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K2: OK to use a bypass cap on the key?

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w2bvh

K2: OK to use a bypass cap on the key?

On my K2 Is it ok to put a 1 - 10 nF bypass cap across my straight key?

I've got a 6M KW amp and evidently rf was getting into the key line at
power levels over ~350 W and keeping the system keyed all the time.
Three turns on the keying wire (mini zip cord) through a split bead
fixed it, but I'm getting on air comments about key clicks. I'm going
to switch to RG174 on the key and intend to add 1 - 10 nF across the key
terminals, if its not harmful to the K2.

73,
Lenny W2BVH
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Jim Brown-10

Re: K2: OK to use a bypass cap on the key?

On 6/6/2014 9:09 AM, w2bvh wrote:
> Three turns on the keying wire (mini zip cord) through a split bead
> fixed it, but I'm getting on air comments about key clicks. I'm going
> to switch to RG174 on the key and intend to add 1 - 10 nF across the
> key terminals, if its not harmful to the K2.

NEVER use any form of parallel wire cable anywhere around RF -- it is
notorious for RF pickup. Always use twisted pair, or coax with a decent
copper braid shield. CAT5 is four twisted pairs, each of which has good
bandwidth and excellent RFI resistance.

73, Jim K9YC
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Rick WA6NHC

Re: K2: OK to use a bypass cap on the key?

In reply to this post by w2bvh

Wouldn't it be of higher concern to keep (greatly reduce) the RF out of the shack first? That would eliminate the need for bypassing the key and may help with your click issue.

What happens with lower power? It there is no click and the key operates normally, that's a HUGE hint you need better RFI work.

Rick, WA6NHC

iPad = small keypad = typos = sorry ;-)

> On Jun 6, 2014, at 9:09 AM, w2bvh <[hidden email]> wrote:
>
> On my K2 Is it ok to put a 1 - 10 nF bypass cap across my straight key?
>
> I've got a 6M KW amp and evidently rf was getting into the key line at power levels over ~350 W and keeping the system keyed all the time. Three turns on the keying wire (mini zip cord) through a split bead fixed it, but I'm getting on air comments about key clicks. I'm going to switch to RG174 on the key and intend to add 1 - 10 nF across the key terminals, if its not harmful to the K2.
>
>
> 73,
> Lenny W2BVH
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

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Rick WA6NHC

Fwd: K2: OK to use a bypass cap on the key?

Apparently I can't type this morning without more coffee... sorry for the repeat, I didn't catch the typos...

Wouldn't it be of higher concern to keep (greatly reduce) the RF coming back into the shack first? That would eliminate the need for bypassing the key and may help with your click issue.

What happens with lower power? If there is no click and the key operates normally, that's a HUGE hint you need better RFI work.

I'd start with copious applications of ferrites (or even coax coils) as a common mode choke although if it's like some shacks I've seen, improved housekeeping would be the first step on bands like 6M where stray capacitance makes a huge difference in functionality.

Rick, WA6NHC

iPad = small keypad = typos = sorry ;-)

Begin forwarded message:

> From: "Rick Bates, WA6NHC" <[hidden email]>
> Date: June 6, 2014 at 9:19:06 AM PDT
> To: Elecraft Reflector <[hidden email]>
> Subject: Re: [Elecraft] K2: OK to use a bypass cap on the key?
>
> Wouldn't it be of higher concern to keep (greatly reduce) the RF out of the shack first? That would eliminate the need for bypassing the key and may help with your click issue.
>
> What happens with lower power? It there is no click and the key operates normally, that's a HUGE hint you need better RFI work.
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Don Wilhelm-4

Re: K2: OK to use a bypass cap on the key?

In reply to this post by w2bvh

Lenny,

I would not think a capacitor across the key would make much
difference. There are other choices - read on.

First of all determine whether the keyclicks are caused by
RF-in-the-shack or not (so you do not go chasing the wrong gremlin).
Operate the K2 (and any amplifiers you may have been using) into a dummy
load while monitoring on another receiver with a wire for an antenna -
space the wire from the dummy load to give an S-9 signal into the
monitor receiver.
Do you hear keyclicks? If not, then look for the mentioned cures for
RF-in-the-shack.

If the K2 (and any amplifiers) still have keyclicks, then I have to ask
what is the serial number of the K2? If it is below SN 4060, it may not
have the keying waveshape mod installed.
If you do have the keying waveshape mod installed, *or* the serial
number is greater than 4060, you likely have a problem with the K2
keying area.

(Note that there are a lot of *ifs* in the statements above - observe
them carefully before digging into your K2).

Currently, the K2 Keying waveshape mod is not available from Elecraft
because the PIN diode that was used on the RF Board is no longer available.

The new K2s use an SMD PIN diode on a carrier board in place of the
original PIN diode.
I have the older K2 keying waveshape mod instructions on my computer and
can email it to any interested parties along with the part number and
information about how to install the SMD PIN diode if you send me a
direct email. I would post the instructions on the reflector, but the
reflector will not accept attachments for the original instructions.

HISTORY - the basic K2/10 did have some keyclicks that were not
troublesome until an amplifier (namely the KPA100) was added which also
amplified the keyclicks. The K2 Keying Waveshape Mod was designed to
eliminate those keyclicks. The first K2 with that keyclick mod added to
the design was SN 4060.

73,
Don W3FPR

On 6/6/2014 12:09 PM, w2bvh wrote:

> On my K2 Is it ok to put a 1 - 10 nF bypass cap across my straight key?
>
> I've got a 6M KW amp and evidently rf was getting into the key line at
> power levels over ~350 W and keeping the system keyed all the time.
> Three turns on the keying wire (mini zip cord) through a split bead
> fixed it, but I'm getting on air comments about key clicks. I'm going
> to switch to RG174 on the key and intend to add 1 - 10 nF across the
> key terminals, if its not harmful to the K2.
>
>
> 73,
> Lenny W2BVH