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SWR/Power Meter Irratic

Dec 5th 2014, 07:33

K6JMQ

Joined: Mar 4th 2014, 04:20
Total Topics: 0
Total Posts: 0
I am operating on a Kenwood 440SAT @ 100w into a Cushcraft R8 vertical. The Kenwood was modified by Cal Fisher to allow the carrier control to adjust the power output in SSB.

My concern is that my Daiwa 801HP and my Diamond SX-600 pin on 20/17 meters and read high on the other bands. It often shows power output at about 120-140W on the other bands. This problem was present before the carrier control mod was done. I can turn my carrier down to bring it to read 100w on the SWR meters but then I get no output reading on the ALC. I only operate in band portions where the native SWR is below 1.8 (measured by an MFJ 259C) and I rarely use the built-in antenna tuner. It makes little difference in the SWR where I operate and it reduces the power output.

I see anywhere from .5 to about 5W reflected power when the antenna is in-line and when I dummy load the radio and all readings are within normal range.

Any ideas? Thanx, K6JMQ
Dec 5th 2014, 23:45

AA6E

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Your typical SWR meter is only accurate for power when it is close to 1:1 SWR. That's what you see with your dummy load. Being 20 - 40% high would not seem unusual to me. If you used the antenna tuner, you'd probably get better readings for power.

73 Martin AA6E
Dec 6th 2014, 15:28

K6JMQ

Joined: Mar 4th 2014, 04:20
Total Topics: 0
Total Posts: 0
Thanks for the response. I have also found that if I read the carrier forward power on both SWR meters as PEP they are normal. The problem only occurs when reading average power.
Dec 17th 2014, 03:24

KM3F

Joined: Mar 6th 2008, 13:50
Total Topics: 0
Total Posts: 0
In my opinion you have not received a reply that addresses your issue.
First, your antenna SWR needs to be matched down to within limits as specified by the mfger..
This is why your power meter shows you more power than the radio makes. The reason it the feedline actually sinks power that is being reflected back and forth between the antenna and the radio such that the 'vector sum' the meter reads, registers as more power. The meters don't know any different!
Your internal turner may not have enough range to handle the mis-match.
Turning the power down under these condition would cause the ALC action to never be achieved because the issue is outside the radio such that you did not accomplish anything by lowering the power.
Lowering the power does not affect the basic issue of poor antenna match.
Fix the antenna condition and the issue will clear.
Good luck.

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