Topics

Low Power on 40 meters


McClain Richard
 

I have an old K3 which has low power on 30, 40 and 60 meters. See chart below.

Other bands are OK. The TX Gain calibration did not fix it.


The K3 PWR knob was at full clockwise with display showing 110 watts for all data shown in chart.

Measurements were done with old Heath HM-102 analog meter. Not accurate, but relative measurements.

Any suggestions to get 40 meters level up to 100 watts?

 

73,

Dick, KD4S

 

BAND

POWER

After
TX Gain Calibration POWER

160

100

100

80

95

100

60

70

75

40

75

80

30

75

90

20

110

125

17

110

60

15

120

125

12

120

125

10

100

125

 


Mike Flowers
 

Hi Dick,

 

What does the K3 report as its input VDC during TX on these bands?

 

I had some issues and when I checked that voltage it was low, so I removed some lossy DC supply line connectors and adjusted my power supply voltage a bit.   All my issues were corrected.

 

Worth a check …

 

- 73 and good DX de Mike, K6MKF, NCDXC Secretary

 

From: Elecraft-K3@groups.io <Elecraft-K3@groups.io> On Behalf Of McClain Richard
Sent: Saturday, July 04, 2020 07:50
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Low Power on 40 meters

 

I have an old K3 which has low power on 30, 40 and 60 meters. See chart below.

Other bands are OK. The TX Gain calibration did not fix it.


The K3 PWR knob was at full clockwise with display showing 110 watts for all data shown in chart.

Measurements were done with old Heath HM-102 analog meter. Not accurate, but relative measurements.

Any suggestions to get 40 meters level up to 100 watts?

 

73,

Dick, KD4S

 

BAND

POWER

After
TX Gain Calibration POWER

160

100

100

80

95

100

60

70

75

40

75

80

30

75

90

20

110

125

17

110

60

15

120

125

12

120

125

10

100

125

 


Wes Stewart
 

I would be tempted to put it on 40 (mid-band) and tweak trimmers C132 and C153 just a little and remember where they are set so you can return if needed.  I've had some of these go intermittent on my K3S.  These will interact with 60-meter as well.  You might even get lucky and have it fix both bands.


Ray Maxfield
 

Are these Test Results into a GOOD Dummy Load ???

Ray WA6VAB.  K3 #2834

 

Sent from Mail for Windows 0

 

From: Mike Flowers
Sent: Saturday, July 4, 2020 7:55 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Low Power on 40 meters

 

Hi Dick,

 

What does the K3 report as its input VDC during TX on these bands?

 

I had some issues and when I checked that voltage it was low, so I removed some lossy DC supply line connectors and adjusted my power supply voltage a bit.   All my issues were corrected.

 

Worth a check …

 

- 73 and good DX de Mike, K6MKF, NCDXC Secretary

 

From: Elecraft-K3@groups.io <Elecraft-K3@groups.io> On Behalf Of McClain Richard
Sent: Saturday, July 04, 2020 07:50
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Low Power on 40 meters

 

I have an old K3 which has low power on 30, 40 and 60 meters. See chart below.

Other bands are OK. The TX Gain calibration did not fix it.


The K3 PWR knob was at full clockwise with display showing 110 watts for all data shown in chart.

Measurements were done with old Heath HM-102 analog meter. Not accurate, but relative measurements.

Any suggestions to get 40 meters level up to 100 watts?

 

73,

Dick, KD4S

 

BAND

POWER

After
TX Gain Calibration POWER

160

100

100

80

95

100

60

70

75

40

75

80

30

75

90

20

110

125

17

110

60

15

120

125

12

120

125

10

100

125

 

 


McClain Richard
 

Still have problem listed above. Following is more data that may provide some clues. I did not adjust the two capacitors as suggested (yet) because the gear belongs to someone else. The data answers the question about the dummy load and DC voltage & current also.

Any advice is appreciated. Thank you. 
Dick, KD4S


McClain Richard
 

The data did not show as expected in my last post. Try again.

  K4SV
CW
s/n 1886
K4SV
CW
s/n 1886
K4SV
CW
s/n 1886
Drake model 1551 Dummy Load neasured through the HM-102 power meter
BAND HEATH
HM-102
HEATH
HM-102 after TX Gain Calibration
(repeat) HEATH
HM-102 after 2nd  TX Gain Calibration
DC Voltage on K3 Display (volts) DC Current on K3 Display (amps) SWR Rs Xs
  RF Out = zero 13.8 0.88      
160 100 100 100 13.2 20.5 1:1.0 48 0
80 95 100 100 13.2 21.5 1:1.0 50 1
60 70 75 75 13.2 21.5 1:1.0 52 0
40 75 80 77 13.3 18.6 1:1.0 53 0
30 75 90 85 13.3 21.4 1:1.1 52 5
20 110 125 125 13.3 18.8 1:1.2 46 8
17 110 60 60 13.3 16.5 1:1.2 40 5
15 120 125 125 13.3 19.2 1:1.2 40 6
12 120 125 125 13.3 22.7 1:1.2 43 9
10 100 125 125 13.3 17.6 1:1.2 52 12
6 23 40 40 13.3 19.9 1:1.6 37 18
                 
                 
  29-Jun-20 29-Jun-20 5-Jul-20      


Keith_WE6R
 

What are your WM (watt meter) cal numbers? LP and HP
Please post the result tables of the 5, 50 (and MW if KXV3 equipped) TX gain Calibrations.
If you have a KAT3 ATU, we recommend removing and jumpering L10 on those old units. (the trap was determined to be redundant).
That is an 8.215 trap and C10 gets damaged as it is on the antenna side of the tuner.
The burned trap can affect just certain frequencies. Usually 6m and 40M.
Keith WE6R Elecraft K3 Tech.