08 PM
Subject: Re: [Elecraft] RS232 Noise

On Wed, 22 Apr 2009 19:11:51 -0400, "Mike Harris"
<[hidden email]> wrote:

Being concerned by your report, I checked my K3 #806 and did not
experience the symptom you describe.

Tom, N5GE
K3 #806, K3 #1055
XV144, XV432
W1 and other small kits.
http://www.n5ge.com

>G'day,
>
>Just in case anyone is interested.
>
>Today I was investigating the effectiveness on a local 6m low level
>signal
>of the various combinations of NO PREAMP, K3 PREAMP ONLY, PR6 ONLY, K3
>PREAMP + PR6 in preparation for a 6m EME test.
>
>All was as expected then I turned on the PC. With the two preamps in
>line
>there was a 1-2 S-point increase in background noise (SSB bandwidth).
>This extra noise vanished when I removed the "RS232" cable from the K3.
>The cable is actually the one I made up for the K2.
>
>Touching the shell of the connector to the K3 shell didn't restore the
>noise, only when actually inserting the pins did it come back.
>
>No noise being carried on the two audio leads to/from the PC so no big
>deal the disconnect the RS232 during the moon run.
>
>No further investigations to date.
>
>Regards,
>
>Mike VP8NO
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

--------------------------------------------------------------------------------

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Mike Harris-9

Re: RS232 Noise

In reply to this post by Jim Brown-10

Hi Jim,

I have your paper and will have another read. I've been meaning to make
up a new cable for a while.

The noise has only become noticeable since I increased the sensitivity on
6m and if I switch out the PR6 I can't hear it. 6m is reasonably quiet
here, particularly when I beam out to sea (north). As mentioned in a half
finished posting that launched, I don't have any benchmark so it is not
known if the "problem" existed before I shorted the chokes on the data
return lines as offered as an option in the app note.

The spooky sigh as the WSJT clock display changes shows up quite well and
the decode has its own longer noise. I turned the monitor off but it is
still there.

Regards,

Mike VP8NO

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: "Reflector Elecraft" <[hidden email]>
Sent: Thursday, April 23, 2009 10:10 AM
Subject: Re: [Elecraft] RS232 Noise

| On Wed, 22 Apr 2009 19:11:51 -0400, Mike Harris wrote:
|
| >This extra noise vanished when I removed the "RS232" cable from the
| K3.
| >The cable is actually the one I made up for the K2.
|
| There are several problems in the setup. First, the K3 connector shells
| are not properly bonded to the chassis, so the cable shield is useless.
| Second, the cable Elecraft sold with the K2-series products used
| parallel conductors, not twisted pairs. That's a recipe for noise and
| RFI.
|
| I live in a fairly quiet area in the Santa Cruz Mountains, and lots of
| small electronics produce noise that I can hear, both HF and VHF. Much
| of that noise is radiated as a common mode signal on the various cables
| connected to the noise source. I have several suggestions for you.
|
| 1) Build the serial cable shown in my RFI application note.
| http://audiosystemsgroup.com/RFI-Ham.pdf It uses CAT5 cable. When VHF
| noise is a concern, shielded CAT5 may offer further improvements.
|
| 2) Use ferrite chokes on every cable to kill common mode current. A
| single turn through a #43 core peaks the choking action around 150 MHz.
| Two-three turns moves the peak down to 6M and provides about three
| times the choking impedance. If you're concerned about both bands, use
| multiple cores in series. The equipment at both ends of any cable can
| be the noise source, so if the cable is longer than about 1/4 wave, use
| chokes at both ends. I did all of this in my station (and around my
| XYL's computers) and killed a lot of noise.
|
| 3) Fix the pin 1 problem in the K3 by bonding the DB-connectors to the
| chassis. Pin 1 problems couple RFI in both directions -- that is, they
| let RF into equipment and they put RF onto cables that radiate it.
|
| 73,
|
| Jim Brown K9YC

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Mike Harris-9

RS232 Noise

In reply to this post by Jim Brown-10

G'day,

Finally got around to making a replacement RS232 rig control cable using
CAT6 patch cable, about three metres long. Method used was as detailed in
the reference below.

