http://elecraft.85.s1.nabble.com/Latest-status-of-dirft-in-K2-100-vs-K2-with-100w-amp-separate-tp372907p372909.html
>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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