K2 Alignment ACCURACY?

[Fred (FL)]

I've got the base K2 # 5422 built - and am doing the
"Alignment & Test, Part III" - Receiver Pre-Alignment,
Transmitter Alignment  (page 74):

The difficulty I'm finding:  It seems like the whole
testing and "peaking" adjustment, is based on BAR
GRAPH 10-LED Display and tweaking the various L1/L2,
L3/L4, C21/C23, L8/L9, L10/L11, C32/C34, L12/L13,
and C44/C46.   There seems to be so much slop in the
various L core adjustment - one can turn one of the
L's - and the LED Display changes little or flickers
side to side.  An analog display, or meter would seem
so much more accurate.  

It almost seems like one could mis-adjust L3, or
any of them - by as much as a 1/2 turn - based
solely on what the flickering of the 10-LED
display looks like.

Is there a better way of peaking and checking,
when I attempt this?

I've gone thru this process twice.  On 40 - I
can copy CW and some SSB sigs too.  (12' copper wire
antenna)

Thanks,
Fred N3CSY

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[Don Wilhelm-3]

Fred,

You can use your ears rather than the S-meter - just tune for the strongest
signal strength.  Close your eyes and listen, you should hear a peak as you
rotate the inductor slug (or capacitor trimmer).  You should be able to
resolve the peak within about 1/4 turn with just your ears.  The peak on 80
meters is a bit more broad than the peak on other bands.

If you get the tuning anywhere close, that should be good enough for now,
read the title on page 76 literally, this is PRE-ALIGNMENT.  When you turn
to page 77, you will be tuning the same inductors and trimmer caps using
transmit mode, and the indication is much more precise than for the receive
pre-alignment.  If you did the steps for 40 meters on page 75, you should
already have a sense for the process - the procedure for the other bands is
similar to that used for 40 meters.

Your 12 foot copper wire is not really a very good antenna, and you will
likely hear only a few signals (perhaps none at certain times of the day) -
when you connect a good outdoor antenna tuned properly for a 50 ohm
impedance, you will hear a lot more.

73,
Don W3FPR

> -----Original Message-----
>
> I've got the base K2 # 5422 built - and am doing the
> "Alignment & Test, Part III" - Receiver Pre-Alignment,
> Transmitter Alignment  (page 74):
>
> The difficulty I'm finding:  It seems like the whole
> testing and "peaking" adjustment, is based on BAR
> GRAPH 10-LED Display and tweaking the various L1/L2,
> L3/L4, C21/C23, L8/L9, L10/L11, C32/C34, L12/L13,
> and C44/C46.   There seems to be so much slop in the
> various L core adjustment - one can turn one of the
> L's - and the LED Display changes little or flickers
> side to side.  An analog display, or meter would seem
> so much more accurate.
>
> It almost seems like one could mis-adjust L3, or
> any of them - by as much as a 1/2 turn - based
> solely on what the flickering of the 10-LED
> display looks like.
>
> Is there a better way of peaking and checking,
> when I attempt this?
>
> I've gone thru this process twice.  On 40 - I
> can copy CW and some SSB sigs too.  (12' copper wire
> antenna)
>
> Thanks,
> Fred N3CSY
>

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[Mike Harris-9]

G'day,

| L's - and the LED Display changes little or flickers
| side to side.  An analog display, or meter would seem
| so much more accurate.

Spot on.

Digital displays are rubbish when it comes to peaking anything.  It is so
much easier to peak the swing of a meter needle than follow changing
numbers or coarse steps on a bar display.  I did all my band pass filter
tuning on TX using a WM-2 watt meter.  Smooth an' easy.

Regards,

Mike VP8NO

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[Don Wilhelm-3]

Mike,

I agree, I personally use a 'scope with its 10X probe connected directly
across the dummy load for my peak indicator - just watch for the highest
deflection on the 'scope and it is 'Spot On' - easy and no ambiguity.

For those not having access to an analog indicator, the K2 display does work
fine, but one must tune slowly because the digital display takes a bit of
time to 'catch up' - with fast tuning, the peak can be missed.

Bottom line - if you have anything analog that will indicate the peak, use
it, the peak will be more obvious than with the digital display. That
includes inserting an analog SWR meter in-line with the dummy load -  no
matter that the SWR meter or Wattmeter is inaccurate, you are interested
only in the peak when doing this tuning, not the absolute power (measurement
of the power comes later).

The original question was about determining the peak during the receive
pre-alignment, be aware that this is only a preliminary alignment, the
better (more precise) alignment will be done using Transmit, so if one gets
the receive pre-alignment reasonably close to correct, the final peaking can
be easily done with the transmit alignment.

73,
Don W3FPR

> -----Original Message-----
>
> G'day,
>
> | L's - and the LED Display changes little or flickers
> | side to side.  An analog display, or meter would seem
> | so much more accurate.
>
> Spot on.
>
> Digital displays are rubbish when it comes to peaking anything.  It is so
> much easier to peak the swing of a meter needle than follow changing
> numbers or coarse steps on a bar display.  I did all my band pass filter
> tuning on TX using a WM-2 watt meter.  Smooth an' easy.
>
>

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