[Amps] Alpha Input SWR

KB8NTY kb8nty at wowway.com
Sat Jan 10 23:53:24 EST 2015


NY9Y -Mike,

Sounds like a neat program, thanks for link... however with all due 
respect...I'm thinking the "feedline" is not being referenced. It is the 
"transmission feedline" the coax that connects the amp to the 
transceiver/transmitter, not the coax that runs to the antenna.

Theory is solid, yet real time first hand experiences speak loudly. When 
users experience controlled SWR by means of "transmission feedline" lengths, 
it's is hard to convince otherwise.
I would think though as has been mentioned there is a dynamic that exists, 
by means of use of various transceiver/amplifier's. So what one finds 
acceptable, may not work the same for others.

I do know that in my past history, there is textbook theory, then there is 
the way I am forced to implement such at times, and darn would ya know it 
still works, for the most part.

I expect the end results all vary based on the variable factors that 
contribute to the results!...Resulting in all the various different 
experiences posted.

Regards,
Ross  KB8NTY
http://www.rossradio.net/
https://groups.yahoo.com/neo/groups/groundradial/conversations/messages

***************************************************************************************





----- Original Message ----- 
From: "MICHAEL HUGHES" <mhughes149 at hotmail.com>
To: "Jim W7RY" <w7ry at centurytel.net>; "KB8NTY" <kb8nty at wowway.com>; 
<amps at contesting.com>
Sent: Saturday, January 10, 2015 9:13 PM
Subject: RE: [Amps] Alpha Input SWR


There is a web site "RFDUDE.com".  There is a free, easy to use Smith Chart 
Program there.

Changing the length of the transmission line merely moves the complex 
impedance around the VSWR circle.  Start with a complex impedance of say, 
30 -j20.  Then insert a piece of transmission line.  You can change the 
length of the transmission line by using the up and down arrows on your 
keyboard.  The impedance does change but it is still on the VSWR circle and 
is not normalized to 50 ohms.

I think someone mentioned this when this question first surfaced.

Handy little program.

Mike  NY9Y

> From: w7ry at centurytel.net
> To: kb8nty at wowway.com; amps at contesting.com
> Date: Sat, 10 Jan 2015 17:06:26 -0800
> Subject: Re: [Amps] Alpha Input SWR
>
> I have found that I use a 6' cable between SB220s and rigs for best SWR.
>
> I also tune the input coils using this length and advise my customers to 
> do
> the same when they use their amps.
>
> 73
> Jim W7RY
>
>
> -----Original Message----- 
> From: KB8NTY
> Sent: Saturday, January 10, 2015 1:01 PM
> To: amps at contesting.com
> Subject: Re: [Amps] Alpha Input SWR
>
> My Amp Supply LK-500ZB GG. amp manual also states to use a 6' length coax
> between your exciter's RF output and the LK-500ZB RF input connector.
> Possibly the feeder length does factor in!
>
> -73-
> Ross  KB8NTY
> http://www.rossradio.net/
> https://groups.yahoo.com/neo/groups/groundradial/conversations/messages
>
>
> ***************************************************************
>
> "Collins Radio recommends a 20.5 ft. coax between exciter and linear amp.
> .Perhaps this would work with the Alpha.
> 73, Jim - w5ifp at gvtc.com"
>
>
>
> -----
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