http://elecraft.85.s1.nabble.com/K2-birdie-at-28-265-MHz-tp380371p380376.html
Thanks for your technical information Geoff.
> 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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