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CW Noise Pedestal

wb6bee
 

I have been told by at least two other stations that I have an intermittent 2.5 khz (minimum) noise pedestal on CW.   Sounds like key clicks according to them, but a bit different.   Without hearing it myself, it is difficult to describe.   The issue is intermittent, they will hear it for a while and it will then be gone.   

I am running the K3s.  I key with a bug.   I have the KPA 1500.   The noise is heard with strong signals, although I dropped to barefoot this morning and the listener said he could still tell they were there.   

At first, we thought an RFI issue.   But, if running barefoot, not likely.    

Any comments/ideas

Don
WB6BEE

Bob McGraw - K4TAX
 

I suggest your find one of the remote SDR's somewhere here in the country and listen to it yourself.    Or use a second receiver suitably protected from overload and listen to it yourself.

Make sure the radio ground terminal is bonded back to the station power supply ground.  I find that the DC Neg is not adequate to accomplish this and thus allows the radio to float up from ground by the resistance in the DC negative circuit. 

73

Bob, K4TAX

On 1/12/2020 10:22 AM, wb6bee wrote:
I have been told by at least two other stations that I have an intermittent 2.5 khz (minimum) noise pedestal on CW.   Sounds like key clicks according to them, but a bit different.   Without hearing it myself, it is difficult to describe.   The issue is intermittent, they will hear it for a while and it will then be gone.   

I am running the K3s.  I key with a bug.   I have the KPA 1500.   The noise is heard with strong signals, although I dropped to barefoot this morning and the listener said he could still tell they were there.   

At first, we thought an RFI issue.   But, if running barefoot, not likely.    

Any comments/ideas

Don
WB6BEE

Rob Sherwood
 

There is a known noise pedestal caused by the cooling fans coming on.  This was supposedly solved in production by adding some electrolytics in the DC fan circuitry.  

I ran into a similar noise problem from the DC fan in my now discontinued IC-781 cooling kit. I had to use an R/C decoupling circuit to keep the noise from getting back into the radio’s 15 volt supply. 

Rob, NC0B


On Jan 12, 2020, at 12:07 PM, Bob McGraw - K4TAX <rmcgraw@...> wrote:



I suggest your find one of the remote SDR's somewhere here in the country and listen to it yourself.    Or use a second receiver suitably protected from overload and listen to it yourself.

Make sure the radio ground terminal is bonded back to the station power supply ground.  I find that the DC Neg is not adequate to accomplish this and thus allows the radio to float up from ground by the resistance in the DC negative circuit. 

73

Bob, K4TAX

On 1/12/2020 10:22 AM, wb6bee wrote:
I have been told by at least two other stations that I have an intermittent 2.5 khz (minimum) noise pedestal on CW.   Sounds like key clicks according to them, but a bit different.   Without hearing it myself, it is difficult to describe.   The issue is intermittent, they will hear it for a while and it will then be gone.   

I am running the K3s.  I key with a bug.   I have the KPA 1500.   The noise is heard with strong signals, although I dropped to barefoot this morning and the listener said he could still tell they were there.   

At first, we thought an RFI issue.   But, if running barefoot, not likely.    

Any comments/ideas

Don
WB6BEE

wb6bee
 

I cannot imagine a correlation, but I have both CW skimmer and NaP3 running on the radio computer.   This morning, something happened and the sound card (I am assuming) began creating hash on the signals on both CW skimmer and the NaP3 spectrum scope.  I was transmitting when that was happening and got two reports of the noise issue on sending (described as close to key clicks).  

I replaced the sound card, running tests later this morning.  Everything was reported as clean.

How can a sound card (through the radio computer) effect the TX single (or can it)

Don
WB6BEE

wb6bee
 

Rob

Are you thinking KPA1500 fans (or K3s fans)

Don

Rob Sherwood
 

K3 fans.  N0QO and I found the problem when monitoring a K3 using a Perseus direct sampling receiver as a spectrum analyzer. 

The noise pedestal was inside the 2.7 kHz or 2.8 kHz roofing filter that is in the circuit on transmit.  The skirts of the roofing filter make the noise fall off rather quickly. The fans have either 3 or 4 speeds, and the noise pedestal gets worse the faster the fans spin. 

