Elecraft-K3@groups.io | Low Power on 40 meters

McClain Richard

#32998

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

#32999

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

Show quoted text

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

#33001

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

#33002

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

Ray WA6VAB. K3 #2834

Sent from Mail for Windows 0

Show quoted text

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

#33013

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

#33014

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

#33036

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.