[Elecraft] K2 Power meter

Mon Jul 20 17:06:05 EDT 2009

I just thought of another thing: I got the KAT2 almost completely built -  
just had to put in one IC and the RAM chip. When I tested the DC voltage on  
Pin 1 of that IC at the end of the Bridge Null section the voltage was 2.56  
V or something, below the spec'd 3-4 volts. I attributed this to the fact  
that R6 was already installed and just went on. Could that be a clue to the  
source of my trouble? Should that have read between 3 and 4 volts even with  
that resistor in there? I'm going to take it out and go through that  
process again tonight and see where that gets me.

Tom W0EA

On Jul 20, 2009 12:54pm, Tom Campie <tom.campie at gmail.com> wrote:
> I redid the C55 null (it was off by quite a bit now) but that did not  
> solve the problem. I re-initialized the tuner and retuned my non-50 ohm  
> load and my power readings were still way off. Worst on 40m. I'm taking  
> the balun off tonight, we'll see if that makes any difference. If not I  
> guess I'll have to go through and see if I can find any mistakes or  
> errors in the build. Any other ideas?

> Tom

> On Mon, Jul 20, 2009 at 9:51 AM, Tom Campie tom.campie at gmail.com> wrote:

> I just realized something that may be throwing it off - I installed the  
> Elecraft 4:1 balun inside the rig and hard wired it to ANT 2 on the tuner  
> after I'd done the bridge null - is it possible that that has thrown off  
> that null and I am not actually getting a 50 ohm load to the front end?  
> I'll have to redo that tonight and report back.

> Thanks for the help so far.

> Tom

> On Sun, Jul 19, 2009 at 11:12 PM, Don Wilhelm w3fpr at embarqmail.com> wrote:

> Tom,

> That is exactly what I said. In CALP, if the load is anything other than  
> 50+j0, the power indication will be incorrect. In other words, the  
> requested power may not equal the actual power.

> When you go to AUTO and do a TUNE, the forward power should be close to  
> the requested power.

> 73,

> Don W3FPR

> Tom Campie wrote:

> I calibrated the tuner to a 50 ohm load on CALP. With the tuner tuned to  
> a non-50 Ohm load, the requested power does not match the output power by  
> any definition of the word.

> Tom

> On Jul 19, 2009, at 9:48 PM, Don Wilhelm wrote:

> Tom,

> No adjustment is required. In CALP state, the tuner must be working into  
> a 50 ohm load for accurate power readings. If you are connected to an  
> antenna that has a feedpoint impedance other than 50+j0 impedance, you  
> can expect "unexpected" results.

> When you change the ATU menu to Auto and do a TUNE, the tuner has done  
> its job of providing a 50 ohm match to the K2 and the power out will be  
> as requested.

> 73,

> Don W3FPR

> Tom Campie wrote:

> This has been beaten over and over I think but I haven't found anything  
> on it yet:

> I just got back from the lab at work and used a very well calibrated  
> power meter to calibrate my KAT2 power meter. Now on 40m at home, I set  
> my power control to 5w and tuner to Pout. The tuner now reads 2.9w. Not  
> until I tune the requested power to 8 watts or so does the tuner say I'm  
> putting out 5 watts. Isn't there a way to adjust it so that the requested  
> power matches the tuner output power so that the S/ Power meter reads the  
> right value? That's the most annoying part...

> Tom

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