Latest status of dirft in K2/100 vs K2 with 100w amp separate

[Tim Logan]

Hi folks -
Could some one bring up to date on what to expect for drift if I build a
new K2/100 vs a K2 with the 100w amp separated? My understanding is that
initially it was a better idea to keep the amp separate  - that
combining it in the box with the K2 increased drift - a bit frustrating
if you have $1600 tied up in  a K2/100. With all the continiual mods and
improvements what should a builder of a new current K2/100 now expect if
he builds it proberly for drift? Thanks for any input.
73/Tim NZ&C
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[Ron D'Eau Claire-2]

Tim, NZ7C asked:

Could some one bring up to date on what to expect for drift if I build a
new K2/100 vs a K2 with the 100w amp separated? My understanding is that
initially it was a better idea to keep the amp separate  - that
combining it in the box with the K2 increased drift - a bit frustrating
if you have $1600 tied up in  a K2/100.

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

I have a K2/100 with the current drift compensation circuits all new K2's
have.

If I really "hammer" it with very high duty cycle transmissions at 100 watts
with the amplifier mounted IN the K2, I've measured drift as high as 50 Hz.
On most bands it's 20 Hz or less.  That's hitting it so hard the internal
temperature of the K2 rises near 60C and the heat sink is too hot to hold my
hand on it. I never run the K2 anywhere near that hard in normal operation.
I "abused" mine specifically to test the PLL Temperature compensation
circuit before it was added to the production kits.

Also, that's after a 15 minute warm-up in receive. From a dead "cold" start,
the drift might approach 100 Hz on the worst bands with the rig sitting in
the shack.

The total drift is a function of both the BFO and PLL Reference Oscillator
drifts. On mine, they tend to add on the higher bands, which produces the
up-to-50Hz number, and cancel on the lower bands. I believe that's typical
behavior of all K2's. On the lower bands the drift on my K2 is too small to
measure reliably - less than 20 Hz.

Rigs may differ slightly, of course. For a short time after it was
discovered that the extra heat from the KPA100 was causing excessive drift,
some ops did avoid mounting it in the K2 for best stability. My K2 drifted
over 200 Hz on the higher bands, running the KPA100, before the mods were
incorporated.

There's no longer any reason to separate them for that purpose now. I'd be
surprised if you saw any difference in a new unit with the KPA100 in or out
of the K2.

And the heavy "abuse" did not harm the KPA100 at all.

Of course, some of the other rigs advertise less than 50 Hz. The tradeoff is
a 'noisier' receiver because they use a fully-synthesized local oscillator
with a fixed reference oscillator in a temperature-controlled oven.    

Ron AC7AC


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[Tim Logan]

Ron -
Thank you - that brings me right up to date and good news as well!
73/Tim NZ7C
Ron D'Eau Claire wrote:

>Tim, NZ7C asked:
>
>Could some one bring up to date on what to expect for drift if I build a
>new K2/100 vs a K2 with the 100w amp separated? My understanding is that
>initially it was a better idea to keep the amp separate  - that
>combining it in the box with the K2 increased drift - a bit frustrating
>if you have $1600 tied up in  a K2/100.
>
>----------------------------------------------------------------------------
>------
>
>I have a K2/100 with the current drift compensation circuits all new K2's
>have.
>
>If I really "hammer" it with very high duty cycle transmissions at 100 watts
>with the amplifier mounted IN the K2, I've measured drift as high as 50 Hz.
>On most bands it's 20 Hz or less.  That's hitting it so hard the internal
>temperature of the K2 rises near 60C and the heat sink is too hot to hold my
>hand on it. I never run the K2 anywhere near that hard in normal operation.
>I "abused" mine specifically to test the PLL Temperature compensation
>circuit before it was added to the production kits.
>
>Also, that's after a 15 minute warm-up in receive. From a dead "cold" start,
>the drift might approach 100 Hz on the worst bands with the rig sitting in
>the shack.
>
>The total drift is a function of both the BFO and PLL Reference Oscillator
>drifts. On mine, they tend to add on the higher bands, which produces the
>up-to-50Hz number, and cancel on the lower bands. I believe that's typical
>behavior of all K2's. On the lower bands the drift on my K2 is too small to
>measure reliably - less than 20 Hz.
>
>Rigs may differ slightly, of course. For a short time after it was
>discovered that the extra heat from the KPA100 was causing excessive drift,
>some ops did avoid mounting it in the K2 for best stability. My K2 drifted
>over 200 Hz on the higher bands, running the KPA100, before the mods were
>incorporated.
>
>There's no longer any reason to separate them for that purpose now. I'd be
>surprised if you saw any difference in a new unit with the KPA100 in or out
>of the K2.
>
>And the heavy "abuse" did not harm the KPA100 at all.
>
>Of course, some of the other rigs advertise less than 50 Hz. The tradeoff is
>a 'noisier' receiver because they use a fully-synthesized local oscillator
>with a fixed reference oscillator in a temperature-controlled oven.    
>
>Ron AC7AC
>
>
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>Elecraft mailing list
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>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft   
>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com
>
>  
>

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