Re: Need help-SWR increases with power...

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From: John J. McDonough (wb8rcr@arrl.net)
Date: Wed Dec 27 2000 - 16:17:16 CST


----- Original Message -----
From: "Steve Hanson" <ke1lg@qsilver.net>
Subject: Need help-SWR increases with power...

> Why does my SWR reading increase when I increase power? For example, on
40M
> at 4 watts into my untuned 130' dipole, SWR reading, both on my TT 580
> Delta, and on outboard Kenwood meter is abt 1.2, BUT, if I increase power
> to, say 80 watts, My SWR will go up to about 2.5+. I can tune the ant. to
> bring it back down, but why does it go up with power? Will I blow my
finals
> if I continue to run at 4 watts to untuned ant with both meters reading
1.2?

If your SWR meter uses silicon diodes, and many do, there is a substantial
voltage drop, which can cause misleadingly low SWRs at lower power. 4 watts
seems like enough, tho. It does seem odd to me, tho, that 2 meters would
show the same error. Somewhat similar I could see, but there are so many
SWR circuits around I'd be surprised to trip across 2 with the same circuit
(and hence the same error) from different manufacturers.

Do you perhaps have some component that can't take 80 watts? Is the change
in SWR abrupt? (Depending on where it occurs, it could be the diode, or it
could be something arcing). Mebbe with 80 watts you're melting the sneaux!

72/73 de WB8RCR http://members.home.com/wb8rcr/index.htm
didileydadidah QRP-L #1446 Code Warriors #35


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