Birdies on 20m

[Michael van Hauten]

Hello all,
my new k2 (4691)is ready and i had some qso,s with it. I have some
birdies on the 20m-band, at 14030, 14151, 14211, 14272 and a very strong
with s6 at 14363 .
What is to do, to avoid them or to bring them in a range " out of band"?
Thanks for your ideas!

Michael, DC0ZO
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[Geoffrey Mackenzie-Kennedy-2]

Hello Michael,

Because the QRN here is very low, I use the preamp most of the time on 40m
when "DXing", birdies are important to me, and for some time I have been on
a Birdy Hunt.

If all the oscillators in K2 are working well and on their correct
frequencies, it is not possible to move a birdy (in frequency) because the
IF of the K2's receiver is fixed at say 4915kHz. Although there are others,
the three major causes of a a birdy are when one or several of the
oscillators, fundamentals and / or harmonics combine to produce a signal at
1) The receiver's tuned frequency 2) At a spurious response frequency of the
receiver (the so-called image is only one of these, there are many more) and
3) At the IF.  I shall not complicate things by bringing in the isolation
between mixer ports or re-mixing.

In cases 2 and 3, IF the birdy signal gets in near the antenna connection,
then the selectivity of the RF tuned circuits usually, but not always, helps
to make the birdy weaker. IF the birdy gets in after the tuned circuits, say
near the mixer input, then in most cases the tuned circuits will not help to
make the birdy weaker. And I have found that many birdies ARE getting in
after the tuned circuits, in the area of relays K16 and K17 on the RF board.
Some of these birdies are created by a combination of three oscillators (or
their harmonics) falling on a spurious response. So life is hard!

Although I had started to "re-engineer" this area, I cannot give you any
cures at this time because of an accident and I am walking like a donkey on
four legs ! And the job will be difficult. And to be sure, when that is
fixed another problem will appear.

It interests me that apart from Grobmutter at 14.363, I can only just hear
your other birdies but have others. I have suspected for some time that the
mechanical construction of K2 might be playing in the birdy game.

My apology for a long story, but I would suggest that you avoid your birdies
for now.

73,
Geoff.
GM4ESD


----- Original Message -----
From: "Michael van Hauten" <[hidden email]>
To: <[hidden email]>
Sent: Sunday, February 27, 2005 7:53 PM
Subject: [Elecraft] Birdies on 20m


> Hello all,
> my new k2 (4691)is ready and i had some qso,s with it. I have some
> birdies on the 20m-band, at 14030, 14151, 14211, 14272 and a very strong
> with s6 at 14363 .
> What is to do, to avoid them or to bring them in a range " out of band"?
> Thanks for your ideas!
>
> Michael, DC0ZO


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[Darrell Bellerive]

Geoff,

Are you proposing that some birdies may be caused by construction methods? If
so, what techniques will reduce or eliminate birdies. Are there specific
components that should be physically mounted in certain positions, either
close to or spaced at a specific distance from the circuit board or other
components? Rather than simply placing a component into the circuit board
holes and soldering, should we be placing certain components into specific
positions relative to the circuit board and other adjacent components?

As I am planning on building another K2, and am a perfectionist by nature, I
would like to be sure that my construction is maximizing performance, and
minimizing adverse effects such as birdies.

Darrell


On February 27, 2005 10:02 pm, Geoffrey Mackenzie-Kennedy wrote:
>I have suspected for some time that the
>mechanical construction of K2 might be playing in the birdy game.
> 73,
> Geoff.
> GM4ESD

--
Darrell Bellerive
Amateur Radio Stations: VA7TO, VE7CLA
Grand Forks, British Columbia, Canada
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