Results; spectacular! Noise on 6m increases approx 1dB when the cable is
connected to the K3 (no antenna). Using the old cable the noise jumps up
approx 9dB and was 6dB up on the noise floor when the antenna is
connected.

I can no longer hear the CRT monitor updating when the seconds tick over
in WSJT. This was audible even when the old cable was disconnected from
the K3 so it was probably being radiated from the cable and picked up by
the antenna.

Regards,

Mike VP8NO

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: "Reflector Elecraft" <[hidden email]>
Sent: Thursday, April 23, 2009 10:10 AM
Subject: Re: [Elecraft] RS232 Noise

| On Wed, 22 Apr 2009 19:11:51 -0400, Mike Harris wrote:
|
| >This extra noise vanished when I removed the "RS232" cable from the
| K3.
| >The cable is actually the one I made up for the K2.
|
| There are several problems in the setup. First, the K3 connector shells
| are not properly bonded to the chassis, so the cable shield is useless.
| Second, the cable Elecraft sold with the K2-series products used
| parallel conductors, not twisted pairs. That's a recipe for noise and
| RFI.

<snip>

| 1) Build the serial cable shown in my RFI application note.
| http://audiosystemsgroup.com/RFI-Ham.pdf It uses CAT5 cable. When VHF
| noise is a concern, shielded CAT5 may offer further improvements.
|
| 3) Fix the pin 1 problem in the K3 by bonding the DB-connectors to the
| chassis. Pin 1 problems couple RFI in both directions -- that is, they
| let RF into equipment and they put RF onto cables that radiate it.
|
| 73,
|
| Jim Brown K9YC

______________________________________________________________
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Ken Wagner K3IU

Re: RS232 Noise

Mike:
From Release Notes
MCU 2.45 / DSP 1.92, 9-29-2008

* TRANSMIT NOISE GATE ADDED: The TX noise gate can be used to suppress
transmitted audio below a certain level, e.g. a noisy fan (not the one
on the K3, of
course). To use the noise gate, locate CONFIG:TX GATE, tap '1' to turn
it ON,
then use VFO A to set the desired threshold. Since there's no visual
indication that
transmit audio is below the threshold, you should adjust it using the
transmit voice
monitor (MON), ideally using headphones. Set the threshold high enough
to cut off
transmit audio due to shack noise, but not so high that it causes your
voice to drop
out too frequently. The TX GATE threshold can be adjusted in TX TEST mode.

Mike Harris wrote:

> G'day,
>
> Finally got around to making a replacement RS232 rig control cable using
> CAT6 patch cable, about three metres long. Method used was as detailed in
> the reference below.
>
> Results; spectacular! Noise on 6m increases approx 1dB when the cable is
> connected to the K3 (no antenna). Using the old cable the noise jumps up
> approx 9dB and was 6dB up on the noise floor when the antenna is
> connected.
>
> I can no longer hear the CRT monitor updating when the seconds tick over
> in WSJT. This was audible even when the old cable was disconnected from
> the K3 so it was probably being radiated from the cable and picked up by
> the antenna.
>
> Regards,
>
> Mike VP8NO
>
> ----- Original Message -----
> From: "Jim Brown" <[hidden email]>
> To: "Reflector Elecraft" <[hidden email]>
> Sent: Thursday, April 23, 2009 10:10 AM
> Subject: Re: [Elecraft] RS232 Noise
>
>
> | On Wed, 22 Apr 2009 19:11:51 -0400, Mike Harris wrote:
> |
> | >This extra noise vanished when I removed the "RS232" cable from the
> | K3.
> | >The cable is actually the one I made up for the K2.
> |
> | There are several problems in the setup. First, the K3 connector shells
> | are not properly bonded to the chassis, so the cable shield is useless.
> | Second, the cable Elecraft sold with the K2-series products used
> | parallel conductors, not twisted pairs. That's a recipe for noise and
> | RFI.
>
> <snip>
>
> | 1) Build the serial cable shown in my RFI application note.
> | http://audiosystemsgroup.com/RFI-Ham.pdf It uses CAT5 cable. When VHF
> | noise is a concern, shielded CAT5 may offer further improvements.
> |
> | 3) Fix the pin 1 problem in the K3 by bonding the DB-connectors to the
> | chassis. Pin 1 problems couple RFI in both directions -- that is, they
> | let RF into equipment and they put RF onto cables that radiate it.
> |
> | 73,
> |
> | Jim Brown K9YC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

