[K2] KPA100 "birdie" at 21029

[K1FFX]

My recently completed KPA100 has a "birdie" (not sure if that's the right word) on
15 meters.  If I set "PA" to "OFF", it goes away.  Unlike the birdie reported at
3589 khz, through which I can tune smoothly, this one appears as "steps":
21029.00  not heard
21029.01  high tone
21029.02  mid tone
21029.03  low tone
21029.04  not heard

Ideas?

Thanks a lot -

Bruce

[K1FFX]

Additional info:

The "birdie" also goes away when the power setting is clicked below
11 watts.

- Bruce

[Don Wilhelm-4]

  Bruce,

That is a bit of a mystery.  I just checked a newly built K2/100 and
could find no instance of any response at all with no antenna connected.

There are no oscillators switched in and out when the KPA100 is active -
both oscillators in the KPA100 run whether the KPA100 is in-line or
not.  Have you grounded the crystal cases?  Try varying the 4 MHz
oscillator capacitor and see if the frequency shifts.  If so, ground the
crystal case near the bottom to see if that takes care of it - I am
speculating that some of the oscillator energy could be picked up by the
T/R switch when the KPA100 is in-line.

The only thing that changes between PA on and off (or with power
above/below 11 watts) is that the receive signal path flows through the
T/R switch instead of through the straight-thru path from relay K1 to
K2.  You might want to check all the components in the T/R switch for
proper value, diode orientation, and good soldering.  The components
associated with the T/R switch are shown in the schematic at the top of
sheet 2.

73,
Don W3FPR

On 1/29/2011 10:02 AM, K1FFX wrote:
> Additional info:
>
> The "birdie" also goes away when the power setting is clicked below
> 11 watts.
>
> - Bruce
>
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[Geoffrey Mackenzie-Kennedy]

Hi Bruce,

During my "Kill Birdie" project with my K2/100 #3255, I found that all of
the "birdies" which disappear if the KPA100 is *not* in use were caused by
the fundamental or a harmonic of the KPA100's HV Bias oscillator mixing with
the fundamental or harmonic of one or more of the other oscillators in the
K2. Any product of this mixing will be heard as a "birdie" if (1) the
frequency of the product is "in band" and the receiver is tuned to the same
frequency, or (2) the frequency of the product is the same as that of a
spurious response of the receiver when tuned to the frequency at which the
"birdie" is heard. Of course the product must be strong enough to be heard
above the noise floor.

Unfortunately I do not have my notes here, but because your "birdie" steps I
suspect that the PLL Reference oscillator could be part of the mix.

In my K2/100 the HV Bias oscillator signal was getting into the K2's RF
board via the KPA100's diode TR switch and the ribbon cable.

Because this rural QTH is very quiet I could hear this type of "birdie" on
different bands, which forced me into repackaging the HV Bias oscillator
into its own shielded enclosure, which solved my problem.

73,

Geoff
GM4ESD



 "K1FFX" <[hidden email]> wrote on Saturday, January 29, 2011 at 3:02
PM:

> Additional info:
>
> The "birdie" also goes away when the power setting is clicked below
> 11 watts.
>
> - Bruce
>
>
> -----
> Bruce Rosen
> K1FFX

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