[Elecraft] Low power KX1

[Richard]

Thank you Don and Ray,

The information proved valuable.  Just pushing around on the toroids made a
change so I knew I had a bad connection somewhere.  With minor surgery I was
able to reheat the joints, and without the ATU board installed I have 40 to
48 VPP across the bands.  I also found that my dummy load was highly
inductive, going over 5 to 1 @ 14Mhz. (using a rigexpert AA-30) I made a new
one that came out at 51ohms resistive.

I think I have something attenuating the signal in the ATU board, as after
it, in both cal and tune modes I have quite a drop in signal.

Results         No tuner       tuner in cal      tuner in tune
3                 51v              25                 20
7                 48v              30                 27
10                46v              45                 45
14                40v              27                 19

 In the test modes, I can hear each relay click. And in cal mode they look
like they bypass by shorting the inductors, so I am lost.  My electronic
skill is at "I wish I had a lot more"  Any and all help is appriciated.

Thank you in advance. 
       Richard
 

-----Original Message-----
From: Don Wilhelm [mailto:w3fpr at embarqmail.com] 
Sent: Sunday, January 17, 2016 2:11 AM
To: richard at inparadise.us; Elecraft at mailman.qth.net
Subject: Re: [Elecraft] Low power KX1

Richard,

Take a careful look at the Low Pass Filter board for the KXB3080 option.
Count the turns.  Each time the wire passes through the toroid core is one
turn.  Make certain you have the correct number of turns.  
That LPF is the downfall of many builders.  In addition, count the turns on
T1 - the ame thing applies.
Also on the same toroids, be certain the leads were well stripped and
tinned.  Look at the solder side.  If you can see a ring around the lead,
that lead was not adequately stripped and tinned.  You should be able to see
a small bit of tinned lead on the component side of the board.
The LPF board should be *exactly* like that shown in the KXB3080 option
manual illustrations.  There is no room for exceptions.  Be certain the
green lead of L2 is oriented away from red lead #4.

You will need an external QRP wattmeter to properly calibrate the wattmeter
in the KXAT1, but if you have a good 50 ohm dummy load, you can use your
'scope to measure the RF voltage across it.  Use a 10X probe on the 'scope
and measure the peak to peak voltage.  If the dummy load is sealed, use a T
adapter to gain access to the center conductor.
The power is the square of the peak to peak voltage divided by 400. 
Derivation of that formula is "left to the student".

73,
Don W3FPR

On 1/16/2016 8:53 PM, Richard wrote:
> From: Richard [mailto:richard at inparadise.us]
> Sent: Saturday, January 16, 2016 8:50 PM
> To: Elecraft at mailman.qth.net'
> Subject: Low power KX1
>
>
> I am very new to the world of CW.  Several months ago I built a KX1.  Once
I
> was able to receive with it, I built the 30-80 band set, and once it was
> installed and working, I built the ATU.  With the ATU was the first time I
> was able to measure power.  I am only getting .4W out of internal, and 1W
> with a 13 volt power supply.  So I did the power modification changing the
> resistors, and now I get .6 internal and 2W with 13V.
>   
> I could sure use some advice.  I do not have a bridge or watt meter.  I do
> have a good scope   Can I measure the signal voltage across 50 ohms?
>   
> Thank you in advance.
>   
>             Richard
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