I don’t know that this is your problem, but I thought I would mention it since it isn’t a widely known issue 
.
Rob, NC0B


On Jan 12, 2020, at 12:29 PM, wb6bee <wb6bee@...> wrote:

Rob

Are you thinking KPA1500 fans (or K3s fans)

Don

 

I believe the excess fan noise problem was eliminated with a capacitor across the fan drive lines. There’s a mod kit for the K3. It should already be present in the K3S. 

There is of course a pedestal within the TX crystal filter passband, but it should be down quite far in relation to either voice or CW keying bandwidth. 

Wayne
N6KR


On Jan 12, 2020, at 12:19 PM, Rob Sherwood <rob@...> wrote:

K3 fans.  N0QO and I found the problem when monitoring a K3 using a Perseus direct sampling receiver as a spectrum analyzer. 

The noise pedestal was inside the 2.7 kHz or 2.8 kHz roofing filter that is in the circuit on transmit.  The skirts of the roofing filter make the noise fall off rather quickly. The fans have either 3 or 4 speeds, and the noise pedestal gets worse the faster the fans spin. 

I don’t know that this is your problem, but I thought I would mention it since it isn’t a widely known issue 
.
Rob, NC0B


On Jan 12, 2020, at 12:29 PM, wb6bee <wb6bee@...> wrote:

Rob

Are you thinking KPA1500 fans (or K3s fans)

Don

wb6bee
 

Wayne

This is what my friend W6QR sent me this morning as a description.  Bear in mind K5KV called me on the phone as he was having difficulty with my signal bothering his QSO up 3.0 Khz.

 It is only when you are 30dB over 9 that I can see the +2.5KHz noise pedestal on the spectrum scope. It is about 50dB below your signal...that would make it S-3/4ish. It shows up on the waterfall when you are S9 + 20. During a transmission it comes and goes, 

Don
WB6BEE

wb6bee
 

PS, Bill also said he never heard it when I had the KPA 500

Don

Roger N1RJ
 

See Elecraft KPAIO3MDKT modification

73, Roger

On 1/12/2020 3:19 PM, Rob Sherwood wrote:
K3 fans. N0QO and I found the problem when monitoring a K3 using a Perseus direct sampling receiver as a spectrum analyzer.
The noise pedestal was inside the 2.7 kHz or 2.8 kHz roofing filter that is in the circuit on transmit. The skirts of the roofing filter make the noise fall off rather quickly. The fans have either 3 or 4 speeds, and the noise pedestal gets worse the faster the fans spin.
I don’t know that this is your problem, but I thought I would mention it since it isn’t a widely known issue
.
Rob, NC0B

On Jan 12, 2020, at 12:29 PM, wb6bee <wb6bee@...> wrote:

Rob

Are you thinking KPA1500 fans (or K3s fans)

Don

wb6bee
 

Roger

This is sideband noise on Transmit not receive.   That mod appears to be for RX (or that's what is said).   I am also experiencing this with the K3s (that supposedly has the fan/cap modification.

Thanks

Don

Drew Vonada-Smith K3PA
 

Don,

He is talking about this mod, which is for TX.

https://ftp.elecraft.com/K3/Manuals%20Downloads/E740287%20KPAIO3MDKT%20Instructions.pdf

73,

Drew K3PA

wb6bee
 

Hi Drew

This is on a K3s, so it should have the modification (unless there is a component/solder failure)

On the comment, I was going off the description on the Elecraft site  pasted in below:

Early K3S/100 and K3/100 with KSYN3A boards. Modification to reduce receiver noise generated by fans. Included on all new K3S radios.

 

KPAIO3MDKT Installation Instructions

Wes
 

Except if you actually look at those instructions you'll see otherwise.

"This modification applies only to K3S transceivers equipped with the KPA3A 100 watt power amplifier, serial
numbers 10732 (factory assembled), 10728 (kits) or below, and to all K3 transceivers with the KPA3 power
amplifier that have been upgraded with KSYN3A synthesizers."

