Birdie at10m: a choice between a turkey and an ostrich !

[Marinos]

Hi to all,
I know there was a recent discussion in the forum about this birdie singing
at the low end of the 10m band, but did not recall seeing any definitive way
to kill it.
In my case, I want to think of the birdie living in my K2/100 as a
substantially bigger one, a turkey (with the K2100 enabled -power >11w) at
28.266 (USB), Signal strength S2 with the preamp enabled changes to .... an
Ostrich (think logarithmically) of a solid S5 !!! at 28.264 when disabling
the 100W option.

These two "birdies" of course are not covered by the background noise of the
quiet 10m band and I am sure can/will interfere with Rx down there once it
becomes active again.

Any thoughts or advice on how to kill/attenuate or move those guys  or do I
have to live with them ? I can settle for a canary but please help me get
these monstrous creatures out of there.

73 to all and enjoy the weekend,
Marinos, ki4gin


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[Geoffrey Mackenzie-Kennedy-2]

Hi Marinos,
Methinks that the Ostrich at 28.266 ( 28.276 in my K2/100 - and a BIG one)
could be one of the mixing products of the LO (PLL) and the BFO. Am thinking
about major surgery in an attempt to get rid of some or all of the many
internal spurii in K2, which can be a problem in single conversion low
frequency IF receivers (and transmitters), but no time at the moment.
You are not alone.
73,
Geoff    GM4ESD


----- Original Message -----
From: "Marinos Markomanolakis, M.D." <[hidden email]>
To: <[hidden email]>
Sent: Saturday, January 15, 2005 11:34 PM
Subject: [Elecraft] Birdie at10m: a choice between a turkey and an ostrich !


> Hi to all,
> I know there was a recent discussion in the forum about this birdie
singing
> at the low end of the 10m band, but did not recall seeing any definitive
way
> to kill it.
> In my case, I want to think of the birdie living in my K2/100 as a
> substantially bigger one, a turkey (with the K2100 enabled -power >11w) at
> 28.266 (USB), Signal strength S2 with the preamp enabled changes to ....
an
> Ostrich (think logarithmically) of a solid S5 !!! at 28.264 when disabling
> the 100W option.
>

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[Sverre Holm]

-----Original Message-----
In my case, I want to think of the birdie living in my K2/100 as a
substantially bigger one, a turkey (with the K2100 enabled -power >11w) at
28.266 (USB).

--------------------------

This birdie is an image of the 18432 KPA100 oscillator since 18432 + 2*4915
= 28262. This is why it is so strong also.

If the KPA100 X-tal is exchanged for a frequency outside of the range given
by:
28000-2*4915 = 18170 and
29700-2*4915 = 19870 it will no longer fall in the 10m band, but I cannot
give any guarantees against other, probably weaker, birdies appearing.

Old 10 Mbps ethernet cards usually have 20000 kHz crystals so that could be
a source for a crystal to test.

73

Sverre
LA3ZA
http://www.qsl.net/la3za/
 

 

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[Geoffrey Mackenzie-Kennedy-2]

Evening Sverre,

Agree with what you say, but I get a strong birdie at 28.276 without the
KPA100 on. This one I think is LO + BFO ,   that is 23.361 + 4.915 = 28.276,
nominal freqs. Being first order it is also strong. Other products + mLO +/-
nBFO also converge here, but are not a problem in my K2.

There is no spur at 28.262 MHz with the KPA100 on as its crystal frequency
is 16,289 MHz (later build?). But that oscillator might be contributing to
the other spurs. I have yet to sit down and do a worst case analysis.

73,  Geoff     GM4ESD


----- Original Message -----
From: "Sverre Holm" <[hidden email]>
To: "'Marinos Markomanolakis, M.D.'" <[hidden email]>;
<[hidden email]>
Sent: Sunday, January 16, 2005 1:43 PM
Subject: RE: [Elecraft] Birdie at10m: a choice between a turkey and an
ostrich!


