Posted by
S55M on
Jul 16, 2005; 8:26pm
URL: http://elecraft.85.s1.nabble.com/K2-birdie-at-28-265-MHz-tp380371p380375.html
Congrats Geoff!
After a long time some usefull info between tons of knobs,brocoli ecc...
stuff.
S55M-Adi
----- Original Message -----
From: "Geoffrey Mackenzie-Kennedy" <
[hidden email]>
To: "wayne burdick" <
[hidden email]>
Cc: "Elecraft Discussion List" <
[hidden email]>
Sent: Saturday, July 16, 2005 9:17 PM
Subject: [Elecraft] Re: K2 birdie at 28.265 MHz
> Hi Wayne,
>
> Many thanks. Believe me I understand the design problem!! I got rid of my
> birdie the 'hard way' by removing the loudspeaker circuit from the
KPA100's
> PCB and hardwiring all the way from the K2's PCB speaker connector to the
> speaker, and clipping a ferrite sleeve onto the ribbon cable - I am sure
> that you know the type. The receiver's 10m spurious responses in my case
> were the 2Fspur = 3Fo - IF and another 3Fspur = 4Fo + IF further down the
> band, where Fspur = 32.578 MHz, the bias oscillator's second harmonic
> frequency. Both were in the region of 7db above noise floor in a bandwidth
> of 1500 Hz, with a dummy load on the antenna input. I have never detected
> the 5Fspur = 7Fo - IF potential birdie even in a 200 Hz bandwidth.
>
> I did the removal the 'hard way' to kill all birdies that involved the
bias
> oscillator in one shot, as other bands were affected.
>
> Again, many thanks.
>
> 73,
> Geoff
> GM4ESD
>
>
> ----- Original Message -----
> From: "wayne burdick" <
[hidden email]>
> To: "Geoffrey Mackenzie-Kennedy" <
[hidden email]>
> Cc: "Elecraft Discussion List" <
[hidden email]>; <
[hidden email]>
> Sent: Saturday, July 16, 2005 6:21 PM
> Subject: Re: K2 birdie at 28.265 MHz
>
>
> > The (-) voltage generator (oscillator) in both the KIO2 or KPA100
> > generates a couple of weak birdies. They will move around a bit from K2
to
> > K2, because the birdies are the result of high harmonics of this crystal
> > oscillator mixing with high harmonics of the K2's VCO, and the
fundamental
> > crystal frequency has a tolerance of about +/- 0.5 kHz.
> >
> > We attempted to position the birdies in obscure parts of the spectrum.
If
> > the 10-meter birdie happens to hit close to a beacon that you want to
> > monitor (28.265 is in the beacon area of the band), you should be able
to
> > move it a bit by changing one capacitor in the crystal oscillator. In
the
> > KIO2 case, the best choice would be C14. It is normally 56 pF, but
> > paralleling another 10 pF across it should shift the oscillator a kHz or
> > two, enough to move the signal off a CW beacon. The value of C14 isn't
> > critical; it could change +/- 20% without significantly affecting output
> > of the oscillator.
> >
> > 73,
> > Wayne
> > N6KR
> >
>
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