Ken Wagner K3IU

Re: RS232 Noise

Oops. I responded to the wrong email. Looks like this has already been
addressed.
73,
Ken K3IU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ken K3IU wrote:

> Mike:
> From Release Notes
> MCU 2.45 / DSP 1.92, 9-29-2008
>
> * TRANSMIT NOISE GATE ADDED: The TX noise gate can be used to suppress
> transmitted audio below a certain level, e.g. a noisy fan (not the one
> on the K3, of
> course). To use the noise gate, locate CONFIG:TX GATE, tap '1' to turn
> it ON,
> then use VFO A to set the desired threshold. Since there's no visual
> indication that
> transmit audio is below the threshold, you should adjust it using the
> transmit voice
> monitor (MON), ideally using headphones. Set the threshold high enough
> to cut off
> transmit audio due to shack noise, but not so high that it causes your
> voice to drop
> out too frequently. The TX GATE threshold can be adjusted in TX TEST mode.
>
>
>
> Mike Harris wrote:
>
>> G'day,
>>
>> Finally got around to making a replacement RS232 rig control cable using
>> CAT6 patch cable, about three metres long. Method used was as detailed in
>> the reference below.
>>
>> Results; spectacular! Noise on 6m increases approx 1dB when the cable is
>> connected to the K3 (no antenna). Using the old cable the noise jumps up
>> approx 9dB and was 6dB up on the noise floor when the antenna is
>> connected.
>>
>> I can no longer hear the CRT monitor updating when the seconds tick over
>> in WSJT. This was audible even when the old cable was disconnected from
>> the K3 so it was probably being radiated from the cable and picked up by
>> the antenna.
>>
>> Regards,
>>
>> Mike VP8NO
>>
>> ----- Original Message -----
>> From: "Jim Brown" <[hidden email]>
>> To: "Reflector Elecraft" <[hidden email]>
>> Sent: Thursday, April 23, 2009 10:10 AM
>> Subject: Re: [Elecraft] RS232 Noise
>>
>>
>> | On Wed, 22 Apr 2009 19:11:51 -0400, Mike Harris wrote:
>> |
>> | >This extra noise vanished when I removed the "RS232" cable from the
>> | K3.
>> | >The cable is actually the one I made up for the K2.
>> |
>> | There are several problems in the setup. First, the K3 connector shells
>> | are not properly bonded to the chassis, so the cable shield is useless.
>> | Second, the cable Elecraft sold with the K2-series products used
>> | parallel conductors, not twisted pairs. That's a recipe for noise and
>> | RFI.
>>
>> <snip>
>>
>> | 1) Build the serial cable shown in my RFI application note.
>> | http://audiosystemsgroup.com/RFI-Ham.pdf It uses CAT5 cable. When VHF
>> | noise is a concern, shielded CAT5 may offer further improvements.
>> |
>> | 3) Fix the pin 1 problem in the K3 by bonding the DB-connectors to the
>> | chassis. Pin 1 problems couple RFI in both directions -- that is, they
>> | let RF into equipment and they put RF onto cables that radiate it.
>> |
>> | 73,
>> |
>> | Jim Brown K9YC
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>
>