[Elecraft] Low power KX1

[Don Wilhelm]

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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