Elecraft

K3 Tune carrier with hum

Classic

List

Threaded

3 messages Options

Ulrich Quandt

K3 Tune carrier with hum

Hi,

on my K3 the tune carrier is modulated by a hum noise. If i press the tune
button i can hear this noise with an independent receiver.
It has nothing to do with my power supply and the problem appears between 1
to 100 watts.
It seems that the noise is generated inside the K3.

I have this noise only during tune, all other transmitting works flawless.

Any idea ?

73 de Uli (DL4YCM)
______________________________________________________________
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

Steve Ellington

Re: K3 Tune carrier with hum

Uli:
I suggest having a local ham station listen to your signal instead of using
an independent receiver. Common mode hum can play tricks on you.
N4LQ Steve
[hidden email]
----- Original Message -----
From: "Ulrich Quandt" <[hidden email]>
To: <[hidden email]>
Sent: Sunday, April 26, 2009 1:36 PM
Subject: [Elecraft] K3 Tune carrier with hum

> Hi,
>
> on my K3 the tune carrier is modulated by a hum noise. If i press the tune
> button i can hear this noise with an independent receiver.
> It has nothing to do with my power supply and the problem appears between
> 1
> to 100 watts.
> It seems that the noise is generated inside the K3.
>
> I have this noise only during tune, all other transmitting works flawless.
>
> Any idea ?
>
> 73 de Uli (DL4YCM)
> ______________________________________________________________
> 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
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

David Gilbert

Re: K3 Tune carrier with hum

In reply to this post by Ulrich Quandt

Do you have a computer connected to your K3, either via the audio
connections or the RS-232 cable? If so, make sure that you have the
chassis of the K3 really well bonded to the chassis of the computer. I
had a similar problem (not only in TUNE, though) and received a few
on-the-air reports about it, so I listened with a second rig (powered by
a battery for ground isolation) while transmitting with the K3 into a
dummy load. I could hear the hum, which wasn't even a clean 60 Hz (more
like a spectrum of multiple tones 30 Hz or so apart), and I could also
see the hum using Spectrogram while feeding the audio from the second
rig into the sound card of the computer.

I assumed I had a ground loop somewhere and began disconnecting other
equipment (amplifier, SWR bridge, UPS, etc) one by one but nothing
worked ... not even operating the K3 off battery power. It wasn't until
I finally disconnected the computer that I no longer heard the hum in
the second rig. I tried using a simple 18 inch clip lead to bond the K3
chassis to the computer chassis and that helped, but it required a 12
inch piece of RG-213 copper shielded braid to make the problem really go
away.

73,
Dave AB7E

Ulrich Quandt wrote:

> Hi,
>
> on my K3 the tune carrier is modulated by a hum noise. If i press the tune
> button i can hear this noise with an independent receiver.
> It has nothing to do with my power supply and the problem appears between 1
> to 100 watts.
> It seems that the noise is generated inside the K3.
>
> I have this noise only during tune, all other transmitting works flawless.
>
> Any idea ?
>
> 73 de Uli (DL4YCM)
> ______________________________________________________________
> 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
>
>