> -----Original Message-----
> In my case, I want to think of the birdie living in my K2/100 as a
> substantially bigger one, a turkey (with the K2100 enabled -power >11w) at
> 28.266 (USB).
>
> --------------------------
>
> This birdie is an image of the 18432 KPA100 oscillator since 18432 +
2*4915
> = 28262. This is why it is so strong also.
>
> If the KPA100 X-tal is exchanged for a frequency outside of the range
given
> by:
> 28000-2*4915 = 18170 and
> 29700-2*4915 = 19870 it will no longer fall in the 10m band, but I cannot
> give any guarantees against other, probably weaker, birdies appearing.
>
> Old 10 Mbps ethernet cards usually have 20000 kHz crystals so that could
be
> a source for a crystal to test.
>
> 73
>
> Sverre
> LA3ZA
> http://www.qsl.net/la3za/




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[Sverre Holm]

-----Original Message-----
>Agree with what you say, but I get a strong birdie at 28.276 without the
>KPA100 on. This one I think is LO + BFO ,   that is 23.361 + 4.915 =
28.276,
>nominal freqs. Being first order it is also strong. Other products + mLO
+/- nBFO also >converge here, but are not a problem in my K2.
---------------

I cannot really explain this one without a 18432 oscillator in the K2. As
far as I can see the sum above is equal to the VFO + IF, so in that case it
would be valid for any frequency in the 15, 12, and 10 m bands?

--------------------
>There is no spur at 28.262 MHz with the KPA100 on as its crystal frequency
is 16,289 MHz >(later build?). But that oscillator might be contributing to
the other spurs. I have yet to
>sit down and do a worst case analysis.
--------------------

The 16289 is the oscillator frequency of the first run of KPA100's which was
later changed to 18432. The reason has been given as:

"The modification kit also includes an 18.432 MHz replacement crystal for
use at X1. A new frequency was chosen to improve rejection of spurious
products, although the KPA100 was in compliance at the original frequency."

Maybe this is concerned with spurious outputs from the transmitter? -and
probably someone on the list, beta-testers of the KPA100 perhaps, would
know?

16289, I believe is the oscillator frequency of the KIO2 and the KRC2 unless
they have been changed also.

73

Sverre
LA3ZA
http://www.qsl.net/la3za/
 

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[G3VVT]

 
In a message dated 15/01/05 23:36:15 GMT Standard Time, [hidden email]  
writes:

I know  there was a recent discussion in the forum about this birdie singing
at  the low end of the 10m band, but did not recall seeing any definitive way
 
to kill it.
In my case, I want to think of the birdie living in my  K2/100 as a
substantially bigger one, a turkey (with the K2100 enabled  -power >11w) at
28.266 (USB), Signal strength S2 with the preamp  enabled changes to .... an
Ostrich (think logarithmically) of a solid S5  !!! at 28.264 when disabling
the 100W option.



------------------------------------------------------------------------------
-----------------------------------------
 
As a benchmark with the antenna socket terminated, i.e. no external antenna  
connected, the only birdie of any real significance with my QRP K2 #4168 is  
at exactly on 28.000MHz.
This is exactly where it should be as the 7th harmonic of a correctly  
adjusted MCU 4.000MHz clock for U6 on the K2 Control board. There are other  birdies
between 28.000 to 29.000MHz, but are so feeble that they fall into  
insignificance and none of them move the S meter at all even with the preamp on.  This
is with a receiver that gives S9 on 28.200MHz at 50uV PD with the preamp  
*off* and meets the MDS spec for the K2. I am aware of the birdie at  28.000MHz as
that clashes with a band edge beacon I receive via an external VHF  
transverter. Even with this present it is possible to copy the beacon down  to an
extremely low level with the K2 preamp on.
 
The reported birdie at 28.276MHz is there, but extremely faint at  about
28.275.6MHz on USB and shifts up to about 28.277.7MHz on LSB. I would  think it
fair to comment that most ham receivers have birdies somewhere if you  want to
try hard enough finding them.
 
With what I have found on my particular QRP K2 it may be a good idea to  
remove all the various options added to the offending K2's and go back to  basics
to see what the effect is then. Once that test is sorted out the  gradual
addition of the various option boards should find the offending one(s)  to enable
a solution to be sought.
 
There or no turkeys or ostriches in my K2!
 
Bob, G3VVT
K2 #4168
 
 
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[Geoffrey Mackenzie-Kennedy-2]

Morning Sverre,

OOOPS How stupid can I get. Of course you are 100% correct about VFO + BFO.
Thank you for the information about the KPA100 modification.
I fear that I am going to have to take a better look at the spurii here as
some are quite intrusive, and some have changed since my last quick look in
August 2004.

73, and thanks.

Geoff    GM4ESD


----- Original Message -----
From: "Sverre Holm" <[hidden email]>
To: "'Geoffrey Mackenzie-Kennedy'" <[hidden email]>
Cc: "'Elecraft Discussion List'" <[hidden email]>
Sent: Sunday, January 16, 2005 9:56 PM
Subject: RE: [Elecraft] Birdie at10m: a choice between a turkey and an
ostrich!

