[Elecraft] Low power KX1

[Don Wilhelm]

Richard,

The power from the basic KX1 is good - excellent work there.
You apparently have something awry in the KXAT1 (it looks good on 30 
meters, but the other bands have problems).

Look the KXAT1 over for soldering problems - solder bridges, 
inadequately heated solder connections (reflow with a soldering 
temperature of 750 degF), and properly stripped and tinned toroid leads.

Good analysis on the dummy load.

On 1/17/2016 4:11 PM, Richard wrote:
> 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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