[Elecraft] K2: Debugging low transmit power

[Don Wilhelm]

  Owen,

That bit of "funny" procedure for setting L8 and L9 first on 20 meters 
(while the capacitors are set to the mid-point) is an interim step that 
only needs to be done once (unless drastic changes are made to the 
30/20m bandpass filter).  It assures that the L8 and L9 are set to 
somewhere close to where they should tune on 10 meters.  Having done 
that once, it is not necessary to repeat it - thereafter align L8 and L9 
only for 30 meters, and after that, align the capacitors for 20 meters.  
It is easier to discern the peak using transmit - you are using a meter 
instead of your ears.  Doing the alignment in receive first assures that 
you adjust the settings somewhere close and you should not have to 
adjust very far to get the transmit alignment correct.

As a matter of fact - in all cases, you should adjust the inductors for 
any band pair before adjusting the capacitors.
In other words, you can align any of the band pairs independently of the 
other bands.
The pairs are 40 and 60 meters (align 40 first), 30 and 20 (align 30 
first), 17 and 15 (align 15 first), and 12 and 10m (align 10 first).  I 
did not mention 80 and 160 yet because they must share a single setting 
if the k160RX is installed.  The way I do that is to first align 80 
(with the frequency set to 3750), then go to 1850 kHz - I look at (and 
remember) the slug position (which has been preset for 80m), then move 
the slug to find the peak on 160, noticing which way I turn the slug - 
it will not be far away, at most a turn - then I turn the slug back 
halfway between those two points and call it done.

Yes, it is important to remember that you are trying to tune for a peak 
(and not to 2 watts).  In fact, the manual tells you to initially set 
the power control to 2 watts, so you should already have about 2 watts 
of output before you start tuning, and the power will go up as you come 
closer to the peak.  Do whatever you have to do to keep the power lower 
than about 5 watts because you can miss the peak when the power goes up 
- exit and re-enter TUNE or rotate the power knob a bit and the power 
will come down.

Actually the initial 2 watts is not important either, I routinely use 
anywhere from 1 to 2 watts when doing an alignment, and that gives me a 
bit more 'headroom' when the power increases.  My arbitrary limit of 5 
watts is not critical either, but if it exceeds that, I back down to a 
low power again and continue to search for the peak.

73,
Don W3FPR

On 10/7/2010 3:38 PM, Owen B. Mehegan wrote:
> Last night I aligned all the bands, first on receive and then on
> transmit. On 10m, when doing the receiver pre-alignment, I couldn't seem
> to detect any audible change in signal level as I adjusted L12 and L13,
> which worried me. But when I did the transmitter alignments I had no
> trouble getting 2 watts on 10. I just had to tune L12 almost all the way
> into its can. I don't think I checked to see if I was getting 10 watts
> out on all the bands when I set the K2 to that level, so I'll do that
> tonight, but it looks like I'm all set! Thanks for all your help Don,
> and I'm happy to hear that the errata will be updated to clarify this. I
> thought, "A diagram would really solve this problem," so I'm glad to
> hear that's exactly what will be added. My friend said, "This is what
> makes the K2 and Elecraft so great. They are constantly updating the kit
> and the manual. You are building on the shoulders of a thousand
> frustrated hams!"
>
> I do have one curiosity question and one comment about this procedure.
> The question: First I did the receiver pre-alignment, and then I went on
> to the transmitter alignment. Both sections include these sentences:
> "Switch to 20 meters (14100 kHz). Set C21 and C23 to their mid-points."
> Then they have you adjust L8 and L9 on 20, then on 30, and then they
> have you go back to 20 and adjust C21 and C23. My question is, should
> the _transmitter_ alignment steps say to set C21 and C23 to their
> mid-points? This would seem to undo the adjustments to them that you
> make in the receiver pre-alignment section. Is this a mistake in the
> manual or am I misunderstanding the procedure?
>
> The comment: during the transmitter alignment procedure, I was confused
> by the fact that I was setting the K2's power to 2 watts, and then
> adjusting things in tune mode that would have the rig showing as much as
> 10-12 watts on its wattmeter. I didn't understand if I was supposed to
> be just adjusting to see exactly 2 watts, or to see the maximum power.
> And when I adjusted for maximum power, exited tune, then entered tune
> again, I would see closer to 2 watts. A quick Google search turned up
> this recent email thread:
> http://www.mail-archive.com/elecraft@mailman.qth.net/msg102763.html  Of
> course it had a helpful response from Don Wilhelm, so I felt better and
> went on my way :)  I would suggest that this information somehow be
> codified in the manual for future builders, because to me it wasn't
> intuitive that I was setting the K2 for 2 watts, and then seeing it hit
> 10+ as I went through the alignment steps.
>