Lwo power in KX1

[Ignacy]

Just acquired used KX1.

Two problems. None of my screwdrivers moves 20m trimmers. Any idea?

The power as indicated by LP100 is 1W or less with 9V alkalines; the lowest in on 20m.

I made more detailed measurements on 20m. At 12V, the maximum power is 2.2 W measured by LP-PAN and 2.6 W with the inside meter; increasing the voltage does not help on 12V. The radio draws about .6A. Assuming the the final draws .5A, the efficiency seems to be 40-45%, much below that of a  C class amplifier.

On 40 and 30, The LP100-measured power is 2.4 at 12 rising to 3W with 14V.

Ignacy



 

[Don Wilhelm-4]

Ignacy,

Look at the slots in those trimmers carefully.  The "proper" screwdriver
would look like a blunted phillips screwdriver, but if you are careful a
blunt point straight blade will work too - use it on one side of the
cross slot.

Check the power with the tuner set to CAL - if it is in 'tun' the power
readings may vary a bit from actual.
If the power on the KX1 display is not correct, follow the instructions
in the KXAT1 manual to balance and re-calibrate the wattmeter.

The power seems slightly on the low side.  You might want to check the
soldering near Q1, Q4, Q5 and Q6 as well as the low pass filter area.  
If that does not help,  try adding the Power Mod - change R11 to 4.7
ohms and R30 to 33 ohms.

Because there were several compromises in the KX1 design to allow 3 or 4
bands using one low pass filter, the power output on 20 meters will
normally be lower than that on 40m or 30m.  It is a rare KX1 that will
develop more than 4.5 watts on any band.  Besides, the voltage ratings
of the LPF capacitors will not allow higher power in any case.  The KX1
is in the 3 to 4 watt transceiver class, and yes - the power output is
highly dependent on the power supply voltage.  I try to get every KX1
leaving my workbench to a minimum of 3.5 watts on 20 meters using a 13.8
volt power supply, and for some, that is the best it can get.

73,
Don W3FPR

Ignacy wrote:

> Just acquired used KX1.
>
> Two problems. None of my screwdrivers moves 20m trimmers. Any idea?
>
> The power as indicated by LP100 is 1W or less with 9V alkalines; the lowest
> in on 20m.
>
> I made more detailed measurements on 20m. At 12V, the maximum power is 2.2 W
> measured by LP-PAN and 2.6 W with the inside meter; increasing the voltage
> does not help on 12V. The radio draws about .6A. Assuming the the final
> draws .5A, the efficiency seems to be 40-45%, much below that of a  C class
> amplifier.
>
> On 40 and 30, The LP100-measured power is 2.4 at 12 rising to 3W with 14V.
>
> Ignacy
>  
>

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