[Elecraft] Do I have a problem? I do have questions! (long)

[Tom Hammond]

Hi Max:

>1.  In switching filters, the received CW signal changes pitch both up and
>down, depending on which of the four bandwidths is selected. In addition,
>the 2nd filter (0.7--all are at default widths) is muffled or noisy, unlike
>the others. (In other words, how much variation is acceptable--these changes
>are definitely beyond the 10-20 Hz DAC variation I read about.)

This is not unusual, though you shouldn't see more than a 20Hz change in 
frequency between individual filters for the same mode (e.g. CW Norm, or CW 
Rev). If you do see more than this amount of frequency change then a 
realignment of the filters is suggested. It's not difficult to accomplish.

>2.  I sometimes draw more than 2.3 A getting 5W indicated CW output, at
>other times or on a different band less than 1.9A. (Again, some difference
>in current draw, just like output, is reported--but what are the
>guidelines?)

Again, normal... based upon the efficiency of the TX on a particular band 
and the amount of power required to drive the finals to the requested output.

If your K2 hasn't been so set, I'd suggest you do a MENU | CAL | CUR  and 
then set CAL CUR to about 3.5A and be done with it.

>3.  The OHR WM-2 (which I re-calibrated a couple of months ago) never shows
>5W output, rarely shows 4W, & sometimes not even 3W, even though both the K2
>bargraph & LCD display show 5W. (Sometimes when I tune the antenna at 2W
>(indicated by the K2) the WM-2 shows 3W, and when I go back to up to 5W on
>the K2, the WM-2 is still less than 4W.) (The WM-2 is inserted between the
>K2 and the ATU & has seemed consistent in the past.)

If your K2 doesn't have the KAT2 ATU installed then this is not terribly 
ABnormal. Here's why...

The 'basic' K2 does not include a built-in wattmeter. Rather it includes an 
RF voltmeter which reads the RF voltage at the ANT connector and the uses 
the detected voltage level to reference a look-up table in the CPU to 
determine what level of output power it should display.

The problem is that this method of power monitoring is based upon having a 
50 Ohm resistive load present at the ANT connector. Any load OTHER than 50 
Ohms resistive will cause the actual RF voltage to be either higher or 
lower than what would be there if a 50 Phm resistive load was present.

So... if your (real life) antenna presents something other than 50 Ohms 
resistive, the displayed power will not be accurately represented on the 
display.

This is taken care of if/when you install the KAT2 (or KAT100) automatic 
transmatches, which do include a directional coupler capable of measuring 
actual power at the ANT connector.

>Here are a few details that may be relevant. What I want is an optimized CW
>QRP rig. The NB, SSB, and I/O accessories are installed  (I didn't know that
>either the SSB or I/O was installed, the seller didn't mention it in his ad
>& I didn't think I needed them.). The K2 has F/W 2.01 & I/O F/W 1.02. I plan
>on installing the AF and 160M accessories and probably the DK3RED approx. 5W
>power control limit mod.

If you plan to EVER run more than 5W output, I'd change the 5W mod for the 
10W  version. Additionally, you should not run SSB if the 5W mod has been 
installed... it's ONLY for QRP CW operation.

>My questions:
>1.  From what I mention, does it sound like the K2 has any problems?

Not so far.

>2.  If so, where do you suggest I look for solutions?

Possibly add one of the ATUs, to get much better power readings and to 
enhacne the K2s ability to work with just about any antenna... good or bad.

>(I've already gathered up the filter adjustment/alignment info at the 
>Elecraft site & there seem to be so many different approaches!!)

Everybody's got an opinion as to what's the best method... <G>

>3.  What Rev. B mods do you think are essential for a CW/QRP-only K2? (my
>impression is that the "BFO Toroid & PLL Ref Osc Xtal Upgrade" and "2nd
>Filter Upgrade" make sense--do you agree?--but I don't know about any of the
>others...)

Don't do the filter upgrade until you have some experience with what you 
have... could be you don't need it...!!

>4.  Another part of the Rev B mods is updating the F/W or I/O F/W? (If I
>understand correctly, the differences between new F/W and my 2.01/1.02 F/W
>wouldn't improve CW QRP operation much--what do you think?)

Probably not.

>I did get on the air yesterday with my Cushcraft R7 vertical. My first K2
>QSO was the main Marconi centenary station on Cape Cod, then Cuba (both on
>10M), next an Argentine ham (12M), finally another of the Marconi stations
>(40M). I know I'm going to like it here!

I think you may, too.

73,

Tom Hammond   N0SS