Wes  N7WS


On 1/13/2020 1:35 PM, wb6bee wrote:
Hi Drew

This is on a K3s, so it should have the modification (unless there is a component/solder failure)

On the comment, I was going off the description on the Elecraft site  pasted in below:

Early K3S/100 and K3/100 with KSYN3A boards. Modification to reduce receiver noise generated by fans. Included on all new K3S radios.

 

KPAIO3MDKT Installation Instructions


Rob Sherwood
 

N0QO and I found the issue on transmit and reported it to Wayne.  I didn’t know there was an issue on receive.  Rob, NC0B


On Jan 13, 2020, at 1:35 PM, wb6bee <wb6bee@...> wrote:

Hi Drew

This is on a K3s, so it should have the modification (unless there is a component/solder failure)

On the comment, I was going off the description on the Elecraft site  pasted in below:

Early K3S/100 and K3/100 with KSYN3A boards. Modification to reduce receiver noise generated by fans. Included on all new K3S radios.

 

KPAIO3MDKT Installation Instructions

wb6bee
 

The Fan noise would explain what I am experiencing.   Variable noise on Transmit.   However, I have a K3s, so the modification should have been factory installed.   Regardless, it could still be the issue with a bad component or solder issue.    I cannot tell if the fans are running on the K3 (out of view and hearing), so I will install some indicators that I can see if when/if they come on.   If the noise is coincidental to the fans running, at least I know the cause of the problem.

Don
WB6BEE

Wes
 

Not necessarily.  Check you S/N with respect to the mod install instructions.

Wes  N7WS

On 1/14/2020 6:29 AM, wb6bee wrote:
...  However, I have a K3s, so the modification should have been factory installed....

Don
WB6BEE


Clay Autery
 

Yep... I have 10643, and I don't know if it's been applied to mine....  Should have... sent it to Watsonville for a full update, but that mod does not appear on my paperwork.  Fortunately, I have it opened up to continue the odyssey of the K144xv ...

Only real way that I know is to look at the PC Board...

______________________
Clay Autery, KY5G
(318) 518-1389
On 01/14/20 08:19, Wes wrote:

Not necessarily.  Check you S/N with respect to the mod install instructions.

Wes  N7WS

On 1/14/2020 6:29 AM, wb6bee wrote:
...  However, I have a K3s, so the modification should have been factory installed....

Don
WB6BEE


wb6bee
 

As maybe a final report.   My K3s serial number is 10474, before the 10732 that is listed as the cutoff for the fan/cap modification.    I called Elecraft and they have no records of the change the one time I sent the K3s back for service (solder issue when under warranty in 2016).    They suggested that you can look through the fan blades and see the big blue capacitor (if it is installed).   

It's a chore to get to the back of the k3s.   For the $5, I just ordered the kit.    I ordered two, as I have an older K3 with Syn boards.    If I am going to pull the K3s out of the cabinet, I am going to have the repair parts on the table ready to install.

Thanks to all for the input.

Don
WB6BEE

Clay Autery
 

Yep, I checked my 10643 yesterday while I had it open...  I've gotten better at taking the KPA out... <smile>  I only had to remove the 9 top panel screws, the three chassis stiffener screws (which were already out), the 4 fan panel screws, and three 3 KPA screws... Hardest (most frustrating) is takeing those 1.4" spade connectors off the breaker without jostling the open soldered connection on the ANT3 (BNC) connector too many times...

Sure enough, the mod was not done when it was in for the IMD mod, checkup, et al. in 2017.  Not a problem...  Just gotta get the cap en route.

73,

______________________
Clay Autery, KY5G
(318) 518-1389
On 01/14/20 18:08, wb6bee wrote:

As maybe a final report.   My K3s serial number is 10474, before the 10732 that is listed as the cutoff for the fan/cap modification.    I called Elecraft and they have no records of the change the one time I sent the K3s back for service (solder issue when under warranty in 2016).    They suggested that you can look through the fan blades and see the big blue capacitor (if it is installed).   

It's a chore to get to the back of the k3s.   For the $5, I just ordered the kit.    I ordered two, as I have an older K3 with Syn boards.    If I am going to pull the K3s out of the cabinet, I am going to have the repair parts on the table ready to install.

Thanks to all for the input.

Don
WB6BEE