Topics

K3 Receiver Noise Troubleshooting - PROBLEM SOLVED


Rick Davenport <Ki1g@...>
 

Many thanks to Henk, PA0C for helping me out with some troubleshooting ideas.

 

As it turns out, I seem to have exceeded the dielectric breakdown voltage of D5 on the KXVA3 board during my SO2R operations. This introduced static bursts on both the main antenna and the receive antenna. I ordered a new part from Mouser for less than $1, it is installed and the radio is back to performing as it should.

 

One non-related item that I did find, was during a thorough inspection of the RF board I found that one half of L37 had never been soldered to the circuit board. The K3 seems to have worked just fine for 10 years without the part being soldered to the board but I soldered it anyways.

 

73

Rick KI1G

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Rick Davenport via groups.io
Sent: Sunday, October 25, 2020 9:25 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] K3 Receiver Noise Troubleshooting

 

Henk,

 

Thank you for the troubleshooting ideas.

 

I have connected the IF output to a second receiver and the noise is still present.

 

I am currently looking into how to look at the synthesizer output with a SpecAn.

 

73

Rick KI1G

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Henk PA0C
Sent: Sunday, October 25, 2020 4:21 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] K3 Receiver Noise Troubleshooting

 

Hi Rick,

 

This could be anything, but sounds like an almost broken capacitor.

 

You need to find out where in the receiver the noise is generated.

A good place to start is the IF output connector.

 

Connect a second receiver to the IF port and see if the noise is still present when tuned to approx. 8.2 MHz

In case not, it is generated in the IF, DSP chain

If yes, most probably it is the front-end.

 

This will lead to the next, more detailed steps. 

 

You should also check the syntheser output on a spectrum analyser to see if the oscillator is "clean" or listen to it on a second rx. 

Best to see if you can use a TMP connector somewhere to tap into the signal.

 

73 Henk

PA0C

 

-------- Oorspronkelijk bericht --------

Van: "Ki1g via groups.io" <Ki1g@...>

Datum: 25-10-2020 01:45 (GMT+01:00)

Aan: Elecraft-K3@groups.io

Onderwerp: [Elecraft-K3] K3 Receiver Noise Troubleshooting

 

I have a K3 that has worked great for many years but now has a noise source somewhere in the receiver. The radio still hears stations but there is a new source of static bursts on all bands. It sounds like there is a thunderstorm in the local area with bursts on 160M peaking at S-9 +40 and on 10M they peak around S-6. When I disconnect the antenna, stations go away but the static noise remains. I have a video that I can send a video of what I am trying to describe.

I have taken the radio apart and reseated all of the connectors (some are gold and some are tin) and the problem persists.

I do not have a sub receiver installed.

I am looking for suggestions on what to try next.

Thanks  and 73
Rick KI1G


Peder Kittelson
 

HI, for those of us monitoring such things, what do you mean by "breakdown voltage of D5 on the KXVA3 board during my SO2R"
Thanks

On Thu, Oct 29, 2020 at 8:04 AM Rick Davenport via groups.io <Ki1g=verizon.net@groups.io> wrote:

Many thanks to Henk, PA0C for helping me out with some troubleshooting ideas.

 

As it turns out, I seem to have exceeded the dielectric breakdown voltage of D5 on the KXVA3 board during my SO2R operations. This introduced static bursts on both the main antenna and the receive antenna. I ordered a new part from Mouser for less than $1, it is installed and the radio is back to performing as it should.

 

One non-related item that I did find, was during a thorough inspection of the RF board I found that one half of L37 had never been soldered to the circuit board. The K3 seems to have worked just fine for 10 years without the part being soldered to the board but I soldered it anyways.

 

73

Rick KI1G

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Rick Davenport via groups.io
Sent: Sunday, October 25, 2020 9:25 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] K3 Receiver Noise Troubleshooting

 

Henk,

 

Thank you for the troubleshooting ideas.

 

I have connected the IF output to a second receiver and the noise is still present.

 

I am currently looking into how to look at the synthesizer output with a SpecAn.

 

73

Rick KI1G

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Henk PA0C
Sent: Sunday, October 25, 2020 4:21 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] K3 Receiver Noise Troubleshooting

 

Hi Rick,

 

This could be anything, but sounds like an almost broken capacitor.

 

You need to find out where in the receiver the noise is generated.

A good place to start is the IF output connector.

 

Connect a second receiver to the IF port and see if the noise is still present when tuned to approx. 8.2 MHz

In case not, it is generated in the IF, DSP chain

If yes, most probably it is the front-end.

 

This will lead to the next, more detailed steps. 

 

You should also check the syntheser output on a spectrum analyser to see if the oscillator is "clean" or listen to it on a second rx. 

Best to see if you can use a TMP connector somewhere to tap into the signal.

 

73 Henk

PA0C

 

-------- Oorspronkelijk bericht --------

Van: "Ki1g via groups.io" <Ki1g=verizon.net@groups.io>

Datum: 25-10-2020 01:45 (GMT+01:00)

Onderwerp: [Elecraft-K3] K3 Receiver Noise Troubleshooting

 

I have a K3 that has worked great for many years but now has a noise source somewhere in the receiver. The radio still hears stations but there is a new source of static bursts on all bands. It sounds like there is a thunderstorm in the local area with bursts on 160M peaking at S-9 +40 and on 10M they peak around S-6. When I disconnect the antenna, stations go away but the static noise remains. I have a video that I can send a video of what I am trying to describe.

