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Re: [Amps] High SWR

To: "amps@hidden-valley.com" <amps@hidden-valley.com>
Subject: Re: [Amps] High SWR
From: Scott McGrath <mcgrath@fas.harvard.edu>
Date: Thu, 23 Apr 2009 14:02:28 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
In the case of a broadcast system you are setting up a single frequency 
system and you want all the components to have an impedance match as you 
want as much of the power as humanly possible to be radiated by the 
purpose built antenna,    You do not want the RF bouncing around the 
transmission system creating heat.    My first experience with broadcast 
transmitters was as an intern working on setting up WEVO FM learned 
stuff there I have never forgotten about transmitters and antenna systems.

I think the list's fascination with CB is due to the fact that many new 
hams got their start in CB where amplifiers are 'forbidden fruit' and a 
whole mythos has evolved around the misconceptions about how 
transmission lines and antennas REALLY work and the only parameters most 
CB'ers can measure is forward power and SWR.

It used to be in the old days 'reflected' power was measured with lecher 
wires and a bulb so you could really 'see' the nodes on the transmission 
line with a meter it's more of a 'black box' and misconceptions arise   
I also use/used a slotted line for X-band measurements.

- Scott   



Jeff Carter wrote:
> Back when I was in broadcasting full-time, VSWR was important, too.  That 
> situation had nothing to do with cheap finals, it was mostly about 
> efficiency.  Things I took for granted working with high power transmitters 
> have contributed to my conservatism with my ham gear.
>
> I was never a CBer.  I'm not sure why this list is fascinated with CB, it 
> makes me think I missed something.  My path went military-Tech Class 
> License-broadcasting-Extra License-Bachelor's in Telecommunications 
> Engineering.
>
> Jeff/KD4RBG
> Society of Broadcast Engineers #25224
>
> On Thursday April 23 2009 11:50, Scott McGrath wrote:
>   
>> SWR is an obsession with the CB set and some others CB's could not
>> tolerate a high SWR due to the cheap finals used the high RF voltages
>> would blow the junction.     This effect created the oral tradition of
>> 1:1 SWR == Antenna System Goodness (tm).   It's hard to counteract what
>> 'everybody' knows.
>>     
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>   

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