Isolating the KPA100 External Keying Line

[Roy Morris-6]

When keying my Alpha 99 via a shielded cable from the KPA100 J7 jack, there is a small amount of stray RF getting into the SSB signal.  This RF is not present when the amp is used with either my 756 PRO2 or 706MK2G, and it is not present when using the K2 at 100 watts barefooted regardless of band or mode.  The PA keying lines for the Icom rigs use external reed relays which isolate the keying lines from the amp.  The Icom rigs produce a transmit voltage to activate the reed relays.  The stray RF might be eliminated from the K2 if an external reed relay could be used in the keying line.  I do not see a transmit voltage available to accomplish this.  Any thoughts on how to isolate the keying line would be appreciated.  Thanks.  Roy Morris  W4WFB
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[Vic K2VCO]

Roy Morris wrote:
> When keying my Alpha 99 via a shielded cable from the KPA100 J7 jack,
> there is a small amount of stray RF getting into the SSB signal.
> This RF is not present when the amp is used with either my 756 PRO2
> or 706MK2G, and it is not present when using the K2 at 100 watts
> barefooted regardless of band or mode.  

How do you know it's RF?  Maybe it's the magnetic field from the big
transformer in the 99?  K6SE claimed that he could hear hum modulation
on my signal when I operated my (unmodified) K2 3-1/2 feet away from an
Alpha 86.

You might try temporarily moving the amp farther away from the K2 or
getting the VCO magnetic shield mod from Elecraft.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Don Wilhelm-3]

Roy,

If you want to try a relay isolated keying line, connect one side of the
relay coil to the K2 amp keying jack and the other side of the coil to a
power source that matches the relay voltage - of course, the power source
common must connet to the KPA100 chassis if that was not obvious.

I fail to understand how an external keying line would couple RF Back into
the K2, especially with the amp chassis and the K2 chassis tied together
(the shield of the coax connector ties them together), but it is worth a
quick experiment to find out if it cures your condition.

73,
Don W3FPR

> -----Original Message-----
>
> When keying my Alpha 99 via a shielded cable from the KPA100 J7
> jack, there is a small amount of stray RF getting into the SSB
> signal.  This RF is not present when the amp is used with either
> my 756 PRO2 or 706MK2G, and it is not present when using the K2
> at 100 watts barefooted regardless of band or mode.  The PA
> keying lines for the Icom rigs use external reed relays which
> isolate the keying lines from the amp.  The Icom rigs produce a
> transmit voltage to activate the reed relays.  The stray RF might
> be eliminated from the K2 if an external reed relay could be used
> in the keying line.  I do not see a transmit voltage available to
> accomplish this.  Any thoughts on how to isolate the keying line
> would be appreciated.  Thanks.  Roy Morris  W4WFB

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[Tom Hammond-3]

Ummm... Vic...

Might be easier (esp. on the back) to move the K2 instead!  Heheh

73,

Tom   N0SS

At 04:26 PM 2/20/2006, Vic K2VCO wrote:

>Roy Morris wrote:
>>When keying my Alpha 99 via a shielded cable from the KPA100 J7 jack,
>>there is a small amount of stray RF getting into the SSB signal.
>>This RF is not present when the amp is used with either my 756 PRO2
>>or 706MK2G, and it is not present when using the K2 at 100 watts
>>barefooted regardless of band or mode.
>
>How do you know it's RF?  Maybe it's the magnetic field from the big
>transformer in the 99?  K6SE claimed that he could hear hum
>modulation on my signal when I operated my (unmodified) K2 3-1/2
>feet away from an Alpha 86.
>
>You might try temporarily moving the amp farther away from the K2 or
>getting the VCO magnetic shield mod from Elecraft.
>--
>73,
>Vic, K2VCO
>Fresno CA
>http://www.qsl.net/k2vco
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
>http://mailman.qth.net/mailman/listinfo/elecraft
>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com

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