I have taken the radio apart and reseated all of the connectors (some are gold and some are tin) and the problem persists.

I do not have a sub receiver installed.

I am looking for suggestions on what to try next.

Thanks  and 73
Rick KI1G


Rick Davenport <Ki1g@...>
 

Hi Peder,

SO2R is a contest category where a single operator uses 2 radios at the same time. While listening on one band with the K3 and transmitting on another band with my second radio I suspect that there may have been a condition where there was excessive RF coming into the receive antenna port of the K3 which caused a hole to be burned through D5.

The KXVA3 board is the transverter board which also houses the recieve only antenna jack.

Additional bandpass filtering has been added external to the receive antenna connector to hopefully prevent this from recurring.

I hope that clears things up for you.

73 Rick KI1G


Gerard <scanneg@...>
 

I have simple diode clipping protection on all rx ports.   Simple solution.

73 EI5KF

On Sat 31 Oct 2020, 14:36 Rick Davenport via groups.io, <Ki1g=verizon.net@groups.io> wrote:
Hi Peder,

SO2R is a contest category where a single operator uses 2 radios at the same time. While listening on one band with the K3 and transmitting on another band with my second radio I suspect that there may have been a condition where there was excessive RF coming into the receive antenna port of the K3 which caused a hole to be burned through D5.

The KXVA3 board is the transverter board which also houses the recieve only antenna jack.

Additional bandpass filtering has been added external to the receive antenna connector to hopefully prevent this from recurring.

I hope that clears things up for you.

73 Rick KI1G


Gerard <scanneg@...>
 

Using 1500 W SO2R.  I have good BPF on it but limit all ex with clipping.


On Sat 31 Oct 2020, 14:40 Gerard, <scanneg@...> wrote:
I have simple diode clipping protection on all rx ports.   Simple solution.

73 EI5KF

On Sat 31 Oct 2020, 14:36 Rick Davenport via groups.io, <Ki1g=verizon.net@groups.io> wrote:
Hi Peder,

SO2R is a contest category where a single operator uses 2 radios at the same time. While listening on one band with the K3 and transmitting on another band with my second radio I suspect that there may have been a condition where there was excessive RF coming into the receive antenna port of the K3 which caused a hole to be burned through D5.

The KXVA3 board is the transverter board which also houses the recieve only antenna jack.

Additional bandpass filtering has been added external to the receive antenna connector to hopefully prevent this from recurring.

I hope that clears things up for you.

73 Rick KI1G


Gerard <scanneg@...>
 

Rx


On Sat 31 Oct 2020, 14:42 Gerard, <scanneg@...> wrote:
Using 1500 W SO2R.  I have good BPF on it but limit all ex with clipping.

On Sat 31 Oct 2020, 14:40 Gerard, <scanneg@...> wrote:
I have simple diode clipping protection on all rx ports.   Simple solution.

73 EI5KF

On Sat 31 Oct 2020, 14:36 Rick Davenport via groups.io, <Ki1g=verizon.net@groups.io> wrote:
Hi Peder,

SO2R is a contest category where a single operator uses 2 radios at the same time. While listening on one band with the K3 and transmitting on another band with my second radio I suspect that there may have been a condition where there was excessive RF coming into the receive antenna port of the K3 which caused a hole to be burned through D5.

The KXVA3 board is the transverter board which also houses the recieve only antenna jack.

Additional bandpass filtering has been added external to the receive antenna connector to hopefully prevent this from recurring.

I hope that clears things up for you.

73 Rick KI1G


Bob McGraw - K4TAX
 

The fallacy in using a diode across the RX input is that when presented with enough RF for the diode to conduct, it produces wide band harmonics.   Those harmonics will then likely be radiated by the antenna attached to that input.  We encounter enough noise pollution on the bands without creating more pollution.  In many instances these harmonics are of significant amplitude that could cause your signal to be transmitted on frequencies outside of the ham bands.

The safe way to protect RX input is with either band pass filter or notch filter.  Either of these will attenuate the offending RF that might cause receiver damage.

73

Bob, K4TAX


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Robert
 

Bob,
I am attaching 3 screenshots of harmonics generation by diodes driven into conduction.
This is theory and I don't know how to quantify the result in case of the K3 input connected to an antenna.
73, Robert


On Sun, Nov 1, 2020 at 1:59 PM Bob McGraw - K4TAX <rmcgraw@...> wrote:
The fallacy in using a diode across the RX input is that when presented
with enough RF for the diode to conduct, it produces wide band
harmonics.   Those harmonics will then likely be radiated by the antenna
attached to that input.  We encounter enough noise pollution on the
bands without creating more pollution.  In many instances these
harmonics are of significant amplitude that could cause your signal to
be transmitted on frequencies outside of the ham bands.

The safe way to protect RX input is with either band pass filter or
notch filter.  Either of these will attenuate the offending RF that
might cause receiver damage.

73

Bob, K4TAX


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https://www.avg.com








Peder Kittelson
 

Thank you for your email.  Fortunately, it appears you untangled a difficult problem, congratulations.