Chirp on K3

[Poul Erik Karlshøj (PKA)]

This is only interesting for users of CW on the K3.

You might want to check and see if your K3 - like mine #3674 with 3.68 firmware - produces a badly chirping signal when the VFO is set to a frequency in a very narrow range of 3525.970 to 3526.030 kHz while the rcvr is using 400 Hz x-tal filter (in my case FL3). Be aware that TX must be set to use FL1. You need to check for chirp on a monitoring rcvr.

It was found by pure coincidence during a QSO and it was quite embarassing to get that kind of report when using a rig like K3. It has nothing to do with RF level, RFI or poor PSU regulation.

Several others have reported to me, that they don't observe this problem on their K3s. So maybe you are just as lucky - if it is a question of luck ;-)

Elecraft have (quickly!) responded that they discovered it "not long ago" and suggest thast I solder in a 51-55 ohm resistor across R20 on the main Synth board. I haven't done this yet, but will report here when I have done so.

I don't know if the chirp only applies to this particular combination of VFO frequency and x-tal filter. Anyone else having relevant info please post here.


73/OZ4UN
Paul
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[Bill W4ZV]

Poul Erik Karlshøj (PKA) wrote

This is only interesting for users of CW on the K3.

You might want to check and see if your K3 - like mine #3674 with 3.68 firmware - produces a badly chirping signal when the VFO is set to a frequency in a very narrow range of 3525.970 to 3526.030 kHz while the rcvr is using 400 Hz x-tal filter (in my case FL3). Be aware that TX must be set to use FL1. You need to check for chirp on a monitoring rcvr.

It was found by pure coincidence during a QSO and it was quite embarassing to get that kind of report when using a rig like K3. It has nothing to do with RF level, RFI or poor PSU regulation.

Several others have reported to me, that they don't observe this problem on their K3s. So maybe you are just as lucky - if it is a question of luck ;-)

Elecraft have (quickly!) responded that they discovered it "not long ago" and suggest thast I solder in a 51-55 ohm resistor across R20 on the main Synth board. I haven't done this yet, but will report here when I have done so.

I don't know if the chirp only applies to this particular combination of VFO frequency and x-tal filter. Anyone else having relevant info please post here.


73/OZ4UN
Paul

I had this problem on my #1361 during the Stew Perry contest in December when a friend forwarded an embarrassing recording.  Here's a comment from the VCO designer KI6WX:

"The problem you are seeing is probably due to ringing in the DDS crystal filter when it shifts from one edge of its passband to the other.  You can confirm this by looking at your DDS frequency in your menu at these two frequencies.  You will probably see that the DDS frequencies are separated by about 2 kHz.  This problem only occurs rarely at specific frequencies.  I had developed a more complicated fix and Wayne figured out the simpler one.  I would recommend making this one change of adding the 51 ohm resistor in parallel (de W4ZV...across R20 on the Main K3SYN board...not necessary on Sub since TX only uses Main).  It is independent of any other synthesizer changes that may occur in the future and will fix this one specific problem."

73,  Bill

[Bob - W0GI]

My K3 #3903 is chirping between 3.525.79 and 3.525.89. It is with the 250Hz engaged in FL3.

Maybe we should have a 60's chirp night net? :>)

Now to find a 50 ohm resistor.

[vk3dbd]

Surely the comment about "tx must use FL1"  is wrong,   as I understand, it
the tx must transmit through the widest filter.   Some, like mine has no
filter in FL1 location
 David VK3DBD

On Mon, Feb 15, 2010 at 8:28 PM, Bob - W0GI <[hidden email]> wrote:

>
> My K3 #3903 is chirping between 3.525.79 and 3.525.89. It is with the 250Hz
> engaged in FL3.
>
> Maybe we should have a 60's chirp night net? :>)
>
> Now to find a 50 ohm resistor.
> --
> View this message in context:
> http://n2.nabble.com/Chirp-on-K3-tp4573921p4576837.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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[lstavenhagen]

Just out of curiosity, is this being fixed or slated to be fixed in the K3? (i.e. wondering what the priority is to fix this)

I'm so impressed with my K2 I'm actually thinking of getting a K3 for use as a base station (K2 will go to portable duty) so I don't have to rehook up the K2 to everything for base station use.

But I don't want a chirping one ;)

Tnx es 73,
LS
W5QD

[lstavenhagen]

Folks,
Got a PM about my post suggesting that I was implying Elecraft was being neglectful and/or evasive about the chirp issue. So I need to short circuit this right away before I start getting more similar PM's from others:

Of course I meant no such thing. I work in a similar industry (SW dev) and I know all about managing/ranking multiple priorities as I'm sure Wayne/Eric have to do with all Elecraft products, so sometimes my questions can come out sounding a little targeted. Again I had no intention of implying anything here.

So let's all stay calm ;) I was only on an information gathering task and nothing else ;)

Tnx es 73,
LS
W5QD

[WB8ENE]

LS,

I was also interested to see if this was something that was being looked at.  I've been checking the K3 Mods + App Notes on the Elecraft web site but haven't seen anything listed yet.  I don't know how long this has been a known issue though.  I'm planning on placing my order for a K3 at the Dayton hamfest.

73,
Art
WB8ENE

[KK7P]

This only affected a few very specific frequency combinations, and the
latest Beta firmware release addresses this:

*Synthesizer PLL Tables Updated...

73,

Lyle KK7P
> Just out of curiosity, is this being fixed or slated to be fixed in the K3?


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[Richard Squire - HB9ANM]

Lucien,

You won't get a chirping K3!
I had the same problem with S/N 586 and mailed Gary at Elecraft who immediately sent me an FPF file and instructions about the 56 ohm resistor etc. Problem solved!
As usual, Elecraft was quick to address the issue recently discovered.
No doubt new K3's will have all the changes so go ahead!

[Brett Howard]

Do we still need to do the 56 ohm resistor?  Is there an expected rework
posted to the site?

~Brett



On Fri, 2010-03-05 at 09:09 -0800, Lyle Johnson wrote:

> This only affected a few very specific frequency combinations, and the
> latest Beta firmware release addresses this:
>
> *Synthesizer PLL Tables Updated...
>
> 73,
>
> Lyle KK7P
> > Just out of curiosity, is this being fixed or slated to be fixed in the K3?
>
>
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>
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