> -----Original Message-----
> >Agree with what you say, but I get a strong birdie at 28.276 without the
> >KPA100 on. This one I think is LO + BFO ,   that is 23.361 + 4.915 =
> 28.276,
> >nominal freqs. Being first order it is also strong. Other products + mLO
> +/- nBFO also >converge here, but are not a problem in my K2.
> ---------------
>
> I cannot really explain this one without a 18432 oscillator in the K2. As
> far as I can see the sum above is equal to the VFO + IF, so in that case

it
> would be valid for any frequency in the 15, 12, and 10 m bands?
>
> --------------------
> >There is no spur at 28.262 MHz with the KPA100 on as its crystal
frequency
> is 16,289 MHz >(later build?). But that oscillator might be contributing
to
> the other spurs. I have yet to
> >sit down and do a worst case analysis.
> --------------------
>
> The 16289 is the oscillator frequency of the first run of KPA100's which
was
> later changed to 18432. The reason has been given as:
>
> "The modification kit also includes an 18.432 MHz replacement crystal for
> use at X1. A new frequency was chosen to improve rejection of spurious
> products, although the KPA100 was in compliance at the original
frequency."
>
> Maybe this is concerned with spurious outputs from the transmitter? -and
> probably someone on the list, beta-testers of the KPA100 perhaps, would
> know?
>
> 16289, I believe is the oscillator frequency of the KIO2 and the KRC2
unless
> they have been changed also.
>
> 73
>
> Sverre
> LA3ZA
> http://www.qsl.net/la3za/
>
>

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[Sverre Holm]

 -----Original Message-----
From: [hidden email] On Behalf Of G3VVT

The reported birdie at 28.276MHz is there, but extremely faint at  about
28.275.6MHz on USB and shifts up to about 28.277.7MHz on LSB. I would  think
it fair to comment that most ham receivers have birdies somewhere if you
want to try hard enough finding them.
 
With what I have found on my particular QRP K2 ....
-----------------------------
Bob,

~28276 is probably not the same birdie as the image of the KPA100 oscillator
at 18432 at 28264. The closest one I can find depends on having the KIO2
with a 16289 oscillator on board. The oscillator's 4. harmonic is at 65156
kHz. It can be mixed with the 3. harmonic of the VFO, when the input dial is
at IF + VFO = 4915 + (65156+4915)/3 = 28272 which is almost 28276. But if
you don't have the KIO2 then ...

73

Sverre
LA3ZA
http://www.qsl.net/la3za/
 

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[Geoffrey Mackenzie-Kennedy-2]

Evening Sverre,

The 16.289 oscillator I mentioned last night is the source oscillatoir for
the KPA's high voltage supply. There is not a 16.289 MHz source in my K2,
and with the KPA100 uninstalled, K2 alone has the birdie at approx 28276 MHz
CW /USB which moves up to 28278.5 approx on LSB. Using the KSB2's filter,
the Birdie / Noise ratio is 12db, far from weak. Receiver's Noise Floor in
spec, and input connected direrctly to a 50 ohm dummy load.

As I have to open up K2 for other reasons, I intend to break the K2's LO to
signal mixer connection, and drive the TUF-1's LO port from a HP signal
generator, properly padded, but still leave the K2's LO running. Hopefully I
should be able to get useful data on many birdies and their birth routes as
the receiver can then be tuned without changing the PLL's frequency, and
vice versa if you follow me.

73,

Geoff    GM4ESD

----- Original Message -----
From: "Sverre Holm" <[hidden email]>
To: <[hidden email]>; <[hidden email]>
Sent: Monday, January 17, 2005 5:59 PM
Subject: RE: [Elecraft] Birdie at10m: a choice between a turkey and
anostrich !


> -----Original Message-----
> From: [hidden email] On Behalf Of G3VVT
>
> The reported birdie at 28.276MHz is there, but extremely faint at  about
> 28.275.6MHz on USB and shifts up to about 28.277.7MHz on LSB. I would
think
> it fair to comment that most ham receivers have birdies somewhere if you
> want to try hard enough finding them.
>
> With what I have found on my particular QRP K2 ....
> -----------------------------
> Bob,
>
> ~28276 is probably not the same birdie as the image of the KPA100
oscillator
> at 18432 at 28264. The closest one I can find depends on having the KIO2
> with a 16289 oscillator on board. The oscillator's 4. harmonic is at 65156
> kHz. It can be mixed with the 3. harmonic of the VFO, when the input dial
is
> at IF + VFO = 4915 + (65156+4915)/3 = 28272 which is almost 28276. But if
> you don't have the KIO2 then ...
>
> 73
>
> Sverre
> LA3ZA
> http://www.qsl.net/la3za/
>

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