[Elecraft] KX1 Output Power & Harmonic Rejection

[Francisco Barros]

Hi to all,

After "alignment and Test - Part III", I got more power on 20 m (3.8 W) than 
40 m (3.2 W).
As the manual says, for best harmonic rejection, it should be the opposite 
(0.3...0.6 W more power on 40 m).
Following some previous posts (thanks Don), I checked very carefully all the 
components, soldering, relay K2 working OK and even the complete TX path 
from the DDS output to the BNC connector.
So, as the manual says, I "squeezed" L2 on the lower pass filter, in order 
to get the best harmonic rejection.

Here are some tests I've made (all measurements at 12 V & with OUTPUT POWER 
MOD done; NO TUNER):

1. L2 turns not squeezed (according Fig. 16 on the manual)

a) 40 m
- output power: 3.17 W
- current drain: 490 mA
- 2nd harmonic: 44 dB
- 3rd harmonic: 62 dB

b) 20 m
- output power: 3.77 W
- current drain: 623 mA
- 2nd harmonic: 54 dB
- 3rd harmonic: 56 dB

2. L2 turns squeezed to 75 % (now, 0.3 W more power on 40 m)

a) 40 m
- output power: 3.06 W
- current drain: 585 mA
- 2nd harmonic: 58 dB
- 3rd harmonic: 59 dB

b) 20 m
- output power: 2.74 W
- current drain: 563 mA
- 2nd harmonic: 48 dB
- 3rd harmonic: 56 dB

Comments:

>with L2 turns well spaced I get: more power on 20 m and even a better 
>harmonic rejection. At 40 m, the current drain is lower, and even the 
>harmonic rejection is 44 dB for the 2nd harmonic, it is between specs (40 
>dB).

>tests done at 9 V (with L2 squeezed): harmonic rejection results similar to 
>12 V tests.

>all tests done with Rohde & Schwarz CMTA-54 Radiocommunication Analyzer & 
>Tektronix 495 P Spectrum Analyzer.

>So, in my case, for my KX1 s/n 1881 and with output power mod done (R11 = 
>4.7 Ohm; R30 = 33 Ohm), I will left L2 "not squeezed" !!.

Hope this helps.

73,
Paco

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