[Amps] Input SWR

[Robert Groh]

The short answer is 'No' - you don't need to 'tune' the input of the amplifier.  A 1.4:1 VSWR is pretty darn good.  The VSWR straight through just says that your load (I'm assuming your antenna) is pretty close to 50 ohms.  When you cut in the amplifier, you are now looking at the amplifier input and it's input impedance is a function of lots of things including the output tuning. So it is not at all uncommon to see a less than perfect VSWR on the input to the amplifier and, indeed, it is not all that important as long as it doesn't the higher VSWR doesn't cause your transceiver or transmitter to cut back the drive too severely.

73
Bob Groh, WA2CKY




________________________________
From: Tomas Hood <nw7us.heliophile at gmail.com>
To: Amps reflector <amps at contesting.com>
Sent: Friday, September 11, 2009 7:00:41 PM
Subject: [Amps] Input SWR

Another question:

When I am bypassing the amp (amp is in Standby mode), the SWR reading
on my Icom IC-7000 exciter shows nearly 1:1 through the amp into the
antenna tuner/matching network.  When I switch from Standby to Operate
mode (Ameritron AL-80A), the SWR reading moves closer to 1.4:1 - is
this an indication that the input stage of the amp needs to be
aligned?

I am very new to this amp world... thanks for helping me get my bearings...

-- 

73 de NW7US, Tomas David Hood - Bitterroot Valley of Montana

Singer/Songwriter/Guitarist : http://tomasdavidhood.com

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